Carbon disulfide has identical microwave and optical dielectric constants, as well as extremely low optical and microwave loss. These properties make it possible to construct long traveling-wave light modulators at microwave frequencies using the Kerr electrooptic effect induced in CS2 by an electric field propagating on a TEM transmission line.
Several experiments with traveling-wave Kerr cells consisting of resonant strip transmission lines immersed in CS2 are described. A decrease in the microwave power required for modulation by a factor of two, by cooling the modulators to a temperature of −55°C, is demonstrated. Simultaneous modulation of light at two microwave frequencies by excitation of two of the longitudinal modes of the strip line resonator is also described. Relatively high efficiency modulation with long devices of this type is also reported. In these experiments, the microwave power required for large depths of modulation is reduced by almost two orders of magnitude compared to previously reported CS2 light modulators, and is within less than a factor of two of the calculated power for cells up to 44 cm in length. For longer cells, increasingly larger than predicted powers are required.
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