Propagation of two beams through a birefringent calcite crystal is considered.Experiments are proposed the same as the ones performed with down conversion photons in nonlinear crystals.
In this work we investigate the spatial and frequency properties of the two-photon estates generated by spontaneous parametric down- conversion in uniaxial crystals of arbitrary length. As a basic tool we use Fourier optics in birefringent media. We present a detailed study of the Fourier optics in uniaxial anisotropic media of finite length. We determinethe quantum states generated in the process of spontaneous parametric down-conversion, considering the anisotropy of the non-linear crystal. We study in detail the transfer of properties from pump beam to the two-photon state and its dependence on anisotropy. We use this state to study the purity and entanglement in polarization, and its dependence with the crystal length, pump beam divergence, detector angular aperture and frequency bandwidth
We present a technique to excite Raman transitions with minimum phase noise. A phase modulator generates the Raman beams and a long calcite crystal rotates the polarization of the sidebands by 90° with respect to the carrier. That polarization converts the destructive interference of the Raman pairs into constructive interference, opening the possibility to drive both co-propagating and counter-propagating transitions at high detuning with the same setup. The technique has low phase noise and a low sensitivity to vibrations or temperature fluctuations. We apply it to drive velocity insensitive Raman transitions. The crystal can be also configured to filter out one of the sidebands.
Nonlinear photonic crystals can be used to provide phase matching for frequency conversion in optically isotropic materials. The phase-matching mechanism proposed here is a combination of form birefringence and phase velocity dispersion in a periodic structure. Since the phase matching relies on the geometry of the photonic crystal, it becomes possible to use highly nonlinear materials. This is illustrated considering a one-dimensional periodic Al0.4Ga0.6As/air structure for the generation of 1.5 microm light. We show that phase-matching conditions used in schemes to create entangled photon pairs can be achieved in photonic crystals.