JP7433958B2 - Laser device and its control method - Google Patents

Description

The present invention relates to a laser device and a method of controlling the same.

In a laser device, a technique is known in which the frequency of output laser light is controlled using a frequency filter that has periodic transmission characteristics with respect to the frequency of input light (see, for example, Patent Document 1).
The laser device described in Patent Document 1 includes a light source section that makes the frequency of the laser light output variable, a first light receiving element that acquires the intensity of the laser light output from the light source section, and a frequency filter such as an etalon. , a second light receiving element that acquires the intensity of the laser beam that has passed through the frequency filter, and a control device (arithmetic circuit) that controls the operation of the light source section.
Here, the control device calculates a monitor value for controlling the frequency of the laser beam based on the intensity of the laser beam acquired by the first and second light receiving elements, respectively. Further, the control device uses the transmission characteristics of the frequency filter at a predetermined temperature to set a control target value that corresponds to the target frequency of the laser beam and serves as a target for the monitor value. The control device then controls the operation of the light source unit so that the monitor value matches the control target value.

Japanese Patent Application Publication No. 2015-60961

Incidentally, the transmission characteristic of a frequency filter is such that when the temperature of the frequency filter deviates from a predetermined temperature, the entire transmission characteristic shifts on the frequency axis. In other words, even though the temperature of the frequency filter deviates from a predetermined temperature, if the control target value corresponding to the target frequency of the laser beam is set using the transmission characteristics at the predetermined temperature, the frequency Since the transmission characteristics of the filter are shifted from the transmission characteristics at a predetermined temperature, the control target value does not correspond to the target frequency of the laser beam. Therefore, if the operation of the light source section is controlled so that the monitor value matches the control target value, the frequency of the laser beam will be controlled to a frequency that deviates from the target frequency.
Therefore, in the laser device described in Patent Document 1, the temperature of the frequency filter is controlled to be constant by a temperature control device.
However, even if the temperature of the frequency filter is controlled to be constant, the temperature of the frequency filter may unintentionally deviate from a predetermined temperature. In particular, in a laser device configured to control the temperature of the light source portion to be constant using a temperature control device, the temperature of the frequency filter often deviates from a predetermined temperature, and the deviation is often large. In such a case, there is a problem in that it is difficult to accurately control the frequency of the laser beam to the target frequency.

The present invention has been made in view of the above, and an object of the present invention is to provide a laser device and a control method thereof that can realize more suitable control when controlling the frequency of laser light.

In order to solve the above-mentioned problems and achieve the objectives, one aspect of the present invention provides a light source unit that makes the frequency of output laser light variable, and a light source unit that changes the transmittance periodically with respect to the frequency of input light. a first temperature sensor that detects an ambient temperature of the light source section; a second temperature sensor for detecting an environmental temperature of the frequency filter; and a first control amount to be applied to the temperature controller according to a first set value. a control unit that controls the temperature of the light source unit by supplying a second control amount to the light source unit and controls the frequency of the laser beam by supplying a second control amount to the light source unit according to a second set value; and a storage unit; The monitor section is arranged so that the temperature changes according to the control of the temperature controller, and the control section is configured to change the temperature based on the environmental temperature of the frequency filter detected by the second temperature sensor. , a first correction value is set for correcting the first setting value so as to offset a change in the transmission characteristic of the frequency filter due to environmental temperature, and the storage unit stores a relationship between the environmental temperature and the first correction value. This is a laser device that stores first relational information indicating.

The temperature controller may be in contact with the monitor section.

The temperature controller may have an installation surface on which the light source section and the frequency filter are installed.

The laser device may further include a casing in which the laser section is housed, and the second temperature sensor may be placed outside the casing.

The monitor section includes a second detection section that detects a second intensity corresponding to the intensity of the laser beam after the laser beam passes through the frequency filter, and the second set value or the monitor value It may also include a value corresponding to two intensities.

The monitor section includes a first detection section that detects a first intensity of the laser beam that corresponds to the intensity of the laser beam, and the second set value or the monitor value is the second intensity that corresponds to the first intensity. It may be a value corresponding to the ratio of

In the frequency filter, the transmission characteristic is shifted in the frequency axis direction depending on the environmental temperature, and the control unit is configured to correct the second control amount according to the first set value corrected by the first correction value. Two correction values may be set, and the storage unit may store second relationship information indicating a relationship between the first setting value and the second correction value.

The control unit is configured to determine, in a frequency direction, a transmission characteristic of the frequency filter under the first set value after setting the first correction value and a transmission characteristic of the frequency filter at a reference temperature of the environmental temperature. The first correction value may be set such that the amount of frequency shift is less than or equal to the capture range at a lock point closest to the pole of the transmission characteristic of the frequency filter.

The control unit may set the first correction value so that the frequency shift amount is 1/2 or less of the capture range.

The control unit sets a third correction value for correcting the monitor value or the second set value according to the environmental temperature, and the storage unit stores a relationship between the environmental temperature and the plurality of third correction values. It may also be one that stores third relational information indicating.

The third correction value may be set with reference to a polar point of the transmission characteristic of the frequency filter.

The control unit may set the first correction value after setting the third correction value.

One aspect of the present invention includes a light source unit that makes the frequency of output laser light variable, and a frequency filter that has a transmission characteristic whose transmittance changes periodically with respect to the frequency of input light. a monitor unit for acquiring a monitor value corresponding to a frequency equivalent amount corresponding to , a first temperature sensor that detects an ambient temperature of the light source unit, and a temperature controller that is thermally connected to the light source unit. A method of controlling a laser device comprising: a first control step of controlling the temperature of the light source section by supplying a first control amount to the temperature controller according to a first set value; a second control step of controlling the frequency of the laser beam by supplying a second control amount to the light source section according to the temperature control, and the temperature of the monitor section changes according to the control of the temperature controller. The first control step includes a first control step of correcting the first setting value based on the environmental temperature of the frequency filter so as to offset a change in the transmission characteristic of the frequency filter due to the environmental temperature. This is a method of controlling a laser device including a correction value setting step of setting a correction value.

According to the present invention, there is an effect that more suitable control can be realized when controlling the frequency of laser light.

FIG. 1 is a diagram showing the configuration of a laser device according to the first embodiment. FIG. 2 is a diagram showing the configuration of the laser section. FIG. 3 is an explanatory diagram of controlling the frequency of laser light. FIG. 4 is a block diagram showing the configuration of the control unit according to the first embodiment. FIG. 5 is an explanatory diagram of a discrimination curve based on the relationship between frequency and PD ratio. FIG. 6 is an explanatory diagram of the frequency shift of the discrimination curve. FIG. 7 is a flowchart showing a control method by the control unit according to the first embodiment. FIG. 8 is an explanatory diagram of the capture range.

EMBODIMENT OF THE INVENTION Below, with reference to drawings, the form for implementing this invention (henceforth, embodiment) is demonstrated. Note that the present invention is not limited to the embodiments described below. Furthermore, in the description of the drawings, the same parts are given the same reference numerals as appropriate. Further, the drawings are schematic, and the dimensional relationship of each element, the ratio of each element, etc. may differ from reality. Furthermore, drawings may include portions with different dimensional relationships and ratios. In addition, xyz coordinate axes are shown as appropriate in the drawings, and directions will be explained using these.

(Embodiment 1)
[Schematic configuration of laser device]
FIG. 1 is a diagram showing the configuration of a laser device according to the first embodiment.
The laser device 1 includes a modularized laser section 2 and a control section 3 that executes a control step for controlling the operation of the laser section 2.
In addition, in FIG. 1, the laser section 2 and the control section 3 are configured as separate bodies, but they may be integrally modularized.

[Configuration of light source section]
Under the control of the control section 3, the laser section 2 makes the frequency of the laser light it outputs variable to one of a plurality of frequencies, and outputs the laser light at the frequency. The laser section 2 includes a light source section 4, a semiconductor optical amplifier (SOA) 5, a planar lightwave circuit (PLC) 6, a photodetector section 7, a temperature sensor 8, and a temperature control section. A container 9 is provided. The planar light wave circuit 6 and the photodetector section 7 constitute a monitor section 10 . Furthermore, a submount 11 is interposed between the temperature controller 9, the light source section 4, and the semiconductor optical amplifier 5. The submount 11 is made of a material with high thermal conductivity, such as metal or ceramic.

FIG. 2 is a diagram showing the configuration of the laser section.
The light source section 4 is, for example, a laser that utilizes the Vernier effect, and outputs a laser beam L1 under the control of the control section 3. The light source section 4 includes a laser main body section 41 that makes the frequency of the output laser beam L1 variable, and a changing section 42. The changing unit 42 has three micro-heaters that generate heat according to the power supplied from the control unit 3, and locally heats the laser main body 41, thereby changing the laser beam L1 output from the laser main body 41. change the frequency.

The laser main body portion 41 includes first and second waveguide portions 43 and 44 respectively formed on a common base portion B1. Here, the base B1 is made of, for example, n-type InP. On the back surface of the base B1, an n-side electrode 45 is formed, which includes, for example, AuGeNi and is in ohmic contact with the base B1.

The first waveguide section 43 has a buried waveguide structure. This first waveguide section 43 includes a waveguide section 431, a semiconductor stacked section 432, and a p-side electrode 433.
The waveguide section 431 is formed within the semiconductor laminated section 432 so as to extend in the z direction.
Further, within the first waveguide section 43, a gain section 431a and a DBR (Distributed Bragg Reflector) type diffraction grating layer 431b are arranged.

Here, the gain section 431a is an active layer having a multiple quantum well structure made of InGaAsP and an optical confinement layer. Further, the diffraction grating layer 431b is composed of a sampling diffraction grating made of InGaAsP and InP.

The semiconductor laminated portion 432 is configured by laminating InP-based semiconductor layers, and has the function of a cladding portion for the waveguide portion 431 and the like.

The p-side electrode 433 is arranged on the semiconductor stack 432 along the gain section 431a. Note that an SiN protective film (not shown) is formed on the semiconductor laminated portion 432. The p-side electrode 433 is in contact with the semiconductor stack 432 through an opening (not shown) formed in the SiN protective film.

Here, the DBR heater 421, which is a micro-heater, is arranged on the SiN protective film of the semiconductor laminated portion 432 along the diffraction grating layer 431b. The DBR heater 421 generates heat according to the power supplied from the control unit 3, and heats the diffraction grating layer 431b. Further, by controlling the power supplied to the DBR heater 421 by the control unit 3, the temperature of the diffraction grating layer 431b changes, and its refractive index changes.

The second waveguide section 44 includes a two-branch section 441, two arm sections 442 and 443, and a ring-shaped waveguide 444.

The 2-branch section 441 is composed of a 1×2 branch waveguide including a 1×2 multimode interference (MMI) waveguide 441a, and the 2-port side is connected to each of the two arm portions 442 and 443. At the same time, the 1 port side is connected to the first waveguide section 43 side. That is, the two arm parts 442 and 443 are integrated at one end by the two-branch part 441 and are optically coupled to the diffraction grating layer 431b.

The arm portions 442 and 443 both extend in the z direction and are arranged to sandwich the ring-shaped waveguide 444 therebetween. These arm portions 442 and 443 are optically coupled to the ring-shaped waveguide 444 with the same coupling coefficient κ. The value of κ is, for example, 0.2. The arm portions 442 and 443 and the ring-shaped waveguide 444 constitute a ring resonator filter RF1. Further, the ring resonator filter RF1 and the two-branch section 441 constitute a reflecting mirror M1.

Here, the RING heater 422, which is a microheater, has a ring shape and is arranged on a SiN protective film (not shown) formed to cover the ring-shaped waveguide 444. The RING heater 422 generates heat in response to the power supplied from the control unit 3 and heats the ring waveguide 444. Further, by controlling the power supplied to the RING heater 422 by the control unit 3, the temperature of the ring-shaped waveguide 444 changes, and its refractive index changes.

The above-mentioned two-branch section 441, arm sections 442, 443, and ring-shaped waveguide 444 all have a high mesa waveguide structure in which an optical waveguide layer 44a made of InGaAsP is sandwiched between cladding layers made of InP. .

Here, the Phase heater 423, which is a micro-heater, is placed on a part of the SiN protective film (not shown) of the arm portion 443. A region of the arm section 443 below the Phase heater 423 functions as a phase adjustment section 445 that changes the phase of light. Then, the Phase heater 423 generates heat in accordance with the power supplied from the control section 3, and heats the phase adjustment section 445. Furthermore, by controlling the power supplied to the Phase heater 423 by the control unit 3, the temperature of the phase adjustment unit 445 changes, and its refractive index changes.

The first and second waveguide sections 43 and 44 described above constitute an optical resonator C constituted by a diffraction grating layer 431b and a reflection mirror M1 that are optically connected to each other. Further, the gain section 431a and the phase adjustment section 445 are arranged within the optical resonator C.

The diffraction grating layer 431b generates a first comb-shaped reflection spectrum having periodic reflection characteristics at predetermined frequency intervals. On the other hand, the ring resonator filter RF1 generates a second comb-shaped reflection spectrum having periodic reflection characteristics at predetermined frequency intervals.

Here, the second comb-like reflection spectrum has a peak with a full width at half maximum narrower than the full width at half maximum of the peak of the first comb-like reflection spectrum, and has a frequency interval different from the frequency interval of the first comb-like reflection spectrum. It has periodic reflection characteristics.

To illustrate the characteristics of each comb-like reflection spectrum, the frequency interval (free spectral range: FSR) between peaks of the first comb-like reflection spectrum is 373 GHz. Further, the full width at half maximum of each peak is 43 GHz. On the other hand, the peak-to-peak frequency spacing (FSR) of the second comb-like reflection spectrum is 400 GHz. Further, the full width at half maximum of each peak is 25 GHz. That is, the full width at half maximum (25 GHz) of each peak in the second comb-like reflection spectrum is narrower than the full width at half maximum (43 GHz) of each peak in the first comb-like reflection spectrum.

The light source section 4 is configured such that one peak of the first comb-like reflection spectrum and one of the peaks of the second comb-like reflection spectrum can be superimposed on the frequency axis in order to realize laser oscillation. . Such superposition is achieved by using at least one of the DBR heater 421 and the RING heater 422 to heat the diffraction grating layer 431b with the DBR heater 421 and change its refractive index by the thermo-optic effect to form the first comb-shaped layer. The reflection spectrum is changed by moving the entire reflection spectrum on the frequency axis, and the ring-shaped waveguide 444 is heated by the RING heater 422 to change its refractive index to change the second comb-shaped reflection spectrum on the frequency axis. This can be achieved by performing at least one of the following: moving and changing the entire structure.

On the other hand, in the light source section 4, a resonator mode due to the optical resonator C exists. In the light source section 4, the resonator length of the optical resonator C is set so that the resonator mode interval (longitudinal mode interval) is 25 GHz or less. In this setting, the resonator length of the optical resonator C is 1800 μm or more, and it can be expected that the line width of the oscillated laser light will be narrowed. Note that the frequency of the resonator mode of the optical resonator C is determined by heating the phase adjustment unit 445 using the Phase heater 423 and changing its refractive index, thereby moving the frequency of the resonator mode as a whole on the frequency axis. This allows for fine adjustments. That is, the phase adjustment unit 445 is a part for actively controlling the optical path length of the optical resonator C.

When the light source section 4 injects current from the n-side electrode 45 and the p-side electrode 433 to the gain section 431a by the control section 3 and causes the gain section 431a to emit light, the peak of the spectral component of the first comb-shaped reflection spectrum, The peak of the spectral component of the second comb-shaped reflection spectrum and one of the resonator modes of the optical resonator C are configured to oscillate at a matching frequency, for example, 193.4 THz, and output the laser beam L1. .

In the light source section 4, the frequency of the laser beam L1 can be changed using the Vernier effect. FIG. 3 is an explanatory diagram of controlling the frequency of laser light. The upper row shows the first comb-like reflection spectrum of the diffraction grating layer 431b (DBR), the middle row shows the second comb-like reflection spectrum of the reflection mirror M1 (RING), and the lower row shows the spectrum of the resonator mode. show.

When the DBR heater 421 is controlled by adjusting the supplied power, the comb-like reflection spectrum shifts from the shape shown by the solid line to the shape shown by the broken line on the frequency axis, as shown by the thick arrow line. Similarly, when the RING heater 422 is controlled, its comb-like reflection spectrum shifts from the shape shown by the solid line to the shape shown by the broken line on the frequency axis. Similarly, when the Phase heater 423 is controlled, its spectrum shifts from the shape shown by the solid line to the shape shown by the broken line on the frequency axis.

In the state shown by the solid line, the laser oscillates at a frequency f1 at which the reflection peak of DBR, the resonator mode of optical resonator C, and the reflection peak of RING coincide. In order to achieve this state, the DBR heater 421 and the RING heater 422 each set the frequency positions at which the reflection spectra of the DBR and RING reach their peaks, based on the supplied power. Furthermore, the Phase heater 423 sets a frequency position at which the resonator mode peaks based on the supplied power. When the state shown by the broken line is achieved by controlling each heater, the frequency at which the reflection peak of DBR, the resonator mode of optical resonator C, and the reflection peak of RING coincide can be set to frequency f2, so the frequency of laser beam L1 can be changed to frequency f2. It can be adjusted to Note that the electric power supplied to each heater can be controlled using current as a control amount. That is, the control section 3 controls the frequency of the laser beam L1 by supplying the light source section 4 with electric power corresponding to the current, which is a control amount. Current or power is an example of a controlled variable.

When changing the frequency of the laser beam L1 from the first frequency to the second frequency, for example, first feedforward control is performed on the DBR heater 421 and the RING heater 422 so that the comb-like reflection spectra of the DBR and RING overlap at the second frequency. Then, the Phase heater 423 is feedback-controlled so that one of the resonator modes matches the second frequency. However, the control method is not limited to this.

Returning to FIG. 1, the explanation will be continued. Although not specifically illustrated, the semiconductor optical amplifier 5 has a buried waveguide structure including an active core layer made of the same material and structure as the first waveguide section 43. However, the diffraction grating layer 431b is not provided. This semiconductor optical amplifier 5 is optically coupled to the light source section 4 by a spatial coupling optical system (not shown). The laser light L1 output from the light source section 4 is input to the semiconductor optical amplifier 5. The semiconductor optical amplifier 5 amplifies the laser beam L1 and outputs the amplified laser beam L2. Note that the semiconductor optical amplifier 5 may be monolithically configured with the light source section 4 on the base section B1.

The planar lightwave circuit 6 is optically coupled to the arm portion 442 by a spatial coupling optical system (not shown). Similarly to the laser beam L1, a portion of the laser beam L3 generated by laser oscillation in the light source section 4 is input to the plane light wave circuit 6 via the arm section 442. Note that the laser beam L3 has the same frequency as the frequency of the laser beam L1, and has an intensity corresponding to the intensity of the laser beam L1. The planar lightwave circuit 6 includes an optical branching section 61, an optical waveguide 62, and an optical waveguide 63 having a frequency filter 63a that is a ring resonator type optical filter.

The optical branching unit 61 branches the input laser beam L3 into two laser beams L4 and L5.
The optical waveguide 62 then guides the laser beam L4 to a PD (Photo Diode) 71, which will be described later, in the photodetector 7. Further, the optical waveguide 63 guides the laser beam L5 to a PD 72 in the photodetector 7, which will be described later.

Here, the frequency filter 63a has a characteristic that its transmittance changes periodically with respect to the frequency of input light, and transmits the laser beam L5 with a transmittance that corresponds to the frequency of the laser beam L5. Then, the laser beam L5 that has passed through the frequency filter 63a is input to the PD 72. That is, the frequency filter 63a is a waveguide type frequency filter. Note that as the frequency filter 63a, an etalon filter or an MZI (Mach-Zehnder Interferometer) filter having periodic transmission characteristics with respect to the frequency of input light may be used.

The photodetector 7 includes PDs 71 and 72. The PD 71 receives the laser beam L4 (which has the same frequency as the laser beam L1 output from the light source section 4 and has an intensity corresponding to the intensity of the laser beam L1), and generates a signal according to the intensity of the laser beam L4. An electrical signal is output to the control section 3. The PD 72 receives the laser beam L5 that has passed through the frequency filter 63a, and outputs an electric signal to the control unit 3 according to the intensity of the laser beam L5. The electric signals output from the PDs 71 and 72 are used for frequency lock control by the control section 3 (control for setting the frequency of the laser beam L1 output from the light source section 4 to a target frequency).

The PD 71 is an example of a first detection unit that detects a first intensity that is the intensity of the laser beam L4 corresponding to the intensity of the laser beam L1. The PD 72 is an example of a second detection unit that detects a second intensity that is the intensity of the laser beam L5 that corresponds to the intensity after the laser beam L1 passes through the frequency filter 63a.

Temperature sensor 8 is arranged above light source section 4 . The temperature sensor 8 is composed of, for example, a thermistor or the like, and detects the ambient temperature of the light source section 4 . Note that the temperature sensor 8 may be placed on the submount 11 or the temperature controller 9. The temperature sensor 8 outputs an electrical signal including information on the detected temperature to the control unit 3. Temperature sensor 8 is an example of a first temperature sensor.

The temperature controller 9 is composed of, for example, a TEC (Thermo Electric Cooler) including a Peltier element. On this temperature controller 9, a light source section 4, a semiconductor optical amplifier 5, a planar light wave circuit 6, a photodetector section 7, a temperature sensor 8, and a submount 11 are mounted. As a result, the temperature controller 9 and the light source section 4 come into contact via the submount 11 and are thermally connected. The temperature controller 9 also contacts the photodetector 7 and is thermally connected. The temperature controller 9 controls the temperatures of the light source section 4, the semiconductor optical amplifier 5, the planar light wave circuit 6, the photodetector section 7, the temperature sensor 8, and the submount 11 according to the supplied power. In this case, the control unit 3 controls the power supplied to the temperature controller 9 based on the temperature information detected by the temperature sensor 8 so that the light source unit 4 has a constant temperature. It is preferable to control the light source section 4 to maintain a constant temperature in order to suppress fluctuations in the frequency of the laser beam L1 due to operating conditions and external environmental temperature.

In the temperature controller 9, the installation surface 91 on which the light source section 4, the semiconductor optical amplifier 5, the planar light wave circuit 6, the photodetector section 7, the temperature sensor 8, and the submount 11 are mounted is connected to the light source section 4, the semiconductor optical When divided into two areas: a first area Ar1 where the amplifier 5, the temperature sensor 8 and the submount 11 are placed, and a second area Ar2 where the planar light wave circuit 6 and the photodetector 7 are placed. The temperature sensor 8 is placed in the first area Ar1.

[Configuration of control unit]
Next, the configuration of the control section 3 will be explained. FIG. 4 is a block diagram showing the configuration of the control section. The control unit 3 is connected to, for example, a higher-level control device (not shown) provided with a user interface, and controls the operation of the laser unit 2 according to instructions from a user via the higher-level control device.

In addition, below, the control of the temperature controller 9 and frequency lock control by the control part 3 will be mainly explained. Further, in FIG. 4, for convenience of explanation, a configuration of the control unit 3 that executes control of the temperature controller 9 and frequency lock control is mainly illustrated.

The control section 3 includes a temperature sensor 31, analog-to-digital converters (ADCs) 32, 33, 34, and 35, a calculation section 36, a storage section 37, and a current source 38.

The temperature sensor 31 is composed of, for example, a thermistor, and detects the environmental temperature of the frequency filter 63a. Temperature sensor 31 is an example of a second temperature sensor. Note that the temperature sensor 31 only needs to be placed at a position where it can detect the environmental temperature of the frequency filter 63a, and its position is not particularly limited. It may be arranged outside the housing. The temperature sensor 31 outputs an electrical signal including information on the detected temperature to the ADC 32.

The ADC 32 converts the analog electrical signal input from the temperature sensor 31 into a digital signal and outputs the digital signal to the calculation unit 36 .

The ADC 33 converts the analog electrical signal input from the temperature sensor 8 into a digital signal and outputs the digital signal to the calculation unit 36.

The ADC 34 converts the analog electrical signal input from the PD 72 into a digital signal and outputs the digital signal to the arithmetic unit 36. The ADC 35 converts the analog electrical signal input from the PD 71 into a digital signal and outputs the digital signal to the arithmetic unit 36.

The calculation unit 36 performs various calculation processes for the control executed by the control unit 3, and is composed of, for example, a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array). The storage unit 37 includes a portion configured with a ROM (Read Only Memory), for example, in which various programs and data used by the calculation unit 36 to perform calculation processing, and a portion that stores various programs and data used by the calculation unit 36 to perform calculation processing. The computer 36 has a work space and a portion constituted of, for example, RAM (Random Access Memory), which is used for storing the results of calculation processing by the calculation unit 36, etc. The control function of the control section 3 is realized in software by the functions of the calculation section 36 and the storage section 37.

The current source 38 supplies power for controlling the frequency of the laser beam L1 to each micro-heater of the light source section 4 based on instructions from the calculation section 36. In this embodiment, the calculation unit 36 instructs the current source 38 to specify a current value as the second control amount. The current source 38 supplies the light source section 4 with a current having a specified current value. Note that the second control amount may be a power value.

Further, the current source 38 supplies power for controlling the temperature of the light source section 4 to the temperature controller 9 based on instructions from the calculation section 36 . In this embodiment, the calculation unit 36 instructs the current source 38 to specify a current value as the first control amount. The current source 38 supplies the temperature controller 9 with a current having a specified current value. Note that the first control amount may be a power value.

Next, the configuration of the calculation section 36 will be explained in detail. The calculation unit 36 includes, as functional units, a PD ratio calculation unit 361, a target frequency setting unit 362, a target PD ratio setting unit 363, a difference acquisition unit 364, a temperature acquisition unit 365, and a target temperature setting unit 366. It includes a PID control section 367, a DBR/RING power setting section 368, and a current correction section 369. These functional units are realized through cooperation between software and hardware resources.

The PD ratio calculation unit 361 calculates the PD ratio from the digital signals input from the ADCs 34 and 35. The PD ratio is the ratio of the second intensity detected by the PD 72 to the first intensity detected by the PD 71. This PD ratio is a monitor value and is also called a monitor PD ratio.

The PD ratio will be explained. FIG. 5 is an explanatory diagram of a discrimination curve based on the relationship between frequency and PD ratio. The PD ratio changes periodically with respect to frequency, corresponding to the transmission characteristics of the frequency filter 63a. Note that in the example shown in FIG. 5, the PD ratio is standardized so that it varies between 0 and 1, but the PD ratio may be standardized so that it varies between -1 and +1. Furthermore, the monitor value may be calculated only from the second intensity detected by the PD 72 and transmitted through the frequency filter 63a. Even in such a case, the subsequent processing can be performed using the monitored value as the PD ratio. In addition, the monitor value of the PD 71 at each frequency is acquired in advance and stored in the storage unit 37 etc., and when calculating the PD ratio, the monitor value of the PD 71 acquired in advance is used according to the value or range of the target frequency. The PD ratio may be calculated using the value. In this way, the set value or monitor value may include a value corresponding to the second intensity.

In FIG. 5, a point P3 indicated by a black circle indicates that when the frequency of the laser beam L1 is f3, the PD ratio calculated by the PD ratio calculation unit 331 is R3. This means that if the light source section 4 is controlled so that the PD ratio becomes R3, frequency locking that locks the frequency of the laser beam L1 to f3 can be achieved. The PD ratio is an amount corresponding to the frequency of the laser beam L1, and is an example of a monitor value corresponding to the frequency equivalent amount. Point P3 is a control target point when controlling the frequency of laser beam L1 to f3, and is also called a lock point. Note that the lock point is usually set in a region between the maximum point and the minimum point where the slope with respect to frequency is large, excluding the dead zone which is near the maximum point and minimum point of the discrimination curve. Hereinafter, when a maximum point or a minimum point is not distinguished, they may be simply referred to as a maximum point.

Furthermore, since the discrimination curve changes periodically, the same PD ratio may be taken for different frequencies. In this laser device 1, when a target frequency is set, power corresponding to the target frequency is supplied to each of the DBR heater 421 and the RING heater 422 according to the frequency. As a result, the first comb-like reflection spectrum and the second comb-like reflection spectrum overlap in a frequency range that includes the target frequency, and the frequency range in which laser oscillation is possible is limited.

Note that, as something equivalent to the PD ratio, a correction coefficient is applied to the electric signal from the PD 72 (second electric signal) with respect to a signal obtained by applying the correction coefficient to the electric signal (first electric signal) from the PD 71 of the photodetector 7. It may also be the ratio of the signals applied. Alternatively, the ratio may be calculated using a signal obtained by applying a correction coefficient to either the first electrical signal or the second electrical signal, as the amount corresponding to the ratio.

The correction coefficients for the first electric signal and the second electric signal are obtained in advance through experiments or the like, and are stored in the recording unit 37 in the form of table data, relational expressions, etc., and are read out and used by the calculation unit 36 as appropriate. The correction coefficient may be determined depending on, for example, the operating conditions of the laser device 1, the temperature detected by the temperature sensor 8, or the like. Further, the correction coefficient may be determined to be suitable for fitting to a standardized PD ratio curve (wavelength discrimination curve). The correction coefficient is applied to the first electrical signal and the second electrical signal by, for example, addition, subtraction, multiplication, or division.

Returning to FIG. 4, the explanation will be continued. The target frequency setting unit 362 sets a target frequency as a target value of the frequency of the laser beam L1, for example, based on an instruction from a higher-level control device. The target value of the frequency of the laser beam L1 is an example of the second set value. The control amount is determined according to the set value.

The target PD ratio setting unit 363 sets a target PD ratio, which is an amount equivalent to the target frequency, based on the target frequency set by the target frequency setting unit 362. The target PD ratio is an example of the second set value. Setting of the target PD ratio is performed using table data, a relational expression, and the like that indicate the correspondence between frequencies and PD ratios stored in the storage unit 37. The table data and relational expressions are determined based on the discrimination curve generated by the frequency filter 63a, and are obtained, for example, when calibrating the laser device 1.

The difference acquisition unit 364 calculates and acquires the difference between the monitor PD ratio calculated by the PD ratio calculation unit 361 and the target PD ratio set by the target PD ratio setting unit 363.

The temperature acquisition unit 365 acquires the ambient temperature of the light source unit 4 and the environmental temperature of the frequency filter 63a from the digital signals input from the ADCs 32 and 33. Ambient temperature and environmental temperature are examples of monitor values.

The target temperature setting section 366 sets a target temperature for the ambient temperature of the light source section 4 based on the ambient temperature of the light source section 4 and the ambient temperature of the frequency filter 63a acquired by the temperature acquisition section 365. Here, as will be described later, the target temperature may be corrected based on the environmental temperature. Setting of the target temperature is performed using table data, a relational expression, etc., which are stored in the storage unit 37 and indicate the correspondence between the environmental temperature and the first correction value for correction. The table data and relational expressions are acquired, for example, when the laser device 1 is calibrated. The target temperature is an example of the first set value.

The PID control unit 367 sets a current value based on the difference between the monitor PD ratio and the target PD ratio, outputs an instruction for the current value to the current source 38, and performs proportional-integral-derivative (PID) control on the Phase heater 423. (second control step). Further, the PID control unit 367 can set a current value based on the difference between the monitor temperature and the target temperature, output an instruction for the current value to the current source 38, and perform PID control on the temperature controller 9. (First control step). However, in this embodiment, PI control is performed on both the Phase heater 423 and the temperature controller 9.

The DBR/RING power setting unit 368 sets the power to be supplied to each of the DBR heater 421 and the RING heater 422 based on the target frequency set by the target frequency setting unit 362. The power setting is performed using table data, a relational expression, and the like that indicate the correspondence between the target frequency and the power stored in the storage unit 37. The table data and relational expressions are acquired, for example, when the laser device 1 is calibrated.

The current correction unit 369 corrects the current value of the power set by the DBR/RING power setting unit 368 based on the target temperature set by the target temperature setting unit 366 using a second correction value, and calculates the corrected current value. Set. The current correction unit 369 can output an instruction of the current value to the current source 38 and perform feedforward control of the DBR heater 421 and the RING heater 422 (second control step). Setting of the current value is performed using table data, a relational expression, or the like that indicates the correspondence between the power value and the current value stored in the storage unit 37. The table data and relational expressions are acquired, for example, when the laser device 1 is calibrated.

[Control method]
Next, a control method executed in the laser device 1 will be explained. The light source section 4 and the planar light wave circuit 6 including the frequency filter 63a are both mounted on a temperature controller 9 and subjected to temperature control. However, the temperature control by the temperature controller 9 is mainly performed so that the temperature sensor 8 detects the ambient temperature of the light source section 4 and the light source section 4 is kept at a constant temperature. As a result, when the environmental temperature changes, the temperature of the frequency filter 63a changes, and for example, the transmission characteristics of the frequency filter shift entirely on the frequency axis. In this case, it is difficult to accurately control the frequency of the laser beam to the target frequency.

FIG. 6 is an explanatory diagram of the frequency shift of the discrimination curve. For example, the discrimination curve by the frequency filter 63a at a predetermined target temperature and a predetermined environmental temperature is shown by curve C1, and the discrimination curve by the frequency filter 63a when the predetermined target temperature is different from the environmental temperature is shown by curve C2. . Point MP is the maximum point of curve C1.
When the environmental temperature changes, the temperature of the frequency filter 63a changes even if the target temperature remains the same, and the entire discrimination curve shifts on the frequency axis (shifts from curve C1 to curve C2). That is, even though the temperature of the frequency filter 63a is shifted and the discrimination curve becomes curve C2, even if frequency lock control is executed with the PD ratio corresponding to the target frequency TF in curve C1 as the target PD ratio PDT, The frequency of the laser beam L1 is controlled to a frequency TF' that deviates from the target frequency TF.

Therefore, in the control method executed in the laser device 1, the first set value of the target temperature of the ambient temperature of the light source section 4 is corrected based on the environmental temperature of the frequency filter 63a detected by the temperature sensor 31. Set a correction value (correction value setting step). The frequency filter 63a is arranged so that its temperature changes according to the control of the temperature controller 9. As a result, by correcting the target temperature, the thermal influence of the temperature controller 9 on the frequency filter 63a changes, so the temperature of the frequency filter 63a also changes. By setting this temperature change so as to offset the change in the transmission characteristic of the frequency filter 63a due to the environmental temperature, it is possible to reduce the shift of the discrimination curve due to the environmental temperature. Here, the term "cancellation" is not limited to completely canceling out the shift of the discrimination curve due to the environmental temperature, but also includes so-called attenuation, in which the shift is made smaller than when the target temperature is not corrected.

Table 1 shows an example of the relationship between the environmental temperature and the first correction value. These relationships are obtained, for example, during calibration of the laser device 1. In Table 1, the first correction value is expressed as the LD offset temperature. In the example shown in Table 1, it is assumed that the environmental temperature varies from -5°C to 80°C. For example, the target temperature for the light source section 4 is a predetermined value higher than 35°C and lower than 80°C. When the environmental temperature is 35°C, the LD offset temperature is 0°C. When the environmental temperature is -5°C, the LD offset temperature is ΔT1 [°C]. When the environmental temperature is 80°C, the LD offset temperature is ΔT2 [°C]. Both ΔT1 and ΔT2 are used for correction by being added to the target temperature. ΔT1 is, for example, a positive value, and ΔT2 is, for example, a negative value. Such a relationship is stored in the storage unit 37 as first relationship information between the environmental temperature and the first correction value. The first relationship information includes table data or a relational expression in which the environmental temperature and the first correction value are associated with each other. Note that the LD offset temperature when the environmental temperature is a value other than -5°C, 35°C, or 80°C may be stored in the storage unit 37 as table data or a relational expression, or when the environmental temperature is -5°C. , 35°C, and 80°C by interpolation.
The environmental temperature when the LD offset temperature is 0° C. may be hereinafter referred to as the reference temperature. In the case of Table 1, the reference temperature is 35°C.

Furthermore, in this control method, power is supplied to the microheater for controlling the frequency of the laser beam L1 according to the target temperature (an example of the first set value) corrected by the first correction value (LD offset temperature). A second correction value is set for correcting the current value (an example of the second control amount supplied to the DBR heater 421 and the RING heater 422) when Note that the second correction value of the Phase heater 423 may be set to the current value used before the Phase heater 423 is feedback-controlled.

When the target temperature for the light source section 4 is corrected, the temperatures of the diffraction grating layer 431b and the ring-shaped waveguide 444 will also be different from before the correction, so in order to optimally realize the target frequency, the DBR heater 421 and the RING heater 422 are The value of the power supplied to each will also differ. For example, when the target temperature for the light source section 4 is corrected to a high temperature, unless the power values supplied to the DBR heater 421 and the RING heater 422 are changed, the diffraction grating layer 431b and the ring-shaped waveguide 444 will be at a higher temperature than the appropriate temperature. As a result, the frequency of each comb-like peak deviates from the target frequency. In this case, it may become difficult to control the power supplied to the Phase heater 423 to match one of the resonator modes to the target frequency, or even if it is matched, the intensity of the laser beam L1 may decrease, etc. There is a possibility that the optical characteristics of the portion 4 may deteriorate.

Therefore, in this control method, by correcting the current value related to the power supplied to the DBR heater 421 and the RING heater 422 according to the corrected target temperature, the deviation of the frequency of the comb-shaped peak from the target frequency is reduced, and the light source The optical properties of portion 4 suppress deterioration.

The relationship between the target temperature and the second correction value can be expressed similarly to Table 1, for example. For example, if the environmental temperature is the reference temperature and the target temperature for the light source section 4 is not corrected, the second correction value is 0 mA. If the target temperature becomes higher due to correction, the second correction value is, for example, a negative value. If the target temperature is lowered by correction, the second correction value is, for example, a positive value.

In addition, the coefficient related to the environmental temperature is k1 [W/℃], the reference temperature is Tref [℃], the acquired environmental temperature is T [℃], the coefficient related to the temperature of the light source section 4 is k2 [W/℃], and the LD offset. When the temperature is ΔT [° C.], the correction amount ΔW [W] of the electric power supplied to the DBR heater 421 and the RING heater 422 is expressed by the following formula.
ΔW=k1×(T-Tref)+k2×ΔT
Note that since k1 and k2 are separately defined for each of the DBR heater 421 and RING heater 422, ΔW is also separately defined for each of the DBR heater 421 and RING heater 422.

The table data or relational expression as described above is stored in the storage unit 37 as second relational information between the first set value and the second correction value. The second relationship information includes table data or a relational expression in which the first setting value and the second correction value are associated with each other. Note that the second correction value for the target temperature for which the second correction value is not stored in the table data may be calculated by interpolation.

〔flowchart〕
FIG. 7 is a flowchart showing an example of a control method by the control section 3 described above. Note that this control flow is executed at a predetermined control cycle during a period in which the PID control unit 367 executes feedback control to control the temperature controller 9 so that the light source unit 4 has a constant temperature.

First, in step S101, the temperature acquisition unit 365 acquires the environmental temperature.

Subsequently, in step S102, the target temperature setting unit 366 acquires a target temperature.

Subsequently, in step S103, the target temperature setting unit 366 corrects the target temperature.

Subsequently, in step S104, the current correction unit 369 corrects the current value of the power set by the DBR/RING power setting unit 368 based on the target temperature set by correction by the target temperature setting unit 366.

Subsequently, in step S105, the difference acquisition unit 364 acquires the difference between the target PD ratio and the monitor PD ratio (target PD ratio−monitor PD ratio).

Subsequently, in step S106, the PID control unit 367 adjusts the Phase heater power based on the difference between the target PD ratio and the monitor PD ratio obtained in step S105.

[Correction of PD ratio shift]
By the way, the discrimination curve as shown in FIG. 6 may shift not only in the frequency axis direction but also in the PD ratio axis direction depending on the environmental temperature. Such a shift is also called a vertical shift, and since the PD ratio at the target frequency shifts, it causes a decrease in frequency lock accuracy.

Therefore, the PD ratio calculation unit 361 or target PD ratio setting unit 363 of the control unit 3 sets a third correction value according to the environmental temperature, and corrects the monitor PD ratio or target PD ratio using the third correction value. Good too. In this case, the storage unit 37 stores third relationship information indicating the relationship between the environmental temperature and the third correction value. The third relational information includes table data or a relational expression in which the environmental temperature and the third correction value are associated with each other. The PD ratio calculation section 361 or the target PD ratio setting section 363 refers to the storage section 37 and sets the third correction value. The third correction value is set to offset the vertical shift depending on the environmental temperature. Thereby, it is possible to suppress a decrease in frequency lock accuracy. For example, the third correction value may be set based on the extreme point of the transmission characteristic of the frequency filter 63a. The extreme point of the transmission characteristic of the frequency filter 63a corresponds to the extreme point MP, which is the maximum point on the curve C1 shown in FIG. 6, for example. As a specific example, the third correction value may be set so that the extreme point of the vertically shifted discrimination curve matches the extreme point of the discrimination curve at the reference temperature. Note that the extreme point is not limited to the maximum point but may be the minimum point.

Also, when setting both the first correction value to cancel the frequency shift and the third correction value to cancel the vertical shift, set the first correction value after setting the third correction value. This allows more effective suppression of deterioration in frequency lock accuracy. When setting the first correction value after setting the third correction value, for example in the case of the flowchart of FIG. 7, between step S102 and step S103, the PD ratio calculation unit 361 or the target PD ratio setting unit 363 A step of setting a third correction value according to the environmental temperature and correcting the monitor PD ratio or the target PD ratio is added.

[Relationship between remaining frequency shift amount and capture range]
In the control method executed by the control unit 3, if the frequency shift is not completely offset, the transmission characteristics of the frequency filter 63a under the target temperature after setting the first correction value and the first correction value are not set. That is, a frequency deviation in the frequency direction from the transmission characteristic of the frequency filter at the reference temperature of the environmental temperature remains.

Here, the capture range will be explained with reference to FIG. 8. Capture range CR(-), CR(+) means that when controlling the frequency of laser beam L1 to target frequency fR1, lock point RP indicating PD1 which is the same PD ratio as target frequency fR1 (discrimination point indicating target frequency fR1) The frequency range between two points on the curve C3 adjacent to the point on the curve C3 (the frequency range from the frequency f1 to the target frequency fR1 and the frequency range from the target frequency fR1 to the frequency f2). When the lock point RP approaches the maximum point MP1, the capture range CR(-) becomes narrower and the capture range CR(+) becomes wider. When the lock point RP approaches the minimum point MP2, the capture range CR(-) becomes wider and the capture range CR(+) becomes narrower. In this specification, the narrower of capture ranges CR(−) and CR(+) is defined as the capture range.

In the control method executed by the control unit 3, the first correction value is preferably set so that the frequency shift amount is equal to or less than the capture range at the lock point closest to the extremity of the transmission characteristic of the frequency filter 63a. It is more preferable to set it to 1/2 or less of the capture range. If frequency lock is performed when the amount of frequency shift exceeds the capture range, the PD ratio will be erroneously locked to a lock point with the same frequency but a different frequency. On the other hand, if the frequency shift amount is less than or equal to the capture range, or even less than 1/2 of the capture range, such erroneous locking can be suppressed. Note that the width of the capture range varies depending on the lock point, but since the capture range for the lock point closest to the pole is the narrowest, by using the capture range for the lock point closest to the pole as a reference, it is possible to eliminate errors for all lock points. Locks can be suppressed. In addition, when frequency lock control is performed by selecting one of a plurality of discrimination curves that have peaks at different frequencies, the amount of frequency shift will vary depending on each discrimination curve at the frequency at which the discrimination curve that performs frequency lock control switches. It is preferable to set the first correction value so that it is less than or equal to the narrowest lock point capture range in .

In the above embodiment, the frequency filter 63a is placed on the temperature controller 9, but if the frequency filter 63a is placed in a state where the temperature changes according to the control of the temperature controller 9, the frequency It is possible to obtain the effect of offsetting the shift. For example, the frequency filter 63a may be placed on a separate temperature controller without contacting the temperature controller 9, or the frequency filter 63a may not be in contact with any temperature controller including the temperature controller 9. Good too.

Furthermore, the present invention is not limited to the above embodiments. The present invention also includes configurations in which the above-mentioned components are appropriately combined. Moreover, further effects and modifications can be easily derived by those skilled in the art. Accordingly, the broader aspects of the invention are not limited to the embodiments described above, but are capable of various modifications.

1 Laser device 2 Laser section 3 Control section 4 Light source section 5 Semiconductor optical amplifier 6 Planar light wave circuit 7 Photodetector section 8, 31 Temperature sensor 9 Temperature controller 10 Monitor section 32, 33, 34, 35 ADC
36 Arithmetic section 37 Storage section 38 Current source 41 Laser body section 42 Changing section 43 First waveguide section 44 Second waveguide section 44a Optical waveguide layer 45 N-side electrode 61 Optical branching sections 62, 63 Optical waveguide 63a Frequency filter 91 Installation surface 361 PD ratio calculation section 362 Target frequency setting section 363 Target PD ratio setting section 364 Difference acquisition section 365 Temperature acquisition section 366 Target temperature setting section 367 PID control section 368 DBR/RING power setting section 369 Current correction section 421 DBR heater 422 RING heater 423 Phase heater 431 Waveguide section 431a Gain section 431b Diffraction grating layer 432 Semiconductor stack section 433 P-side electrode 441a Waveguides 442, 443 Arm section 444 Ring-shaped waveguide 445 Phase adjustment section Ar1 First region Ar2 Second Region B1 Base C Optical resonator C1, C2, C3 Curve CR (+), CR (-) Capture range MP Pole point MP1 Maximum point MP2 Minimum point L1, L2, L3, L4, L5 Laser beam M1 Reflection mirror RF1 Ring resonance filter

Claims (13)

A frequency equivalent amount corresponding to the frequency of the laser beam, including a light source section that makes the frequency of the output laser beam variable, and a frequency filter having a transmission characteristic whose transmittance changes periodically with respect to the frequency of the input light. a laser unit that includes a monitor unit that acquires a monitor value corresponding to a monitor value, a first temperature sensor that detects an ambient temperature of the light source unit, and a temperature controller that is thermally connected to the light source unit;
a second temperature sensor that detects the environmental temperature of the frequency filter;
The temperature of the light source section is controlled by supplying a first control amount to the temperature controller according to a first set value that is a target temperature of the ambient temperature of the light source section, and the temperature of the light source section is controlled according to a second set value. a control unit that controls the frequency of the laser beam by supplying a control amount to the light source unit;
storage section,
Equipped with
In the frequency filter, the transmission characteristic is shifted in the frequency axis direction depending on the environmental temperature,
The monitor unit is arranged in a state where the temperature changes according to control of the temperature controller,
The control unit is configured to perform a first correction to correct the first setting value based on the environmental temperature of the frequency filter detected by the second temperature sensor so as to offset a change in the transmission characteristic of the frequency filter due to the environmental temperature. set the value,
The first correction value is set so that the shift in the frequency axis direction of the transmission characteristic of the frequency filter due to the environmental temperature is smaller than when the first set value is not corrected,
The storage unit stores first relationship information indicating a relationship between the environmental temperature and the first correction value. The laser device. The laser device according to claim 1, wherein the temperature controller is in contact with the monitor section. The laser device according to claim 2, wherein the temperature controller has an installation surface on which the light source section and the frequency filter are installed. further comprising a casing in which the laser unit is housed,
The laser device according to claim 1 or 2, wherein the second temperature sensor is arranged outside the housing. The monitor section includes a second detection section that detects a second intensity corresponding to the intensity of the laser light after the laser light passes through the frequency filter,
The second setting value or the monitor value includes a value corresponding to the second intensity.
A laser device according to any one of claims 1 to 4. The monitor unit includes a first detection unit that detects a first intensity of the laser beam corresponding to the intensity of the laser beam,
The laser device according to claim 5, wherein the second set value or the monitor value is a value corresponding to a ratio of the second intensity to the first intensity. The control unit sets a second correction value that corrects a second control amount according to the first setting value corrected by the first correction value,
The laser device according to claim 5, wherein the storage unit stores second relationship information indicating a relationship between the first set value and the second correction value. The control unit is configured to determine, in a frequency direction, a transmission characteristic of the frequency filter under the first set value after setting the first correction value and a transmission characteristic of the frequency filter at a reference temperature of the environmental temperature. The laser device according to claim 7, wherein the first correction value is set so that the amount of frequency shift is equal to or less than a capture range at a lock point closest to a pole of transmission characteristics of the frequency filter. The laser device according to claim 8, wherein the control unit sets the first correction value so that the frequency shift amount is 1/2 or less of the capture range. The control unit sets a third correction value that corrects the monitor value or the second set value according to the environmental temperature,
The laser device according to any one of claims 1 to 9, wherein the storage unit stores third relationship information indicating a relationship between the environmental temperature and the third correction value. The laser device according to claim 10, wherein the third correction value is set with reference to the extreme point of the transmission characteristic of the frequency filter. The laser device according to claim 10 or 11, wherein the control unit sets the first correction value after setting the third correction value. A light source section that makes the frequency of the output laser beam variable, and a frequency filter that has a transmission characteristic whose transmittance changes periodically with respect to the frequency of the input light, and a frequency equivalent to the frequency of the laser beam. A method for controlling a laser device, comprising: a monitor section for acquiring a corresponding monitor value; a first temperature sensor for detecting ambient temperature of the light source section; and a temperature controller thermally connected to the light source section. There it is,
a first control step of controlling the temperature of the light source unit by supplying a first control amount to the temperature controller in accordance with a first set value that is a target temperature of the ambient temperature of the light source unit;
a second control step of controlling the frequency of the laser beam by supplying a second control amount to the light source section according to a second set value;
including;
In the frequency filter, the transmission characteristic shifts in the frequency axis direction depending on the environmental temperature,
The monitor unit is arranged in a state where the temperature changes according to control of the temperature controller,
The first control step is a correction value that sets a first correction value that corrects the first setting value based on the environmental temperature of the frequency filter so as to offset a change in the transmission characteristic of the frequency filter due to the environmental temperature. Contains configuration steps,
The first correction value is set so that the shift of the transmission characteristic of the frequency filter in the frequency axis direction due to environmental temperature is smaller than when the first set value is not corrected.
Control method for laser equipment.

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