High Power 2nd Stokes Diamond Raman Optical Frequency Conversion

Currently, the achievable average power from single-mode Yb-doped fiber lasers is in the multi-kW range [1]. However, the transmission range or the spectral gain of the active medium often limits the output power of highly demanded laser sources at uncommon wavelengths. Nonlinear frequency conversion represents a versatile approach to extend the spectral range at high power levels and is thus beneficial for wavelength-dependent applications. Compared to optical parametric oscillators (OPOs) the Raman laser technology is less complex and does not require management of phase matching. Furthermore, the spatial-hole-burning-free characteristic of the Raman gain provides an advantage for narrow band, high power operation [2]. Industrial CVD-diamond is an attractive medium for Raman frequency conversion and especially suitable for high power regions due to its unique combination of thermal and optical properties [3]. Using a second-Stokes setup lowers the threshold and increases the obtainable wavelength shift ever further [4]. Here, we employ this technology to achieve record power at 1478 nm in cw-operation.