Efficient potassium gadolinium tungstate Raman lasers generating single or multiple wavelengths spanning the green to red

We review our recent studies into external cavity and intracavity KGd(WO₄)₂ Raman lasers generating output wavelengths in the range 555 nm to 669 nm. We have characterised the performance external cavity Raman lasers pumped by Q-switched 532 nm pump lasers at 5-10 kHz pulse repetition rates generating either single output wavelengths or multiple wavelengths simultaneously. Single output wavelengths are obtained with slope efficiencies up to 68% and maximum output powers ∼0.5 W. Simultaneous output at 5 wavelengths (eg., 532 nm, 559 nm, 589 nm, 622 nm and 658 nm) is demonstrated with ∼100 mW output power for at least 3 lines. Using the intracavity Raman laser scheme, we demonstrate a 0.3-1.8 W laser that is "user switchable" amongst wavelengths spanning the green to red eg., 532 nm - 555 nm - 579 nm - 606 nm, the wavelengths corresponding to frequency sums and mixing of Stokes and fundamental intra-cavity fields.