C. M. Savage

A multimode quantum theory of a degenerate parametric amplifier in a cavity

Abstract We undertake a detailed treatment of a Fabry-Perot cavity containing a degenerate parametric amplifier (DPA). Boundary conditions appropriate to the mirrors and DPA are applied to the Fourier components of travelling wave light fields inside and outside the cavity. Solving the resulting algebraic equations gives an expression for the output field in terms of the cavity input fields. Hencw we can calculate the squeezing in the output field. The maximum squeezing is found in a narrow frequency component of the field around the degeneracy frequency.

Single atom optical bistability

Absorptive optical bistability is shown to exist for a single two-level atom inside a resonant optical cavity. Solutions for the quantum-mechanical density operator are obtained numerically for a parameter regime at the interface between the quantum limit, in which quantum-mechanical noise invalidates the semiclassical prediction of bistability, and the classical limit, in which quantum noise is a negligible perturbation on semiclassical results. Bimodal photon number distributions and Q functions are obtained, and two-state transition rates are calculated. >

Optical Chaos in Second-harmonic Generation

Instabilities leading to self-pulsing, period doubling and chaos are predicted to occur in two simple systems in nonlinear optics. Namely, second-harmonic generation, inside a coherently driven optical cavity, and subharmonic generation internal to the laser cavity.

Macroscopic quantum superpositions by means of single-atom dispersion.

We show that macroscopic quantum superpositions of the electromagnetic field can be generated through amplification of microscopic quantum superpositions prepared in a single atom. Our scheme has the advantage that dissipation is negligible, and hence the superpositions are not rapidly destroyed.

Squeezing by parametric oscillation and intracavity four-wave mixing

We present a unified quantum analysis of parametric oscillators and intracavity four-wave mixers. The squeezing spectra below and above threshold for the degenerate cases are compared. Similarities between the systems are discussed and the optimum operating regimes identified.

Optical multistability and self oscillations in three level systems

Abstract The steady state behaviour of two cavity modes of the electromagnetic field interacting with a three level atomic medium is studied. This system may display optical tri- and quadra-stability. The results of Kitano et al. appear as a limit of our solutions in the dispersive and unsaturated regime. With the inclusion of saturation in the dispersive limit the asymmetric steady state may become unstable and give rise to self oscillations, period doubling and a new form of “optical turbulence”.

Direct overwrite in magneto‐optical recording

We have used a numerical model of thermomagnetic recording to investigate direct overwrite by domain destabilization in magneto‐optical thin films. Our model includes a linear dependence of domain wall velocity on the net wall pressure due to the demagnetizing field and the wall energy density. Direct overwrite by domain destabilization can be accomplished in one step, without bias fields or prior reading or erasure.

Parametric amplifiers in phase-noise-limited optical communications

Gordon and Mollenauer [ Opt. Lett.15, 1351 ( 1990)] have shown that the nonlinear Kerr effect limits the range of coherent communications systems using laser amplifiers. We show that parametric amplifiers avoid this limitation. Our method is novel in that we use quantum-optical master equations to model the communications systems. These are solved numerically for systems with either laser amplifiers or parametric amplifiers, with and without the nonlinear Kerr effect. Parametric amplifiers perform better because they preserve the signal-to-noise ratio and decrease the phase noise.

Collapse and three-body loss in a 85 Rb Bose-Einstein condensate

Collapsing Bose-Einstein condensates are rich and complex quantum systems for which quantitative explanation by simple models has proved elusive. We present experimental data on the collapse of high-density {sup 85}Rb condensates with attractive interactions and find quantitative agreement with the predictions of the Gross-Pitaevskii equation. The collapse data and measurements of the decay of atoms from our condensates allow us to put new limits on the value of the {sup 85}Rb three-body loss coefficient K{sub 3} at small positive and negative scattering lengths.

Squeezed light from conventionally pumped multilevel lasers.

We calculate amplitude squeezing spectra for the light from a variety of conventionally pumped three- and four-level lasers. Hence we extend a recent prediction that a certain three-level laser can generate nonclassical light without the need for rigged pumping.