Laser diode injected intracavity-doubled Ti:sapphire laser for single-mode tunable UV sources

Intracavity frequency doubling of a pulsed Ti:sapphire laser is shown to be well described by multimode rate equations nonlinearly coupled through the homogeneous gain linewidth of the amplifying medium. Hole burning in the fundamental wave spectrum is observed at the phase-matched frequency and is explained well by theory in terms of the dynamic depletion of the fundamental waves phase-matched to the nonlinear output mirror. The doubling conversion efficiency is shown to be greatly improved by injection seeding at the same frequency as the “spectral hole” with a low power continuous-wave-tunable laser diode. This leads, for the first time to our knowledge, to single-mode UV-tunable (380-410 nm) emission using this technique. Finally, the source is shown to exhibit a minimum yield at the coincidence between injection and exactly phase-matched wavelengths while maintaining high efficiency when injecting a few nanometers away from the phase-matching maximum