Temperature Dependent Refractive Index, Thermo optic Coefficient and Birefringence of Negative Biaxial Imidazolium L Tartrate Non linear Optical Crystal
Abstract Imidazolium L tartrate (IMLT) single crystal has been grown by slow cooling seed rotation technique. The temperature dependent refractive index (RI) has been measured along the principal axes in the temperature range 30 125 degC. The prism coupling technique has been used to determine the refractive index with accuracy 5x10 4. The transmission spectra depict good transparency in the range 340 1350 nm. The principal axes directions have been identified using polarized light microscopy. Principal directions have been found rotated by 44deg in the orthogonal xz plane with respect to the crystallographic x axis. The generalized temperature dependent equations for the Sellmeier's and thermo optic (dn/dT) coefficients have been determined. The thermo optic coefficients (TOC) in the above specified range have been found to be negative and are ~10 5 /degC. An important set of empirical relations between TOC and wavelength (407 1551 nm) has also been established which is useful for estimating TOC in the temperature range of 30 125 degC. Based on the birefringent measurement it has been confirmed that the IMLT crystal is a negative biaxial crystal.