Optical control of wave propagation in microstrip-slot lines at D band

The dispersion relationships for microstrip-slot lines are analysed by the spectral domain method and evaluated numerically as a function of plasma density for an optically induced plasma. The frequency range considered corresponds to the W and D band range, and the microstrip is realised on high-resistivity silicon. The experimental work was undertaken at frequencies ranging from 90 to 170 GHz using 5 kΩ cm silicon substrates with different strip widths irradiated by light emitting diodes radiating at a wavelength of 820 nm. Optical control was confirmed by measuring the change in propagation loss resulting from the illumination. A wave attenuation of 10 dB was determined for a line length of 30 mm, and a plasma relaxation time of 120 μs was measured at 137 GHz. Applications of this line are briefly discussed