Su-Heng Zhang

Enhancing visibility and resolution in Nth-order intensity correlation of thermal light

The arbitrary Nth-order intensity correlation measurement with thermal light is both theoretically and experimentally investigated. In a double-slit interference scheme with thermal light, we compare the results for higher- and lower-order intensity correlation and demonstrate that the visibility of the interference pattern can be dramatically enhanced while the resolution can also be improved when the order N becomes larger. The experimental results are in agreement with our theoretical analysis.

Spatial Interference : From Coherent to Incoherent

We report an optical interference experiment which seems to contradict our common knowledge, in that the formation of the interference pattern originates from a spatially incoherent light source. Our experimental scheme is very similar to Gabors original proposal of holography [Nature (London) 161, 777 (1948)], except that an incoherent source replaces the coherent one. Though an instantaneous interference pattern between an object wave and reference wave fluctuates irregularly, a well-defined pattern appears in the statistical average, in accord with a hologram in the coherent light case.

Phase-reversal diffraction in incoherent light

Phase reversal occurs in the propagation of an electromagnetic wave in a negatively refracting medium or a phase-conjugate interface. Here we report the experimental observation of phase-reversal diffraction without the above devices. Our experimental results and theoretical analysis demonstrate that phase-reversal diffraction can be formed through the first-order field correlation of chaotic light. The experimental realization is similar to the phase-reversal behavior in negatively refracting media.

Cloaking of a phase object in ghost imaging

Ghost imaging is a nonlocal imaging technique in which the image or diffraction pattern of an object can be observed through the intensity correlation measurement other than the intensity itself. Here, we report the experimental observation of invisibility cloaking in ghost imaging with thermal light. We show that when two identical phase-modulated objects are placed at equal distances from the thermal light source, they are offset completely in ghost imaging. The experimental results can be understood through the phase conjugation established by the intensity correlation of thermal light.

Interference from a nonlocal double-slit through one-photon process

In this paper, we report an interference experiment in which a spatially incoherent light source illuminates two spatially separated apertures, whose superposition at the same place forms a double-slit. The experimental result exhibits a well-defined interference fringe solely through intensity measurements, in agreement with the theoretical analysis by means of the first-order spatial interference of the incoherent light. Consequently, the nonlocal double-slit interference with thermal light should be attributed to the first-order spatial correlation of incoherent field.