JP7189664B2 - LASER DEVICE AND LASER DEVICE CONTROL METHOD - Google Patents

Description

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

2. Description of the Related Art Conventionally, various techniques have been disclosed for suppressing changes in oscillation wavelength caused by changes in the amount of heat generated in laser devices such as semiconductor laser devices (Patent Documents 1 to 3). These techniques control the drive current and temperature of the laser element to suppress changes in the oscillation wavelength.

On the other hand, in a wavelength tunable laser device, a configuration is disclosed in which the oscillation wavelength is made variable using the vernier effect (Patent Document 4). In this wavelength tunable laser element, the wavelength characteristic is changed by heating a wavelength characteristic variable element such as a diffraction grating or a ring resonator with a heater, thereby changing the oscillation wavelength. In some cases, a semiconductor optical amplifier is integrated in the tunable laser device.

Japanese Patent No. 6000494 JP 2015-201549 A Japanese Patent No. 5473451 JP 2016-178283 A

A laser element such as the wavelength tunable laser element disclosed in Patent Document 4 has a plurality of heat sources such as heaters and semiconductor optical amplifiers in the laser element. These heat sources are for controlling the oscillation wavelength or optical output of the laser element by being supplied with electric power, and are hereinafter referred to as control elements.

As a result of the presence of a plurality of control elements in the laser element, heat generated by one control element may affect other control elements, causing the oscillation wavelength of the laser element to change from its set value.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a laser device and a laser element control method capable of suppressing changes in the oscillation wavelength of a laser element.

In order to solve the above-described problems and achieve the object, a laser device according to an aspect of the present invention includes a laser element having a plurality of control elements for controlling an oscillation wavelength or an optical output when power is supplied; a control unit configured to control the electric power supplied to the plurality of control elements, wherein the control unit includes, as the electric power, a compensation amount set according to an index value indicating an amount of heat generated by at least one of the control elements. to at least one other control element.

In the laser device according to an aspect of the present invention, the plurality of control elements include a heater that heats a wavelength characteristic variable element that controls the oscillation wavelength of the laser element, and a semiconductor that controls the optical output of the laser element. It is characterized by including an optical amplifier.

A laser device according to an aspect of the present invention includes a plurality of wavelength characteristic variable elements having different wavelength characteristic change periods, and the laser element utilizes a vernier effect due to a combination of the plurality of wavelength characteristic variable elements. It is characterized in that the oscillation wavelength is controlled.

A laser device according to an aspect of the present invention is characterized in that the control unit temporally changes the compensation amount in accordance with a temporal change in the index value of the at least one control element.

A laser device according to an aspect of the present invention includes a laser element having a plurality of control elements for controlling an oscillation wavelength or an optical output when power is supplied, and a controller for controlling the power supplied to the plurality of control elements. a unit, wherein the plurality of control elements include a plurality of heaters for heating a plurality of wavelength characteristic variable elements that control the oscillation wavelength of the laser element; Power determined by a correlation of power supplied to the plurality of heaters, which is determined according to at least one index value indicating a heat generation amount and a set oscillation wavelength, is supplied to the plurality of heaters. .

A method of controlling a laser element according to an aspect of the present invention is a method of controlling a laser element having a plurality of control elements for controlling an oscillation wavelength or an optical output by supplying electric power, wherein the plurality of control elements have a control step of controlling the electric power to be supplied, wherein the electric power is at least electric power compensated by a compensation amount set in accordance with an index value indicating the amount of heat generated by at least one of the control elements; It is characterized in that it is supplied to one other control element.

A method for controlling a laser element according to an aspect of the present invention includes a plurality of control elements that control an oscillation wavelength or an optical output by being supplied with power, and the plurality of control elements control the oscillation wavelength. A control method for a laser element including a plurality of heaters for heating a wavelength characteristic variable element of the above, comprising a control step of controlling the power supplied to the plurality of control elements, wherein the power is the supplying to the plurality of heaters the power determined by the correlation of the power supplied to the plurality of heaters, which is determined according to at least one index value indicating the amount of heat generated by the control element and the set oscillation wavelength; Characterized by

Advantageous Effects of Invention According to the present invention, it is possible to suppress changes in the oscillation wavelength of a laser element.

FIG. 1 is a configuration diagram of a laser device according to an embodiment. FIG. 2 is a diagram illustrating a control flow of Control Example 1. FIG. FIG. 3 is a diagram illustrating an example of temporal changes in SOA current and compensation amount. FIG. 4 is a diagram showing an example of the relationship between DBR current, ring current, and oscillation wavelength. FIG. 5 is a diagram showing an example of changes in the relationship between the DBR current, ring current, and oscillation wavelength. FIG. 6 is a diagram illustrating a control flow of Control Example 2. FIG.

Embodiments of the present invention will be described in detail below with reference to the drawings. In addition, this invention is not limited by this embodiment. Further, in each drawing, the same or corresponding elements are denoted by the same reference numerals as appropriate, and redundant description is omitted.

FIG. 1 is a configuration diagram of a laser device according to an embodiment. This laser device 100 includes a laser element 101 , a control section 102 and a light receiving element 103 .

The laser element 101 is a wavelength tunable semiconductor laser element composed of an optical waveguide disclosed in Patent Document 4, for example, and includes a ring waveguide 101a, arm portions 101b and 101c, and a DBR (Distributed Bragg reflector) diffraction grating 101d, a gain section 101e, a semiconductor optical amplifier (SOA) 101f, and heaters 101g, 101h, and 101i.

The combination of the ring-shaped waveguide 101a and the arm portions 101b and 101c functions as a reflection mirror having a first comb-shaped reflection spectrum with periodic reflection peaks in terms of light frequency. The DBR diffraction grating 101d is, for example, a sampling diffraction grating, and functions as a diffraction grating having a second comb-shaped reflection spectrum with frequency-periodic reflection peaks of light. The first comb-shaped reflection spectrum and the second comb-shaped reflection spectrum have different periods of reflection peaks (periods of changes in wavelength characteristics). Also, the reflecting mirror and the diffraction grating constitute a laser resonator in the laser element 101 . The gain section 101e has an active core layer, emits light when supplied with power, and exhibits an optical amplification effect. The laser element 101 oscillates at a wavelength at which the reflection peak of the first comb-shaped reflection spectrum of the reflecting mirror, the reflection peak of the second comb-shaped spectrum of the diffraction grating, and the longitudinal mode of the laser resonator coincide. A laser beam generated by laser oscillation is optically amplified by the SOA 101f that has an active core layer and exerts an optical amplification action by being supplied with power, and is output as laser beam L. FIG.

The heater 101g is a ring-shaped heater provided in the ring-shaped waveguide 101a, and heats the ring-shaped waveguide 101a by being supplied with electric power from the control section 102. FIG. By heating the ring-shaped waveguide 101a, the reflection peak of the first comb-shaped reflection spectrum shifts on the wavelength axis.

The heater 101h is a heater provided in a portion of the arm portion 101c, and heats a portion of the arm portion 101c by being supplied with power from the control portion 102. FIG. By heating a part of the arm portion 101c, the cavity length (optical length) of the laser cavity changes, and the wavelength of the longitudinal mode shifts as a whole on the wavelength axis. The portion heated by the heater 101h functions as a phase adjuster.

The heater 101i is a heater provided in the DBR diffraction grating 101d, and heats the DBR diffraction grating 101d by being supplied with power from the control unit 102. FIG. By heating the DBR diffraction grating 101d, the reflection peak of the second comb-shaped reflection spectrum shifts on the wavelength axis.

By heating with at least one of the heater 101g and the heater 101i and the heater 101h, the reflection peak of the first comb-shaped reflection spectrum of the reflecting mirror, the reflection peak of the second comb-shaped spectrum of the diffraction grating, and the vertical The wavelength that matches the mode, that is, the oscillation wavelength can be changed. Thereby, the laser element 101 functions as a wavelength tunable laser element.

As described above, the oscillation wavelength of the laser element 101 is controlled using the vernier effect resulting from the combination of the two wavelength characteristic variable elements, the diffraction grating and the reflecting mirror. The heaters 101g, 101h, and 101i are control elements that control the oscillation wavelength of the laser element 101 by being supplied with electric power. The SOA 101f is a control element that controls the optical output of the laser element 101 (the power of the laser light L) by supplying power. The heaters 101g, 101h, and 101i are heat generating elements, and the SOA 101f is a heat generating element that generates heat from a part of the energy of the supplied electric power that is not used for optical amplification.

The control unit 102 controls power supplied to the heaters 101g, 101h, 101i, the SOA 101f, and the gain unit 101e. The light receiving element 103 is, for example, a photodiode, receives part of the laser light L output from the laser element 101, and outputs a current signal corresponding to the received light intensity to the control unit 102. FIG.

The control unit 102 includes at least a calculation unit 102a, a recording unit 102b, an input unit 102c, an output unit 102d, and a power supply unit 102e. The calculation unit 102a includes, for example, a CPU, and performs various calculation processes for control. The recording unit 102b includes a recording unit such as a ROM in which various programs and data used by the calculation unit 102a for arithmetic processing are stored, a work space when the calculation unit 102a performs calculation processing, and a storage space for the calculation unit 102a. It also has a recording unit such as a RAM used for recording the results of arithmetic processing.

The input unit 102c receives an instruction signal from a host device of the laser device 100, a current signal from the light receiving element 103, and a current monitor signal from the SOA 101f. Information contained in the received signal is recorded in the recording unit 102b. Input section 102c comprises, for example, an analog-to-digital converter (ADC). The output unit 102d receives the instruction signal generated by the arithmetic processing performed by the arithmetic unit 102a, converts it into an appropriate instruction signal, and outputs it to the power supply unit 102e. Output section 102d comprises, for example, a digital-to-analog converter (DAC). The power supply unit 102e supplies power to the heaters 101g, 101h, 101i, the SOA 101f, and the gain unit 101e based on the instruction signal, and includes, for example, a DC power supply.

(Control example 1)
Next, control example 1 of the laser device 101 executed by the control unit 102 will be described with reference to the flowchart of FIG. First, in step S101, the calculation unit 102a sets power to be supplied to the heaters 101g, 101h, 101i, the SOA 101f, and the gain unit 101e, based on an instruction signal from a host device of the laser device 100 or the like. This power is a reference power for compensation. In this example, since the voltage is constant, the current is set instead of the power, and the power and the current can be appropriately converted. These supplied current values may be included as information in the instruction signal, or may be recorded as table data in the recording unit 102b. It may be selected from the table data based on the output value information.

Subsequently, in step S102, the calculation unit 102a acquires the compensation amount. In this example, as shown in Table 1, the current compensation amount (DBR current compensation amount) for the current set to the heater 101i is set to the heater 101g corresponding to the value of the current (SOA current) set to the SOA 101f. A current compensation amount (ring current compensation amount) for the set current and a current compensation amount (phase current compensation amount) for the current set to the heater 101h are recorded as table data in the recording unit 102b. The calculation unit 102a reads and acquires the compensation amount from the table data recorded in the recording unit 102b. The SOA current is an index value indicating the amount of heat generated by the SOA 101f, and each compensation amount is set according to the current value, which is the index value. Specifically, each amount of compensation is set to the ring-shaped waveguide 101a, part of the arm portion 101c (phase adjustment portion), and the DBR diffraction grating 101d in order to obtain the set oscillation wavelength by the inflow of heat generated by the SOA 101f. This is to offset the influence of receiving excessive heat with respect to the amount of heat that should originally be received. As can be seen from Table 1, the larger the SOA current, the larger the amount of heat generated by the SOA 101f, and the larger the amount of compensation. If the set SOA current does not exist in the table data, a compensation amount obtained by interpolating the SOA current in the table data by linear interpolation or the like may be used.

Subsequently, in step S103, the calculation unit 102a calculates how to raise the compensation amount. When changing the SOA current, instead of stepwise changing the current value before change to the target value after change, as shown in FIG. In some cases, the time is changed so that the target value is reached at t1. In this case, it is preferable to continuously change the compensation amount from the current value to the target value in accordance with the time change of the SOA current. In such a case, if any one of the DBR current compensation amount, the ring current compensation amount, and the phase current compensation amount is to be changed with time according to the change in the SOA current, they are changed with different time constants. You can do it. This makes it possible to apply an optimum amount of compensation at each time according to the time change of the SOA current.

Subsequently, in step S104, the calculation unit 102a calculates an instruction value as information included in the instruction signal to be output to the power supply unit 102e. 102e. The power supply unit 102e supplies current to the heaters 101g, 101h, 101i, the SOA 101f, and the gain unit 101e based on the indicated value.

Here, currents supplied from the power supply unit 102e to the heaters 101g, 101h, and 101i, which are control elements other than the SOA 101f, are supplied to the heaters 101g, 101h, and 101i based on instruction signals from a higher-level device of the laser device 100 or the like. It is a compensated current obtained by subtracting the amount of each compensation from the current value (value that serves as a reference for compensation) set for each. When the SOA current is changed with time as shown in FIG. 3, the indicated values in steps S104 and S105 are also changed with time. As a result, the ring-shaped waveguide 101a, part of the arm portion 101c (phase adjustment portion), and the DBR diffraction grating 101d are given the amount of heat that they should receive in order to obtain the set oscillation wavelength. This can suppress the change in the oscillation wavelength of the laser element 101 due to the heat generated by the SOA 101f.

In the above embodiment, the DBR current compensation amount, the ring current compensation amount, and the phase current compensation amount are recorded as table data in the recording unit 102b corresponding to the set value of the SOA current. The DBR power compensation amount, the ring power compensation amount, and the phase power compensation amount may be recorded as table data in the recording unit 102b corresponding to the set value of the SOA current.

Also, in the table data of Tables 1 and 2, the SOA current is a set value, but the current monitor value of the SOA 101f may be used instead of the set value. Further, corresponding to the optical output of the SOA 101f, DBR current compensation amount, ring current compensation amount, phase current compensation amount, or power compensation amount corresponding to these are recorded as table data in the recording unit 102b. The optical output of the SOA 101f may be monitored based on the current signal from the SOA 101f, and the compensation amount corresponding to the monitored SOA optical output may be obtained from the table data.

In the above embodiment, the SOA current is used as an index value indicating the amount of heat generated by the SOA 101f, and each compensation amount is set according to the current value, which is the index value. However, the present invention is not limited to this. As shown in Table 3, the DBR current and the ring current are used as index values indicating the amount of heat generated by the heaters 101i and 101g, respectively, and the phase compensation amount is set according to each current value. You may make it Alternatively, any two of the DBR current, the ring current, and the phase current may be used as index values, and another compensation amount may be set according to each current.

(Control example 2)
Next, control example 2 of the laser device 101 executed by the control unit 102 will be described. The oscillation wavelength of the laser element 101 is mainly determined by the coincidence of the reflection peak of the first comb-shaped reflection spectrum of the reflecting mirror and the reflection peak of the second comb-shaped spectrum of the diffraction grating. The first comb-shaped reflection spectrum changes according to the ring current, and the second comb-shaped spectrum changes according to the DBR current. It can be represented by a curved surface. It can be said that this curved surface represents the correlation between the DBR current and the ring current.

This curved surface changes depending on the operating state of the laser element 101 . The operating state of the laser element 101 is determined by the operating state of the heaters 101g, 101h, 101i, the SOA 101f, the gain section 101e, etc. The power supplied to each element changes according to the operating state of each element.

FIG. 5 is a diagram showing an example of changes in the relationship between the DBR current, the ring current, and the oscillation wavelength, and represents the curve shown in FIG. 4 in another format. It should be noted that even if DBR power and ring power are used as parameters instead of DBR current and ring current, the same graph is obtained.

5, λa1, λa2, . . . , λak, . . . , λb1, λb2, . The oscillation wavelengths obtained by combining the current and the DBR current are shown, which are different wavelengths. Also, for example, λa1, λa2, . . . , λak, . Similarly, λb1, λb2, . . . , λbk, . . Therefore, when it is desired to continuously change the oscillation wavelength, the combination of the ring current and the DBR current can be changed along the inclined dashed line connecting λa1, λa2, . Let it be.

Here, when the operating state of the laser element 101 is changed, the shape of the curved surface changes, and the inclination angle of the inclined dashed line connecting λa1, λa2, . This means that the correlation between the DBR current and the ring current changes depending on the operating state of the laser device 101 . The reason why the correlation changes depending on the operating state is considered as follows. That is, for example, the SOA current supplied to the SOA 11f and the phase current supplied to the heater 101h change depending on the operating state of the laser element 101, and the amount of heat generated by each changes. changes in the correlation with

In this control example 2, the DBR current and the ring current are determined using the correlation between the DBR current and the ring current, which is determined according to the index value indicating the heat generation amount of at least one of the control elements and the set oscillation wavelength. , heaters 101i and 101g.

A control example 2 of the laser element 101 executed by the control unit 102 will be described below with reference to the flowchart of FIG. First, in step S201, the calculation unit 102a sets the power to be supplied to the heater 101h, the SOA 101f, and the gain unit 101e based on an instruction signal from a host device of the laser device 100 or the like. Also in this example, since the voltage is constant, the current is set instead of the power. These supplied current values may be included as information in the instruction signal, or may be recorded as table data in the recording unit 102b. It may be selected from the table data based on the output value information.

Subsequently, in step S202, the calculation unit 102a acquires the correlation. In this example, the correlation between the DBR current and the ring current determined according to the SOA current and the set oscillation wavelength is recorded in the recording unit 102b as table data or a function. The SOA current is an index value indicating the amount of heat generated by the SOA 101f. The amount of heat generated by the SOA 101f affects the correlation between the DBR current and the ring current when achieving the set oscillation wavelength. If the set SOA current is not found in the table data, the correlation obtained by complementing the SOA current found in the table data by linear interpolation or the like may be used.

Subsequently, in step S204, the calculation unit 102a calculates an instruction value as information included in the instruction signal to be output to the power supply unit 102e. 102e. The power supply unit 102e supplies current to the heaters 101g, 101h, 101i, the SOA 101f, and the gain unit 101e based on the indicated value.

The currents (ring current and DBR current, respectively) supplied to the heaters 101g and 101i by the power supply unit 102e are currents determined by the correlation determined according to the SOA current and the set oscillation wavelength. As a result, the ring-shaped waveguide 101a and the DBR diffraction grating 101d are given an appropriate amount of heat to obtain the respective set oscillation wavelengths. This can suppress the change in the oscillation wavelength of the laser element 101 due to the heat generated by the SOA 101f.

In the control example 2, the correlation between the DBR current and the ring current, which is determined according to the SOA current, which is an index value indicating the amount of heat generated by the SOA 101f, and the set oscillation wavelength, is used. A correlation between the DBR current and the ring current, which is determined according to the phase current and the set oscillation wavelength, which are index values, may be used.

Moreover, the present invention is not limited by the above embodiments. The present invention also includes those configured by appropriately combining the respective constituent elements described above. Further effects and modifications can be easily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the above-described embodiments, and various modifications are possible.

100 laser device 101 laser element 101a ring-shaped waveguides 101b, 101c arm portion 101d DBR diffraction grating 101e gain portions 101g, 101h, 101i heater 102 control portion 102a calculation portion 102b recording portion 102c input portion 102d output portion 102e power supply portion 103 light receiving Device L Laser light

Claims (2)

A laser element,
a plurality of wavelength characteristic variable elements having different cycles of wavelength characteristic change for controlling the oscillation wavelength of the laser element;
a plurality of heaters that heat the plurality of wavelength characteristic variable elements by being supplied with electric power;
a semiconductor optical amplifier that controls the optical output of the laser element by being supplied with electric power;
a laser element comprising
a control unit that controls the power supplied to the plurality of heaters and the semiconductor optical amplifier;
a storage unit that stores a correlation of power supplied to the plurality of heaters in association with an oscillation wavelength and an index value indicating an amount of heat generated by the semiconductor optical amplifier;
with
the index value indicating the amount of heat generated by the semiconductor optical amplifier affects the correlation of power supplied to the plurality of heaters when realizing a predetermined oscillation wavelength,
The control unit controls the oscillation wavelength by using a vernier effect resulting from a combination of the plurality of wavelength characteristic variable elements, and uses a monitor value of power supplied to the semiconductor optical amplifier as the index value. and a power determined by the correlation of the power supplied to the plurality of heaters, which is determined according to the set oscillation wavelength, to the plurality of heaters. A laser element, comprising: a plurality of wavelength characteristic variable elements having different wavelength characteristic change periods for controlling an oscillation wavelength of the laser element; and a plurality of wavelength characteristic variable elements heated by being supplied with electric power. and a semiconductor optical amplifier that controls the optical output of the laser element by being supplied with electric power . A method of controlling a laser element that affects the correlation of power supplied to the plurality of heaters of
a control step of controlling the power supplied to the plurality of heaters and the semiconductor optical amplifier;
In the control step, the oscillation wavelength is controlled using a vernier effect resulting from a combination of the plurality of wavelength characteristic variable elements, and the oscillation wavelength is associated with the index value indicating the amount of heat generated by the semiconductor optical amplifier. obtaining the correlation of power supplied to the plurality of heaters, setting a monitor value of the power supplied to the semiconductor optical amplifier as the index value, and determining according to the index value and a set oscillation wavelength; A method of controlling a laser element, wherein the electric power determined by the correlation of the electric power supplied to the heater is supplied to a plurality of the heaters.

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