Investigation results on linear and non-linear optical properties, damage threshold and potential efficiencies of biaxial negative LiInS_(2) crystal are represented. It shows that the crystal has phase-matching and groupvelocity matching in wide spectral range for second harmonic, sum- and difference-frequency generation of visible, near and middle IR lasers. The possibilities of designing middle IR optical parametric oscillator (OPO) pumped by Nd:YAG and dye lasers and specially possibility of frequency conversion with 3 μm range femtosecond erbium lasers are given.