Dark-line laser.

ABSTRACT

A laser is meant to emit coherent radiation at a particular wavelength. Here, we demonstrate a laser that is prohibited to emit at a particular wavelength, called a dark line in the emission background of its gain spectrum. Specifically, we installed a 150 µm thick etalon mirror on an ytterbium-doped fiber laser. The laser suffers from 100% loss at the resonance of the etalon and generates a dark line in its emission spectrum. The interplay among the etalon resonance, homogenous gain broadening, and gain competition allows wavelength tuning and multiple-color emission from the laser.