High-impedance pump noise suppression was used to generate amplitude squeezing in an index-guided quantumwell laser. Light exhibiting photon-number noise 1.4 dB below the shot-noise limit was observed, and the corresponding polarization properties were examined. an unsaturated detector revealed 2.9 dB of squeezing.
Amplitude noise spectra from the nonclassical output of an injection-locked low-temperature quantum-well laser analyzed along orthogonal polarization axes reveals correlated polarization-dependent noise. Using polarization-preserving balanced homodyne detection to suppress these effects, we demonstrate photon-number fluctuations 4.5 dB below the semiclassical shot-noise limit (within 95% of the expected squeezing based on the device efficiency). Polarization mixing through birefringent components and, more significantly, correlated fluctuations originating in the laser gain medium are shown to account for the observations.
In this dissertation measurements are presented that extend our understanding of the important noise processes involved in the semiconductor laser generation of photon-number squeezed light. Strong sub-shot noise correlations between photon-number fluctuations on orthogonal polarization axes are observed in the output of a low temperature injection-locked quantum-well laser. Such polarization dependent effects are accounted for by intrinsic correlations generated in the laser gain medium and polarization mixing due to birefringence. Using polarization preserving balanced homodyne detection, up to 4.5 dB of photon-number squeezing is reported, which is within 95% of the expected maximum squeezing based on the device quantum efficiency. The work in this dissertation demonstrates the application of such nonclassical fields to practical measurements that achieve sub-shot noise sensitivity. Coherent nonlinear optical spectroscopy with a photon-number squeezed probe field is used to measure the Urbach tail and exciton resonances in a GaAs/AlGaAs multiple quantum well with sensitivity below the semiclassical shot-noise limit. Direct drive current modulation of an injection-locked room temperature laser results in a nonclassical amplitude modulated field with a signal to noise ratio that exceeds the maximum ratio permitted for a classical source under equivalent modulation conditions.