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Journal of the Optical Society of America B

Traveling-wave optical parametric amplifier: investigation of its phase-sensitive and phase-insensitive gain response

Sang-Kyung Choi, Ruo-Ding Li, Chonghoon Kim, Prem Kumar

Published Jul 1, 1997• 35 citations

Abstract

We experimentally investigate the gain response of a frequency-degenerate but polarization-nondegenerate traveling-wave optical parametric amplifier that consists of a type II phase-matched potassium titanyl phosphate crystal pumped by a frequency-doubled Q-switched mode-locked Nd:YAG laser. Both the optical phase-sensitive and phase-insensitive configurations of the parametric amplifier are studied. Experimental results are in excellent agreement with the theory of an optical parametric amplifier when the Gaussian-beam nature of the various fields is taken into account. In the phase-sensitive configuration a gain of >100 (20 dB) could be easily obtained in the amplified quadrature, which is limited only by the available pump power. Because of gain-induced diffraction and phase fluctuations, however, maximum deamplification in the orthogonal quadrature is limited to <0.5(-3 dB).

DOI: 10.1364/josab.14.001564

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We experimentally demonstrate a single-pumped, non-degenerate phase-sensitive parametric amplifier with a precise control of phase and amplitude of the in-going waves and investigate in detail its gain, attenuation and saturation properties in comparison with operation in phase insensitive amplifier (PIA) mode. We experimentally observe the variation of the gain and attenuation as a function of the relative phase, pump power and the signal-idler power ratio. The phase sensitive gain spectrum is studied over a 24 nm symmetrical bandwidth and we achieve a maximum phase sensitive amplification (PSA) gain of 33 dB. A departure from the theoretical maximum attenuation as the gain increases is observed and explained.

We investigate experimentally the eigenmodes of a Gaussian-beam-pumped traveling-wave phase-sensitive optical parametric amplifier (PSA). By varying the waist of an input LG(00) signal mode, we show that PSA performance improves with increasing spatial overlap between the input and the theoretically predicted fundamental eigenmode. For optimum waist, we report amplification and deamplification markedly higher than those observed for the traditional case of signal waist=√2× (pump waist). Lastly, we demonstrate the generation and verification of the PSA fundamental eigenmode.

Pulsed squeezed light and intensity-correlated twin beams are generated by means of a traveling-wave optical parametric amplifier (OPA) consisting of a type-II phase-matched KTiOPO4 crystal that is pumped by a Q-switched and frequency-doubled Nd:YAG laser. Q switching of the laser results in a high peak pump intensity and a large peak parametric gain. Squeezed light is generated by amplifying the vacuum input field to the OPA, and it is detected by a balanced homodyne configuration that uses the fundamental beam of the laser as a local oscillator.1 Twin beams are generated by supplying a small input signal to the OPA. The amplified signal and idler beams are direct-detected individually and yield quantum-noise reduction when the two photocurrents are subtracted.