JPH01151283A - Excitation controller of laser amplifier device - Google Patents

Abstract

PURPOSE:To prevent laser power from decreasing, by detecting time difference between a detection signal of an excitation current detecting means and a repetitive pulse signal of an oscillator and by modifying the fluctuating value into a correct delay time and always sending commands to a corresponding variable delay circuit. CONSTITUTION:When in high voltage pulse power sources 2a and 2b of laser amplifiers 1a and 1b delay times until excitation currents are generated in a delay time after trigger signals are received slowly fluctuate, a processor rapidly cancels these fluctuation and sends commands of delay time values to variable delay circuits 6a, 6b of the laser amplifiers 1a, 1b and modifies the delay times. Application time of the high-voltage pulses for excitation accordingly follows the laser beam reaching time, and so drops in output powers of the laser amplifiers 1a, 1b can be avoided to keep the laser beam output power constant.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Industrial Field of Application) The present invention relates to an excitation control device for a laser amplifier device in which a plurality of discharge excitation pulse lasers are connected in cascade.

(Prior art) For example, as a method to increase the output of a laser used for laser processing, photoreaction processes, excited ionization of isotope atoms, etc., following the first stage laser device that works as a laser oscillator, the output of the previous stage laser is increased. A laser amplifier device is used in which laser devices that receive and operate are connected in multiple stages in series.

For example, metal gas lasers are used in this type of laser amplifier device, and excitation by pulsed discharge is often used to obtain high output.

In this case, the discharge of the laser device in the subsequent stage must be performed in synchronization with the arrival time of the laser beam, which is delayed by the propagation time of the laser beam between two stages from the discharge time of the laser device in the previous stage. A delay circuit is used in the signal circuit for

(Problems to be Solved by the Invention) In the laser amplifier device as described above, a thyratron is often used as a switch for the discharge excitation pulse power supply circuit of each laser device constituting the device. However, in this thyratron, the delay time from when the trigger signal for starting is given to the grid until the completion of discharge, that is, the ionization time, is about 20 to 100nsee (for example, hydrogen thyratron), but this ionization time is Voltage 1 varies depending on external conditions such as ambient temperature or reservoir voltage of the circuit in which the thyratron is used. Therefore, the pulse width of the laser light handled by the laser amplifier device is, for example, 3. However, due to fluctuations in the ionization time of this thyratron,
A problem has arisen in that the laser light arriving from the previous stage and the discharge time of the subsequent laser device do not match, and the laser output to the subsequent stage decreases, reducing the effectiveness of the laser amplifier device.

An object of the present invention is to provide an excitation control device for a laser amplifier device that can correct fluctuations in the ionization time of a thyratron for a discharge excitation circuit and suppress fluctuations in the decrease in laser output.

[Structure of the invention]

(Means for Solving the Problems) In the present invention, a laser oscillator and a laser amplifier are optically connected in cascade, a high-voltage pulse power supply for laser excitation provided on each side of the laser oscillator and the laser amplifier, and In an excitation control device for a laser amplifier device, the delay time can be controlled. Each delay circuit that is a variable delay circuit, the excitation current detection means of each high-voltage pulse power supply, each detection signal of these excitation current detection means and the repetitive pulse signal of the oscillator are input, and a control signal is sent to each variable delay circuit. The processor is provided with a processor that outputs the delay time to each variable delay circuit, and also outputs the delay time when a variation in the time difference between the detection signal of the excitation current detection means and the repetitive pulse signal of the oscillator is detected. A processing means is provided for changing the variable value to a corrected delay time and sequentially instructing the corresponding variable delay circuit.

(Function) The variable delay circuit of the laser amplifier has a delay time between the respective high-voltage pulse power supplies of the laser oscillator and the laser amplifier with respect to the propagation time of the laser light from the laser oscillator to the laser amplifier, based on the delay time of the variable delay circuit of the laser oscillator. If the processor instructs in advance a delay time that is long enough to compensate for the difference in the delay time until the trigger signal receiver excitation current is generated, the laser amplifier will be excited in accordance with the arrival time of the laser beam from the laser oscillator. The output efficiency of the laser amplifier is best maintained.

Here, even if the high-voltage pulse power supply of the laser amplifier causes a gradual fluctuation in the delay time until the trigger signal receiver excitation current is generated, the processor immediately uses the variable delay time of the laser amplifier to offset this fluctuation. Since the delay time is changed by commanding the circuit, the application time of the excitation high voltage pulse follows the arrival time of the laser beam, and a drop in the output of the laser amplifier can be avoided. Note that when multiple stages of laser amplifiers are connected in cascade, and also for the laser oscillator located at the first stage, the same effect as described above occurs for each of them.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

In the figure, a laser amplifier 1a that operates in response to the laser light output of the laser oscillator 1 is placed at a certain distance (for example, 3 m) from a pulse-excited laser oscillator 1 constituted by, for example, a metal gas laser, and a laser amplifier 1a that operates in response to the laser light output of the laser oscillator 1, and further a certain distance Laser amplifiers 1b which operate in response to the laser light output of the laser amplifier 1a are installed at the same time, so that the light output of the laser amplifiers 1b can be used for desired purposes.

Note that both the laser amplifier 1a and the laser amplifier ib are metal gas lasers like the laser oscillator 1.

A high-voltage pulse power supply 2 for excitation is connected to the laser oscillator 1, and its main parts include a thyratron 3, a trigger circuit 4° connected to the grid of the thyratron 3, and a current transformer for current detection also provided on the cathode conductor. It is composed of a container 5. Laser amplifier 1a and laser amplifier ib
A high voltage pulse power source 2a and a high voltage pulse power source 2b are also connected to the high voltage pulse power source 2a and the high voltage pulse power source 2b, respectively. Since the configuration of these essential parts is equivalent to that of the high voltage pulse power source 2, the corresponding component numbers in the high voltage pulse power source 2 will be denoted by a or b, and individual explanations will be omitted.

A clock signal generator 7 is provided as a common trigger signal generation source for the trigger circuits 4, 4a, and 4b. This repetition frequency is selected to be approximately 5 kHz, for example. The output signal of the clock signal generator 7 is transmitted to variable delay circuits 6, 6.
trigger circuits 4, 4a, 4 via a and 6b, respectively.
connected to b. The delay time of the variable delay circuit 6 and the like can be individually set by an external signal.

Further, a processor 8 is provided for delay time control of the variable delay circuit 6, etc., and this processor 8 receives the clock signal of the clock signal generator 7 and the current transformers 5, 5a, 5.
Each detection signal of b is inputted, and the variable delay circuit 6
, 6a, and 6b so as to output delay time control signals, respectively. The processor 8 stores the delay time initially set for each of the variable delay circuits 6, 6a, and 6b (set so that the maximum value of the laser output is obtained at the start of operation), and based on this value. The delay time setting value of the variable delay circuit 6 and the like is instructed by using the control circuit 6. After the laser amplifier device starts operating, if the elapsed time from the clock signal to the detection signal of the current transformer 5, for example, changes from the value at the start of operation, the difference is calculated and the delay time command value is determined from this. It is possible to correct the signal and send it to the variable delay circuit 6. Note that similar processing can be performed for the variable delay circuits 6a and 6b.

Next, the effect of this will be described.

When the clock signal generator 7 is started, the clock signal passes through the variable delay circuit 6 and is delayed, then becomes a trigger pulse by the trigger circuit 4 and is applied to the grid of the thyratron 3. After the ionization time has elapsed, the thyratron 3 discharges and generates a high voltage pulse to repeatedly excite the laser oscillator 1 with pulses. The pulsed laser light output of the laser oscillator 1 generated by this is repeatedly transmitted to the laser amplifier 1.
given to a. The pulsed laser light that reaches the laser amplifier 1a is delayed from its generation time in the laser oscillator 1 by the propagation time of the distance between the laser oscillator 1 and the laser amplifier la. The laser amplifier 1a is pulse excited to coincide with the arrival time of this delayed pulsed laser beam. That is, the clock signal from the clock signal generator 7 is delayed by the variable delay circuit 6a and then output to the high voltage pulse power supply 2a.
given to.

The delay time set in the variable delay circuit 6a is roughly as follows:
The value is the sum of the delay time set in the variable delay circuit 6 and the propagation time of the pulsed laser beam described above. More details will be described later. The laser amplifier 1a is excited by the high-voltage pulse generated by the high-voltage pulse power supply 2a after undergoing the same process as for the laser oscillator 1 described above, and repeatedly supplies the generated laser light output to the laser amplifier 1b.

Note that the operational relationship of the laser amplifier 1b with respect to the laser amplifier 1a is the same as that of the laser amplifier 1a with respect to the laser oscillator 1, and since it can be easily deduced from the above explanation, the explanation will be omitted.

I briefly described the delay time set in the variable delay circuit 6a earlier, but I will explain this in detail.
When the ionization time force of thyratron 3a is equal to
As mentioned earlier, the delay time set in the variable delay circuit 6a is the sum of the delay time set in the variable delay circuit 6 and the propagation time of the pulsed laser beam between the laser oscillator 1 and the laser amplifier 18. It is said that However, there are generally individual differences in the ionization times of thyratron 3 and thyratron 3a. Therefore, for example, if the ionization time of the thyratron 3a is longer than that of the thyratron 3, the delay time of the variable delay circuit 6a is set shorter by the difference.

The initial setting of the delay time of the variable delay circuit 6, etc., including the correction for individual differences in ionization time of the thyratron 3, etc., is as follows:
For example, at the start of operation of the laser amplifier device, in other words, with constant external conditions of the laser amplifier device, the processor 8 is operated by an external means (not shown) to obtain the maximum output of the laser amplifier 1b with a variable delay. circuit 6
This can be done by adjusting the delay time to 8 or less.

- Once each laser amplifier 18 etc. is excited in this manner in accordance with the input of the pulsed laser light from the previous stage and the laser amplifier device starts operating, the thyratron 38 etc. Even if the ionization time of the thyratron 38, etc. changes due to changes in the voltage applied to the cathode heater, ambient temperature, reservoir voltage, etc., the processor 8 adjusts the delay time of the corresponding variable delay circuit 68, etc. is reset to compensate for this change. As a result, the excitation of the laser amplifier 18 etc. always coincides with the input timing of the pulsed laser light from the previous stage and does not deviate significantly, so the laser light output of the laser amplifier 1b can maintain the maximum value at the start of operation. can.

That is, the fluctuation period of the ionization time mentioned above is.

Laser amplifier 18 determined by clock signal generator 7
The repetition frequency of the excitation pulse, for example, is much longer than the period of 5 kllz, whereas the processor 8
For each clock signal of the clock signal generator 7, for example, based on the detection signal from the current transformer 5a, the generation time of the excitation pulse applied to the laser amplifier 1a at that time is monitored. The delay time of the variable delay circuit 6a can be reset by the next clock signal.

Therefore, the delay time setting of the variable delay circuit 68 etc. can completely track and correct the ionization time fluctuation of the thyratron 38 etc.

Note that variations in the ionization time of the thyratron 3 of the laser oscillator 1 do not affect the laser light output of the laser oscillator 1 itself, but if this varies, the input of pulsed laser light from the previous stage of the subsequent laser amplifier 18 etc. Since this would induce variations in timing and between excitation pulses, the variable delay circuit 6 acts in the same manner as the variable delay circuit 68 and the like described above to prevent this.

〔Effect of the invention〕

According to the present invention, fluctuations in the generation time of the excitation pulse of each laser device constituting the laser amplifier device are prevented, and the timing of the pulsed laser light input from the previous stage can always be made to coincide with the input timing of the pulsed laser light from the previous stage. Output can be kept constant.

[Brief explanation of the drawing]

The figure is a block connection diagram showing one embodiment of the present invention. 1...Laser oscillator 1a, lb...Laser amplifier 2.2a, 2b...High voltage pulse power supply 4...Trigger circuit 5, 5a, 5b...Current transformer 6, 6a, 6b... Variable delay circuit 7...Clock signal generator 8...Processor agent Patent attorney Noriyuki Chika Ken Yudo Ken Daishimaru

Claims (3)

[Claims] 1. A laser oscillator and a laser amplifier optically connected in cascade, a high-voltage pulse power supply for laser excitation provided individually for the laser oscillator and the laser amplifier, and a delay provided in front of the trigger circuit of each of these high-voltage pulse power supplies. and an oscillator that commonly supplies a repetitive pulse signal to these delay circuits, wherein each of the delay circuits is a variable delay circuit whose delay time can be controlled; An excitation current detection means of a high-voltage pulse power supply, and a processor which receives each detection signal of these excitation current detection means and the repetitive pulse signal of the oscillator as input and outputs a control signal to each of the variable delay circuits is provided. instructs each of the variable delay circuits to set their delay times, and when a time difference fluctuation between the detection signal of the excitation current detection means and the repetitive pulse signal of the oscillator is detected, a modified delay time is obtained by correcting the fluctuation value. 1. An excitation control device for a laser amplifier device, characterized in that the excitation control device for a laser amplifier device is provided with processing means for changing and sequentially instructing the corresponding variable delay circuit. 2. 2. The excitation control device for a laser amplifier device according to claim 1, wherein said excitation current detection means is a current transformer. 3. 2. The excitation control device for a laser amplifier device according to claim 1, wherein the switching element of said high-voltage pulse power source is a thyratron.