Low Power Demonstration of a W-band Active Pulse Compressor for High Power Millimeter Waves

An active pulse compressor has been designed for operation at megawatt power levels at W-band frequencies. Low power tests at 95 GHz are reported. The pulse compressor consists of an 8-mirror quasioptical resonant ring, a quartz coupler, and a laser-driven semiconductor switch that dumps energy stored in the ring. The semiconductor switch is a half-wavelength thick, high resistivity silicon wafer. The number of focusing mirrors in the resonant ring can be varied from 2 to 6, adjusting the length of the resonator round trip time from 3.3 to 10 ns. Critical coupling was achieved in each configuration by varying the thickness of the quartz wafer used as a coupling element. The compressor demonstrated power gain (Pout/Pin\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$P_{out} / P_{in}$$\end{document}) of 37 in the 10 ns, 8-mirror configuration, limited by the 23 ns rise time of the 532 nm Nd:YAG laser used to drive the semiconductor switch. A laser that delivered 24 mJ in <10\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$<10$$\end{document} ns would yield gain of 46 with the current design. Resonator losses measured in the 3.3 ns configuration could yield gain of 63, though this would require a laser that could deliver 24 mJ in ≤3.3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\le 3.3$$\end{document} ns in the constructed device.