Efficient octave-bandwidth microwave light modulators

The use of wide-bandwidth interdigital microwave circuits to provide electrooptic modulation of light is discussed. Two models employing lithium niobate crystals of different aspect ratios have been constructed and tested. Both have nominal bandwidth from 1.0 to 2.0 GHz but actually give somewhat greater modulation bandwidth. Single-pass modulation tests made using 6328-Å light at RF drive power level of 5 watts show that 30 percent modulation depth over a 1.5-GHz frequency band is obtained for one model while approximately 50 percent modulation depth over a 1.1-GHz band is obtained for the other. These results show excellent agreement with analytical predictions. Measurement techniques are also discussed.