title: A new method for locking the signal-field phase difference in a type-II optical parametric oscillator above threshold.
abstract: We propose and demonstrate a new method for phaselocking the signal fields emitted above threshold by a nondegenerate, type-II optical parametric oscillator (OPO). This method is based on the observation that amplitude modulation of the pump beam produces a related modulation of the frequency difference of the OPO signals via the temperature-tuning of the index of refraction in the nonlinear crystal. We successfully use pump modulation as a correction for phase-difference locking of the OPO signals and observe a 1 kHz beat note stable over more than 10 s, both figures solely limited by the measurement time. This method eliminates the need for applying electronic phase-correction signals directly to the nonlinear crystal which caused crystal damage in a previous phaselocking technique.
authors.affiliation: Department of Physics, University of Virginia, Charlottesville, Virginia 22904-4714, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Pysher
authors.forename: Yoshichika
authors.initials: Y
authors.lastname: Miwa
authors.forename: Reihaneh
authors.initials: R
authors.lastname: Shahrokhshahi
authors.forename: Daruo
authors.initials: D
authors.lastname: Xie
authors.forename: Olivier
authors.initials: O
authors.lastname: Pfister
mesh_terms: D000669:Amplifiers, Electronic; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005246:Feedback; D007834:Lasers; D009991:Oscillometry / Q000295:instrumentation*