Metasurface Glass for Wireless Communication and Energy Saving.

With the growing global energy demand and environmental issues, energy saving technologies are becoming increasingly important in the building sector. Conventional windows lack energy saving and thermal insulation capabilities, while Low emissivity glass (Low-e glass) attenuates mobile communication signals while reflecting infrared. Therefore, this paper aims to design a type of windows for the "Sub 6GHz" frequency band of 5G. These windows combine the inherent transparency of traditional glass windows with the energy saving properties of Low-e glass, while also ensuring optimal communication performance within the 5G (Sub 6G) band. The metasurface glass is fabricated and subjected to simulation-guided experiments to evaluate their reliability and practicality. The metasurface glass is rigorously assessed in terms of microwave transmission performance, infrared low emissivity performance, and energy saving and thermal insulation capabilities.

Transparent broadband absorber based on a multilayer ITO conductive film.

Present study reports a novel visible-light transparent, microwave broadband absorbing metamaterial. The designed structure is implemented using three different sizes of indium tin oxide (ITO) conductive film patch arrays, which is capable of achieving a reflection coefficient ≤ -10 dB from 2.2 to 18 GHz in simulations. Moreover, a fractional bandwidth of about 156.4% and the absorber thickness of only 0.088 times the cutoff wavelength (the lowest absorption frequency) was achieved. Changing the angle of incidence ensures a good absorption effect with large angle stability, and the absorber has good transmission in the visible range. In accordance with the simulation, a sample with a size of 299 × 299 mm was fabricated, and its wave absorption performance was assessed. The experimental results and the various incidence angles in the simulation of the TE and TM modes correspond well, allowing for the realization of large angle broadband absorption at frequencies ranging from 2.2 to 18 GHz. Thus, it has been found that the structure has good optical transparency and broadband radar absorption capability, both of which will have a wide range of applications in the fields of multi-spectrum stealth and electromagnetic compatibility.

High-quality and high-diversity conditionally generative ghost imaging based on denoising diffusion probabilistic model.

Deep-learning (DL) methods have gained significant attention in ghost imaging (GI) as promising approaches to attain high-quality reconstructions with limited sampling rates. However, existing DL-based GI methods primarily emphasize pixel-level loss and one-to-one mapping from bucket signals or low-quality GI images to high-quality images, tending to overlook the diversity in image reconstruction. Interpreting image reconstruction from the perspective of conditional probability, we propose the utilization of the denoising diffusion probabilistic model (DDPM) framework to address this challenge. Our designed method, known as DDPMGI, can not only achieve better quality but also generate reconstruction results with high diversity. At a sampling rate of 10%, our method achieves an average PSNR of 21.19 dB and an SSIM of 0.64, surpassing the performance of other comparison methods. The results of physical experiments further validate the effectiveness of our approach in real-world scenarios. Furthermore, we explore the potential application of our method in color GI reconstruction, where the average PSNR and SSIM reach 20.055 dB and 0.723, respectively. These results highlight the significant advancements and potential of our method in achieving high-quality image reconstructions in GI, including color image reconstruction.

Observing two-photon subwavelength interference of broadband chaotic light in a polarization-selective Michelson interferometer.

We demonstrated a method to achieve the two-photon subwavelength effect of true broadband chaotic light in polarization-selective Michelson interferometer based on two-photon absorption detection. To our knowledge, it is the first time that this effect has been observed with broadband chaotic light. In theory, the two-photon polarization coherence matrix and probability amplitudes matrix are combined to develop polarized two-photon interference terms, which explains the experimental results well. To make better use of this interferometer to produce the subwavelength effect, we also make a series of error analyses to find out the relationship between the visibility and the degree of polarization error. Our experimental and theoretical results contribute to the understanding of the two-photon subwavelength interference, which shed light on the development of the two-photon interference theory of vector light field based on quantum mechanics. The characteristic of the two-photon subwavelength effect have significant applications in temporal ghost imaging, such as it helps to improve the resolution of temporal objects.

Controllable superbunching effect from four-wave mixing process in atomic vapor.

Correlation property of light limits the performance in related applications such as the visibility of ghost imaging or intensity interferometry. To exceed these performance limits, we here manipulate the degree of second- and higher-order coherence of light by changing controllable variables in four-wave mixing (FWM) process. The measured degree of second- and third-order coherence of the output light beams considerably exceed those of the incident pseudothermal light. Namely superbunching effects, g(2)(0) value up to 7.47 and g(3)(0) value up to 58.34, are observed experimentally. In addition, strong second- and third-order cross-correlation exist between the output light beams. Further insights into the dependence of superbunching light on the temperature of Rb vapor, the laser detuning and the optical power of all the incident light beams show that it can serve as a light source with a tunable superbunching degree.

Bi-frequency 3D ghost imaging with Haar wavelet transform.

Recently, ghost imaging has been attracting attention because its mechanism could lead to many applications inaccessible to conventional imaging methods. However, it is challenging for high-contrast and high-resolution imaging, due to its low signal-to-noise ratio (SNR) and the demand of high sampling rate in detection. To circumvent these challenges, we propose a ghost imaging scheme that exploits Haar wavelets as illuminating patterns with a bi-frequency light projecting system and frequency-selecting single-pixel detectors. This method provides a theoretically 100% image contrast and high-detection SNR, which reduces the requirement of high dynamic range of detectors, enabling high-resolution ghost imaging. Moreover, it can highly reduce the sampling rate (far below Nyquist limit) for a sparse object by adaptively abandoning unnecessary patterns during the measurement. These characteristics are experimentally verified with a resolution of 512×512 and a sampling rate lower than 5%. A high-resolution (1000×1000×1000) 3D reconstruction of an object is also achieved from multi-angle images.

Ptychographical intensity interferometry imaging with incoherent light.

Intensity interferometry (II), the landmark of the second-order correlation, enables very long baseline observations at optical wavelengths, providing imaging with microarcsecond resolution. However, the unreliability of traditional phase retrieval algorithms required to reconstruct images in II has hindered its development. We here develop a method that circumvents this challenge, which enables II to reliably image complex shaped objects. Instead of measuring the whole object, we measure it part by part with a probe moving in a ptychographic way: adjacent parts overlap with each other. A relevant algorithm is developed to reliably and rapidly recover the object in a few iterations. Moreover, we propose an approach to remove the requirement for a precise knowledge of the probe, providing an error-tolerance of more than 50% for the location of the probe in our experiments. Furthermore, we extend II to short distance scenarios, providing a lensless imaging method with incoherent light and paving a way towards applications in X-ray imaging.

Studying fermionic ghost imaging with independent photons.

Ghost imaging with thermal fermions is calculated via two-particle interference based on the superposition principle for different alternatives in Feynman's path integral theory. It is found that ghost imaging with fully polarized thermal fermions can be simulated by ghost imaging with fully polarized thermal bosons and classical particles. Photons in pseudothermal light are employed to experimentally study fermionic ghost imaging. Ghost imaging with thermal bosons and fermions is discussed based on the point-to-point (spot) correlation between the object and image planes. The employed method offers an efficient guidance for future ghost imaging with real thermal fermions, which may also be generalized to study other second-order interference phenomena with fermions.

The first- and second-order temporal interference between thermal and laser light.

The first- and second-order temporal interference between two independent thermal and laser light beams is discussed by employing the superposition principle in Feynman's path integral theory. It is concluded that the first-order temporal interference pattern can not be observed by superposing two independent thermal and laser light beams, while the second-order temporal interference pattern can be observed in the same condition. These predictions are experimentally verified by employing pseudothermal light to simulate thermal light. The relationship between the indistinguishability of alternatives and photons is analyzed. The conclusions are helpful to understand the interference of different kinds of light and the difference between the coherence properties of thermal and laser light.

Interactions of Airy beams, nonlinear accelerating beams, and induced solitons in Kerr and saturable nonlinear media.

We investigate numerically interactions between two in-phase or out-of-phase Airy beams and nonlinear accelerating beams in Kerr and saturable nonlinear media in one transverse dimension. We discuss different cases in which the beams with different intensities are launched into the medium, but accelerate in opposite directions. Since both the Airy beams and nonlinear accelerating beams possess infinite oscillating tails, we discuss interactions between truncated beams, with finite energies. During interactions we see solitons and soliton pairs generated that are not accelerating. In general, the higher the intensities of interacting beams, the easier to form solitons; when the intensities are small enough, no solitons are generated. Upon adjusting the interval between the launched beams, their interaction exhibits different properties. If the interval is large relative to the width of the first lobes, the generated soliton pairs just propagate individually and do not interact much. However, if the interval is comparable to the widths of the maximum lobes, the pairs strongly interact and display varied behavior.

Polarization dressed multi-order fluorescence of Pr³âº:Y2SiO5.

We report polarization dressed second-, fourth- and sixth-order fluorescence processes in a Pr(3+):Y2SiO5 crystal. By changing the polarization states of dressing fields and generating fields, the fluorescence baselines, suppression and Autler-Townes splitting of emission peaks can be controlled. The polarization dependencies of fluorescence generated from two inequivalent crystallographic sites are compared. The experimental results agree with the dressing theoretical calculations well.

Rydberg dressing evolution via Rabi frequency control in thermal atomic vapors.

We report for the first time the theoretical and experimental research on Rydberg electromagnetically induced transparency and second-order fluorescence dressing evolution by Rabi frequency control in thermal atomic vapors, in which the controlled results are well explained by the dressing effect and the Rydberg excitation blockade. Based on the certification of the Rydberg excitation blockade fraction through the dependence on principle quantum number n, we obtain dressing evolution curves, consisting of single-dressing and double-dressing in local and nonlocal blockade samples by scanning the probe and dressing fields. In addition, the competition between the Rydberg dressing second-order fluorescence and fourth-order fluorescence is first investigated. A corresponding theory is presented, which is consistent with the experimental results. Such blockade evolution regularity has potential applications in quantum control, and the Rydberg dressing may be useful for investigating multiple-body interactions, as well as for inducing short range interactions in Bose-Einstein condensates.

Observation of angle-modulated switch between enhancement and suppression of nonlinear optical processes.

We simultaneously investigate the four-wave mixing and the fluorescence signals via two cascade electromagnetically induced transparency (EIT) systems in atomic rubidium vapor. By manipulating the deflection angle between the probe beam and certain coupling beams, the dark state can extraordinarily switch to bright state, induced by the angle-modulation on the dressing effect. Besides, in the fluorescence signal, the peak of two-photon fluorescence due to classical emission and the dip of single-photon fluorescence due to dressing effect are distinguished, both in separate spectral curves and in the global profile of spectrum. Meanwhile, we observe and analyze the similarities and discrepancies between the two ground-state hyperfine levels F = 2 and F = 3 of Rb 85 for the first time.

Dressed multi-wave mixing process with Rydberg blockade.

We investigate the way to control multi-wave mixing (MWM) process in Rydberg atoms via the interaction between Rydberg blockade and light field dressing effect. Considering both of the primary and secondary blockades, we theoretically study the MWM process in both diatomic and quadratomic systems, in which the enhancement, suppression and avoided crossing can be affected by the atomic internuclear distance or external electric field intensity. In the diatomic system, we also can eliminate the primary blockade by the dressing effect. Such investigations have potential applications in quantum computing with Rydberg atom as the carrier of qubit.

Soliton pair generation in the interactions of Airy and nonlinear accelerating beams.

We investigate numerically the interactions of two in-phase and out-of-phase Airy beams and nonlinear (NL) accelerating beams in Kerr and saturable NL media, in one transverse dimension. We find that bound and unbound soliton pairs, as well as single solitons, can form in such interactions. If the interval between two incident beams is large relative to the width of their first lobes, the generated soliton pairs just propagate individually and do not interact. However, if the interval is comparable to the widths of the maximum lobes, the pairs interact and display varied behavior. In the in-phase case, they attract each other and exhibit stable bound, oscillating, and unbound states, after shedding some radiation initially. In the out-of-phase case, they repel each other and, after an initial interaction, fly away as individual solitons. While the incident beams display acceleration, the solitons or soliton pairs generated from those beams do not.

Electromagnetically induced transparency and fluorescence in blockaded Rydberg atomic system.

We investigate the interaction between dark states and Rydberg excitation blockade by using electromagnetically induced transparency (EIT), fluorescence, and four-wave mixing (FWM) signals both theoretically and experimentally. By scanning the frequency detunings of the probe and dressing fields, respectively, we first observe these signals (three coexisting EIT windows, two fluorescence signals, and two FWM signals) under Rydberg excitation blockade. Next, frequency detuning dependences of these signals are obtained, in which the modulated results are well explained by introducing the dressing effects (leading to the dark states) with the corrected factor of the Rydberg excitation blockade. In addition, the variations by changing the principal quantum number n of Rydberg state shown some interesting phenomena resulting from Rydberg blockade are observed. The unique nature of such blockaded signals can have potential application in the demonstration of quantum computing.

Suppression and enhancement of coexisting super-fluorescence and multi-wave mixing processes in sodium vapor.

Different aspects of the properties of the coexisting super-fluorescence (SFL), multi-wave mixing with the fluorescence signal in the sodium vapor are studied both theoretically and experimentally. First, by scanning the dressed-state, the properties of these coexisting processes, such as the SFL signal modulated by using the dark and bright states, the interplay between dressed-states, are observed for the first time. Then, by scanning the probe field, the interplay between the one-photon and two-photon processes of the coexisting signals is obtained with or without the external dressing fields. Such control on each process in such coexisting system has an important potential application in quantum communication.

Four-wave-mixing between the upper excited states in a ladder-type atomic configuration.

Four-wave-mixing (FWM) radiation is generated between the hyperfine structures of the 5D and 5P states in a thermally broadened rubidium atomic vapor using resonant atomic coherence. Background-free unidirectional signals having narrow spectral linewidths are isolated and experimentally studied in the frequency domain, and the effects of the driving beam parameters on the properties of the radiation are discussed. The radiation has several new properties compared to traditional FWM radiations generated between the 5P and 5S states. The high-resolution signals obtained in this method could make it favorable in spectroscopic procedures that rely on two-photon fluorescence.

Observation of multi-component spatial vector solitons of four-wave mixing.

We report the observation of multi-component dipole and vortex vector solitons composed of eight coexisting four-wave mixing (FWM) signals in two-level atomic system. The formation and stability of the multi-component dipole and vortex vector solitons are observed via changing the experiment parameters, including the frequency detuning, powers, and spatial configuration of the involved beams and the temperature of the medium. The transformation between modulated vortex solitons and rotating dipole solitons is observed at different frequency detunings. The interaction forces between different components of vector solitons are also investigated.

Controlling cascade dressing interaction of four-wave mixing image.

We report our observations on enhancement and suppression of spatial four-wave mixing (FWM) images and the interplay of four coexisting FWM processes in a two-level atomic system associating with three-level atomic system as comparison. The phenomenon of spatial splitting of the FWM signal has been observed in both x and y directions. Such FWM spatial splitting is induced by the enhanced cross-Kerr nonlinearity due to atomic coherence. The intensity of the spatial FWM signal can be controlled by an additional dressing field. Studies on such controllable beam splitting can be very useful in understanding spatial soliton formation and interactions, and in applications of spatial signal processing.