An area of future research for the Photonic Microsystems Group is in coupled optical-microwave systems. The high carrier frequency offered by optical fields, when coupled to microwave systems, can enable optical-microwave systems with performance that dramatically exceeds that of the microwave system alone. In particular, the high-Q resonators offered by microphotonics can be used to filter microwave signals placed on the optical carrier. Given the small size of microphotonic resonators, these filtering operations can be performed in a tiny fraction of the space and at far greater fidelity than would otherwise be possible in an analogous all-microwave system. And, in future, Extremely High Frequency (EHF) wireless systems (e.g. 30-to-300GHz), optical generation of the microwave frequencies is both more efficient and compact than traditional approaches. Further, additional processing elements, such as delays, limited by losses in the microwave regime, are readily implemented in microphotonics. In other coupled optical-microwave systems such as low phase noise optically-enabled microwave oscillators, the high optical carrier frequency enables high-Q optical-microwave oscillators and/or phased locked loops with phase noise levels that approach the best microwave systems with potential for greatly reduced size and power consumption. If successfully integrated on a microphotonic chip, these timing elements can be widely deployed in RADAR, radio, and GPS applications for reduced noise, enhanced range and greater accuracy. Already, in collaboration with Professor Kaertner of MIT, we have demonstrated a ~30dB reduction in the phase noise of a microwave oscillator by using a microphotonic chip to lock the oscillator to a mode-locked laser.
Microphotonic elements, circuits, systems and networks will profoundly impact the field of electrical engineering, enabling advances in sensing, computing, imaging and image processing, wired and wireless communications, and precision timing that could not otherwise be achieved. And, from nanophotonic electromagnetic interactions to very large-scale microphotonic integration techniques, considerable research effort remains. Much as was experienced in the development of CMOS electronics; breakthroughs in microphotonics will lead to new fields of research, multiplying the impact of the initial successes.