Self frequency shift near 2 µm in periodically poled lithium niobate waveguides

In this experiment, the PPLN waveguides are seeded with a coherent Raman soliton source, based on a Tm oscillator and amplifier. The pulses have a FWHM duration of 100 fs around a center wavelength of 2040 nm, and their energy is 6 nJ at a repetition rate of 70 MHz (average power 420 mW), with up to 2 nJ coupled into the PPLN waveguides. After propagation through an 18.5-mm-long quasi-phasematching (QPM) grating with period 24.3 μm, the peak wavelength of the pulse was shifted to 2175 nm.