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Hu X.,Columbia University | Hu X.,Massachusetts Institute of Technology | Hu X.,Tianjin University | Hu X.,Key Laboratory of Opto Electronic Information Science and Technology | And 8 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics

We present an investigation of the temporal correlation of time-energy entangled photon pairs propagating through multi-frequency-channel dispersive media, in which photon spectra spread over multiple discrete frequency channels with dispersions. We have observed more complex coincidence structures including double coincidence envelopes and dependence on frequency detuning that are absent in the single-channel case. Our results on the correlation of the time-energy photonic entanglement in dispersive media with channel divisions would impact the fields of quantum metrology and communication. © 2015 American Physical Society. Source

Hu H.,Nankai University | Wang X.,Nankai University | Zhai H.,Key Laboratory of Opto Electronic Information Science and Technology
Journal of Physics D: Applied Physics

A pump-probe technique is employed to investigate the dynamic process of femtosecond laser ablation of silica glass, and three stress waves are observed inside the silica glass in the time-resolved shadowgraphs at a fluence of 40 J cm-2. It is believed that the first stress wave is a thermoelastic wave generated by thermal expansion, while the second and the third are generated subsequently by the mechanical expansions as a result of the extremely high pressure induced by the laser. By employing digital holography, the ablation crater is investigated to identify the ablation results, and high-density silica glass is found beneath the ablation crater, which is also the result of the laser-induced pressure. Furthermore, it is found that more stress waves will be generated at a higher fluence, and the thresholds for the generation of the first, second and third stress wave are measured to be about 2 J cm-2, 6 J cm-2 and 31 J cm-2, respectively. The theoretical calculation result shows that the laser-induced pressure increases with the increase in fluence and can be on the scale of TPa, and we believe a higher pressure will induce more mechanical expansions and therefore more stress waves. © 2011 IOP Publishing Ltd. Source

Kuang D.,Nankai University | Fang Z.,Key Laboratory of Opto Electronic Information Science and Technology
Proceedings of SPIE - The International Society for Optical Engineering

For the laser spot size, the blazed diffractive grating fabricated with direct laser writing will has a slantwise lateral facet edge. To evaluate the influence of the slope of the facet edge of blazed diffractive grating, we calculate the diffraction efficiencies in +1 order and zero order as a function of the angle for the slantwise lateral facet edge with rigorous coupled wave analysis. As the lateral facet edge is getting more slantwise, the diffraction efficiency in +1 order decrease more, which degrades the image quality in monochromatic imaging. But the diffraction efficiency in zero order always keeps very low to assure the application in optical limiting. © 2010 Copyright SPIE - The International Society for Optical Engineering. Source

Ge J.-J.,Nankai University | Ge J.-J.,Key Laboratory of Opto Electronic Information Science and Technology | Wang Z.-Q.,Nankai University | Wang Z.-Q.,Key Laboratory of Opto Electronic Information Science and Technology
Chinese Physics Letters

In order to obtain the influence of the luminance at photopic level on the neural mechanism, a neural contrast sensitivity function (NCSF) measurement system is established. The contrast sensitivity function (CSF) of the visual system and the modulation transfer function (MTF) of the eye's optical system are first measured with correspondent instruments respectively. Then the NCSF is calculated as the ratio of CSF to MTF. Four individual eyes are involved in the cases of green light and white light. With increasing luminance, the tendency of the variation of the CSFs is similar to that of the NCSFs, while the gain is larger than that of the NCSFs, especially in the region of higher spatial frequency. It is the NCSF, rather than CSF, that reflects tie luminance sensitivity in the retina-brain neural system, because the influence of the eye's optical system is excluded. © 2011 Chinese Physical Society and IOP Publishing Ltd. Source

Rao F.,Nankai University | Rao F.,Key Laboratory of Opto Electronic Information Science and Technology | Wang Z.-Q.,Nankai University | Wang Z.-Q.,Key Laboratory of Opto Electronic Information Science and Technology | And 2 more authors.

Customized hybrid diffractive-refractive intraocular lens (IOL) has been designed based on an individual pseudophakic eye model constructed with the measured corneal topography data and the eye's axial lengths. The detailed designing and optimizing procedure is given. It is found that an eye with achromatic customized IOL would achieve super modulation transfer function (MTF) in both the scotopic and photopic conditions. The variation of MTF as colors is negligible, the chromatic focus shift is no more than 0.1 D, and the depth of focus is 3.0 D with quite high MTF. The achromatic customized IOL provides excellent visual performance for cataract patients. Moreover, individual pseudophakic eye model can be an effective tool for evaluating the optical performance of pseudophakic eye and the influence of clinical surgery deviation. © 2008. Source

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