Coherent amplifier design

Wataru Imajuku, Atsushi Takada

This paper investigates the gain characteristics of coherent optical amplifiers that amplify only one of two quadrature phase components in an input signal light according to the phase of pump light. It is constructed around a Mach-Zehnder interferometer with Kerr media. To heuristically obtain the design parameters of the coherent optical amplifier, small-signal analysis is adapted to the Mach-Zehnder interferometer with Kerr media. The theoretical results are then compared to experimental results and shown to agree well, which confirms the validity of this design approach. By utilizing low-loss and high-nonlinearity silica fiber as the Kerr medium and optimizing its length, a coherent optical amplifier is constructed that yields high-gain (up to 26 dB) operation.

Y. Yamamoto, Takaaki Mukai

Chuanxin Bian, Guofeng Zhang, Joseph H. W. Lee

The purpose of this article is to present an efficient coherent feedback control technique for squeezing enhancement of degenerate parametric amplifiers (DPAs). The feedback controllers to be designed are in the form of linear quantum stochastic systems which can be described by quantum feedback networks theory recently developed. The problem of squeezing enhancement is formulated as a non-convex constrained nonlinear programming problem, whose solution yields the coherent feedback controllers to be designed. Compared with the previous study, the proposed approach reveals clear advantage when DPAs are lossy, as is always the case in practice. Based on the recently developed quantum network synthesis theory, we show how the designed coherent feedback controllers can be implemented by means of quantum optical devices.

Crispin W. Gardiner, Matthew J. Collett

Valery S. Butylkin, Yu. G. Khronopulo, M F Shalyaev

Design calculations are given for image contrast amplifiers in which the saturation of an absorption line of a substance is used. Expressions are obtained for the optimal parameters of such amplifiers.

Vitaliy V. Shtykov, Sergey M. Smolskiy