Showing papers by "Jeffrey H. Shapiro published in 1984"

Degenerate four-wave mixing as a possible source of squeezed-state light

Abstract: The suitability of degenerate four-wave mixing (DFWM) as a source of squeezed-state (two-photon coherent state) light is investigated, both theoretically and experimentally. In previous semiclassical theory, which neglected pump quantization and loss in the nonlinear medium, Yuen and Shapiro [Opt. Lett. 4, 334 (1979)] showed that such states would be generated by 50%-50% combination of the transmitted probe (TP) and the phase-conjugate (PC) output beams of DFWM. Here the effects of quantum fluctuations in the amplitudes and phases of the pump beams are calculated in a traveling-wave finite-interaction-length DFWM configuration. It is shown that in the limit of strong pump beams and weak nonlinear coupling, the classical-pumps assumption of Yuen and Shapiro is valid. With use of this assumption, loss in the nonlinear medium is incorporated into the model by coupling the interacting modes to a set of reservoir modes. It is shown that loss presents an absolute limit on the degree of squeezing that can be achieved with DFWM. Also, for comparison with experimental work, the photoelectron statistics of the TP, PC, and 50%-50% combination modes are calculated for lossy DFWM; significant deviations are found from the predictions for lossless operation. Quantum-noise measurements on the PC and TP beams generated in sodiumvapor DFWM are described. The mixer is pumped and probed by the nearly transform-limited pulses produced by a continuous-wave-oscillator-pulse-amplifier chain dye laser at 589 nm wave-length. The normalized second-factorial moment ${g}_{2}$ of the PC and TP beams is determined from photoelectron-counting measurements. Inability to simultaneously achieve high DFWM reflectivity and acceptably low scattered-plus-fluorescent background, coupled with low photomultiplier quantum efficiency, restrict the experiment to a DFWM regime wherein theory predicts Poisson statistics. Experimental ${g}_{2}$ values corroborate this prediction, indicating that systematic and excess noises have been eliminated. No attempt was made to measure the quantum statistics of the 50%-50% combination mode.

Microchannel spatial light modulator

Abstract: A microchannel spatial light modulator that has a photocathode to receive incident light and to provide a spatial distribution of photoelectrons (herein called an electron image) whose spatial number density is proportional to the spatial intensity of the incident light. A microchannel plate is provided to receive the photoelectrons and to amplify the electron image. An electro-optic plate is provided to receive the amplified electron image; there is a dielectric mirror coating and an insulating light-blocking layer at one major surface thereof to receive the electron image and a transparent electrode at the other major surface thereof for biasing purposes. All of the foregoing elements are contained within a vacuum housing; suitable electrical potentials are applied to effect the necessary results. The modulator is capable of real-time phase or intensity modulation.

Squeezed-state generation via forward degenerate four-wave mixing

Abstract: Degenerate four-wave mixing has been suggested as a possible generation scheme for squeezed-state light. A recent analysis of the quantum effects of probe-conjugate loss in backward degenerate four-wave mixing has shown that such loss puts an absolute limit on the squeezing that can be obtained via this generation scheme. In this Rapid Communication we show that it is the counter-propagating beam geometry of backward degenerate four-wave mixing that makes it ill suited for squeezed-state generation. On the other hand, the nominally copropagating beam geometry of forward degenerate four-wave mixing is shown to alleviate the absolute probe-conjugate loss limit on squeezing.

Pump and Loss Effects on Degenerate Four-Wave Mixing Quantum Statistics

Abstract: Degenerate four-wave mixing (DFWM) has been identified by Yuen and Shapiro1 as a possible way to generate two-photon coherent state (TCS) light. Their model, although quantum mechanically consistent, quantized only the probe waves; the pump waves and the medium were treated classically. Furthermore, other real effects that sometimes hamper DFWM experiments, such as loss and self focusing, were ignored. Because the key non-classical characteristic of TCS light, its quadrature noise squeezing, is destroyed by excessive loss and fluctuations, it is desirable to include these effects in analyzing a DFWM TCS-generation experiment. In this paper, we extend the model of Yuen and Shapiro to include the effects of pump quantum noise, and loss in the four-wave mixer. The two problems will be treated separately.

Quantum Noise Measurements in Degenerate Four-Wave Mixing

Abstract: Recent work has highlighted the potential applications of two-photon coherent states (TCS), also known as squeezed states, in optical communications and precision measurements. These states have non-classical noise statistics. Their predicted generation schemes include the degenerate parametric amplifier, degenerate four-wave mixing (DFWM), and multi-photon optical bistability. The preceding generation schemes have been analyzed to varying degrees of approximation, but no experimental observation of TCS has been reported as yet. In this paper we describe an experiment measuring the quantum statistics of light that has undergone DFWM to look for squeezed-state generation via this process.