Broadband Magnetically Tunable Electro-optic Modulators

Abstract

In coherent CO2 laser radars, it is often desirable to track out the target translational Doppler frequency by shifting the laser LO. A single sideband (SSB) electro–optic (EO) modulator can be used for this purpose. The output from the SSB EO modulator considered here1,2 is high in mode quality and spectral purity. However, the bandwidth is limited by the dispersion of the modulation circuit. The new scheme described here (see Fig. 1) uses a ferrite-loaded waveguide containing an active CdTe EO crystal. A wide tuning range can be achieved by changing the phase velocity of the composite waveguide with an applied magnetic field.