At high optical irradiance of short pulse lasers, the absorption and refraction of materials changes temporarily. We have been developing nonlinear spectroscopic tools for measuring these changes of nonlinear absorption (NLA) and nonlinear refraction (NLR). Our goal is to build an automated nonlinear optical spectrometer. For one of the instruments we are building, the "femtosecond white-light-continuum (WLC) spectrometer", we get the bonus of simultaneously obtaining the dispersion of the NLR. This instrument is based on our "Z-scan" technique but replaces the usual tunable sources such as optical parametric devices with the femtosecond WLC - an extremely broad pulse of light lasting for ~10-13 s . This is very useful in allowing automation. I will describe this system along with a WLC pump-probe spectrometer that gives the frequency nondegenerate NLA spectrum. From these measurements over a sufficiently broad spectral range we can apply causality to obtain nonlinear Kramers-Kronig relations to give the NLR. Additionally I will describe some applications of these nonlinearities, including ultrafast switching, uncooled IR detection using nondegenerate 2-photon absorption, optical switching and 2-photon lasing. This research on nonlinear optical materials has been a collaborative effort requiring the skills and expertise of materials scientists, chemists and materials manufacturers.
He received a PhD in Physics in 1976, from the Univ. of Arizona, Optical Sciences Center, where he worked on optical coherent transients and photon counting statistics, and then postdoc at the Center for Laser Studies, Univ. of Southern California. He joined the physics department at the Univ. of North Texas in l978 helping to form the Center for Applied Quantum Electronics. In l987 he joined the newly formed CREOL (Center for Research and Education in Optics and Lasers) at the Univ. of Central Florida. He developed the Z-scan technique and established the methodology for applying Kramers-Kronig relations to ultrafast nonlinearities and developed the field of cascaded second-order effects. The JQE publication on Z-scan is the most highly cited paper in the journal’s 30 year history by a factor of 2 ~ 4,000. He is a fellow of the Optical Society of America (OSA), IEEE, SPIE and APS, a past member of the OSA and LIA Boards of Directors. He also served as a topical editor for Optics Letters. He was elected President of the OSA for 2006. He graduated 31 Ph.D.'s and published ~300 papers and is on the ISI ‘highly cited’ list. In 2003 he was awarded the highest honor UCF bestows, the Pegasus Award (earlier he was co-recipient of UNT's highest award). He was Director of the School of Optics/CREOL from 1999 to 2004. With the elevation of the School to a College, he became its first Dean. He established the Florida Photonics Center of Excellence (FPCE) in 2003 and was the Director of that Center along with CREOL, and co-founded the Townes Laser Institute. In January, 2009 he retired as Dean but continues as a faculty member in the College, and he received UCF’s Researcher of the Year Award. He became a Trustee Chair in 2012, and was awarded the R.W. Wood Prize of the OSA in 2012.