Multiwatt, Continuous-Wave, Tunable Diamond Raman Laser With Intracavity Frequency-Doubling to the Visible Region

Multiwatt emission from a continuous-wave diamond Raman laser pumped within a diode-pumped InGaAs-based semiconductor disk laser (SDL) is reported. The Raman laser achieved a maximum output power of 4.4 W at 1228 nm with a beam quality factor (M²) of 1.4 and diode-to-Stokes conversion efficiency of 14.2%. Via tuning of the SDL oscillation wavelength, the diamond Raman laser was tuned from 1209 to 1256 nm, with output power exceeding 4 W over a 10-nm range. The evolution of the emission spectra and beam quality of both the SDL and the Raman laser have been investigated for different pump powers, revealing the onset of spectral broadening and beam “clean-up” effects with increasing power. The SDL spectral linewidth and beam overlap are then taken into account in calculations of the efficiency of the Raman laser. Using intracavity frequency-doubling in lithium triborate (LBO) within the Raman laser, up to 1.5-W output power at orange wavelengths was achieved with M² <; 1.3 and linewidth ~0.1 nm full-width at half-maximum. Tuning of the visible emission was achieved via tuning of the SDL and temperature control of the LBO and covered the range 604.5-619.5 nm.