The Matisse 2 TR Ti:Sapphire ring laser provides a spectral linewidth of <4 MHz and can be readily upgraded to the higher resolution Matisse 2 TS. In fact, because of its modularity, any Matisse 2 tunable laser can be field upgraded to either a Ti:Sapphire or dye gain medium, or to a configuration with higher resolution – from an R-Series to an S-Series or an X-Series. The Matisse 2 R-Series ring laser with its mechanically quiet design provides excellent passive stability and ultra-low noise, single-frequency operation. Electronically controlled wavelength-selecting elements—a birefringent filter, a thick etalon, and a thin etalon—keep the laser centered on a single longitudinal mode. This enables long, mode-hop-free wavelength scans while maintaining constant, low-noise output power levels.