摘要： A new nonlinear optical crystal, ‘Bis(2-methyllactato)borate tetrahydrate’ (BMBT) has been crystallized by slowly evaporating the solvent. It crystallizes in the space group P21212. Sharp peaks present in powder XRD profile reveals the good crystallinity. Its transmission bandwidth (220 nm – 1100 nm) suggest that it can be used to generate UV radiation upto 220 nm and also in optoelectronic applications. Vibrations of functional groups (B-O, CH3, CO) associated with the crystal structure have been identified through FTIR and FT-Raman spectral studies. OH stretching vibrations have been observed near 3000 cm-1 clearly endorses the existence of water molecule in the BMBT structure. The chemical shifts observed in 1H and 13C NMR spectral results establishes the molecular structure of BMBT crystal. Second harmonic generation (SHG) efficiency is obtained as 0.9 times of KDP. The third order nonlinear susceptibility (χ3), nonlinear refractive index (n2) and nonlinear absorption co-efficient (β) were found using Z-scan technique. χ3 of title crystal is found to be 4.16 X10-5 esu. The existence of SHG efficiency and the enhanced χ3 value are due to the hydrogen bonded intermolecular interactions present in the BMBT crystal structure. The observed results suggest that BMBT can be used in Q-switching, mode locking and optical sensors like night vision devices.