Options
Z-scan investigation of third-order optical nonlinearities in second-harmonic-generation crystals
Author
Li, Heping
Supervisor
Zhou, Feng
Abstract
KTiOPO4 (KTP), KTiOAsO4 (KTA), β-BaB2O4 (BBO), LiB3O5 (LBO) and LiNbO3 are important nonlinear optical materials for second harmonic generation (SHG) and optical parametric oscillation (OPO). We present a comprehensive investigation on the two-photon absorption (TPA) and bound electronic Kerr nonlinearity in these crystals using a picosecond, 532-nm-wavelength laser beam. By using Z-scan technique the nonlinear refractive indexes and two-photon absorption coefficients in the z-cut crystals are measured, as well as in KTP, BBO and LBO along the phase-matching angles for the SHG of 1064-nm radiation. The obtained TPA-coefficient and nonlinear-refractive-index data for the SHG crystals have extended the database of third-order optical nonlinearities in nonlinear optical crystals. The microscopic origin of the observed refractive nonlinearity can be understood in terms of bound electronic effects, and the theoretical predictions are in agreement with our measurements. Finally, we introduce an experimentally simple method to study the laser-induced damage in these crystals by extending the Z-scan technique. The measured damage threshold is inversely proportional to the nonlinear refractive index and the thickness of a crystal. The effect of self-focusing on laser-induced damage in these crystals is also discussed.
We begin Chapter 1 with a brief introduction to nonlinear optical materials. The third order-optical nonlinear processes in nonlinear optical crystals are described, and the past research on the third-order nonlinearities of SHG crystals is reviewed in brief. The purpose of our research work and the outline of the thesis are also given.
In Chapter 2 we describe the technical details of the Z-scan method used for the evaluation of the optical nonlinearities in the SHG crystals, including the experimental set-up and theoretical background directly related to the experimental data analysis.
Chapter3 presents our experimental study on the third-order optical nonlinearities of KTP, KTA, BBO, LBO and LiNbO3 crystals. We first measured the nonlinear refractive indexes and two-photon absorption coefficients in the crystals using Z-scan technique with linearly polarized 25-ps, 532-nm laser pulses. The anisotropy of the measured nonlinearities in the crystals is also determined by analyzing our experimental data through computer simulation. The microscopic origin of the measured refractive nonlinearity is compared with a theoretical model based on bound electronic effects, indicating that bound electronic Kerr effect associated with the two-photon absorption should be responsible for the refractive nonlinearity in SHG crystals under picosecond laser radiation.
In Chapter 4, we introduce a new method for measuring laser-induced damage in nonlinear optical crystals by extending Z-scan technique, and determine the optical damage thresholds in KTP, BBO, LBO and LiNbO3 crystals. We also discuss the effect of self-focusing on laser-induced damage in the crystals.
Chapter 5 summarizes all the important experimental findings and the conclusions.
We begin Chapter 1 with a brief introduction to nonlinear optical materials. The third order-optical nonlinear processes in nonlinear optical crystals are described, and the past research on the third-order nonlinearities of SHG crystals is reviewed in brief. The purpose of our research work and the outline of the thesis are also given.
In Chapter 2 we describe the technical details of the Z-scan method used for the evaluation of the optical nonlinearities in the SHG crystals, including the experimental set-up and theoretical background directly related to the experimental data analysis.
Chapter3 presents our experimental study on the third-order optical nonlinearities of KTP, KTA, BBO, LBO and LiNbO3 crystals. We first measured the nonlinear refractive indexes and two-photon absorption coefficients in the crystals using Z-scan technique with linearly polarized 25-ps, 532-nm laser pulses. The anisotropy of the measured nonlinearities in the crystals is also determined by analyzing our experimental data through computer simulation. The microscopic origin of the measured refractive nonlinearity is compared with a theoretical model based on bound electronic effects, indicating that bound electronic Kerr effect associated with the two-photon absorption should be responsible for the refractive nonlinearity in SHG crystals under picosecond laser radiation.
In Chapter 4, we introduce a new method for measuring laser-induced damage in nonlinear optical crystals by extending Z-scan technique, and determine the optical damage thresholds in KTP, BBO, LBO and LiNbO3 crystals. We also discuss the effect of self-focusing on laser-induced damage in the crystals.
Chapter 5 summarizes all the important experimental findings and the conclusions.
Date Issued
1997
Call Number
QD905.2 Li
Date Submitted
1997