Double-slit interference experimental platform based on a Sagnac interferometer.

In this paper, we build a Young's double-slit experimental platform with adjustable multiparameters by inserting a single slit in a Sagnac interferometer. Our experiment proves that this platform can easily control the parameters related to double slits. In addition, a new, to the best of our knowledge, type of double-slit experiment is performed on the platform. Our approach provides a detailed conceptual and experimental analysis for wave-particle duality and will be useful for research on quantum optics.

Sub-Rayleigh dark-field imaging via speckle illumination.

We demonstrate sub-Rayleigh dark-field imaging via speckle illumination. Imaging is achieved with second-order autocorrelated measurement by illuminating objects with hollow conical pseudothermal light. Our scheme can work well for highly transparent amplitude objects, pure phase objects, and even more complex transparent objects. The autocorrelated dark-field images show better resolution than intensity-averaged images and an ability in filtering out low-frequency noises.

Observation of positive-negative sub-wavelength interference without intensity correlation calculation.

We report an experimental demonstration of positive-negative sub-wavelength interference without correlation. Typically, people can achieve sub-wavelength effects with correlation measurement no matter by using bi-photon or thermal light sources. In this paper, we adopt a thermal light source, and we count the realizations in which the intensities of the definite symmetric points are above or below a certain threshold. The distribution of numbers of these realizations which meet the restriction will show a sub-wavelength effect. With proper constrictions, positive and negative interference patterns are demonstrated.

Dark-field ghost imaging.

Ghost imaging is a promising technique for shape reconstruction using two spatially correlated beams: one beam interacts with a target and is collected with a bucket detector, and the other beam is measured with a pixelated detector. However, orthodox ghost imaging always provides unsatisfactory results for unstained samples, phase objects, or highly transparent objects. Here we present a dark-field ghost imaging technique that can work well for these "bad" targets. The only difference from orthodox ghost imaging is that the bucket signals rule out the target's unscattered beam. As experimental proof, we demonstrate images of fine copper wires, quartz fibers, scratched and damaged glass plates, a pure phase object, and biospecimens.

Mode conversion via wavefront shaping.

In recent years, wavefront shaping has been utilized to control and correct distorted light for enhancing a bright spot, generation of a Bessel beam or darkening a complete area at the output of a scattering system. All these outcomes can be thought of as enhancing a particular mode of the output field. In this letter, we study the relation between the attainable enhancement factor, corresponding to the efficiency of mode conversion, and the field distribution of the target mode. Working in the limit of a thin diffuser enables not only a comparison between experimental and simulated results, but also allows for derivation of an analytic formula. These results shed light on the ability to use a scattering medium as a mode converter and on the relationship between the desired shape and the efficiency.

Multimode quantum states with single photons carrying orbital angular momentum.

We propose and experimentally demonstrate a scheme for generating multimode quantum states with single photons carrying orbital angular momentum (OAM). Various quantum states have been realized by superposing multiple OAM modes of single photons in two possible paths. These quantum states exhibit NOON-like "super-resolving" interference behavior for the multiple OAM modes of single photons. Compared with the NOON states using many photons, these states are not only easily prepared, but also robust to photon losses. They may find potential applications in quantum optical communication and recognizing defects or objects. The method to identify a particular kind of defect has been demonstrated both theoretically and experimentally.

Two-photon Lau effect.

The Lau effect is an interference phenomenon in which two transmission gratings are located in tandem and illuminated incoherently. Here we report the experimental observation of the quantum Lau effect using a two-photon entangled source. Two experimental schemes are proposed and performed. In one scheme, two gratings are nonlocally set in two different paths of two field modes. However, in the other scheme, only one grating is employed to receive the two-mode photons. In both schemes, the Lau interference patterns can be reproduced in a two-photon coincidence measurement where one photon is collected by a bucket detector.

Experimental observation of quantum Talbot effects.

We report the first experimental observation of quantum Talbot effects with single photons and entangled photon pairs. Both the first- and second-order quantum Talbot self-images are observed experimentally. They exhibit unique properties, which are different from those produced by coherent and incoherent classical light sources. In particular, our experiments show that the revival distance of two-photon Talbot imaging is twice the usual classical Talbot length and there is no net improvement in the resolution, due to the near-field effect of Fresnel diffraction, which is different from the case of previous proof-of-principle quantum lithography experiments in the far field.