Quantum Intensity Noise Correlation in a Type - II Phase Matched Optical Parametric Oscillator

A type-II phase matched optical parametric oscillator is investigated for the generation of intensity correlated twin photon beams using potassium titanyl phosphate (KTP) as a nonlinear medium. The input pump source is a Kr'-ion laser at XP = 531nm with signal and idler twin photon beams at X,, = 1.06gm. Mirror and crystal losses were characterized for use in cavities of two-and three-piece construction. A detection system consisting of two photodetector/transimpedance amplifiers and a summing circuit were developed with a bandwidth of = 40MHz. A feedback stabilization circuit was also implemented to allow locking of the parametric oscillator cavity length to a resonance peak. The twin beam intensity-difference spectrum of a two-piece optical parametric oscillator was measured yielding 38% correlation (2.1dB) in good agreement with the expected correlation inferred by the loss measurements.