White, Richard THe, YabaiOrr, Brian JKono, MitsuhikoBaldwin, Kenneth2009-06-042010-12-202009-06-042010-12-2015/11/20041094-4087http://hdl.handle.net/10440/400Optical-heterodyne measurements are made on ~842-nm signal output of an injection-seeded optical parametric oscillator (OPO) based on periodically poled KTiOPO4 pumped at 532 nm by long (~27-ns) pulses from a Nd:YAG laser. At low pump energies (≤ 2.5 times the free-running threshold), the narrowband tunable OPO output is single-longitudinal-mode (SLM) and frequency chirp can be <10 MHz, much less than the transformlimited optical bandwidth (~17.5 MHz). We explore the transition from SLM operation to multimode operation as pump energy or phase mismatch are increased, causing unseeded cavity modes to build up later in the pulse.6 pagesapplication/pdfen-AUAttribution 4.0 International (CC BY 4.0)Optical Society of Americaphase measurementparametric oscillators and amplifiers200410.1364/OPEX.12.0056552015-12-11