JPS6232635B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Q-switch laser oscillator that generates giant laser pulses.

A gigantic laser pulse can be obtained from a Q-switch laser oscillator, but the mode and time of appearance of the laser pulse are unstable. Conventionally, the following methods have been used to stabilize this.

The first method is to excite with energy slightly higher than the threshold energy, observe spike pulses due to relaxation oscillation, and then operate the Q switch. According to this, a laser pulse with relatively stable mode and intensity can be obtained. However, there is a large jitter in the appearance time of the spike pulse, and therefore it is not suitable for obtaining a gigantic laser pulse with little jitter, and the degree of control of the laser pulse is often insufficient.

The second method is to keep the optical loss of the Q-switch element constant, control the excitation power to a level above the power that slightly sustains oscillation, maintain the quasi-steady oscillation state for a while, and then turn off the Q-switch. It is something that makes it work. Although this method is close to the ideal, it has many problems in practice because it requires extremely high precision control of the excitation power and the resonator. A gigantic laser pulse controlled to the same degree of precision is
The aim is to obtain it more practically and easily than the method described above. This invention will be explained below.

First, the principle of this invention will be described.

In normal oscillation without Q-switch operation, when pulse excitation is performed with energy above the threshold, several spike pulses called relaxation oscillation appear. The mode of relaxation oscillation is unstable due to instability of excitation, resonator, etc.

However, the present invention has found and experimentally confirmed that by increasing the excitation energy extremely so that five or more spike pulses appear, it is possible to achieve a state of quasi-steady oscillation. In this state, the electric field within the resonator is sufficiently controlled by various control elements within the resonator, and when the Q-switch is operated, an extremely stable, high-quality, gigantic laser pulse with little jitter can be obtained.

Next, embodiments of the invention will be described.

FIG. 1 is a schematic diagram showing an embodiment of the present invention. In this figure, reference numerals 1 and 8 are reflecting mirrors, and a resonator made up of both causes the YAG rod 4 to be excited by a flash lamp to cause laser oscillation.
The pinhole 5 and etalon 6 control the horizontal and vertical modes. In order to obtain very short pulses, an acousto-optic element 7 for mode locking is also arranged.
A Pockels cell 2 and a polarizer 3 are used for the Q switch. The threshold energy is about 7 Joules, but pulse excitation of about 16 Joules is performed. A huge laser pulse train appears approximately 200 nanoseconds after the Q-switch is activated.

FIG. 2 shows the temporal relationship between the Q-switch operation and the pulse train, and is a reproduction of a waveform photograph taken by a synchroscope.

In FIG. 2, the sharply falling electric signal on the left side is an electrical signal indicating the Q-switch operation, and the pulse train in the center is the obtained laser pulse. The peak of the pulse train appears approximately 200 nanoseconds after the Q-switch operation. The obtained laser pulse train has extremely high quality and energy stability of less than ±1%. Moreover, the jitter is extremely small at less than ±10 nanoseconds.

If the optical loss of the Q-switch element is gradually increased after the start of pulse excitation, a quasi-steady oscillation state can be achieved more quickly, and Q-switch laser oscillation can be achieved with lower energy.

In the example described above, a giant laser pulse with an energy stability of about 1% was obtained with an estimated accuracy of about 100 picoseconds 350 microseconds after generating the electrical signal to start oscillation. In principle, as long as we have an accurate clock, we can generate laser pulses with a time accuracy of 100 picoseconds infinitely long into the future. Furthermore, a laser pulse can be obtained without jitter approximately 200 nanoseconds after an event occurs. Such highly synchronous and highly stable pulses greatly expand the range of applications of conventional Q-switch lasers.

As explained above, the present invention has the advantage of being able to obtain high-quality, highly stable laser pulses with extremely high synchronization using an extremely simple method of simply performing strong pulse excitation.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a diagram showing the temporal relationship between the Q switch and the appearing laser pulse train. In the figure, 1 and 8 are reflecting mirrors, 2 is a Pockels cell, 3 is a polarizer, 4 is a YAG rod, 5 is a pinhole, 6 is an etalon, and 7 is an acousto-optic element.

Claims (1)

[Scope of Claims] 1. In a laser oscillator in which a Q-switch element is disposed in a resonator, a means for exciting a pulse of energy sufficiently larger than the oscillation threshold energy of the laser oscillator to cause condensed steady oscillation. A Q-switch laser oscillator characterized by: 2. The Q-switch laser oscillator according to claim 1, wherein the Q-switch element gradually increases optical loss after the start of pulse excitation.