Phase-sensitive reflection of squeezed vacuum field in optical cavity

Abstract

We experimentally investigate the optical cavity for various coupled regimes with an injected squeezed vacuum state. We measure the quantum fluctuation spectra of the reflected field of an optical cavity using the homodyne detection and present the spectral dependence on the absorption and dispersion properties of the cavity in the under-coupled, critically-coupled, and over-coupled regimes. The spectra lineshape is phase sensitive with the phase shift induced by the cavity. Moreover, we find that the over-coupled optical cavity has obvious advantage in the manipulation of quantum fluctuation.OCIS codes: 190.4360, 230.1150, 270.1670. doi: 10.3788/COL201210.091901.The optical cavity has a wide range of applications in scientific and commercial instruments, such as laser, spectroscopy, frequency stabilization, etc. An important property of optical cavity is its dispersive and absorptive response. A cavity can be over-coupled, criticallycoupled (impedance matched) [1] , or under-coupled. The phase of the field reflected from the cavity is also important for frequency lock acquisition [2−4] and optical pulse transmission. More specifically, on-resonance, over-coupled cavity results in slow light, whereas undercoupled cavity results in fast light, and critically-coupled cavity results in zero reflection [5−7] . The quantum noise of light can be manipulated by employing the optical cavity. Quantum sidebands of bright light beam are modified by the optical cavity, in which original quantum phase fluctuations of the incident bright beam are converted into amplitude fluctuations [3,8−13] (note that only amplitude fluctuations of bright light beam can be detected directly by the photodiode). The tomography of quantum states of bright light beam can be performed using this method [10,11] . The quantum fluctuation spectra of the subharmonic reflected field of a degenerate optical parametric amplifier (OPA) inside an optical cavity have been studied theoretically [14] and experimentally [15] , which is driven by the squeezed vacuum state. The quantum fluctuation spectra for an optical empty cavity and the two-coupled cavities with an injected squeezed vacuum state have also been investigated in Refs. [15] and [16]. In these works, only over-coupled cavity is considered since its phase response undergoes a 2π phase shift. In this letter, we experimentally study the quantum fluctuation spectra of the reflected field from an optical cavity with various coupled regimes when injecting the squeezed vacuum state systematically. The squeezed quadrature components of the reflected beam of the optical cavity are measured by choosing the phase of the local beam relative to the input squeezed vacuum state. We demonstrate how the absorption and dispersion properties of the cavity determine the quantum fluctuation spectra of the reflected field. To the best of our knowledge, this work is completely different from the most previous studies for bright light injecting an optical cavity [3,8−13] . An optical cavity is assumed to be a st...