As part of the Analog Optical Signal Processing (AOSP) program, researchers at the Jet Propulsion Laboratory (JPL) and OEwaves developed resonant electro-optic modulators with extremely high efficiency. The devices only require sub-milliwatt of applied microwave power for deep modulation of light. The modulators, made with ferroelectric materials, are fabricated as whispering gallery mode (WGM) resonators, exhibiting optical quality factors in excess of 8 x 108. By controlling the size of the resonator, the modulator center frequency can be set at the microwave signal’s carrier frequency. Also, the nonlinearity of the ferroelectric material serves as a mixer which allows a generation of down-converted frequency products, including the modulation signal frequency, at baseband.
The use of WGM modulator is a key capability for devising a receiver front end via photonic means. This entire photonic receiver front end can be packaged in a one cubic centimeter size and can open a wide range of applications in special communication markets where size and power are important.