Polarization effects in nonlinear interference of down-converted photons.

We study polarization effects in the nonlinear interference of photons generated via frequency nondegenerate spontaneous parametric-down conversion. Signal and idler photons, which are generated in the visible and infrared (IR) range, respectively, are split into different arms of a nonlinear Michelson interferometer, and the interference pattern for signal photons is detected. Due to the effect of induced coherence, the interference pattern for the signal photons depends on the polarization rotation of idler photons, which are introduced by a birefringent sample. Based on this concept, we realize two new methods of measuring sample retardation in the IR range by using well-developed and inexpensive components for visible light. The methods' accuracy reaches specifications that are reported for industrial-grade optical elements. The developed IR polarimetry technique is relevant to material research, optical inspection, and quality control.

One-wavelength tuning method for a tunable optical filter based on a cascaded polarization interference filter.

A one-wavelength tuning method is proposed to solve the tuning difficulty in a tunable optical filter based on cascaded cells. This method ensures that the optical path difference variation of all of the cells for the tuning is less than one wavelength and lowers the relative tuning accuracy requirement. Simulations show that different cells have different cross talk and loss deterioration when they undergo an error in optical path difference between the O-ray and the E-ray. An optimal error ratio in each cell is obtained. Under the error ratio, the deterioration from the random error in every cell is further simulated.