Generation and application of squeezed light

Abstract

This thesis investigates some aspects of future applications of squeezed states. Subsequent to an introductory part summarizing a few basic notions and facts related to squeezing, a detailed study of the generation of squeezed light and its effects in two different quantum optical systems is presented. Firstly a more technology-oriented application of squeezed states is discussed, namely a four-wave mixing optical rotation sensor. In an optical rotation sensor or “laser gyroscope” an external rotation is measured by means of the so-called Sagnac effect; that is one detects the relative phase shift which is induced between a co-rotating and a counter-rotating beam, when the cavity or fiber is in a state of rotation. It is demonstrated that the non-linearity in the fiber medium of a laser gyroscope can be used to produce squeezed light, which leads to a better signal to noise ratio in the subsequent heterodyne detection of the Sagnac phase shift. The major part of this thesis is dedicated to the analysis of the “squeezed reservoir laser”, which is of a more theoretical nature. The laser is treated as an open quantum system which is coupled to a squeezed environment. Both possibilities have been investigated: squeezing the reservoir which models the incoherent pumping process and the spontaneous emission or, alternatively, squeezing the other heatbath, modelling the vacuum modes entering the laser cavity. The analysis includes a detailed discussion of the semiclassical theory, the rotating wave van der Pol oscillator model for the squeezed reservoir laser, the derivation of the laser linewidth and the calculation of the spectrum of fluctuations from a linearized theory. Two main results are the locking of the laser phase due to the anisotropy of the fluctuations in the squeezed reservoirs and the possibility of generating squeezed laser light.