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We experimentally investigate ghost imaging with bucket detection and point detection in which three types of illuminating sources are applied: (a) pseudo-thermal light source; (b) amplitude modulated true thermal light source; (c) amplitude modulated laser source. Experimental results show that the quality of ghost images reconstructed with true thermal light or laser beam is insensitive to the usage of bucket or point detector, however, the quality of ghost images reconstructed with pseudo-thermal light in bucket detector case is better than that in point detector case. Our theoretical analysis shows that the reason for this is due to the first order transverse coherence of the illuminating source.

We theoretically study the influence of degree of polarization (DOP) of thermal light on the contrast-to-noise ratio (CNR) of the reflective ghost imaging (RGI), which is a novel and indirect imaging modality. An expression for the CNR of RGI with partially polarized thermal light is carefully derived, which suggests a weak dependence of CNR on the DOP, especially when the ratio of the object size to the speckle size of thermal light has a large value. Different from conventional imaging approaches, our work reveals that RGI is much more robust against the DOP of the light source, which thereby has advantages in practical applications, such as remote sensing.

The exploration of 2D waveguide structures on optoelectronic materials is important for applications in integrated optics devices. In this work, 2D waveguides on the magneto-optical glass were fabricated via combining the carbon ion implantation and the femtosecond laser ablation. Firstly, the 1D waveguide was formed by the double energy (6.0+5.5) MeV carbon ion implantation with fluences of (8.0+4.0) × 1013 ions/cm2. Subsequently, the femtosecond laser ablation with 800-nm central wavelength and 1.0-kHz repetition rate was conducted on the 1D waveguide surface to manufacture 2D guiding structures. The end-facet images were captured by an optical microscope. The near-field modal profiles of the 2D waveguides were recorded by an end-face coupling system at near-infrared (976 nm) and visible (532 nm) bands. The research results provide the feasibility and the experimental basis for the preparation of a magneto-optical waveguide isolator.

The influence of detector response speed on the contrast-to-noise ratio (CNR) of reflective ghost imaging (RGI) is studied. To mimic the situation of a slow response detector, the illuminating speckle patterns are replaced with the sum of uncorrelated speckle patterns for each measurement. An expression for the CNR of RGI with added speckle patterns is derived. By employing a light projector to provide spatially incoherent structured illumination in a computational ghost imaging system, we perform computational RGI based on added speckle patterns. The experimental results show that when up to 40 uncorrelated speckle patterns are added together in each measurement, the CNR of computational RGI obtained from 5000 effective measurements remains almost the same as the conventional computational ghost imaging. The reason for this is that the image quality of RGI depends on the kurtosis of intensity fluctuation of speckle field instead of the contrast ratio of speckle pattern. The experimental results agree with the theoretical prediction.

We present theoretical analysis and experimental demonstration of near field and far field spatial correlations of thermal light. Similar to the inequality Δ x − Δ p + 1 for a two-photon entangled source, we obtain an inequality Δ x − Δ p − 1 which also concerns both photon position and transverse wavevector correlations of thermal light. To test this inequality, we carry out an experiment in which ghost diffraction and ghost imaging can be simultaneously observed without the aid of any lenses. Meanwhile, the inequality is examined experimentally.

Lau effect is a self-imaging formed in the far field of a pair of gratings illuminated by spatially incoherent light. We report the experimental demonstration of the second-order Lau effect with incoherently pseudo-thermal light. Spatially periodic structures were nonlocally superposed giving rise to interference patterns in intensity correlation measurement. The experimental results are in agreement with the theoretical analysis. The second-order Lau effect can be well understood by the unfolded version of the experimental setup where the bucket detection can be thought as the incoherent illumination in classical Lau effect.

Simultaneous slow and fast light can be realized all-optically by connecting a four-level closed-loop atom–light interaction scheme to Λ - type electromagnetically induced transparency system. Through manipulation of the relative phase of one of the coupling lights, probe light can be switched among dual-slow light, dual-fast light and simultaneous slow and fast light. A theoretical analysis based on dressed state picture is given.

The spatial correlation between signals arising from a pair of constituent transmitters in a spatial multiple-input–multiple-output (MIMO) system is investigated. General formulations for the spatial correlation functions considering Gaussian-beam waves and receiver aperture effects are given under weak turbulence condition. Based on the analytical expressions, we find that spatial correlation decreases with separation distance, but increases with receiver aperture sizes, turbulence strength and wavelengths. In particular, receiver aperture averaging effects can evidently increase the correlation. It is also shown that decreasing the beam widths can generally reduce the spatial correlation, and convergent beams have lower spatial correlation than their collimated counterparts. It is found that Gaussian beams with the Fresnel ratios larger than 1 have advantages in reducing both the spatial correlation and the beam scintillations.

Based on extended Huygens-Fresnel principle, analytical expressions of beam width and far-field angular spreading for electromagnetic Gaussian Schell-model (EGSM) beams propagating in atmospheric turbulence are obtained. The effects of coherence and polarization on beam spreading and directionality in atmospheric turbulence are investigated in detail. A condition is obtained under which beams with different degrees of spatial coherence and polarization will generate the same far-field angular spreading in atmospheric turbulence. Our results have potential application in long-distance free space optical communications.

The bit-error-rate (BER) performance of coherent free-space optical (FSO) links employing phase compensation techniques is investigated in weak non-Kolmogorov turbulence. Assuming that the amplitude fading and phase fluctuation follow lognormal model and Gaussian distribution respectively and using the expression of non-Kolmogorov turbulence in terms of Zernike polynomials, the signal-to-noise ratio (SNR) at the coherent receiver is analyzed and as a special case, a new closed-form expression using chi-square distribution is obtained. Thus, the influence of different compensation modes and normalized receiver diameter on BER performance is evaluated and an optimum normalized receiver diameter is suggested to achieve the minimum BER. Moreover, the impact of outer scale L 0 and the exponent value α in non-Kolmogorov spectrum is studied with the optimum diameter, which reveals that the BER has an obvious decrease with larger values of L 0 and α.

Based on the cross-spectral density matrix, closed form result for propagation equation of electromagnetic J 0 -correlated Schell-model beams (EJSMBs) through a paraxial optical system is obtained and the focusing properties are studied. Both numerical calculation and physical interpretation are obtained. It is found that a tunable dark hollow area, which has potential applications in optical trapping, can be obtained by altering the coherence parameter and the focal length. It is also shown that even though the original field is unpolarized, the beams can become fully polarized in the focal region with its width being tunable by changing the coherence parameter. The relevance of this work to applications such as coherent detection in optical communication is also discussed.

The anomalous spectral behaviors of partially coherent polychromatic hollow Gaussian Schell-model beams (HGSMBs) diffracted by a slit are investigated. Besides spectral switches, asymmetrical dual-peak spectral split and multi-peak spectral split are observed. In the vicinity of the positions where spectral switches occur, flat-topped spectrum can be obtained, the bandwidth of which is adjustable by changing the transverse coherence width and the observation position. The flat-topped spectrum has potential application for creating probe beams in optical metrology systems and generating broadband optical sources in fiber optic sensor interface systems.

On the basis of diffraction integral and the expansion of the hard-aperture function into a finite series of complex Gaussian functions, an approximate expression for spatially fully coherent polychromatic hollow Gaussian beams passing through aperture lens is obtained. Detailed numerical results indicate that remarkable spectral changes always occurs near the points where the field amplitude has zero value. The effects of truncation parameter, Fresnel number and the beam order on spectral shifts and spectral switches are investigated numerically.

Based on the Rayleigh diffraction integral and the expansion of the hard-aperture function into a finite series of complex Gaussian functions, an approximate analytical spectrum expression for a Gaussian schell-model (GSM) beam passing through an aperture is given. The spectral shifts and spectral switches of near-zone off-axis are studied. The effect of the coherence and hard-edge on the spectral behavior are also presented.

The propagation of flat-topped beam passing through a paraxial optical ABCD system is extended to partially coherent case and has been studied in detail. Based on Wigner distribution function (WDF), the irradiance distribution of partially coherent flat-topped beam is derived. Furthermore, two propagation parameters, such as M 2 -factor and Power in Bucket (PIB) are illustrated analytically and numerically.

The paraxial propagation of partially coherent beams with the Hermite–Gauss modes is investigated. A more generalized and simple expression of the mean-squared width and the beam propagation ratio ( M 2 ) of the beam with different mode order is obtained in terms of the cross-spectral density. Our results show that the higher order strengthens the variations of the mean-squared width and the beam propagation ratio for partially coherent beams, and the relation between the two parameters of partially coherent beams is independent of the coherence length.

Applying the analogies between beam propagation and pulse propagation, so-called space and time variance matrices are presented, respectively. Straightforwardly, characteristics of paraxial light beam propagation and pulse propagation are described in space and time variance matrices, respectively.

The presented paper points out that the ChG beam can be generated by using the graded phase mirror (GPM). The theory expressions of the amplitude and the phase of the ChG beams are derived, respectively. Subsequently, the phase function of the GPM is deduced, which is necessary to design the surface of the GPM. A procedure is proposed to design the geometrical parameters of the resonator to generate the desired ChG beam. The quality of the output beam can be nearly ideal due to the high selectivity of the GPM and the intracavity aperture. Furthermore, the thermal lensing and gain saturation are taken into accounts. Finally, the theory expression of the kurtosis at the waist plane is derived to point out that the profile of the ChG beams are platykurtic except for the case of b =0, which corresponds to the Gaussian beam.

So far, the elegant Hermite–Gaussian (EHG) beams and cosh-Gaussian (ChG) beams have been studied in detail, respectively. In this present paper, a more generalized beam containing this two beams is introduced and studied. Just as the more generalized cases for the standard Hermite–Gaussian (SHG) beams and ChG beams are called Hermite–cosh-Gaussian (HChG) beams, the more generalized cases for EHG beams and ChG beams are named elegant Hermite–cosh-Gaussian beams (EHChG). This kind of beam is also another special case in Hermite–sinusoidal-Gaussian (HSG) family as well as the HChG beam. An analytical solution of the EHChG beam propagating through a first-order ABCD system is derived. The closed form of M 2 -factor and the power in bucket are presented to characterize the quality of these beams, and correspondingly, the beam width and the curvature radius are expressed in terms of generalized ABCD law. Moreover, the kurtosis is employed to describe the sharpness of the EHChG beams and its variation versus the propagation distance is plotted numerically.

We study the influence of space-time focusing (STF) on spatiotemporal instability (STI) in nonlinear dispersive media using a modified (3 + 1)-dimensional nonlinear Schrodinger equation (NLSE). We find that, for both normal and anomalous group-velocity dispersions (GVD), STF exerts no influence on the maximum gain of instability spectra, yet alters the instability regions fundamentally. In the normal GVD case, STF significantly shrinks the instability region by suppressing the growth of the higher frequency components; while in the anomalous GVD case, it slightly shrinks the original instability region obtained from the standard (3 + 1)-dimensional NLSE. Most importantly, in both cases, STF may lead to the appearance of new instability regions. Expressions for temporal frequency widths for new instability regions dependent on spatial frequency and STF parameter are obtained. In addition, we find that, the main role played by self-steepening (SS) in STI is that it reduces the instability gain and, comparatively, it exerts much more influence on the new instability region resulted from STF.

In this present comments, we have two questions about “the Propagation properties of Hermite-cosh-Gaussian (HChG) laser beams” in Opt. Commun. 186 (2000). One is Eq. (16) in [Opt. Commun. 186 (2000) 269] and its consequent derivation. The other is the method applied to generate the HChG beams.