Upconversion of the mid-IR pulses to the near IR in LiGaS_2

摘要

This paper reports on the phase-matching properties of LiGaS_2 for upconverting a Nd:YAG laser-pumped KTP and AgGaS_2 optical parametric oscillator (OPO) at mid-IR to the near-IR by mixing with its pump source together with the new Sellmeier equations that provide a good reproduction of the present experimental results as well as the published data points of second-harmonic generation (SHG) and sum-frequency generation (SFG) of a CO_2 laser, a Ti: Al_2O_3 laser-pumped optical parametric amplifier (OPA), and a Nd:YAG laser-pumped OPO in the mid-IR. This index formula gives the important information that group velocity mismatch (GVM) (△_(sp) 1/v_s- 1/v_p) of LiGaS_2 in the 4-11 μm range is 12 ~ 27 fs/mm lower than that of the widely used LiInS_2, which makes it ideal for the upconversion of the mid-IR femtosecond pulses having large spectral bandwidths to the near-IR.