Millimeter-wave diffraction by a photo-induced plasma grating

Abstract

I. SEMICONDUCTOR MATERIAL HIGH RESISTIVITYA was grown by the float-zone technique. Its long carrier lifetime ( T > s) enabled it to obtain a high electron-hole plasma density at moderate illumination levels. A 75"-diameter, 1.9-mm-thick slab was cut from the ingot. To decrease surface recombination, both of the flat sides of the slab were finished by chemical-mechanical polishing. EXPERIMENTAL SETUPTo produce a nonequilibrium plasma, we illuminated the slab with a pulsed xenon lamp through a grating mask (Fig. l), fabricated by printing opaque strips on transparent film, and .entirely transparent to MMW. The incident MMW beam was formed by a horn antenna. The combination of the MMW frequency, 92 GH7, the refractive index of silicon, 3.45, and the slab thickness, 1.9 mm, satisfied the conditions for suppressing Fresnel reflection at normal incidence. The MMW beam that passed through the silicon slab was detected by a GaAs Schottky diode coupled with a second horn antenna. The detector was mounted on a rotating arm to measure the angular distribution of the diffracted beam. The pumping light pulses were monitored using a reference photodiode that detected pumping light reflected from the slab. Both the rectified signal

<title>Analytical design of an achromatic double grating coupler for microwave and millimeter-wave regions of the spectrum</title>

“…We now change wavelengths from X to A2 • The direction ofthe outgoing ray at is (4) where L A1 1 A2 is the ratio between the first and the second wavelengths. By tracing the ray onto G (dashed lines) we can calculate the grating function 4 i on x1 to be (5) By switching back to we can continue the procedure and calculate the input angle at x1 to be, G(x) Fig. 1.…”

Scattering of millimeter waves by metallic strip gratings on an optically plasma-induced semiconductor slab

“…To enhance the efficiency of the optical control of millimeter waves, a nipi-doped semiconductor slab was recently demonstrated [4]. Millimeter-wave diffraction by a photo-induced plasma grating has also been studied for applications using an optically controllable quasioptical antenna, since the grating parameters, such as periodicity and plasma strip width, can easily be changed by the illumination pattern [5]. We have theoretically and experimentally investigated the scattering characteristics of a TM electromagnetic plane wave by metallic strip gratings on the optically induced plasma in a semiconductor at Q band [6].…”

Millimeter‐wave optically scanning antenna based on photoinduced plasma grating

“…In Ref. 6, we described experiments with a 2-D photoinduced plasma grating ͑PIPG͒ that makes 2-D beam scanning possible. In those experiments, the output beam was the first-order diffraction beam generated by the PIPG when a MMW beam passed through a silicon plate ͑transmitting geometry͒.…”