On the detection of single mode quantum coherence at optical frequencies

Philippe B. Gallion, Francisco Javier Mendieta, R. Leconte

The phase noise affecting the beat photocurrent produced by coherent detection of a single-frequency laser field with a time-delayed and frequency-shifted image of itself in a heterodyne two-wave interferometric system using a single-mode optical fiber is investigated as a function of source spectrum and phase-decorrelation time under the assumptions of quantum laser phase noise and high-local-oscillation level. The influence on the photocurrent spectrum of partial correlation between detected fields is pointed out. These calculations are an extension of a previously reported high-resolution spectroscopic method and account for the phase-noise limitation in unbalanced heterodyne fiber sensors and heterodyne-transmission receivers with an optical reference wave generated from the received signal. An experimental study is reported consisting of a Mach–Zender-type interferometer employing a single-frequency amplitude-stabilized laser, an acousto-optical single-side-band modulator for frequency shifting one of the arms, and several lengths of single-mode optical fiber to decorrelate the detected fields partially. Results are found to be in good agreement with theory.

Daniel F. Walls, Gerard J Milburn

Roy J. Glauber

Mojtaba Moazzezi, Yuri V. Rostovtsev

Using quantum coherence effects, we have developed a new technique of detection of motion of single atoms or ions in an optical cavity. We have theoretically demonstrated that the presence of a single atom or ion inside cavity leads to a shift in cavity frequency and phase of transmitted probe beams. It has been shown by the use of EIT technique, the change of the phase is extremely sensitive to probe detuning in the vicinity of resonance frequency and can be in the order of 10−4.

Nicolas K. Fontaine, Ryan P. Scott, J.P. Heritage +1 more

Four-quadrature spectral interferometry using balanced coherent detection enables single-shot full-field characterization of complex-shaped optical waveforms with near quantum-limited sensitivity. A 90 degrees optical hybrid places a waveform in four-quadrature-phases with a stronger, well-characterized reference pulse. Measurement of the four spectra with an integrating two-dimensional detector array followed by balanced detection uniquely determines the signal field. Balanced coherent detection provides common-mode noise rejection and coherent gain enabling near quantum-limited sensitivity. The single-shot waveform was temporally gated from a 100 ps periodic train of arbitrary optical waveforms generated using line-by-line pulse shaping on a 10 GHz optical frequency comb. The measurements show arbitrary waveforms with 200-ps record lengths, 500 GHz optical bandwidths and only 1200 detected photons.

Richard M. Sillitto