De-Zhong Cao

Geometrical optics in correlated imaging systems

We discuss the geometrical optics of correlated imaging for two kinds of spatial correlations corresponding, respectively, to a classical thermal light source and a quantum two-photon entangled source. Due to the different features in the second-order spatial correlation, the two sources obey different imaging equations. The quantum entangled source behaves as a mirror, whereas the classical thermal source looks like a phase-conjugate mirror in the correlated imaging.

Experimental observation of classical subwavelength interference with a pseudothermal light source.

We report the experimental observation of classical subwavelength double slit interference with a pseudothermal light source. The experimental results are in good agreement with the theoretical simulation using the second order correlation function for the thermal light.

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.

Experimental observation of one-dimensional quantum holographic imaging

We report the experimental observation of quantum holographic imaging of one-dimensional object with entangled photon pairs, generated in a spontaneous parametric down-conversion process. The signal photons play both roles of “object wave” and “reference wave” in holography but are recorded by a point detector providing only encoding information, while the idler photons travel freely and are locally manipulated with spatial resolution. The holographic image is formed by the two-photon correlation measurement, although both the signal and idler beams are incoherent. Three types of quantum holography schemes are analyzed according to the detection regime of the signal photons.

Flexible Two-Photon Interference Fringes with Thermal Light.

Flexible interference patterning is an important tool for adaptable measurement precisions. We report on experimental results of controllable two-photon interference fringes with thermal light in an incoherent rotational shearing interferometer. The two incoherent beams in the interferometer are orthogonally polarized, and their wavefront distributions differ only in an angle of rotation. The spacings and directions of the two-photon interference fringes vary with the rotation angle, as illustrated in three cases of two-photon correlation measurements in experiment.