CC BY
5The 30th International Conference on Advanced Laser Technologies N-O-4
ALT'23
Laser driven high power microwave compressor
G.Denisov, A.Palitsin, D.Sobolev, V.Parshin, S.Morozov,_M. Glyavin
Institute of Applied Physics RAS (IAP RAS), 46 Ul 'yanov str., Nizhny Novgorod, Russia
glyavin@ipfran. ru
Studies related to pulse shortening are currently becoming relevant for various promising applications of microwave and THz radiation, such as spectroscopy [1] and particle acceleration [2]. The shortening of the duration with simultaneous increase in the power of pulses makes it possible to increase accelerating gradients when sub-THz and THz sources are used. Active and passive pulse compressors are widely used for producing short microwave pulses [3,4] from continuous wave radiation or rather long pulses. In experimental realizations of microwave pulse compressors based on ring resonator and semiconductor silicon switch the minimum duration of the compressed pulses cannot be less than the round-trip time in the resonator. In the report we present the experimental study of the pulse compressor [5] based on three-mirror ring resonator and GaAs switch with carrier relaxation time less than resonator round-trip time. It is especially important in the case of compression of high-power output radiation of gyrotrons. The minimum dimensions of the resonator and, accordingly, the round-trip time are limited by microwave breakdown on the resonator elements, primarily on the semiconductor switch. Thus, compared to compressors based on silicon switches, the developed GaAs based compressor is preferable for obtaining short sub-ns and ns pulses with maximum power.
It should be noted that for both silicon and GaAs switches, it is possible to shorten the compressed pulses by installing an additional switch, which is also activated by laser radiation and cuts off part of the generated compressed pulse after a given time interval. In this case, obviously, the compressor becomes more complicated due to the presence of the second switch and an additional laser pulse is required. This means the need for increasing the power of the laser used (or using an additional laser synchronized with sub-ns accuracy). Nevertheless, this method may be attractive especially of further pulse shortening to sub-ns durations when femtosecond lasers are used.
In the experiments we used a backward wave oscillator (BWO) as a microwave source and 532 nm laser with a pulse duration of about 100 ps and a pulse energy of about 50 mJ to activate the GaAs switch. BWO operated in CW mode with the power of about 10 mW; the frequency of BWO was stabilized by external generator. To form an input wave beam with the required parameters (transverse dimensions and waist located on a corrugated mirror), a quasi-optical system, consisting of a horn and two mirrors was used.
In fact, the switch "cuts" the part of radiation from the wave beam circulating in the resonator. The measured compression coefficient 25 is in a good agreement with its theoretical value calculated for the total measured losses and coupling coefficient. As the next project steps in 2023 we plan experiments with 170 GHz gyrotrons [6,7] as radiation source.
The work is supported by the RSI project #19-79-30071
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[3]S.C. Schaub, M.A. Franzi, and B.W. Hoff, "Low power demonstration of a W-band active pulse compressor for high power millimeter waves," J Infrared Milli Terahz Waves, vol. 43, pp. 819-828, November 2022.
[4]J. Genouda, E.L. Claveau, S.K. Jawla, et al., "Generation of nanosecond THz pulses using a high gain ring resonator with a semiconductor switch," Appl. Phys. Lett., vol. 121, 044101, July 2022.
[5]G.G. Denisov, A.V. Palitsin, D.I. Sobolev, V.I. Belousov, I.A. Gorbunov, O.V. Kulagin, S.V. Morozov, A.A. Murzanev, A.N. Stepanov, M.Yu. Glyavin. Formation of short microwave pulses by laser-driven GaAs switch with sub-nanosecond transient response. 2021 46th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz), 2021, pp. 1-2.
[6]G.G.Denisov, A.N.Kuftin, V.N.Manuilov et al., "Development of master oscillator for frequency locking of a complex of megawatt level microwave sources". Microwave and Optical Technology Letters 62, 6, 2137, 2020
[7]A.Litvak, G.Denisov, M.Glyavin, "Russian gyrotrons: achievements and trends". IEEE Journal of Microwaves, 1, 1, 260, 2021
