In this paper, we review the developments of crystalline Raman lasers over the past five years. Average powers exceeding 5 W and pulse energies above 1 J in the near infrared have been demonstrated for larger scale devices. There has been a rapid development of all-solid-state sources based on the standard diode-pumped lasers, especially intracavity crystalline Raman lasers, which offer wavelength versatility at high conversion efficiencies (overall diode Stokes optical conversion efficiencies up to 17%) in the near infrared, including the 1.5- mum eye-safe band. Passively Q-switched intracavity Raman lasers based on self-Raman laser materials offer many advantages for miniaturization of short-pulse (1 ns) sources. Intracavity frequency-doubled crystalline Raman lasers have also emerged as practical and versatile sources in the yellow orange region at 1-W power levels with diode-visible efficiencies near 10%. Recent developments of all-solid-state continuous-wave (CW) intracavity crystalline Raman lasers offer many possibilities for the future: intracavity frequency doubling has already resulted in the demonstration of CW visible sources with powers approaching 1 W at 5% diode-visible efficiency.
We report a continuous-wave self-Raman laser based on diode-pumped Nd:GdVO4 giving first-Stokes output at 1173 nm and intracavity frequency-doubled output at 586.5 nm. A maximum cw output power at 1173 nm of 2 W was obtained for diode pump powers of 22 W and a maximum cw power at 586 nm of 678 mW with 16.3 W pump power. Infrared and yellow powers were limited by thermal lensing in the gain medium and parasitic oscillations of weak Nd3+ transitions. Quasi-cw operation at 50% duty-cycle reduced the thermal load in the laser/Raman crystal, allowing cavity stability to be obtained near maximum available pump power (25.7 W) for which the maximum quasi-cw yellow output power was 1.88 W.
Efficient multi-Watt continuous-wave (CW) yellow emission at 586.5 nm is demonstrated through intracavity frequency-doubling of a Nd:GdVO4 self-Raman laser pumped at 880 nm. 2.51 W of CW yellow emission with an overall diode-to-yellow conversion efficiency of 12.2% is achieved through the use of a 20 mm long Nd:GdVO4 self-Raman crystal and an intracavity mirror which facilitates collection of yellow emission generated within the resonator, and reduces thermal loading of the laser crystal.