Abstract

We consider a scheme for quantum nondemoliton (QND) measurements involving a cavity containing a Faraday rotator and a nonlinear crystal for (frequency degenerate) parametric downconversion into orthogonal polarizations. For the case of nondepletion of the pump field we analyze the coupled equations for the quadrature amplitudes of the fields using both semiclassical and quantum mechanical approaches. We show that when the magnitudes of the coupling coefficients κ of the crystal and σ of the Faraday rotator are appropriately chosen, the Hamiltonian of the system is of an ideal QND form for the intracavity field in the absence of dissipation. With the inclusion of cavity damping in the form of a single mirror of finite transmissivity, we demonstrate that information in the quadrature amplitude X₁ of one polarization of the incident field can be measured (in a QND sense) by monitoring the quadrature amplitude Y₂ of the orthogonal polarization.

© 1987 Optical Society of America