Laser Interferometry & Detector Design: Physical Mechanisms

A Michelson-style detector splits coherent laser light into orthogonal kilometer-scale arms containing suspended mirrors. Light reflects many times in optical cavities, recombines at a beam splitter, and forms an interference signal whose phase responds to differential arm-length changes.

A passing gravitational wave stretches one transverse direction while compressing the perpendicular direction, then reverses. This produces a tiny differential optical phase shift. Seismic isolation, multi-stage suspensions, ultra-high vacuum, feedback control, and squeezed-light techniques improve sensitivity across different frequency bands.

Independent observatories record consistent waveforms with relative arrival times compatible with light-speed propagation. Calibration systems inject known mirror motions and simulated signals, while environmental sensors distinguish astrophysical candidates from local disturbances.

A passing gravitational wave stretches one arm while compressing the other in an ideal polarization orientation, changing recombined laser phase. Multiple reflections increase effective optical path, while quantum and thermal noises set sensitivity limits.