Lasers operating at wavelengths that pass through the atmosphere are required for many applications, including lidar/ladar, spectroscopy, and pollution detection. One window of particular interest is between 2050 and 2300 nm. A Tm:silica fiber laser may be a candidate for operating in this window, but reported solutions using double clad fibers only achieved wavelengths up to 2090nm even though the emission spectrum of the lasing band extends beyond 2200nm. By carefully selecting the dopant concentration, mirror reflectivities, and fiber length the operating wavelength may be adjusted. A laser based on a double clad Tm:silica fiber coupled to a bulk grating for wavelength selection was constructed. By changing the output coupler reflectivity the maximum obtainable wavelength shifted from 2040nm to 2140nm, and another mirror resulted in 2188nm lasing operation.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.