Patent ID: 7466726

Claim:
A fiber-based ring laser, comprising: a laser gain medium configured to produce a first laser beam; a mode-selection filter configured to filter the first laser beam to produce a second laser beam, wherein the mode-selection filter has a transmission spectrum that includes a plurality of transmission peaks, wherein one of the plurality of transmission peaks has a first bandwidth at a first wavelength and is separated from one of its adjacent transmission peaks by a frequency difference; a first optical fiber configured to transmit the first laser beam from the laser gain medium to the mode-selection filter; and a band-pass filter configured to filter the second laser beam and to produce a third laser beam, wherein the band-pass filter has a second bandwidth wider than the first bandwidth but narrower than the frequency difference, wherein the band-pass filter is configured to pass the one of the plurality of transmission peaks at the first wavelength while filtering out other transmission peaks in the plurality of transmission peaks in the second laser beam, wherein the laser gain medium, the first optical fiber, the mode-selection filter, and the band-pass filter in part form a ring cavity in the fiber-based ring laser; wherein the mode-selection filter comprises: a first reflective plate; a second reflective plate parallel to the first reflective plate; and an electro-optical material disposed between the first parallel reflective plate and the second reflective plate.