Z-Scan Spectroscopy of BaFeGaO₄

There have been reliable methods in the past for determining the nonlinear optical properties of materials (i.e. nonlinear absorption and nonlinear refraction) that can be used for multiple applications such as optical limiting, multi-photon polymerization, and optical switching. Of these methods, z-scan, which was developed by Eric Van Stryland [1] is found to be the optimal method for determining the third order optical susceptibility of a material.<br/><br/>The goal of my Masters project was to build a z-scan system for nonlinear optical measurements of materials fabricated in the NSF CREST Center for Research and Education in Quantum-leap Science (CREQS) at Norfolk State University (NSU). The optical system uses 100 fs pulses emitted at a repetition rate of 1 kHz from a Spectra Physics Solstice regenerative amplifier. These pulses at 800 nm are converted to visible wavelengths using a Spectra Physics TOPAS Prime optical parametric amplifier. The wavelength used in this study was 650nm. Pulses were detected using standard silicon photodiodes that were amplified and fed into an AD converter for input into the computer. Labview was used to monitor all detectors and control the position of the sample using a Newport Corp. precision translator.<br/>The sample used for system development was a BaTiO3 crystal grown at NSU. The data was analyzed using a Mathcad Prime computer model of the z-scan process that was written as part of this project. This semester this includes computer modeling the z-scan technique using the computer program Mathcad, to determine the experimental parameters for building the Z-Scan system.<br/>Preliminary results are consistent with the z-scan model but further refinements in the optical and detection system are underway and will be reported at the conference.<br/><br/>[1] M. Sheik-Bahae, A. A. Said, and E. W. Van Stryland, “High sensitivity single beam n₂, measurement,” Opt. Lett., vol. 14, 955–957 (1989)