| Shot noise is a ubiquitous feature of physical measurements. The origin of optical shot noise, and methods for overcoming it, are quantum mechanical in nature. Despite its esoteric origins, shot noise is the fundamental noise source in almost any suitably quiet optical measurement, from remote controls in consumer electronics to high-power lasers in gravity-wave detection.;Semiconductor lasers allow electrical control of photon fluctuations. This dissertation describes the first spectroscopic experiments with sub-shot-noise light from semiconductor lasers and discusses several new techniques for stabilizing and modulating amplitude-squeezed semiconductor lasers.;The quantum mechanical origin of shot noise is briefly reviewed in the introduction. The discussion begins with a review of the quantum mechanical description of light, starting with a review of the classical description, followed by an overview of the quantum mechanical description of squeezed states.;The first experiment we performed was sub-shot-noise FM spectroscopy on an atomic vapor using an amplitude-squeezed semiconductor laser. This experiment was the first demonstration of non-classical spectroscopy with a semiconductor laser. The demonstration included a new technique for inducing pure frequency modulation sidebands on the output from a semiconductor laser using only pump current modulation. It also highlighted some of the advantages of using a semiconductor laser for ultra-low-noise measurements.;The second experiment used the large phase noise of output from a semiconductor laser to perform a novel, noise-based spectroscopy on an amplitude-squeezed background. Amplitude squeezing was critical for improving the signal-to-noise ratio since both the signal and the background noise are intrinsic properties of the semiconductor laser itself.;Perhaps one of the most striking aspects of these experiments is that they use mostly off-the-shelf optical components and semiconductor lasers. In contrast to most other sources of squeezing, semiconductor-laser-based squeezing is potentially very inexpensive and widely available. |
