JP5834981B2 - Solid state laser equipment - Google Patents

Description

  The present invention relates to a solid-state laser device, and more particularly to a solid-state pulse laser device that outputs a third harmonic.

  In a solid-state laser device having a semiconductor laser, a method of generating a giant pulse by arranging a Q switch element in a resonator is known in order to obtain a larger output. As one of the methods of this Q switch, an AOQ switch using an acousto-optic element (AO element) is known (Patent Document 1).

  The AOQ switch controls the loss in the resonator by propagating an ultrasonic wave in the acoustooptic medium and diffracting the laser light transmitted through the acoustooptic medium, thereby performing a switching action.

  The operation principle of a solid-state pulse laser device using a conventional acousto-optic element is performed as follows.

(1) The gain of the resonator is sufficiently increased by turning on the acoustooptic device and increasing the loss of the resonator.

(2) The acousto-optic element is turned off, the loss of the resonator is sharply reduced, and the energy stored in the laser medium is taken out as a laser output in a short time. After the pulse laser output, the processing returns to (1).

JP 2010-251448 A

  However, when the acoustooptic element is turned on, an RF signal of approximately 10 W is generally applied to the acoustooptic element, and thus the element temperature rises with a large amount of heat generation. Further, when the acousto-optic element is turned off, heat generation is lost and the element temperature rapidly decreases. For this reason, the fluctuation range of the acousto-optic element temperature is large, which has been a cause of deterioration in laser characteristics.

  An object of the present invention is to provide a solid-state laser device capable of stabilizing laser characteristics by keeping the amount of heat generated in an acousto-optic element constant and suppressing the fluctuation range of element temperature to be small.

In order to solve the above-described problems, a solid-state laser device according to the present invention includes a semiconductor laser that generates excitation light, a solid-state laser medium that generates stimulated emission light in response to excitation light from the semiconductor laser, and the solid-state laser device. An acoustooptic element disposed in a resonator including a laser medium and controlling a loss in the resonator to generate a giant pulse; a heater disposed on the acoustooptic element and heating the acoustooptic element; An acoustooptic device driving circuit that inputs an RF signal to the acoustooptic device to turn the acoustooptic device on / off, and a heater that is driven when the acoustooptic device is turned off and the acoustooptic device is turned on And a heater drive circuit for stopping the heater.

According to the solid-state laser apparatus according to the present invention, fitted with a heater to acousto-optic device, the heater is stopped when the heater is an acousto-optic element is driven is turned on when the acousto-optic device is turned off Runode acoustooptic Even when the element is turned off, heat equivalent to the heat generated when the acoustooptic element is turned on by the RF signal can be applied to the acoustooptic element. Accordingly, the laser characteristics can be stabilized by keeping the amount of heat generated in the acousto-optic element constant and suppressing the fluctuation range of the element temperature to be small.

It is a block diagram which shows the structure of the solid-state laser apparatus which concerns on Example 1 of this invention. It is a timing chart for demonstrating operation | movement of the solid-state laser apparatus which concerns on Example 1 of this invention. It is a timing chart for demonstrating operation | movement of the conventional solid-state laser apparatus.

  Hereinafter, embodiments of the solid-state laser device of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a solid-state laser apparatus according to Embodiment 1 of the present invention. This solid-state laser device includes a semiconductor laser 1, two condenser lenses 2, a mirror 3, a solid-state laser medium 4, an acoustooptic device 5, a mirror 6, a heater 7, an acoustooptic device drive circuit 8, and a heater drive circuit 9. Yes.

  A portion composed of the solid-state laser medium 4, the acoustooptic device 5, and the mirrors 3 and 6 is called a resonator.

  The semiconductor laser 1 is constituted by a laser diode, for example, and generates excitation light. The condenser lens 2 focuses the laser light generated by the laser diode. Excitation light generated by the semiconductor laser 1 passes through the mirror 3 and is irradiated onto the solid-state laser medium 4.

  The solid-state laser medium 4 is a substance that causes laser oscillation. For example, in a solid-state laser called a YAG laser, substances such as yttrium, aluminum, and garnet (Yttrium Aluminum Garnet) are used. The solid-state laser medium 4 generates stimulated emission light when irradiated with excitation light from the semiconductor laser 1. The stimulated emission light generated by the solid-state laser medium 4 is sent to the acousto-optic element 5.

  The acoustooptic device 5 constitutes a Q switch, and modulates the fundamental wave of the stimulated emission light generated in the solid-state laser medium 4 in accordance with the RF signal input from the acoustooptic device drive circuit 8, thereby causing the inside of the resonator. The loss is controlled, and a pulse with a narrow peak and a large peak (giant pulse) is output.

  The AOQ drive circuit 8 generates an RF signal, sends the RF signal to the acoustooptic element 5, and turns the acoustooptic element 5 on and off.

  A heater 7 is attached on the acoustooptic device 5. The heater drive circuit 9 drives the heater 7 when the acoustooptic device 5 is turned off. The heater drive circuit 9 is synchronized with the acoustooptic device drive circuit 8, and when the acoustooptic device 5 is turned on, the heater 7 is turned off, and when the acoustooptic device 5 is turned off, the heater 7 is turned on.

  Next, the operation of the solid-state laser device according to the first embodiment of the present invention configured as described above will be described with reference to the timing chart shown in FIG.

  First, when the solid state laser device is activated, the semiconductor laser 1 generates excitation light and irradiates the solid state laser medium 4. Thereby, the solid-state laser medium 4 generates stimulated emission light and sends it to the acoustooptic device 5.

  In parallel with this, the acoustooptic device drive circuit 8 generates an RF signal having a duty ratio as shown in FIG.

  As shown in FIG. 2, in the on period of the RF signal output from the acousto-optic device drive circuit 8, the loss in the resonator is larger than the gain and laser oscillation is not performed, and the gain of the solid-state laser medium 4 is increased. To go. When the RF signal is turned off from this state, laser oscillation is enabled from the falling edge, and the laser is transmitted from the solid laser medium 4 having the maximum gain through the acoustooptic device 5 as shown in FIG. A pulse is output.

  As shown in FIG. 2, when the RF signal is on, the heater signal is turned off. In this case, the element temperature of the acoustooptic device 5 is increased by the energy of the RF signal. Next, since the heater signal is turned on when the RF signal is off, the element temperature of the acousto-optic element 5 rises due to the heating of the heater 7.

  That is, by suppressing the change in the element temperature of the acoustooptic element 5, the temperature variation of the acoustooptic element 5 at the moment when the pulse is generated is reduced, and the output stability is improved. The offset time Δt2 between the RF signal being turned off and the heater 7 being turned on can be finely adjusted and optimized depending on the configuration and use environment of the solid-state laser device.

The offset time Δt2 is set smaller than the time Δt1 from the falling time of the RF signal to the rising time of the laser pulse.
FIG. 3 is a timing chart for explaining the operation of the conventional solid-state laser device. In the conventional solid-state laser device, as shown in FIG. 3, there is a delay time from when the acoustooptic element 5 is turned off to when the pulsed light of the laser oscillates, during which the temperature of the acoustooptic element 5 is present. Begins to decline. Therefore, pulse laser oscillation is performed while the element temperature is changing.

  Further, since there is jitter in the timing of pulse generation, the temperature of the acoustooptic device 5 at the moment when the pulse is generated varies from shot to shot, which is a factor that deteriorates output stability.

  As described above, according to the solid-state laser device according to the first embodiment of the present invention, the heater 7 is attached to the acoustooptic element 5 and the heater 7 is driven when the acoustooptic element 5 is turned off. Even when the optical element 5 is turned off, heat equivalent to the heat generated when the acoustooptic element 5 is turned on by the RF signal can be applied to the acoustooptic element 5. Accordingly, the laser characteristics can be stabilized by keeping the amount of heat generated in the acousto-optic element 5 constant and suppressing the fluctuation range of the element temperature to be small.

  In addition, this invention is not limited to the solid-state laser apparatus of Example 1 mentioned above. For example, a nonlinear optical element may be provided between the acoustooptic element 5 and the mirror 6. In this case, the pulse laser output from the acoustooptic device 5 is sent to the nonlinear optical device. The nonlinear optical element converts the wavelength of the fundamental wave of the pulse laser output from the acoustooptic element 5 and outputs the converted signal.

  The present invention can be used for a solid-state pulse laser device.

DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Condensing lens 3, 6 Mirror 4 Solid-state laser medium 5 Acoustooptic device 7 Heater 8 Acoustooptic device drive circuit 9 Heater drive circuit

Claims (3)

A semiconductor laser for generating excitation light;
A solid-state laser medium that generates stimulated emission light in response to excitation light from the semiconductor laser;
An acoustooptic device disposed in a resonator including the solid-state laser medium and controlling a loss in the resonator to generate a giant pulse;
A heater disposed on the acoustooptic device and heating the acoustooptic device;
An acoustooptic device driving circuit for inputting an RF signal to the acoustooptic device to turn on / off the acoustooptic device;
A heater drive circuit that drives the heater when the acoustooptic element is turned off and stops the heater when the acoustooptic element is turned on ;
A solid-state laser device comprising:   The solid-state laser device according to claim 1, further comprising a wavelength conversion element that converts a wavelength of a fundamental wave from the solid-state laser medium and outputs a harmonic. The offset time between turning off the RF signal and driving the heater is set to be shorter than the time from the falling time of the RF signal to the rising time of the pulse. 3. The solid-state laser device according to 2.

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