a Langevin Equation Approach to Squeezed States of Light.

Francisco Javier Bermejo, P. García Fernández, Pere Colet +3 more

Pierre Meystre, Murray Sargent

Trevor W. Marshall, Emilio Santos

We show that the Langevin equation for a nonlinear-optical system may be obtained directly from the Heisenberg equation of motion for the annihilation operators, provided a certain linearization procedure is valid. We apply the technique to the parametric oscillator used to generate squeezed light and compare our results to those obtained from Fokker-Planck-type equations. We argue that, only when the Wigner, as opposed to the P or Q, representation of quantum optics is used, do we get a correct description of the underlying stochastic process. We show how the linearization procedure may be carried out to describe the operation of the parametric oscillator both below threshold, where a squeezed vacuum state results, and above threshold, where we find a squeezed coherent state. In the region of the threshold a heuristic extension of the method leads to a possible description of the system by means of a nonlinear Langevin equation.

Daniel F. Walls

Misrak Getahun, Edris Salih

We study the squeezing properties of the light generated by nondegenerate three-level laser in which the three-level atoms are in cascade configuration with degenerate parametric oscillator. We obtain the c-number Langevin equations associated with the normal ordering using the pertinent master equation. Making use of the solutions of the c-number Langevin equations, we calculate the quadrature variances. The results show that the two-mode light produced by the system under consideration is in squeezed state and the squeezing occurs in the minus quadrature. The degree of squeezing increase with the linear gain coefficient and almost perfect squeezing can be obtained for large values of the linear gain coefficient and the atoms initially prepared in lower level slightly greater than in the upper level. Moreover, the presence of nonlinear crystal increases the degree of squeezing for single mode and two-mode lights.

Daniel B. Erenso, Reeta Vyas, Surendra Singh

A quantum well with a single exciton mode in a microcavity driven by squeezed vacuum is studied in the low exciton density regime. By solving the quantum Langevin equations, we study the intensity, spectrum, and intensity correlation function for the fluorescent light. An expression for the Q function of the field inside the cavity is derived from the solutions of the quantum Langevin equations. Using the Q function, the intracavity photon number distribution and the quadrature fluctuations for both the cavity and fluorescent fields are studied. Several interesting and new effects due to squeezed vacuum are found.