Wavelength conversion of a broadband ASE source based on intra-cavity difference-frequency-mixing in a Cr³⁺:LiCAF-PPSLT laser

摘要

We present an intra-cavity assisted broadband wavelength conversion system for an incoherent (ASE) continuous-wave input source (signal) in the spectral region around 1535–1635 nm. The wavelength converting system is based on single-pass difference frequency generation in a PPSLT crystal placed inside the V-folded cavity of a tuneable self-injection-locked diode-pumped Cr³⁺:LiCAF laser oscillating around 792±8 nm (Fig.1). Tuning is achieved with an externally coupled cavity based on a Littrow-mounted ruled diffraction grating. The spectral allocation of the converted spectrum can be varied due to the tuning capabilities of the laser [1] and the crystal quasi-phase matching acceptance of the PPSLT (periodically poled stoichiometric lithium tantalate) resulting from the typical domain period dispersion in fabrication. Due to the nature of DGF processes the conversion efficiency becomes independent of the input power and increases with the DFG pump power (intra-cavity laser power).