Ring-Resonator/Bragg-Grating Laser-Feedback Elements

Integrated optical structures that contain ring resonators and Bragg gratings have been proposed as external feedback elements for semiconductor lasers. These feedback elements would constrain the laser spectra to narrow lines (more precisely, narrow spectral bands) centered at desired wavelengths. In the original intended applications, these feedback elements and the associated lasers would be constructed and operated in pairs to generate pairs of spectral lines separated by known wavelength intervals in the approximate range of 1 to 10 nm, as needed to resolve integer-multiple-of-wavelength ambiguities in laser metrology.