Significance The study of ultrashort pulse laser and its interaction with matter is one of the most popular research fields at present. In order to obtain laser pulse output with higher energy and higher quality, it is needed to make continuous breakthroughs in the research on pulse energy and peak pulse power. Compared with the solid-state laser, excimer laser with the inert gas as the gain medium has its unique advantages in the amplification of the deep ultraviolet femtosecond pulses. Using femtosecond laser pulse as the seed light source, the seed source sends the working signal through the signal controller, and the excimer laser amplifier correspondingly receives the trigger signal sent by the signal controller for pulse amplification, which can obtain high power ultraviolet ultra-short pulse laser. However, in practical application, the pulse repetition rate of seed light under the action of signal controller is unstable and time jitter occurs. Therefore, in order to improve the time synchronization between femtosecond seed light and excimer laser amplifier, the effects of three factors, namely, operation repetition rate, working voltage and gas state, on the luminescence delay time and luminescence time temperature drift of excimer laser amplifier with hydrogen thyratron as high voltage switch were studied in this paper.
Progress The alignment molecular laser amplifier is designed in a low-jitter working mode with the hydrogen brake tube as a high-voltage switch (Fig.1). A thyratron trigger circuit with a jitter less than 4 ns is used to trigger the on-off hydrogen thyratron (Fig.5), which in the external design can produce an external charging signal and light signal circuit board and can get rising along the range of about 5 ns light signal (Fig.4). From the external trigger signal to the excimer light signal there is a certain delay time (Fig.5). Before realizing the low jitter light output, there will be a certain light output delay drift phenomenon in the thermal equilibrium process of the excimer laser amplifier system (Fig.6). In the laboratory, the PLD20 Excimer Laser was used to study the time synchronization characteristics of excimer amplifier, and the influence of laser operation repetition rate (Fig.7), operating voltage and gas state on the temperature drift and thermal equilibrium state (Fig.8) was discussed, which realizes the excimer light pulse signal in low jitter within 5 ns at different repetition frequencies, and provides a reference for the effective synchronous operation of seed light and excimer amplifier laser.
Conclusions and Prospects A low-jitter excimer laser amplifier system with the hydrogen switch as a high voltage switch is designed. The trigger circuit with a jitter less than 4 ns is used to trigger the hydrogen gate to obtain the light signal along the range of about 5 ns. Experimental results show that the stable delay time increases with the increase of laser repetition frequency under the same operating voltage. The higher the operating voltage is, the greater the increase of the stability delay time becomes. After gas deterioration, the delay time of optical pulse stability decreases. The higher the laser operating voltage and repetition rate is, the greater the delay drift time becomes. After a certain temperature drift, the internal system of the excimer laser reaches thermal balance. Based on the external trigger signal, the excimer optical pulse signal achieves low jitter output within 5 ns at the repetition rates of 5 Hz, 10 Hz and 15 Hz.
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