Ridged Waveguides for Ultra-Broad-Band Light Modulators

The electromagnetic field of the dominant mode propagating in the inhomogeneously dielectrically loaded double ridged waveguide is given in terms of a modal series expansion. The numerical evaluation of the propagation constant reveals a remarkably linear dispersion diagram in close agreement with measurements performed in the 8-40-GHz range. Based on this analysis, the bandwidth of a ridged waveguide CO/sub 2/ -laser modulator is calculated to exceed 40 GHz, when a 25-mm long CdTe crystal is used as electrooptic material.