Production of orbital angular momentum states of optical vortex beams using a vortex half-wave retarder with double-pass configuration.

Higher orders of orbital angular momentum states (OAMs) of light have been produced with a double-pass configuration through a zero-order vortex half-wave retarder (VHWR). This double-pass technique can reduce the number of VHWR plates used, thus reducing costs. The OAM states of the vortex beams are identified by the near-field Talbot effect. Polarization dependence of the vortex states can also be demonstrated with this VHWR using Talbot effect. Without using the Talbot patterns, this effect of the polarization on the vortex beam can not be recognized. A theoretical validation has also been provided to complement the experimental results. Our study gives an improved understanding of this approach to use a VHWR plate.

High-precision grating period measurement.

We introduce a method for measuring a periodic structure, particularly a grating period. The method is based on the high-precision laser Talbot effect. The combination of a rubidium-locked external cavity diode laser and the Talbot interferometer provides an excellent and simple tool for this purpose. Some experimental results are provided to demonstrate the approach.

High-contrast optical vortex detection using the Talbot effect.

We apply the near-field Talbot effect to distinguish, characterize, and detect optical vortices. We perform experiments with single-, double-, multiple-slit, and grating diffraction. High-contrast image detection is achieved with the Talbot effect of a grating, even for higher than l=±1 orbital angular momentum states. Furthermore, we manipulate the vortex beam with different vortex states and use the Talbot effect for detecting. The experimental results are supported by theoretical simulations and demonstrate that the Talbot effect provides an excellent tool for optical vortex detection.

Realization of the single photon Talbot effect with a spatial light modulator.

We demonstrate the quantum Talbot effect using a beam of single photons produced by parametric down conversion. In contrast to the previous works, we use a programmable spatial light modulator to behave as a diffraction grating. Thus, the investigation of the Talbot diffraction patterns under the variation of grating structure can be easily performed. The influence of spectral bandwidth of the down-converted photons on the diffraction pattern is also investigated. A theoretical model based on the wave nature of photons is presented to explain the Talbot diffraction patterns under varying conditions. The measured diffraction patterns are in good agreement with the theoretical prediction. We are convinced that our study improves the understanding of the quantum Talbot effect.