Table of contents

The authors have observed a quantum noise reduction of 69% around 2 MHz on the intensity difference between the two beams generated by a non-degenerate optical parametric oscillator operating above threshold.

Local and global deadtime effects in imaging photon detectors are studied. A local deadtime is defined in the general sense that an event in one pixel generates deadtimes in itself and among neighbouring pixels of arbitrary proximity to that pixel. The case resulting from an arbitrary but stationary intensity distribution is considered. Both simple and probabilistic non-paralysable models are used to derive expressions for the reduced mean count rates. In certain limits and derived expressions are shown to reduce to previously published results. The validity of the expressions are confirmed by comparison with the results of computer simulations.

Presents an analysis of a two-photon double-beam bistable device, in the dispersive and high-finesse limits. The expressions for the mean fields inside the cavity are given above the destabilization thresholds, and quantum fluctuations of the outcoming fields are analyzed below these thresholds. It appears that this device yields several new quantum noise reduction schemes, which are closely related to the mean fields behaviour.

The authors derive the equation of motion for the field density matrix of the non-degenerate two-photon laser under conditions of two-photon resonance starting from the full microscopic hamiltonian. They calculate the mean photon numbers and establish which solutions are stable. The results are compared with the corresponding quantities obtained from the effective hamiltonian. In general, there are significant differences. It is shown how the full diagonal density matrix equations tend to the effective hamiltonian density matrix equations in an appropriate limit. The same limit applied to the microscopic off-diagonal elements does not however give the off-diagonal equations of motion obtained in the effective hamiltonian approach. The off-diagonal elements determine, for example, the laser linewidths and cross-correlation coefficient so that the effective hamiltonian approach leads to correct results for these quantities. The results show that for a full understanding of the two-photon laser, the microscopic approach is essential.

Berry's phase for photons is derived from Maxwell's theory and is shown to be classical. The approach is geometrically obvious and is shown to be equivalent to those of F.D.M. Haldane (1987) and J. Segert (1987). The phase remains the same for plane wave solutions in the Heisenberg-Euler nonlinear electrodynamics.

The author has found solutions in the Heisenberg representation for the basic operators of the Jaynes-Cummings model with intensity-dependent coupling. The dipole-dipole correlation function has been evaluated for the most general initial state of the atom-field system. The atomic inversion for various initial states of the cavity field has been obtained in a closed form for the resonant case.

A full multimode theory for parametric down-conversion is used to calculate the two-photon detection amplitude. From this amplitude a heuristic argument is given for the configuration space extent of the single photons that are involved. These single phonons have a configuration space localisation consistent with an asymptotic fall off with distance r or r^-5/4 in the radial direction.

The possible use of parametric fluorescence photon slipping in range measurement experiments is described. In the proposed method a CW laser is used and the return travel time of individual photons is used to estimate the range. A signal to noise ratio analysis is presented and comparisons are made with the conventional optical method of pulsed range finding. Conditions under which a photon splitting technique could be advantageous are established.