Sub-shot-noise Interferometry using Amplitude Squeezed Light from an Injection-locked Semiconductor Laser.

Huazhen Wang, MJ Freeman, Duncan G. Steel +2 more

Daniel C. Kilper

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.

Jungsang Kim, Seema Somani, Y. Yamamoto

Steven Kasapi, Seema Lathi, Y. Yamamoto

We have demonstrated sub-shot-noise FM spectroscopy on thermal cesium atoms, using amplitude-squeezed light from a semiconductor laser. The light source used in our experiment was a custom-made GaAs transverse junction stripe semiconductor laser featuring broadband amplitude squeezing and a large FM bandwidth. We have also developed a new technique by which a semiconductor laser can be frequency modulated with infinitesimally small residual AM and with complete preservation of the squeezed-amplitude fluctuations.

Jean-Luc C. Vey, Wolfgang E. Elsaesser

Steven Kasapi, Seema Lathi, Y. Yamamoto

We have developed a frequency-modulated, tunable, amplitude-squeezed, diode-laser-based source and used it to perform FM spectroscopy on rubidium. The setup consists of a free-running diode laser injection locked by a frequency-stabilized, current-modulated diode laser. The injection-locked slave laser beam adopted the frequency spectrum of the master laser beam while rejecting residual AM in the master laser beam by more than 50 dB. Injection locking also enhanced amplitude squeezing in the slave laser beam by suppressing uncorrelated longitudinal sidemodes. The noise floor of the measurement was 0.8 dB below the shot-noise level.