Abstract: Systems and methods/processes for optical interferometric sensing using digitally enhanced interferometry (DI).

Abstract: A system and method for spectroscopic detection of loss in a resonator cavity is disclosed. The system can include a number of components. A tunable laser source can generate a laser beam. A frequency locking system can lock the frequency of the laser beam to a resonance of the resonator cavity or lock the length of the cavity to the frequency of the laser beam. The first modulation element can modulate the laser beam at a first modulation frequency to generate a modulated laser beam. The input coupler can direct the modulated laser beam into the resonator cavity. The first directing element can direct a first portion of light reflected from the input coupler to a first photodetector. The first demodulator can demodulate the first modulation signal to generate a first error signal which is a function of the loss in the resonator cavity.

Abstract: A system and method for spectroscopic detection of a loss in a resonator cavity. The system comprises: a tunable laser source for generating a laser beam; a frequency locking system for either locking the frequency of the laser beam to a resonance of the resonator cavity or locking the length of the cavity to the frequency of the laser beam; a first modulation element for modulating the laser beam at a first modulation frequency to generate a modulated laser beam; an input coupler adapted for directing the modulated laser beam into the resonator cavity; a first directing element for directing a first portion of light reflected from the input coupler to a first photodetector to generate a first detected signal; and a first demodulator capable of demodulating the first modulation signal from the first detected signal to generate a first error signal which is a function of the loss in the resonator cavity.

Abstract: This invention provides a method and an optical system for sensing and controlling the frequency for a laser with respect to an optical cavity and for sensing and controlling the length difference of interferometer paths in a two beam interferometer. A misalignment is introduced in the incident laser radiation to produce a fundamental mode (TEM00) in the cavity or interferometer and the reflection of a least one higher order mode (TEM01). A split photodetector (10) allows the interference between these two modes to be measured separately by detecting two spatially distinct portions of the single reflected beam. An error signal indicative of the difference between the fundamental mode frequency and the cavity resonant frequency is obtained by substracting the outputs from the two parts of the photodetector.