3.77 μm fiber laser based on cascaded Raman gain in a chalcogenide glass fiber

Laser emission is demonstrated at a wavelength of 3.766 μm in a cascaded Raman gain device. The laser cavity is made of two nested pairs of fiber Bragg gratings inscribed in a 2.8 m length of low-loss As2S3 fiber. An erbium-doped fluoride glass quasi-CW fiber laser emitting at 3.005 μm is used to pump the cascaded Raman cavity, which converts the pump wavelength successively to the first and second Stokes orders, respectively at 3.340 and 3.766 μm. A laser output peak power in excess of 100 mW is obtained with a lasing efficiency of about 8.3% with respect to the launched pump power. This represents the highest emission wavelength delivered by a fiber laser operating at room temperature.