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We propose and experimentally demonstrate a high-efficiency single-pixel imaging (SPI) scheme by integrating time-correlated single-photon counting (TCSPC) with time-division multiplexing to acquire full-color images at extremely low light level. This SPI scheme uses a digital micromirror device to modulate a sequence of laser pulses with preset delays to achieve three-color structured illumination, then employs a photomultiplier tube into the TCSPC module to achieve photon-counting detection. By exploiting the time-resolved capabilities of TCSPC, we demodulate the spectrum-image-encoded signals, and then reconstruct high-quality full-color images in a single-round of measurement. Based on this scheme, the strategies such as single-step measurement, high-speed projection, and undersampling can further improve the imaging efficiency., Comment: 5 pages, 4 figures

Background Long-term mechanical ventilation with hyperoxia can induce lung injury. General anesthesia is associated with a very high incidence of hyperoxaemia, despite it usually lasts for a relatively short period of time. It remains unclear whether short-term mechanical ventilation with hyperoxia has an adverse impact on or cause injury to the lungs. The present study aimed to assess whether short-term mechanical ventilation with hyperoxia may cause lung injury in rats and whether deferoxamine (DFO), a ferrous ion chelator, could mitigate such injury to the lungs and explore the possible mechanism. Methods Twenty-four SD rats were randomly divided into 3 groups (n = 8/group): mechanical ventilated with normoxia group (MV group, FiO2 = 21%), with hyperoxia group (HMV group, FiO2 = 90%), or with hyperoxia + DFO group (HMV + DFO group, FiO2 = 90%). Mechanical ventilation under different oxygen concentrations was given for 4 h, and ECG was monitored. The HMV + DFO group received continuous intravenous infusion of DFO at 50 mg•kg− 1•h− 1, while the MV and HMV groups received an equal volume of normal saline. Carotid artery cannulation was carried out to monitor the blood gas parameters under mechanical ventilation for 2 and 4 h, respectively, and the PaO2/FiO2 ratio was calculated. After 4 h ventilation, the right anterior lobe of the lung and bronchoalveolar lavage fluid from the right lung was sampled for pathological and biochemical assays. Results PaO2 in the HMV and HMV + DFO groups were significantly higher, but the PaO2/FiO2 ratio were significantly lower than those of the MV group (all p 2 and PaO2/FiO2 ratio between HMV + DFO and HMV groups did not differ significantly. The lung pathological scores and the wet-to-dry weight ratio (W/D) in the HMV and HMV + DFO groups were significantly higher than those of the MV group, but the lung pathological score and the W/D ratio were reduced by DFO (p Conclusions Mechanical ventilation with hyperoxia for 4 h induced oxidative injury of the lungs, accompanied by a dramatic reduction in the concentrations of SP-C and SP-D. DFO could mitigate such injury by lowering XOD activity and elevating GR activity.

This research presents a coherent structured illumination single-pixel imaging scheme to image objects with complex amplitudes. By utilizing a phase-only spatial light modulator for phase modulation, we can efficiently generate the Hadamard basis structured light and the reference light that interfere with each other to form the coherent structured illumination. Using the 4-step phase-shifting, the spectrum of the object is acquired by detecting the zero-frequency component of the object light with a single-pixel photodetector. The desired complex-amplitude image can be further retrieved by applying an inverse Hadamard transform. The proposed scheme is experimentally demonstrated by imaging two etched glass objects, a dragonfly wing, and a resolution test chart. Benefiting from the phase modulation, this scheme has a high efficiency, a high imaging quality, a high spatial resolution, and a simple and stable configuration to obtain both the phase and amplitude information of the target object. The proposed scheme provides a promising complex-amplitude imaging modality with single-pixel detection. Thus it might find broad applications in optical metrology and biomedical science.

Regarding a phase-only Fourier hologram, coherent illumination is required in its optical reconstruction. However, this requirement faces a challenge in lensless Fourier-transform correlated imaging with thermal sources. In this research, a correlated reconstruction scheme for the phase-only Fourier hologram with spatially incoherent illumination by utilizing intensity fluctuation correlation measurements is proposed. Numerical simulation and optical experiments were conducted to verify the feasibility of the correlated reconstruction scheme. Because the proposal requires neither a coherent light source nor a lens, holographic reconstruction can circumvent the limitation of the spatial coherence light source and the influence of lens aberrations.

Ghost imaging with thermal light inevitably has a noise background, which greatly decreases the visibility of the reconstructed image. In this paper we formulate a fundamental equation that the integration of the distribution of any ghost image equals a constant in relation to the coherence of the thermal light source. With this equation we strictly demonstrate that the average visibility of ghost imaging is inversely proportional to its image resolution. In the same time, this inherently inverse relation is verified by our numerical simulation and experimental results.

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.

We present an experimental realization of a compact and reliable way to build a nondegenerate polarization-entangled photon-pair source based on a dual-periodically-poled $ {\rm Ti}:{{\rm LiNbO}_3} $Ti:LiNbO3 waveguide, which is in the telecommunication window and compatible with the fiber quantum networks. The dual-periodic structure allows two inherently concurrent quasiphase-matching spontaneous parametric down-conversion processes pumped by a single laser beam, hence enabling our source to be compact and stable. We show that our source has a high brightness of $ B = 1.22{\rm } \times {\rm }{10^7}\;{\rm pairs}/(\rm s \times mW \times nm) $B=1.22×107pairs/(s×mW×nm). With quantum state tomography, we estimate an entanglement fidelity of $ 0.945 \pm 0.003 $0.945±0.003. A violation of Clauser-Horne-Shimony-Holt inequality with $ S = 2.75 \pm 0.03 $S=2.75±0.03 is also demonstrated.

The relationship between the imaging visibility of arbitrary Nth-order intensity correlation with thermal light and light’s degree of polarization is investigated. It is shown that for the same order correlation, the value of visibility with partially polarized light is greater than that with natural light but smaller than that with completely polarized light, and the visibility in all three cases is remarkably enhanced as N increases.

We perform an interference experiment in which a pseudo-thermal light beam illuminates two spatially separated apertures, whose superposition at the same place forms a double-slit. The experimental result exhibits a typical double-slit interference fringe in the intensity correlation measurement, in agreement with the theoretical analysis by means of the property of the second-order spatial correlation of field of the thermal light.

We propose an experimental scheme in which two orthogonally polarized thermal light beams with antisymmetrical wavefronts are overlapped. The experimental results demonstrate that this setup can focus the beam in two-photon and multiphoton correlation measurements. The focused ``two-photon'' spot possesses subwavelength resolution, surpassing the classical diffraction limit. Since the experimental setup consists of only two right-angle-mirror devices without the help of lenses, the two-photon focusing effect does not apparently rely on the beam focusing. Physically, the phenomenon signifies that the photon bunching can be localized within a very small region through two-photon interference in contrast to the conventional Hanbury Brown\char21{}Twiss effect of thermal light. In the higher-order intensity correlation measurement, the multiphoton bunching can be limited within a very small central region while the background is greatly suppressed.

The time-reversal process provides the possibility to counteract the time evolution of a physical system. Recent research has shown that such a process can occur in the first-order field correlation of chaotic light and result in the spatial interference and phase-reversal diffraction in an unbalanced interferometer. Here we report experimental investigations on the invisibility cloak and illusion phenomena in chaotic light. In an unbalanced interferometer illuminated by thermal light, we have observed the cloak effect and the optical transformation of one object into another object. The experimental results can be understood by the phase-reversal diffraction, and they demonstrate the theoretical proposal of similar effects in complementary media.

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.

We report an experiment in which the correlated imaging in an interferometer with chaotic light can be observed in the intensity pattern rather than the intensity correlation measurement. Similar to ghost imaging with thermal light, object and objective lens are not necessarily set in the same path. Moreover, the two imaging schemes satisfy the same imaging equation. The theoretical analysis shows that the correlated imaging of thermal light is ascribed to the first-order field correlation of the two separate paths, and as a result, it can also be performed through one-photon interference in an incoherent interferometer. Our experiment suggests a phase-sensitive imaging technique using a spatially incoherent light source.

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 phase reversal behavior in negatively refracting media., 8 pages, 5 figures

It is well known that direct observation of interference and diffraction pattern in the intensity distribution requires a spatially coherent source. Optical waves emitted from portions beyond the coherence area possess statistically independent phases, and will degrade the interference pattern. In this paper we show an optical interference experiment, which seems contrary to our common knowledge, that the formation of the interference pattern is related to a spatially incoherent light source. Our experimental scheme is very similar to Gabor's original proposal of holography[1], just with an incoherent source replacing the coherent one. In the statistical ensemble of the incoherent source, each sample field produces a sample interference pattern between object wave and reference wave. These patterns completely differ from each other due to the fluctuation of the source field distribution. Surprisingly, the sum of a great number of sample patterns exhibits explicitly an interference pattern, which contains all the information of the object and is equivalent to a hologram in the coherent light case. In this sense our approach would be valuable in holography and other interference techniques for the case where coherent source is unavailable, such as x-ray and electron sources., Comment: 8 pages, 5 figures

A pseudo-white-thermal light source is prepared by projecting three (red, green, and blue) laser beams onto a rotating ground glass disk. Based on the RGB color model, we investigate the color Hanbury-Brown-Twiss (HBT) effect and color ghost imaging with thermal light. The color HBT effect indicates that photons of the same color will bunch. This fact ensures the chromatic discrimination power of ghost imaging with thermal light. We retrieve the RGB ingredients of the object through intensity correlation measurements. A method of white balance to properly form the ghost images is proposed.

Incorporation of positive charges into the passivation layer has been shown to improve the drive current of n-channel offset-gate polysilicon thin film transistors (TFTs). Previously we have shown that hydrogen plasma treatment can induce such positive charges. In this paper we propose another method, i.e. ion implantation, to achieve the same goal. Cesium was chosen as the implanting element because it is easy to form a single positive ion and has relatively high atomic mass that prevents the penetration of ions into the underlying semiconductor layer. MOS capacitors were used to monitor the charging effect of Cs/sup +/ in the dielectric layer which was thermally grown silicon dioxide of thickness in the range of 100 to 300 nm. Results indicate that the fixed oxide charge density is proportional to the ion dosage; however, for a Cs dose over 1/spl times/10/sup 15/ cm/sup -2/ the MOS capacitors could not be accumulated easily. Increasing the ion energy was found to enhance the charging effect in the oxide layer; however, if the energy penetrates into the Si-SiO/sub 2/ interface, then the MOS capacitor was damaged by creating defects in the interface. A 20 times increase of drive Si TFTs with single passivation layer after a 1/spl times/10/sup 14/ cm/sup -2/ and 40 keV Cs implantation.

Here we present a pattern recognition scheme based on the intensity correlation of thermal light. We prove theoretically that under spatially incoherent illumination the matched filtering technique can be realized in the ghost imaging field. Using the matched filtering technique, it is possible to distinguish an object from a preestablished set of objects through their ghost images, which are extracted by means of intensity correlation measurement. According to the pattern recognition scheme, we present a numerical simulation in which we can easily identify the character inserted into the object arm from a set of two characters through the position of the autocorrelation peak. This pattern recognition scheme opens up the possibility of performing coherent optical processing under spatially incoherent illumination.

Few-layer graphene was transferred directly on top of Ag nanoparticles, and the coupling between graphene and localized surface plasmons (LSPs) of Ag nanoparticles was investigated. We found that the surface enhanced Raman spectroscopy of graphene was increased approximately 7-fold by near-fields of plasmonic Ag nanoparticles and the enhancement factor of graphene G peak increased with the particle size. Meanwhile, the LSP resonances of Ag nanoparticles exhibit a 10 nm redshift and a 13 nm broadening by the presence of graphene, which can be attributed to the coupling between the Ag LSPs and the graphene.

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.

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.