Intracavity Frequency Doubling for the Generation of Squeezed States of Light

Abstract

While squeezed states of light represent a manifestation of the nonclassical character of the electromagnetic field and hence are of great intrinsic interest in quantum optics, there are as well a number of applications in measurement science associated with the possibility of sensitivity beyond the standard quantum limit. Given the landmark initial observation of this phenomenon by Slusher et al., a number of experimental groups are concentrating on making their own “first” observations and on subsequently exploring limitations on the degree of achievable and detectable squeezing. Most of the experimental research thus far has concentrated on squeezing produced by four-wave mixing, either in atomic vapors or in condensed media. The tack that we have taken is to investigate a completely different technique with a new set of potential advantages (and disadvantages). Our experiments attempt to produce squeezed states of light by second harmonic generation within an optical cavity resonant at both fundamental and harmonic frequencies. Of course the Hamiltonian describing the two-mode coupled system in the limit of a lossless medium is related to a broad class analyzed by Yuen, and hence it is not surprising that squeezing is predicted in this system. However, an issue that is of prime importance in our investigation is the extent to which these parametric models of quantized nonlinear processes are realistic. This issue is naturally entangled with a number of other technological and scientific questions that we are only beginning to unravel. We begin in Section II with an overview of the relevant theoretical predictions before turning in Section III to the actual experiment. Other contributions to this volume as well as review articles should be consulted for a more comprehensive view of the field.