title: Nonlinear spectra of ZnO: reverse saturable, two- and three-photon absorption.
abstract: We present a broadband (460 - 980 nm) analysis of the nonlinear absorption processes in bulk ZnO, a large-bandgap material with potential blue-to-UV photonic device applications. Using an optical parametric amplifier we generated tunable 1-kHz repetition rate laser pulses and employed the Z-scan technique to investigate the nonlinear absorption spectrum of ZnO. For excitation wavelengths below 500 nm, we observed reverse saturable absorption due to one-photon excitation of the sample, agreeing with rate-equation modeling. Two- and three-photon absorption were observed from 540 to 980 nm. We also determined the spectral regions exhibiting mixture of nonlinear absorption mechanisms, which were confirmed by photoluminescence measurements.
authors.affiliation: Instituto de Física de São Carlos, Universidade de São Paulo, Caixa Postal 369, 13560-970 São Carlos, SP, Brazil.
authors.forename: M G
authors.initials: MG
authors.lastname: Vivas
authors.forename: T
authors.initials: T
authors.lastname: Shih
authors.forename: T
authors.initials: T
authors.lastname: Voss
authors.forename: E
authors.initials: E
authors.lastname: Mazur
authors.forename: C R
authors.initials: CR
authors.lastname: Mendonca