Abstract

A single-sideband (SSB) electrooptic modulator with three segmented [111]-cut CdTe crystals totaling 11.6 cm in length inside a Ku band 5.46-mm square waveguide was fabricated with broadband microwave matching structures capable of highpower pulsed operation. For accurate centering of microwave modulation frequency, the segmented crystals were gold plated on all sides to eliminate air gaps which otherwise would be present between the walls and crystal medium. For a microwave power of 10 kW at a pulse width of 5–10 μs, SSB conversion efficiency of >25% was achieved with a 3-dB bandwidth of ~1.5 GHz. The measured conversion efficiency as a function of modulation frequency fits exceedingly well over the 14–18-GHz range with the calculated results using an extended version of the coupled-mode theory reported by Carter and Haus¹ for a dielectric constant value of 10.25 measured by us and a refractive index of 2.672 for CdTe.

© 1988 Optical Society of America