300 mW of coherent light at 488 nm using a generic approach

We present a generic approach for efficient generation of CW light with a predetermined wavelength within the visible or UV spectrum. Based on sum-frequency generation (SFG), the circulating intra-cavity field of a high-finesse diode pumped CW solid-state laser (DPSSL) and the output from a tapered, single-frequency external cavity diode laser (ECDL) are mixed inside a 10 mm periodically poled KTP crystal (pp-KTP). The pp-KTP is situated inside the DPSSL cavity to enhance conversion efficiency of the nonlinear mixing process. This approach combines different solid state technologies; the tuneability of ECDLs, the high intra-cavity field of DPSSLs and flexible quasi phase matching in pp-KTP. We demonstrate the potential of the proposed method by synthesizing a beam at 488 run using a single-frequency tapered ECDL with a center wavelength of 766 run in combination with a high finesse Nd:YVO4 laser at 1342 nm. Up to 308 mW of light at 488nm was measured in our experiments. The conversion of the ECDL beam was up to 47% after it was transmitted through a PM fiber, and up to 32% without fiber coupling. Replacing the seed laser and the nonlinear crystal makes it possible to generate light at virtually any desired wavelength within the visible spectrum.