JPH06848Y2 - Q switch laser device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a Q-switch laser device, and more particularly to a Q-switch laser device that oscillates a Q-switch pulse by a acousto-optical Q-switch method in a continuously pumped solid-state laser.

2. Description of the Related Art In this type of Q-switch laser device, as one method for generating a highly stable laser output, a high-frequency signal is pulse-modulated by a modulation pulse to obtain a high-frequency modulation signal in phase with the modulation signal. There is a method of applying a modulation signal to an acousto-optic modulator. As an example thereof, there is one in which the phases of a high frequency signal and a laser gate signal which is a modulation pulse are synchronized, and the high frequency signal is gated (modulated) by this synchronized gate signal to generate a high frequency modulated signal. Such a technique is disclosed in JP-A-57-178392.

In this method, a D-FF (delayed flip-flop) is used to synchronize the phase of the high frequency signal and the laser gate signal, and the square wave clock signal input to the clock terminal of this D-FF is used as the high frequency signal. Generated using
A laser gate signal (modulation pulse signal) applied to the data input of the D-FF is latched by this clock signal. By doing this, the D-FF Q
A gate signal synchronized with the high frequency signal is derived from the output,
The high-frequency signal can be gated by this gate signal to obtain a pulse-modulated high-frequency modulated signal.

In this circuit system, a D-FF is operated by obtaining a square wave clock signal synchronized with a high frequency signal, and the Q output of this D-FF is directly used as a laser gate signal, so that it has the following drawbacks. . That is, the high frequency signal is, for example, 40
Since a signal with a very high frequency of MHz is used, it is difficult to stably obtain a square wave clock pulse that is synchronized with this signal, and operate with this unstable clock pulse.
If the latch output of the D-FF is directly used as a laser gate pulse, it is unavoidable that it will become unstable again.

DISCLOSURE OF THE INVENTION Therefore, the present invention has been made to solve the above drawbacks of the related art, and an object of the present invention is to provide a Q switch laser device capable of performing Q switch laser oscillation with better stability. To do.

According to the present invention, a high frequency signal is pulse-modulated with a modulation pulse to obtain a high frequency modulated signal in phase with the high frequency signal,
A Q-switch laser device in which a continuously pumped solid-state laser is caused to perform Q-switch pulse oscillation by applying this high-frequency modulation signal to an acousto-optical modulator, and the modulation is performed using the modulation pulse and the high-frequency signal. Means for generating a first pulse synchronized with the zero cross timing of the high frequency signal following the start timing of the pulse and a second pulse synchronized with the zero cross timing of the high frequency signal following the end timing of the modulated pulse; A Q-switch laser device including a flip-flop that is set and reset in response to first and second pulses, and gate means that gates the high-frequency signal using the output of the flip-flop. can get.

Embodiment Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. In the figure, a solid-state laser substance 1 is excited by an excitation light source 2 and a condenser 3, and is installed in a laser resonator constituted by reflecting mirrors 4 and 5.

On the other hand, in this laser resonator, an acousto-optic light modulator 6 for pulsing laser oscillation is provided, and this light modulator 6 includes an ultrasonic cell 7 made of a fused silica plate,
The ultrasonic cell 7 is composed of an electroacoustic transducer 9 that induces an ultrasonic diffraction grating 8. A high frequency modulation signal is applied from the high frequency driver circuit 10 to the electroacoustic transducer 9.

The high frequency driver circuit 10 includes, for example, a high frequency signal generating section 11 that oscillates a continuous sine wave of 40 MHz, a modulation signal generating section 12 that generates a modulation pulse that has no phase relationship with the high frequency signal, and these high frequency signals. Signal and a modulated pulse signal to generate a set / reset signal, a set / reset signal generation unit 13, an FF (flip-flop) 14 that operates by the set / reset signal, and this FF
The gate circuit 15 opens the gate by the output of 14 and gates the output of the high frequency signal generator 11 to perform pulse modulation.
Have and. The pulse modulation signal output from the gate circuit 15 is applied to the electroacoustic transducer 9 via the class A power amplifier 16.

FIG. 2 is a time chart showing operation waveforms of the apparatus shown in FIG. FIG. 2 (A) is a continuous sine wave of 40 MHz generated by the high frequency signal generator 11, (B) is a modulation pulse generated by the modulation signal generator 12, and waveforms (A) and (B) are shown. There is no topological relationship with.
So, where the phases of both waveforms need to be synchronized,
In the present invention, these set of signals (A) and (B) are used to generate a pulse train signal as shown in (C) in the set / reset signal generator 13.

That is, the first pulse a1, a2, ... That rises in synchronization with the zero-cross timing of the high-frequency signal following the start timing of the modulated pulse (the falling timing of the pulse in the time chart of the figure) and the end timing of the modulated pulse. The second pulses b1, b2, ... That rise in synchronization with the zero-cross timing of the high-frequency signal subsequent to (the rising timing of the pulse in the time chart of the figure) are generated.

Each rising edge of these pulses a1, a2, ...
F14 is set and is set at each rising edge of the pulses b1, b2, .... Therefore, the Q output waveform of the FF 14 becomes as shown in FIG. 2 (D), and the gate pulse (D) synchronized with the high frequency signal (A) is obtained. The gate circuit 15 is opened by this gate pulse, while the high frequency signal is gated as shown in (E), resulting in stable Q-switch pulse laser oscillation as shown in (F).

FIG. 3 shows the set / reset signal generator 1 in FIG.
3 is a circuit diagram showing a specific example of an FF 14 and a gate circuit 15. FIG. The modulated pulse from the modulated signal generator 12 is D-FF3.
1 is a CK (clock) input, and a high level is fixedly applied to this D (data) input. This D-FF3
The Q output of 1 is the D input of D-FF 32.
The output of the comparator 34 is applied to the CK input of 32. This comparator 34 compares a high frequency sine wave signal of 40 KHz with a reference level, and the reference level in this case becomes a zero level and operates as a so-called zero level comparator. Therefore, this comparator 34
A clock pulse train that is phase-synchronized with the zero-cross timing of the high-frequency signal is obtained at the output of C
It becomes the K input and also becomes the 1 input of the 2-input NAND gate 33. The other input of this NAND gate 33 is Q of D-FF32.
The output is applied, and this gate output is the inverter 4
2 is inverted by the first pulse signal (a1, a2, ...
…)

The modulated pulse becomes one input of the two-input NAND gate 38 via the inverter 35, and is input to the time constant circuit composed of the resistor 36 and the capacitor 37 and delayed for a predetermined time to become the other input of the NAND gate 38. Therefore, a pulse having a pulse width corresponding to the delay time of the time constant circuit is generated at the output of the gate 38 in synchronization with the end timing of the modulation pulse (shown as the stop timing in the figure). This pulse is the CK input of the D-FF 39, and a high level is fixedly applied to the D input of the D-FF 39. The Q output of the D-FF 39 becomes the D input of the D-FF 40, and the output of the comparator 34 is applied to the CK input of the D-FF 40.

The Q output of this D-FF 40 and the output of the comparator 34 are 2
It becomes each input of the input NAND gate 41, and this gate output is inverted by the inverter 43 and becomes the second pulse signal (b1, b2, ...). This second pulse signal is
It serves as each CLR (clear) input of the D-FFs 31 and 32, and also serves as a reset input of the FF 14 including the 2-input NAND gates 44 and 45. The first pulse signal is D-
It serves as each CLR input of the FFs 39 and 40 and also serves as a set input of the FF 14.

In this way, the first pulse (third pulse) synchronized with the zero-cross timing of the high frequency signal following the start timing of the modulation signal is generated using the modulation pulse and the sinusoidal high frequency signal.
The second pulse (stop pulse) synchronized with the zero cross timing of the high frequency signal following the end timing of the modulation signal and the end timing of the modulation signal is the second pulse.
These are obtained respectively as shown in FIG. Since the FF 14 is set and reset in response to these first and second pulses, the pair of Qs and the output of the FF 14 are as shown in FIG. 2D (one of Q and Q is shown in this waveform). The gate pulse synchronized with the sine wave will be obtained.

The high frequency signal is timed through the buffer 58 and the delay line 59 and then input to the analog gate circuit 15. Since the analog gate circuit 15 needs to have a high-speed switching characteristic, a diode bridge type switch is adopted as shown in the figure. A bridge is formed by the diodes 46 to 49 to form a switch circuit, and a high speed bipolar transistor 50 is used to turn on / off the DC bias of the bridge circuit.
A control circuit using 54 is provided. This control circuit includes, in addition to the transistors 50 and 54, bias resistors 51, 52, 55 and 56, and a zener diode 53,
It consists of 57. One output of the FF 14 is applied to the Zener diode 53, and the other output of the FF 14 is applied to the Zener diode 57.

Since these two outputs of the FF14 have an opposite phase relation to each other,
Zener diode 53 while gate pulse is present
And 57 are turned on at the same time, thus transistor 50
And 54 are also turned on at the same time. Therefore, all the diodes in the bridge circuit are forward biased and turned on,
The high frequency signal of 40 MHz is gated during that time and is led to the power amplifier 16 to have a waveform as shown in FIG. As a result, Q-switched laser pulse oscillation as shown in FIG. 2 (F) is obtained.

In this way, the modulated pulse and the high frequency signal are used to obtain the first and second pulses synchronized with the zero-cross timing of the high frequency signal, and the FF is set and reset by both of these pulses to complete the cycle of the high frequency signal. Since a stable gate pulse can be obtained, a stable Q-switch laser pulse oscillation can also be obtained.

In the above embodiment, the high frequency signal is gated every half cycle of the modulation pulse, but it is gated every cycle and the fourth
You may operate like a time chart of a figure. In this case, a pulse having a doubled period as in (C) is generated by using a frequency divider with respect to the modulated pulse in (B), and the doubled pulse (C) is shown in FIG. It suffices to supply it to the modulated pulse input terminal of. Gate circuit 1 at that time
The output of No. 5 is shown in (D), and the Q-switched laser pulse waveform is shown in (E).

As described above, according to the present invention, first and second pulses are obtained which are synchronized with the zero-cross timing of the high frequency signal following the start and end timings of the modulation pulse, and the first and second pulses are obtained. Since the gate signal synchronized with the high frequency signal is obtained by setting and resetting the FF based on the pulse of, the D-FF is driven by the conventional unstable clock pulse and the output of this D-FF is directly gated. There is an effect that a more stable gate signal can be obtained as compared with the case of using a signal. Therefore, finally, more stable Q-switched laser pulse oscillation becomes possible.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a time chart showing the operation of the blocks of FIG. 1, and FIG.
FIG. 4 is a diagram showing a partial circuit of the block shown in FIG. 4, and FIG. 4 is a time chart showing the operation of another embodiment of the present invention. Description of symbols of main parts 1 ... Solid-state laser material 6 ... Acousto-optical modulator 9 ... Electroacoustic transducer 10 ... High frequency driver circuit 11 ... High frequency signal generator 12 ... Modulation signal generator 13 ... … Set / reset signal generator 14 …… FF 15 …… Gate circuit

Claims (1)

[Scope of utility model registration request] 1. A Q-switch of a continuously pumped solid-state laser by pulse-modulating a high-frequency signal with a modulation pulse to obtain a high-frequency modulation signal in phase with the high-frequency signal, and applying the high-frequency modulation signal to an acousto-optical modulator. A Q-switched laser device for pulse oscillation, comprising: a first pulse synchronized with a zero-cross timing of the high-frequency signal following the start timing of the modulation pulse using the modulation pulse and the high-frequency signal; Means for generating a second pulse synchronized with the zero-cross timing of the high-frequency signal following the end timing of the pulse, a flip-flop set and reset in response to each of the first and second pulses, and the flip-flop. Gate means for gating the high-frequency signal by using the output of the amplifier. Switch laser device.