JP4600129B2 - Solid state laser equipment - Google Patents

Description

  The present invention relates to a solid-state laser device, and more particularly to a solid-state laser device that can control a mode wavelength at high speed and does not consume a large amount of power.

Conventionally, a semiconductor laser that emits excitation laser light, a laser medium that is excited by excitation laser light and stimulates and emits fundamental wave laser light, an etalon for making a longitudinal mode into a single unit, and one end of an optical resonator are configured. 2. Description of the Related Art A solid-state laser device including an output mirror that transmits output laser light and a temperature tuning unit that minimizes high-frequency noise by changing the temperature of a heater that heats an etalon is known (for example, a patent) Reference 1).
JP 2003-158318 A

In the conventional solid-state laser device, the mode wavelength can be controlled by changing the optical thickness of the etalon by changing the temperature of the heater that heats the etalon.
However, since control by temperature is slow in response, there is a problem that the mode wavelength cannot be controlled at high speed according to disturbance, for example. In addition, the heater has a problem of consuming large electric power.
Therefore, an object of the present invention is to provide a solid-state laser device that can control the mode wavelength at high speed and does not consume a large amount of power.

In a first aspect, the present invention relates to a semiconductor laser that emits excitation laser light, a laser medium that is excited by the excitation laser light and stimulates and emits fundamental wave laser light, an etalon for making the longitudinal mode into a single unit, An output mirror that constitutes one end of an optical resonator and transmits output laser light; and a mode wavelength control unit that controls a mode wavelength by applying a predetermined voltage to the etalon to adjust a refractive index of the etalon. A solid-state laser device is provided.
In the solid-state laser device according to the first aspect, a voltage is applied to the etalon, the voltage is changed, and the refractive index of the etalon is changed by the electro-optic effect, thereby controlling the mode wavelength. Since the response of the electro-optic effect is fast, the mode wavelength can be controlled at high speed according to a disturbance, for example. In addition, since almost no current flows, large power is not consumed.

In a second aspect, the present invention provides the solid-state laser apparatus according to the first aspect, wherein the etalon is made of lithium tantalate or lithium niobate.
In the solid-state laser device according to the second aspect, since the etalon is made of a material having a large electro-optic effect, the control efficiency can be improved.

In a third aspect, the present invention provides the solid-state laser device according to the first or second aspect, further comprising etalon temperature adjusting means for adjusting the temperature of the etalon, and the mode wavelength control means includes: A solid-state laser device characterized by controlling a mode wavelength by using both a voltage applied to the etalon and a temperature of the etalon in combination.
In the solid-state laser device according to the third aspect, for example, when a disturbance is applied, the voltage applied to the etalon is adjusted to control the mode wavelength at a high speed, and thereafter, the control margin due to the voltage applied to the etalon increases. Adjust the etalon temperature and readjust the voltage. Thereby, it can respond suitably also when a disturbance repeatedly occurs.

  According to the solid-state laser device of the present invention, the mode wavelength can be controlled at high speed because the electro-optic effect having a quick response is used. In addition, since no current flows, large power is not consumed.

  Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. Note that the present invention is not limited thereby.

FIG. 1 is a configuration explanatory diagram illustrating a solid-state laser device 100 according to the first embodiment.
The solid-state laser device 100 includes a semiconductor laser 1 that emits excitation laser light Le, a condensing lens 2 that condenses the excitation laser light Le on an Nd: YAG laser medium 3, and a fundamental laser that is excited by the excitation laser light Le. An Nd: YAG laser medium 3 that stimulates and emits light, a nonlinear optical element 4 that converts fundamental laser light into harmonic laser light, an etalon 5 for making a longitudinal mode into a single unit, and one end of an optical resonator 7 An output mirror 6 configured to transmit the output laser light Lo, a beam splitter 8 for extracting a part of the output laser light Lo, and a semiconductor laser driving circuit 9 for driving the semiconductor laser 1 are provided.

  The solid-state laser device 100 controls the semiconductor laser 1 via the light receiving element 11 that receives the laser light extracted by the beam splitter 8 and the semiconductor laser driving circuit 9 so that the light reception intensity at the light receiving element 11 is constant. Under the control of the control device 12, an optical resonator temperature controller 21 for heating or cooling the entire optical resonator 7, an etalon temperature controller 22 for heating or cooling the etalon 5, and the control device 12. A first temperature controller driving circuit 23 that drives the optical resonator temperature controller 21, a second temperature controller driving circuit 24 that drives the etalon temperature controller 22 under the control of the control device 12, and control of the control device 12. A DC power supply circuit 30 for applying a DC voltage V to the etalon 5 via the electrodes 31 and 32 is provided.

  The etalon 5 is made of a material having a large electro-optic effect, such as lithium tantalate or lithium niobate.

As shown in FIG. 2, the distance between the electrodes 31 and 32 is d, the thickness of the etalon 5 is L, the refractive index and n _e for light polarized in the z-direction incident on the etalon 5 advances in the x-direction, When the Pockels constant is r ₃₃ and the voltage V is applied between the electrodes 31 and 32, the magnitude of the refractive index change | Δn |
| Δn | = 0.5 · _ne ³ · r ₃₃ · | V | / d (1)
(Shintaro Miyazawa “Optical Crystal” Baifukan, p. 74).

On the other hand, the M-order mode wavelength λ _M of the etalon 5 is
λ _M = 2 · _ne · L / M (2)
Therefore, the magnitude of the wavelength change | Δλ | when the magnitude of the refractive index change is | Δn |
| Δλ | = 2 · | Δn | · L / M (2 ′)

(1) When (2 ′) is transformed by (2),
| Δλ | = 2 · | Δn | · L / M
= 2 · | Δn | · L / (2 · _ne · L / λ _M )
_{= Λ M · | Δn | /} n e
_{= 0.5 · λ M · n e} 2 · r 33 · | V | / d (3)
It becomes.

As numerical examples, λ _M = 1.0 [μm], _ne = 2.2, r ₃₃ = 36 × 10 ⁻¹² [m / V], V = 100 [V], d = 0.4 [mm] given that,
| Δλ | = 22 [pm]
It becomes.

  The value 22 [pm] is a longitudinal mode interval near the oscillation wavelength of a laser having a resonator length of 23 [mm] and a wavelength of 1.0 [μm] (however, the resonator is calculated as hollow). Therefore, if the resonator length of the optical resonator 7 is 23 [mm] or more and the laser wavelength is 1.0 [μm], the oscillation longitudinal mode can be hopped by applying a voltage V of about 100 [V]. Is possible.

First, when the adjustment range of the voltage V is set to Vo ± Vh, the control device 12 sets the output voltage V = Vo of the DC power supply circuit 30 so that the output is stabilized by the second temperature controller driving circuit 24. Adjust the temperature of the etalon 5 and operate.
If the output becomes unstable during operation, the output voltage V of the DC power supply circuit 30 is adjusted to stabilize the output with a high-speed response. Thereafter, when the output voltage V of the DC power supply circuit 30 becomes constant, the temperature of the etalon 5 is adjusted by the second temperature controller driving circuit 24 in a direction in which the output voltage V approaches Vo. Thereby, the adjustment range of the voltage V can be returned to the maximum margin ± Vh.

  According to the solid-state laser device 100 of the first embodiment, the voltage V is applied to the etalon 5, the voltage V is changed, and the refractive index of the etalon 5 is changed by the electrooptic effect, thereby controlling the mode wavelength. . Since the response of the electro-optic effect is fast, for example, the mode wavelength can be controlled at high speed according to disturbance. In addition, since almost no current flows, large power is not consumed. Further, since the etalon is made of a material having a large electro-optic effect such as lithium tantalate or lithium niobate, the control efficiency can be improved. Furthermore, since the mode wavelength is controlled by using both the voltage V applied to the etalon 5 and the temperature of the etalon 5, the control margin by the voltage V applied to the etalon 5 can be increased.

  The solid-state laser device of the present invention can be used in the bioengineering field and the measurement field.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration explanatory diagram illustrating a solid-state laser device according to a first embodiment. It is an expansion schematic diagram of an etalon.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Condensing lens 3 Nd: YAG laser medium 4 Nonlinear optical element 5 Etalon 6 Output mirror 7 Optical resonator 8 Beam splitter 9 Semiconductor laser drive circuit 100 Solid state laser apparatus

Claims (2)

A semiconductor laser that emits pump laser light; a laser medium that is pumped by the pump laser light and stimulates and emits fundamental wave laser light; an etalon for unifying the longitudinal mode of the fundamental laser light; and an optical resonator In a solid-state laser having an output mirror that constitutes one end and transmits output laser light,
Applying a voltage to the etalon and controlling the voltage to stabilize the output laser light,
The output stabilization of the solid-state laser, characterized in that, when the voltage becomes constant, the temperature of the etalon is adjusted so that the voltage changes in a direction approaching the median value of the adjustment range of the voltage. Method. 2. The output stabilization method for a solid-state laser according to claim 1, wherein the etalon is made of lithium tantalate or lithium niobate.

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