Propagation-invariant beams have attracted major attention and presented applications in research areas such as particle acceleration, optical tweezers, and optical coherence tomography. On the basis of the introduced radial cosine phase gratings with high diffraction efficiency, this study observes a kind of novel shape-invariant radial lattice by assessing its Fresnel diffraction. Then, on the stationary phase principle, we originally construct and experimentally generate a family of new propagation-invariant (non-diffracting) radial lattices with polar symmetry. Their optical structures, propagation characteristics, and distinctive phase characteristics are studied. This study has important value for applying it in scientific fields in the future given that lattices have offered many applications, including optical communication in free space, quantum computation, quantum phase transition, spin–exchange interaction, and realization of magnetic fields.

Perfect Poincaré beams (PPBs) are highly esteemed for their topological charge-independent radius and intensity profile. However, the generation and manipulation of PPBs typically involve two-dimensional planes perpendicular to the optical axis, hindering broader usability. Here, leveraging a single-layer all-dielectric geometric metasurface platform, we numerically showcase the generation and manipulation of multiple multidimensional PPBs. Multiple dimensions of PPBs, involving orbital angular momentum (OAM), polarization state, and three-dimensional (3D) spatial propagation, can be manipulated independently via tailoring topological charges assigned to two orthogonal perfect vortex beam (PVB) components, varying initial phase difference and amplitude ratios between two orthogonal PVB components, and strategizing 3D propagation trajectories. To demonstrate the feasibility of the recipe, two metasurfaces are designed: one is for generating an array of PPBs with tailored polarization states along cylindrical helical trajectories, and the other is for creating dual arrays of PPBs with personalized OAM and polarization eigenstates across two misaligned focal planes. As a proof-of-concept illustration, we showcase an optical information encryption scheme through a single metasurface encoding personalized polarization states and OAM in parallel channels of multiple PPBs. This work endeavors to establish an ultra-compact platform for generating and manipulating multiple PPBs, potentially advancing their applications in optical encryption, particle manipulation, and quantum optics.

We experimentally demonstrate an optical isolator utilizing high-quality-factor whispering gallery modes in a yttrium iron garnet (YIG) microsphere, coupled with an integrated Si3N4 waveguide. By applying a magnetic field in the vertical direction of the resonator equator, we achieve the breaking of degeneracy between the clockwise (CW) and counterclockwise (CCW) modes, driven by photonic spin–orbit coupling (SOC) and the Faraday effect. The maximum wavelength separation observed is about 7.9 pm, comparable with the linewidth of the mode. The better effect of the refractive index matching between the YIG microsphere and the Si3N4 waveguide enables an isolation ratio of 16.9 dB under the critical coupling condition. This work presents a novel integrated approach for realizing non-reciprocity in photonic circuits, advancing the development of compact high-performance photonic devices.

Optical gyroscopes in microcavity platforms have attracted much attention for their vast applications. For Sagnac effect enhancement, the exceptional surface (ES) concept holds the potential to stabilize exceptional points (EPs), allowing for EP splitting amplification and robustness in sensors. We propose a new optical microcavity gyroscope near the ES. Under the mechanical mode assistance, theoretical analysis reveals its prominent advantages compared with conventional gyroscopes, especially achieving higher levels for extremely low rotational speeds. This breakthrough opens possibilities in high-precision angular velocity measurement, facilitating the development of more accurate and stable sensor technologies.

The exceptional temporal and spatial photon confinement properties of whispering gallery mode (WGM) microcavities render them ideally suitable for nonlinear frequency conversion. Here, we present a reliable packaged microcavity device with vibration isolation, air tightness, temperature adaptability, and quality factors greater than 2 billion that can serve as a compact and stable platform for soliton optical comb generation. Low-noise soliton combs can be initiated with a repetition rate of 24.98 GHz at wavelengths near 1550 nm with 4 mW threshold power. Our work provides innovative solutions for investigating and manufacturing miniature, economical, and robust microcomb devices.

Autofocusing beams are powerful photonic tools for manipulating micro/nanoparticles. Here, we propose a special type of dislocated-superimposed swallowtail vortex beam (DSVB) and analyze its propagation properties and optical manipulating capability. By modulating the parameters of the superposition number N and the topological charge l, DSVBs show asymmetric autofocusing propagation phenomena and unconventional orbital angular momentum (OAM), especially for opposite topological charges. Furthermore, when N = |l|, DSVBs form multiple solid focuses while preserving OAM during propagation, suggesting potential applications in multi-point trapping and rotational manipulation. These results deepen the understanding of autofocusing and OAM behaviors, highlighting DSVBs’ potential as photonic tools for optical manipulation.

We report the experimental observation of a three-dimensional abruptly autofocusing effect by synthesizing a radially distributed Airy beam with two counter-propagating Airy pulses in time. As the wave packet propagates in a dispersive medium, the radially distributed Airy beam converges inward to the center point. Two Airy pulses counter-propagate toward each other to merge to form a high-peak-power pulse. As a result, high intensity emerges abruptly as the wave packet achieves three-dimensional focusing. This autofocusing effect is believed to have potential applications such as material modification, plasma physics, and nanoparticle manipulations.

For bicolor regulation in laser protection compatible with visible light stealth, a metal–dielectric–enhanced reflection asymmetric Fabry–Perot structure is proposed that has high reflectance at the laser wavelength and the color control of the visible spectrum. The six-layer reflection enhancement unit is composed of an Al metal mirror, SiO2, Ta2O5, and an ultrathin Nb metal layer. The synergistic relationship between the background color and laser wavelength reflectance was analyzed and simulated. Six different colors from blue to red with high reflectance at 1064 nm laser wavelength up to 97.84% were prepared. The thin films can withstand 2535 W cm-2 power density continuous irradiation for 60 s without being destroyed. Moreover, a symmetrical structure presents the spectrum consistency from both directions, which makes the potential to be applied to the laser protective coatings. The blue symmetrical microreflector sample was prepared and sprayed on the nonplanar models to demonstrate the actual application effect. This simple and efficient scheme provides an innovative technical approach in the field of surface laser protection.

Under a specified loss condition, the resonant mode in a three-turn lossy microfiber coil resonator exhibits periodic evolution among normal resonance, white-light cavity effect, and resonance mode splitting in response to alterations in the phase shift and coupling state. It exhibits normal resonance when the coupling state exceeds a threshold with specific loss. The white-light cavity effect is activated when the coupling state matches loss. The resonant phase bifurcates as the coupling state falls below the threshold. The excitation conditions for each resonant mode have been derived, and the critical coupling conditions exist for both normal resonance and mode splitting in the case of relatively small losses.

Recently, the Fano resonance has played an increasingly important role in improving the color performance of structural colors. In this study, we further elucidate the asymmetric spectral shape generated by Fano resonance from a phase perspective and explore four distinct continuum state structures. By integrating the proposed cavity-like structure with a metal–dielectric–metal discrete state, multilayered thin-film structural colors with minimal background reflection, as low as 8%, were successfully achieved. The reflection peak of this structure exhibits a bandwidth of approximately 50 nm and reaches up to 80%, indicating heightened saturation and color brightness. Moreover, by adjusting the thickness, we effortlessly obtained a broader color gamut compared to Adobe RGB (45.2%), covering 56.7% of the CIE color space. Even adjusting a single layer can achieve a color gamut of 47.1%. In experiments, by deliberately choosing low oxygen-dependent materials, excellent RGB colors with high brightness and in high consistency with simulation results were successfully achieved. Therefore, the scheme’s simple process for structural color creation, along with its excellent color performance and the ability to effectively replicate simulation characteristics makes it highly valuable in fields like anticounterfeiting, decoration, display devices, and solar cell panels.

Frequency-modulated continuous-wave (FMCW) Lidar has the characteristics of high-ranging accuracy, noise immunity, and synchronous speed measurement, which makes it a candidate for the next generation of vehicle Lidar. In this work, an FMCW Lidar working at the single-photon level is demonstrated based on quantum compressed sensing, and the target distance is recovered from the sparse photon detection, in which the detection sensitivity, bandwidth, and compression ratio are improved significantly. Our Lidar system can achieve 3 GHz bandwidth detection at photon count rates of a few thousand, making ultra-long-distance FMCW Lidar possible.

In this work, we introduce a kind of new structured radial grating, which is named the even-type sinusoidal amplitude radial (ETASR) grating. Based on diffraction theory and the principle of stationary phase, a comprehensive theoretical investigation on the diffraction patterns of ETASR gratings is conducted. Theoretical results show that novel carpet beams with beautiful optical structures and distinctive characteristics have been constructed on the basics of the ETASR grating. Their diffraction patterns are independent of propagation distance, that is, the new carpet beams have diffraction-free propagating characteristics. The non-diffracting carpet beams are divided into two types by beam characteristics: non-diffracting integer-order and half-integer-order carpet beams. Subsequently, we experimentally generate these carpet beams using the ETASR grating. Finally, their particularly interesting optical morphology and features are explored through numerical simulations and experiments.

Based on the transverse-longitudinal mapping of Bessel beams, we propose a simple method to construct a self-similar Bessel-like beam whose transverse profile maintains a stretched form during propagation. Specifically, the propagating-variant width of this beam can be flexibly predesigned. We experimentally demonstrate three types of self-similar Bessel-like beams whose width variations are linear, piecewise, and period functions of propagation distance, respectively. The experimental results match well with the theoretical predictions. We also demonstrate that our approach enables the generation of self-similar higher-order vortex Bessel-like beams.

We numerically demonstrate that the tight focusing of Bessel beams can generate focal fields with an ultra-long depth of focus (DOF). The ultra-long focal field can be controlled by appropriately regulating the order of the Bessel function and the polarization. An optical needle and an optical dark channel with nearly 100λ DOF are generated. The optical needle has a DOF of ∼104.9λ and a super-diffraction-limited focal spot with the size of 0.19λ2. The dark channel has a full-width at half-maximum of ∼0.346λ and a DOF of ∼103.8λ. Furthermore, the oscillating focal field with an ultra-long DOF can be also generated by merely changing the order of the input Bessel beam. Our results are expected to contribute to potential applications in optical tweezers, atom guidance and capture, and laser processing.

Discriminating two spatially separated sources is one of the most fundamental problems in imaging. Recent research based on quantum parameter estimation theory shows that the resolution limit of two incoherent point sources given by Rayleigh can be broken. However, in realistic optical systems, there often exists coherence in the imaging light field, and there have been efforts to analyze the optical resolution in the presence of partial coherence. Nevertheless, how the degree of coherence between two point sources affects the resolution has not been fully understood. Here, we analyze the quantum-limited resolution of two partially coherent point sources by explicitly relating the state after evolution through the optical systems to the coherence of the sources. In particular, we consider the situation in which coherence varies with the separation. We propose a feasible experiment scheme to realize the nearly optimal measurement, which adaptively chooses the binary spatial-mode demultiplexing measurement and direct imaging. Our results will have wide applications in imaging involving coherence of light.

Considerable progress has been made in organic light-emitting diodes (OLEDs) to achieve high external quantum efficiency, among which dipole orientation has a remarkable effect. In most cases, the radiation of the dipoles in OLEDs is theoretically predicted with only one orientation parameter to match with corresponding experiments. Here, we develop a new theory with three orientation parameters to fully describe the relationship between dipole orientation and power density. Furthermore, we design an optimal test structure for measuring all three orientation parameters. All three orientation parameters could be retrieved from non-polarized spectra. Our theory provides a universal plot of dipole orientations in OLEDs, paving the way for designing more complicated OLED devices.

A new type of power-exponent-phase vortex-like beams with both quadratic and cubic azimuthal phase gradients is investigated in this work. The intensity and orbital angular momentum (OAM) density distributions are noticeably different when the phase gradient increases or decreases along the azimuth angle, while the orthogonality and total OAM remain constant. The characteristics of the optical field undergo a significant change when the phase shifts from linear to nonlinear, with the variation of the power index having little impact on the beam characteristics under nonlinear phase conditions. These characteristics provide new ideas for applications such as particle manipulation, optical communications, and OAM encryption.

On the basis of the stationary phase principle, we construct a family of shaping nondiffracting structured caustic beams with the desired morphology. First, the analytical formula of a nondiffracting astroid caustic is derived theoretically using the stationary phase method. Then, several types of typical desired caustics with different shapes are numerically simulated using the obtained formulas. Hence, the key optical structure and propagation characteristics of nondiffracting caustic beams are investigated. Finally, a designed phase plate and an axicon are used to generate the target light field. The experimental results confirm the theoretical prediction. Compared with the classical method, the introduced method for generating nondiffracting caustic beams is high in light-energy utilization; hence, it is expected to be applied conveniently to scientific experiments.

Underwater optical wireless communication, which is useful for oceanography, environmental monitoring, and underwater surveillance, suffers the limit of the absorption attenuation and Mie–Rayleigh scattering of the lights. Here, Bessel-like beams generated by a fiber microaxicon is utilized for underwater wireless propagation. Underwater, the cone angle for generating Bessel-like beams starts from 46°, which is smaller than that in air for Bessel-like beams. When the cone angle of the fiber microaxicons is about 140°, the depth of focus underwater, which is four times as long as the depth of focus in air, has enlarged about 28 µm, 36.12 µm, and 50.7 µm for 470 nm, 520 nm, and 632 nm visible lights. The transmission distance of the Bessel beams for visible lights has been simulated by using Henyey–Greenstein–Rayleigh phase function methods and spectral absorption by bio-optical model due to Monte Carlo methods. The results show that the propagation distance could reach 4000 m, which overcome the limit of the Mie–Rayleigh scattering and absorption attenuation underwater.

We introduce a new class of partially coherent asymmetric array beams. When the beam propagates, the spectral density of each lobe and the corresponding degree of coherence have rotating behavior. Especially, not only can array-like lattices revolve arbitrarily, but also they can move freely by controlling transverse plane shifts. Furthermore, we have generated this kind of beam experimentally, and the experimental phenomena are consistent with the numerical simulation results. Such a rotating beam with free movement and revolution may broaden the way for optical applications. More importantly, it inspires further studies in the field of asymmetric coherence gratings and lattices.

Polarization underwater imaging is of great potential to target detection in turbid water. Typical methods are challenged by the requirement on degrees of polarization (DoPs) of both target light and backscattering. A polarization descattering imaging method was developed using the Mueller matrix, which in turn derived a depolarization (Dep) index from the Mueller matrix to characterize scattering media by estimating the transmittance map by combining a developed optimal function. By quantifying light attenuation with the transmittance map, a clear vision of targets can be recovered. Only using the information of scattering media, the underwater vision under diverse water turbidity was enhanced by the results of experimental data.

We propose a method for detecting the symmetry of rotating patterns based on the rotational Doppler effect (RDE) of light. The basic mechanisms of the RDE are introduced, and the spiral harmonic distribution of rotating patterns is analyzed. By irradiating the rotating pattern using a superimposed optical vortex and analyzing the amplitude of the RDE signal, the spiral harmonic distribution of the pattern can be measured, and then its symmetry can be detected. We demonstrate this method experimentally by using patterns with different symmetries and shapes. As the method does not need to receive the scattered light completely and accurately, it promises potential application in detecting symmetrical rotating objects at a long distance.

Ghost imaging (GI) is a technique to retrieve images by correlating intensity fluctuations. In this Letter, we present a novel scheme for GI referred to as second-order cumulants GI (SCGI). The image is retrieved from fluctuation information, and resolution may be enhanced compared to traditional GI. We experimentally performed SCGI image reconstruction, and the results are in agreement with theoretical predictions.

Fringe projection profilometry (FPP) has been extensively studied in the field of three-dimensional (3D) measurement. Although FPP always uses high-frequency fringes to ensure high measurement accuracy, too many patterns are projected to unwrap the phase, which affects the speed of 3D reconstruction. We propose a high-speed 3D shape measurement method using only three high-frequency inner shifting-phase patterns (70 periods), which satisfies both high precision and high measuring speed requirements. Besides, our proposed method obtains the wrapped phase and the fringe order simultaneously without any other information and constraints. The proposed method has successfully reconstructed moving objects with high speed at the camera’s full frame rate (1700 frames per second).

Recent advances in the research of vortex beams, structured beams carrying orbital angular momentum (OAM), have revolutionized the applications of light beams, such as advanced optical manipulations, high-capacity optical communications, and super-resolution imaging. Undoubtedly, the methods for generation of a vortex beam and detection of its OAM are of vital importance for the applications of vortex beams. In this review, we first introduce the fundamental concepts of vortex beams briefly and then summarize approaches to generating and detecting the vortex beams separately, from bulky diffractive elements to planar elements. Finally, we make a concise conclusion and outline that is yet to be explored.

We investigate the Airy–Talbot effect of an Airy pulse train in time-dependent linear potentials. The parabolic trajectory of self-imaging depends on both the dispersion sign and the linear potential gradient. By imposing linear phase modulations on the pulse train, the Airy–Talbot effects accompanied with positive and negative refractions are realized. For an input composed of stationary Airy pulses, the self-imaging follows straight lines, and the Airy–Talbot distance can be engineered by varying the linear potential gradient. The effect is also achieved in symmetric linear potentials. The study provides opportunities to control the self-imaging of aperiodic optical fields in time dimension.

Topological photonics provides a new opportunity for the examination of novel topological properties of matter, in which the energy band theory and ideas in topology are utilized to manipulate the propagation of photons. Since the discovery of topological insulators in condensed matter, researchers have studied similar topological effects in photonics. Topological photonics can lead to materials that support the robust unidirectional propagation of light without back reflections. This ideal transport property is unprecedented in traditional optics and may lead to radical changes in integrated optical devices. In this review, we present the exciting developments of topological photonics and focus on several prominent milestones of topological phases in photonics, such as topological insulators, topological semimetals, and higher-order topological phases. We conclude with the prospect of novel topological effects and their applications in topological photonics.

We suggest tailoring of the illumination’s complex degree of coherence for imaging specific two- and three-point objects with resolution far exceeding the Rayleigh limit. We first derive a formula for the image intensity via the pseudo-mode decomposition and the fast Fourier transform valid for any partially coherent illumination (Schell-like, non-uniformly correlated, twisted) and then show how it can be used for numerical image manipulations. Further, for Schell-model sources, we show the improvement of the two- and three-point resolution to 20% and 40% of the classic Rayleigh distance, respectively.

In this work, inspired by advances in twisted two-dimensional materials, we design and study a new type of optical bi-layer metasurface system, which is based on subwavelength metal slit arrays with phase-gradient modulation, referred to as metagratings (MGs). It is shown that due to the found reversed diffraction law, the interlayer interaction that can be simply adjusted by the gap size can produce a transition from optical beam splitting to high-efficiency asymmetric transmission of incident light from two opposite directions. Our results provide new physics and some advantages for designing subwavelength optical devices to realize efficient wavefront manipulation and one-way propagation.

Floquet topological insulators (FTIs) have been used to study the topological features of a dynamic quantum system within the band structure. However, it is difficult to directly observe the dynamic modulation of band structures in FTIs. Here, we implement the dynamic Su–Schrieffer–Heeger model in periodically curved waveguides to explore new behaviors in FTIs using light field evolutions. Changing the driving frequency produces near-field evolutions of light in the high-frequency curved waveguide array that are equivalent to the behaviors in straight arrays. Furthermore, at modest driving frequencies, the field evolutions in the system show boundary propagation, which are related to topological edge modes. Finally, we believe curved waveguides enable profound possibilities for the further development of Floquet engineering in periodically driven systems, which ranges from condensed matter physics to photonics.

We develop a method for completely shaping optical vector beams with controllable amplitude, phase, and polarization gradients along three-dimensional freestyle trajectories. We design theoretically and demonstrate experimentally curvilinear Poincaré vector beams that exhibit high intensity gradients and accurate state of polarization prescribed along the beam trajectory.

We demonstrate a configuration optimization process of an off-axis parabolic mirror to maximize the focused peak intensity based on a precise knowledge of the tight focusing properties by using a full vector-diffraction theory and obtain an optimum configuration scaling rule, which makes it possible to achieve the maximum peak intensity. In addition, we also carry out an assessment analysis of the offset and off-axis angle tolerances corresponding to a 5% drop of the maximum focused peak intensity and present scaling laws for the tolerances of the offset and off-axis angle. Understanding these scaling laws is important to enhance the focusability of a laser beam by an off-axis parabolic mirror in the optimum configuration, in particular, which is valuable for structural design and selection of an off-axis parabolic mirror in ultrashort and ultraintense laser–matter interaction experiments.

Encoding information using the topological charge of vortex beams has been proposed for optical communications. The conservation of the topological charge on propagation and the detection of the topological charge by a receiver are significant in these applications and have been well established in free-space. However, when vortex beams enter a diffuser, the wavefront is distorted, leading to a challenge in the conservation and detection of the topological charge. Here, we present a technique to measure the value of the topological charge of a vortex beam obscured in the randomly scattered light. The results of the numerical simulations and experiments are presented and are in good agreement. In particular, only a single-shot measurement is required to detect the topological charge of vortex beams, indicating that the method is applicable to a dynamic diffuser.

The unevenly distributed Lorentz–Gaussian beams are difficult to reproduce in practice, because they require modulation in both amplitude and phase terms. Here, a new linearly polarized Lorentz–Gauss beam modulated by a helical axicon (LGB-HA) is calculated, and the two various experimental generation methods of this beam, Fourier transform method (FTM) and complex-amplitude modulation (CAM) method, are depicted. Compared with the FTM, the CAM method can modulate the phase and amplitude simultaneously by only one reflection-type phase-only liquid crystal spatial light modulator. Both of the methods are coincident with the numerical results. Yet CAM is simpler, efficient, and has a higher degree of conformance through data comparison. In addition, considering some barriers exist in shaping and reappearing the complicated Lorentz–Gauss beam with heterogeneous distribution, the evolution regularities of the beams with different parameters (axial parameter, topological charge, and phase factor) were also implemented.

The evolution of the spin density vectors (SDVs) is studied in a strongly focused composite field. It is found that the SDVs can be spiral along the propagation axis, and they are perpendicular to the ys direction on the ys axis. This behavior is governed by the Gouy phase difference between the field polarization components. The 60° rotation of the spatial distribution of the transverse SDVs is also generated, which is found to be controlled by the Gouy phase difference between the field orbital angular momentum modes. Additionally, the spin density singularities are observed in the evolution of the SDVs.

Vector vortex beams (VVBs) have attracted significant attention in both classical and quantum optics. Liquid crystal (LC), beyond its applications in information display, has emerged as a versatile tool for manipulating VVBs. In this review, we focus on the functions and applications of typical LC devices in recent studies on controlling the space-variant polarized vortex light. Manipulation of VVBs through patterned nematic LC optical elements, patterned cholesteric LC optical elements, self-assembled defects, and LC spatial light modulators is discussed separately. Moreover, LC-based novel optical applications in the field of quantum information are reviewed.

Photonic nanojets (PNJs) are subwavelength jet-like propagating waves generated by illuminating a dielectric microstructure with an electromagnetic wave, conventionally a linearly polarized plane wave. Here, we study the donut-like PNJ produced when a circularly polarized vortex beam is used instead. This novel PNJ also has a reverse energy flow at the donut-like focal plane depending on both the optical vortex topological charge and microsphere size. Our tunable PNJ, which we investigate numerically and analytically, can find applications in optical micromanipulation and trapping.

A new phase unwrapping method based on dual-frequency fringe is proposed to improve both high accuracy and large measurement range of three-dimensional shape measurement by synthesizing the projected dual-frequency fringes obtaining higher and lower frequencies. The lower-frequency one is their phase difference, which can help unwrap the wrapped phase of the higher-frequency one from their phase sum. In addition, the relationship between the measuring accuracy and the frequencies of the projected fringes is studied to guide the frequency selection in actual measurement. It is found that the closer the two frequencies are, the higher the measurement accuracy will be. The computer simulation and experiment results show the viability of this method.

In this Letter, we propose a broadband near-infrared (NIR) absorber based on the phase transition material VO2. By designing different arrangements of the VO2 square lattice at high and low temperatures on fused silica substrates, the absorption rate reaches more than 90% in the entire 1.4–2.4 μm range. Using a finite-difference time-domain simulation method and thermal field analysis, the results prove that the absorber is polarization-independent and has wide-angle absorption for incident angles of 0°–70°. The proposed absorber has a smoother absorption curve and is superior in performance, and it has many application prospects in remote sensing geology.

Imaging through scattering media via speckle autocorrelation is a popular method based on the optical memory effect. However, it fails if the amount of valid information acquired is insufficient due to a limited sensor size. In this Letter, we reveal a relationship between the detector and object sizes for the minimum requirement to ensure image reconstruction by defining a sampling ratio R, and propose a method to enhance the image quality at a small R by capturing multiple frames of speckle patterns and piecing them together. This method will be helpful in expanding applications of speckle autocorrelation to remote sensing, underwater probing, and so on.

We experimentally demonstrated optical wireless power transfer (OWPT) using a near-infrared laser diode (LD) as the optical power transmitter. We considered a photovoltaic (PV) cell and a photodiode (PD) as the optical power receivers. We investigated the characteristics of the LD, PD, and PV cell in order to determine the optimum operating condition from the viewpoint of transfer efficiency. We also experimentally demonstrated a whole system optimization process to maximize the DC-to-DC transfer efficiency of the OWPT. Our experimental results showed that the optimization process can improve the OWPT efficiency by up to 48%.

We investigate the influence of the source’s energy fluctuation on both computational ghost imaging and computational ghost imaging via sparsity constraint, and if the reconstruction quality will decrease with the increase of the source’s energy fluctuation. In order to overcome the problem of image degradation, a correction approach against the source’s energy fluctuation is proposed by recording the source’s fluctuation with a monitor before modulation and correcting the echo signal or the intensity of computed reference light field with the data recorded by the monitor. Both the numerical simulation and experimental results demonstrate that computational ghost imaging via sparsity constraint can be enhanced by correcting the echo signal or the intensity of computed reference light field, while only correcting the echo signal is valid for computational ghost imaging.

In this Letter, vortex phase and sinusoidal phase modulations of Hermite–Gaussian beams are studied theoretically and experimentally. The coding method of the experiment is introduced in detail, and the evolution law of focus under different beam order (m, n) and topological charge (l) is given. In order to verify the accuracy of the generation experiment, the optical field distribution under sinusoidal vortex modulation is analyzed deeply. The relevant analysis and methods provided in this Letter have certain practical significance for the development of laser mode analysis, optical communication, and other fields.

Orbital angular momentum (OAM), as a fundamental parameter of a photon, has attracted great attention in recent years. Although various properties and applications have been developed by modulating the OAM of photons, there is rare research about the non-uniform OAM. We propose and generate a new kind of continuously tunable azimuthally non-uniform OAM for the first time, to the best of our knowledge, which is carried by a hybridly polarized vector optical field with a cylindrically symmetric intensity profile and a complex polarization singularity. We also present the perfect vector optical field carrying non-uniform OAM with a fixed radius independent of topological charges, which can propagate steadily without radial separation, solving the problem of the unsteady propagation due to the broadened OAM spectrum of the non-uniform OAM. This new kind of tunable non-uniform OAM with a cylindrical symmetric intensity profile, complex polarization singularity, and propagation stability enriches the family of OAMs and can be widely used in many regions such as optical manipulation, quantum optics, and optical communications.

Optical orbital angular momentum (OAM) is a special property of photons and has evoked research onto the light–matter interaction in both classical and quantum regimes. In classical optics, OAM is related to an optical vortex with a helical phase structure. In quantum optics, photons with a twisted or helical phase structure will carry a quantized OAM. To our knowledge, however, so far, no experiment has demonstrated the fundamental property of the OAM at the single-photon level. In this Letter, we have demonstrated the average photon trajectories of twisted photons in a double-slit interference. We have experimentally captured the double-slit interference process of twisted photons by a time-gated intensified charge-coupled device camera, which is trigged by a heralded detection. Our work provides new perspectives for understanding the micro-behaviors of twisted particles and enables new applications in imaging and sensing.

We theoretically investigate the delay-dependent attosecond transient absorption spectra in the helium atom dressed by an infrared laser pulse in the wavelength range of 800–2400 nm. By numerically solving the three-dimensional time-dependent Schr dinger equation, we find that the absorption spectrogram exhibits a multiple-fringe structure for using the mid-infrared dressing pulse. The quantitative calculation of the transition matrix between different Floquet states provides direct evidence on the origin of the multiple-fringe structure. Our result shows that the wavelength of the dressing pulse is an important parameter and the unique feature of attosecond transient absorption spectroscopy can be induced in the mid-infrared regime.

We report a universal approach based on the surface plasmon resonances (SPRs) attained in filamentation in water doped with gold nanoparticles for enhancing the nonlinear refractive index. The filament-induced supercontinuum spectrum in water overlaps with SPRs of gold nanospheres, which further leads to a modification on the Kerr nonlinear refractive index. In our experiment, the measured nonlinear refractive index (n2) in water doped with gold nanoparticles increases by six times, as compared with that in pure water. Such enhancement may be useful for filament-induced nonlinear applications with modest incident intensity.

A method for calculating the atmospheric parameters measurement accuracy requirement based on polarized reflectance retrieval is proposed. The at-sensor polarization states with different atmospheric parameters content are simulated based on the atmospheric radiative transfer model in order to select the key parameter affecting the polarization observation. The accuracy requirement of atmospheric parameters is derived through the polarized reflectance retrieval method. Experiment results show that retrieval accuracy of polarized reflectance of typical ground objects can be up to 90%. The atmospheric parameters measurement accuracy requirement when the retrieval accuracy is more than 75% is derived.

We propose theoretically and verify experimentally a compact optical configuration to directly generate arbitrary vector vortex beams on a hybrid-order Poincaré sphere with good flexibility and high efficiency based on a reflective phase-only liquid crystal spatial light modulator (LC-SLM). The conversion system, consisting of an LC-SLM and a quarter-wave plate, can be considered a flexible dielectric metasurface to simultaneously modulate inhomogeneous polarization and helical phase-front. This approach has some advantages, including a simple experimental setup, good flexibility, and high efficiency. Orthogonally polarized modes alignment and an explicit superposition existing in the conventional method are not necessary in the proposed method, which exhibits potential applications in many advanced domains.

A full-transparent zone plate (FTZP), which can reuse the wave blocked in the focusing of the Fresnel zone plate (FZP), is proposed to improve the efficiency of terahertz (THz) focusing without aberration. We find that the substrate thickness of the FTZP has a great influence on the focusing intensity, which results from the Fabry–Perot effect. The focusing efficiency of FTZPs could be about twice as high as that of FZPs, but the widths of both focus spots are comparable with the wavelength. The experimental results are in good agreement with the simulation.

We report the generation of asymmetric Mathieu beams: invariant intensity optical profiles that can be described by three parameters. The first one describes the amount of ellipticity, the second one takes into account the degree of asymmetry of the profile, and the third parameter denotes the angular position, where it is localized with the respective asymmetry. We propose a simple angular spectrum to generate these nondiffracting beams, and we report how it changes their distribution of power and orbital angular momentum in function with their ellipticity and degree of asymmetry. We confirm the existence of these invariant beams by propagation in an experimental setup.

A setup for the generation of arbitrary vector beams is proposed. The setup mainly consists of a spatial light modulator (SLM), an angle-adjustable polarization beam splitter modulator, and a spatial filtering imaging system. Compared with the system using a birefringent beam splitter with a non-adjustable splitting angle, the polarization splitting angle of the improved setup can be adjusted by slightly rotating the related mirrors, which will bring more convenience when different wavelengths and different pixel sizes of SLMs are involved. The experimental results also demonstrate that the setup possesses a good polarization-selective imaging ability, which reveals that the setup may also be useful in polarization-selective spatial filtering imaging and polarization-encoded encryption.

In our work, a high-quality broadband femtosecond optical vortex is obtained by use of a continuous spiral phase plate (SPP) to modulate an ultrashort femtosecond (fs) laser with a broadband spectrum. The experimental results demonstrate that the continuous SPP is of good quality and that it can be used to efficiently produce a high-power fs optical vortex.

The nonideal semi-Gaussian beam generated in our work has a certain ascent border width. Due to its asymmetry, the propagation properties of a nonideal semi-Gaussian laser beam in nonlinear materials have some unique characters. In our work, the propagation properties of a nonideal semi-Gaussian laser beam with a small ascent border width through a ZnSe nonlinear crystal is theoretically studied, and the relations of the propagation properties and the various parameters of the nonlinear medium and the semi-Gaussian beams are also analyzed theoretically in detail.

We present a technique and algorithm for measuring the phase retardation of a wave plate based on spectral transmission curve. Through accurately extracting the intersection points' wavelengths from the spectral transmission curve, the effective phase retardation, absolute phase retardation, order, and physical thickness of the wave plate can be measured simultaneously in a wide spectral range. Experimental results show that the proposed technique has many advantages, such as higher data utilization, simpler extraction algorithm, and no strict requirement for the directions of transmission axes of the polarizer and analyzer, and the fast axis of the wave plate.

We focus on the need for azimuthal orientation angles of a system. If one azimuthal orientation angle is a function of other angles and these angles turn independently by the same axis, the sum of the partial differential of the function to the other angles is 1. We use this property of the azimuthal orientation angles turning by the same axis of the system to analyze the experimental phenomena of the terahertz polarization, and then quantum theory is used to explain the experimental phenomena.

The propagation characteristics of lightwave in spatial and temporal domains are reviewed, and a general analogy of spatial diffraction and temporal dispersion is presented in details. By using the transformation pairs of spatial location and time, wave number and dispersion parameter, some more general expressions, such as spot size/wavefront curvature and pulse-width/chirps, space-angle spectrum product and time-bandwidth product, spatial Fresnel number and temporal Fresnel number, focal length of lens and focusing time, are derived.

Transmission and reflection of an electromagnetic pulse through a dielectric slab doped with the quantum dot molecules are investigated. It is shown that the transmission and reflection coefficients depend on the inter-dot tunneling effect and can be simply controlled by applying a gate voltage without any changing in the refractive index or thickness of the slab. Such simple controlling prepares an active beam splitter which can be used in all optical switching, optical limiting, and other optical systems.

The angular emission spectra of the distributed feedback (DFB) cavity are investigated theoretically and experimentally. An angular emission model of the relationship between the DFB cavity and its angular emission spectra is proposed. In the model, the DFB cavity can be decomposed into two parts: a grating and an active waveguide layer. So, the angular emission spectra of the DFB cavity are mainly determined by the period of the grating, the thickness of the waveguide and the material absorption during the feedback process. The theoretical model agrees well with the experimental results. It provides a convenient estimate for designing more efficient DFB polymer lasers and highly directional emission devices.

The far-field analytical expressions for the electromagnetic fields of amplitude of vector-vortex beams having a Bessel–Gauss (BG) distribution propagating in free space are obtained based on the vector angular spectrum and the method of stationary phase. The far-field energy flux distributions and the beam quality by the power in the bucket (PIB) in the paraxial and nonparaxial regimes are investigated. The PIB of the vector-vortex BG beams depend on the ratio of the waist width to wavelength and the polarization order. The analyses show that vector-vortex BG beams with low polarization order have better energy focusability in the farfield.