CASCADED RAMAN FIBER LASER SYSTEM BASED ON FILTER FIBER

摘要

A light generation and amplification system includes a length of laser-active filter fiber having a refractive index profile that suppresses unwanted Stokes orders at wavelengths longer than a target wavelength and that has normal dispersion over its operating wavelength. A nested series of reflectors is provided at the fiber's input and output ends, and are configured to provide a nested series of Raman cavities, separated in wavelength by approximately the respective Stokes shifts. The first cavity in the series is a combined cavity that provides laser oscillation due to a combination of ionic gain and feedback at a selected first wavelength and that provides Raman gain to light at the first Stokes shift of the first wavelength when shift at the first wavelength has an energy exceeding a Raman scattering threshold. The Raman cavities provide a stepwise transition between the first wavelength and the target wavelength.