Design of Quasi-Optical Microwave Pulse Compressor with Laser-Driven GaAs Switch

Quasi-optical microwave pulse compressor with laser-driven GaAs switch has been designed and developed. The compressor is based on three-mirror travelling wave resonator and a disk-shaped GaAs wafer, which serves as a switch activated by a picosecond 532 nm laser with pulse energy up to 50 mJ. The wafer with a diameter of 150 mm and a thickness of 0.6 mm is installed at Brewster's angle to the operating wave traveling in the resonator, that almost eliminates loss corresponding to parasitic reflection from the wafer. Resonator is thermostabilized in order to maintain its resonant frequency with precision of 0.5 MHz, which is less than the resonance bandwidth amounted to 2.7 MHz for the operating mode with resonant frequency of 170 GHz and the Q-factor of 6*10 ⁴ . Stabilization of temperature is provided by water circulating in channels inside the resonator base. According to results of preliminary experiments with GaAs switch, in the developed compressor a formation of nanosecond and sub-nanosecond output microwave pulses with compression ratio of about 40 is achievable. For the input pulses produced by 170 GHz, 1 MW gyrotron, maximum power of output compressed microwave pulses is expected to be of about 40 MW. According to our estimations, this level of output radiation pulse power will not lead to development of surface microwave discharge at any element of compressor resonator in vacuum conditions.