This paper reports on the new experimental results for second-harmonic generation and sum-frequency generation in LiGaSe2 in the 1.026-10.5910μm range, and the improved Sellmeier equations that provide a good reproduction of the present experimental results, as well as the published data points for a Ti:Al2O3 laser (λ=0.8200 μm)-pumped optical parametric amplifier and a Nd:YAG laser-pumped optical parametric oscillator in the mid-IR.