Caltech/JPL Association for Gravitational-Wave Research Seminar

Digitally-enhanced interferometry (DI) is a new technique for optical metrology that combines spread spectrum phase modulation with digital signal processing to accurately measure the phase of interfered beams, allowing multiple interferometric signals to be measured using a single photodetector. As this signal isolation is based on the optical propagation time of signals through the system, the technique can also effectively reject scattered light and electronic crosstalk. Displacement sensitivities of 5 pm/sqrt(Hz) have already been demonstrated using a DI readout. The technique has potential application in LIGO and LISA, as well as in systems such as fiber sensors. In this talk I will provide a thorough introduction to the technique. I will also talk about several experiments that could or have already benefitted from DI, including lock acquisition for ground-based gravitational wave detectors, optical-bench simplifications for LISA, beam forming/shaping/steering for both ground and space-based applications, and fiber systems for displacement sensing and frequency noise reduction. Finally, I will talk about the next generation of DI based on quadrature phase shift keying encoding that promises improved sensitivity, flexibility and simplified optical hardware.