Uncertainty Analysis in Z-Scan Spectroscopy: A Systematic Approach for Budget Estimation

Nonlinear optical phenomena and techniques challenge existing in-line metrology. In order to validate a wide range of classical and nonclassical photonic outcomes, it is now crucial to broaden the scope of metrological aspects which were initially confined to fundamental SI units. The conventional method to determine third-order nonlinear optical coefficients is Z-scan spectroscopy. Carbon Disulfide (CS₂) is the most extensively used reference material for various nonlinear optical setups including Z-scan spectroscopy. However, variation in the incident laser beam’s pulse duration drastically alters the nonlinear optical response of CS₂. Therefore, till date all the available literature quotes relative nonlinear optical coefficients of CS₂ and a consensus over the absolute nonlinearity of the reference material itself is missing. In order to overcome this limitation, the present article employs the Law of Propagation of Uncertainties (LPU/GUM) to establish a generic model to assess the uncertainties involved in the nonlinear absorption coefficient and nonlinear refractive index in the standard CS₂ solution using transmission mode Z-scan spectroscopy. This would not only help in expanding the bounds of nonlinear optical metrology but also permit assessment, comparison, and commercialization of the results obtained from different third-order nonlinear optical measurements.