Squeezed states of the electromagnetic field have been generated by nondegenerate four-wave mixing due to Na atoms in an optical cavity. The optical noise in the cavity, comprised of primarily vacuum fluctuations and a small component of spontaneous emission from the pumped Na atoms, is amplified in one quadrature of the optical field and deamplified in the other quadrature. These quadrature components are measured with a balanced homodyne detector. The total noise level in the deamplified quadrature drops below the vacuum noise level.

Observation of squeezed states generated by four-wave mixing in an optical cavity

We point out in this paper the possibility of demonstrating the Einstein-Podolsky-Rosen paradox via quadrature phase measurements performed on the two output beams of a nondegenerate parametric amplifier. A technique that might be used to demonstrate the paradox has already been partly developed experimentally.

Demonstration of the Einstein-Podolsky-Rosen paradox using nondegenerate parametric amplification.

Summary form only given. We derive an exact expression for the electromagnetic mode density, and hence the group velocity, for a finite N period, one-dimensional photonic band-gap structure. We begin by deriving a general formula for the mode density in terms of the complex transmission coefficient of an arbitrary index profile. Then we develop a formula that gives the N-period mode density in terms of the transmission coefficient of the unit cell. The special cases of mode-density enhancement and suppression at the photonic band edge and at mid gap, respectively are derived. The specific example of a quarter-wave stack is analyzed, and applications to 3D structures, spontaneous emission control, delay lines, band-edge lasers, and superluminal tunneling times are discussed.

Analytic expressions for the electromagnetic mode density in finite, one-dimensional, photonic band-gap structures

An important development in modern physics is the emerging capability for investigations of dynamical processes for open quantum systems in a regime of strong coupling for which individual quanta play a decisive role. Of particular significance in this context is research in cavity quantum electrodynamics which explores quantum dynamical processes for individual atoms strongly coupled to the electromagnetic field of a resonator. An overview of the research activities in the Quantum Optics Group at Caltech is presented with an emphasis on strong coupling in cavity QED which enables exploration of a new regime of nonlinear optics with single atoms and photons.

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Strong interactions of single atoms and photons in cavity QED

The author reviews methods for generating sub-Poissonian light and related concepts. This light has energy fluctuations reduced below the level which corresponds to a classical Poissonian process (shot-noise level). After an introduction to the concept of nonclassical light, an overview is given of the main methods of quantum-noise reduction. Sub-Poissonian processes are exemplified in different areas of optics, ranging from single-atom resonance fluorescence to nonlinear optics, laser physics, and cavity quantum electrodynamics. Emphasis is placed on the conceptual foundations, and on developments in laser theory that lead to the possibility, already demonstrated experimentally, of linewidth narrowing and sub-Poissonian light generation in lasers and masers. The sources of quantum noise in these devices are analyzed, and four noise-suppression methods are discussed in detail: regularization of the pumping, suppression of spontaneous-emission noise, nonadiabatic evolution of the atomic variables, and twin-beam generation.

https://www.if.ufrj.br/~ldavid/arquivos/rmp.pdf

Sub-Poissonian processes in quantum optics

A quantum analysis of the intensity fluctuations is given for the nondegenerate parametric oscillator both above and below threshold. Theoretical analysis and experiments by Heidmann, Horowicz, Reynaud, Giacobino, and Fabre [Phys. Rev. Lett. 59, 2555 (1987)] have shown that a noise suppression below the vacuum level is possible in the difference of the intensities of the signal and idler modes. The effect of nonequal cavity decay rates and intracavity losses is shown to modify significantly the fluctuation spectra for the difference in the intensity of the signal and idler beams. The results of exact nonlinear solutions for the internal cavity modes are discussed. We demonstrate that a very sensitive absorption detector may be made by operating the oscillator near threshold.

Quantum analysis of intensity fluctuations in the nondegenerate parametric oscillator

Description d'un nouveau spectrometre a absorption: utilisation d'un oscillateur parametrique, avec element absorbant place a l'interieur de la cavite

Absorption spectroscopy beyond the shot-noise limit.

We investigate stabilization of the laser amplitude by the use of intracavity nonlinear elements. The goal is to achieve subshot noise operation of an active laser system by a feedback system internal to the laser cavity. The prototype of such a system is a laser with a two-photon absorber present.

Amplitude noise reduction in lasers with intracavity nonlinear elements

There is considerable activity in the generation of light fields with less quantum fluctuations than a coherent field, for example squeezed or sub-Poissonian light:(1–3) With such light, it is possible to beat the usual shot noise limit which leads to an enhanced sensitivity in many optical measurements. Such sensitivity is required in measurements such as the detection of gravitational radiation by optical interferometry where the signal is comparable to the quantum noise.

Quantum Noise Reduction in Optical Systems

We consider lasers with intracavity nonlinear elements, e.g., two-photon absorption, second-harmonic generation, as a possible means to reduce the amplitude fluctuations in a laser. While amplitude squeezing up to 37% may be obtained for the internal field, only a modest amount of noise reduction (10% for two-photon absorption, effectively zero for second-harmonic generation) is found in the output field at the laser frequency. In the second-harmonic field an amplitude-noise reduction of 50% below the shot-noise level may be achieved.

A. S. Lane

Papers

Quantum analysis of intensity fluctuations in the nondegenerate parametric oscillator

Absorption spectroscopy beyond the shot-noise limit.

Amplitude noise reduction in lasers with intracavity nonlinear elements

Quantum Noise Reduction in Optical Systems

Amplitude-noise reduction in lasers with intracavity nonlinear elements.