Vascular permeability (VP) plays a critical role in liver and kidney fibrosis progression. Traditional VP quantification methods use single-wavelength photoacoustic microscopy (PAM) with Evans Blue (EB) dye, which have limitations including signal attenuation and decreased accuracy. To overcome these issues, we developed a dual-wavelength PAM method with a spectral unmixing algorithm for quantitative VP evaluation in liver and kidney microvasculature. This approach allows for an accurate assessment of VP dynamics by analyzing hemoglobin and EB absorption. Using murine models of fibrosis, we found that fibrosis reduces vessel density and increases vessel diameter, providing valuable insights into VP changes during fibrosis progression.

Single-molecule localization microscopy (SMLM) has pushed resolution to sub-40 nm. Combined with structured illumination, lateral resolution can be doubled or the axial resolution can be improved fourfold. However, current techniques are challenging in balancing the lateral and axial resolutions. Here, we report a new modulated illumination single-molecule localization modality, isoFLUX. Utilizing two objective lenses to form interference patterns along the x–z and y–z directions, the lateral and axial resolutions can be improved simultaneously. Compared to SMLM, isoFLUX maintains a twofold average enhancement in both lateral and axial resolutions under an astigmatic point spread function (PSF), 1.5-fold in the lateral resolution and 2.5-fold in the axial resolution under the saddle-point PSF.

Non-line-of-sight (NLOS) imaging has potential in autonomous driving, robotic vision, and medical imaging, but it is hindered by extensive scans. In this work, we provide a time-multiplexing NLOS imaging scheme that is designed to reduce the number of scans on the relay surface. The approach introduces a time delay at the transmitting end, allowing two laser pulses with different delays to be sent per period and enabling simultaneous acquisition of data from multiple sampling points. Additionally, proof-of-concept experiments validate the feasibility of this approach, achieving reconstruction with half the scans. These results demonstrate a promising strategy for real-time NLOS imaging.

The relative motion between an imaging system and its target usually leads to image blurring. We propose a motion deblurring imaging system based on the Fourier-transform ghost diffraction (FGD) technique, which can overcome the spatial resolution degradation caused by both laterally and axially translational motion of the target. Both the analytical and experimental results demonstrate that when the effective transmission aperture of the receiving lens is larger than the target’s lateral motion amplitude and even if the target is located in the near-field region of the source, the amplitude and mode of the target’s motion have no effect on the quality of FGD, and high-resolution imaging in the spatial domain can be always achieved by the phase-retrieval method from the FGD patterns. Corresponding results based on the conventional Fourier diffraction system are also compared and discussed.

Terahertz (THz) imaging based on the Rydberg atom achieves high sensitivity and frame rates but faces challenges in spatial resolution due to diffraction, interference, and background noise. This study introduces a polarization filter and a deep learning-based method using a physically informed convolutional neural network to enhance resolution without pre-trained datasets. The technique reduces diffraction artifacts and achieves lens-free imaging with a resolution exceeding 1.25 lp/mm over a wide field of view. This advancement significantly improves the imaging quality of the Rydberg atom-based sensor, expanding its potential applications in THz imaging.

The integration of deep learning into computational imaging has driven substantial advancements in coherent diffraction imaging (CDI). While physics-driven neural networks have emerged as a promising approach through their unsupervised learning paradigm, their practical implementation faces critical challenges: measurement uncertainties in physical parameters (e.g., the propagation distance and the size of sample area) severely degrade reconstruction quality. To overcome this limitation, we propose a deep-learning-enabled spatial sample interval optimization framework that synergizes physical models with neural network adaptability. Our method embeds spatial sample intervals as trainable parameters within a PhysenNet architecture coupled with Fresnel diffraction physics, enabling simultaneous image reconstruction and system parameter calibration. Experimental validation demonstrates robust performance with structural similarity (SSIM) values consistently maintained at 0.6 across diffraction distances spanning of 10–200 mm, using a 1024 × 1024 region of interest (ROI) from a 1624 × 1440 CCD (pixel size: 4.5 μm) under 632.8 nm illumination. This framework has excellent fault tolerance, that is, it can still maintain high-quality image restoration even when the propagation distance measurement error is large. Compared to conventional iterative reconstruction algorithms, this approach can transform fixed parameters into learnable parameters, making almost all image restoration experiments easier to implement, enhancing system robustness against experimental uncertainties. This work establishes, to our knowledge, a new paradigm for adaptive diffraction imaging systems capable of operating in complex real scenarios.

A cross air‬–water interface hydroacoustic signal detection method based on microvibration detection at the air–water interface is proposed. Laser speckles modulated by water surface acoustic waves are recorded and used as an information carrier. Phase correlation and multichannel fusion algorithms are used to extract and enhance hydroacoustic signals. Wide frequency range (200 Hz to 20 kHz) underwater acoustic signals are detected with a frequency relative error smaller than 0.5%. Several common artificial and natural hydroacoustic signals are used as source signals and correctly reconstructed. The average intelligibility of recovered humpback whale signals evaluated with the normalized subband envelope correlation algorithm is 0.52 ± 0.02.

The high-power and frequency-stabilized laser is urgently required in short-exposure interferometry. In this paper, a light source based on the semi-external-cavity HeNe laser is proposed for application. By optimizing the parameters of the resonant cavity, a high-finesse valley corresponding to monomode operation is generated on the temperature-tuned power curve of the laser. A frequency stabilization device by locating the power valley is constructed, achieving the frequency-stabilized output of about 2.5 mW. The monomode-power conversion efficiency, which is the ratio of the frequency-stabilized output and the resonator output, can reach up to 97.6%, due to the avoidance of the polarized mode selection in the internal-cavity resonator. Compared with the commercial frequency-stabilized HeNe laser, the proposed laser can improve the interferogram contrast from 0.26 to 0.70 in the vibration environment by shortening the camera exposure time. The proposed laser exhibits the high conversion efficiency of monomode power, which is very suitable for short-exposure interferometry.

The detection accuracy of frequency shift is crucial in microwave detection based on the Rydberg atomic alternating current (AC) Stark shift effect. We design a frequency shifter system that can provide a high-precision frequency reference signal and improve the detection accuracy of frequency shift. This system utilizes acoustic-optic modulators to generate two coupling lights with a fixed frequency interval and completes double Rydberg atomic excitation. The detection accuracy of the AC Stark shift (±1.33 MHz) is 6.08 times better than that of the wavelength meter-reading scheme (±8.09 MHz), and the minimum detectable frequency shift is improved by a factor of 3.13.

Electric field poling of electro-optic polymer (EOP) in hybrid waveguides is highly challenging due to the discontinuity in electric field distribution, which leads to a low Pockels electro-optic (EO) coefficient or dielectric breakdown. We propose the segmented poling technique in Si3N4/EOP hybrid waveguides to address this challenge. Dipolar chromophores near an electrode interface first align with a weak poling electric field, and then a strong field is applied for the chromophore alignment near the waveguide interface. This technique effectively avoids dielectric breakdown, and the tuning efficiency of the EO Mach–Zender interferometer (MZI) filters is improved from 31.7 pm/V to higher than 50 pm/V, with a highest Pockels coefficient of 114 pm/V.

On-chip microlasers and waveguide amplifiers offer promising applications in optical communication, sensing, and photonic computing, presenting efficient, compact, and scalable light source solutions for integrated photonics systems. We demonstrated a low-threshold on-chip microdisk resonator laser and a high-gain optical waveguide amplifier on thin-film erbium-doped tantalum pentoxide (Er:Ta2O5). The fabricated Er:Ta2O5 microdisk microlaser achieved a low threshold of 225 µW, and the fabricated Er:Ta2O5 waveguide amplifier achieved an on-chip gain of 8.8 dB/cm. These results demonstrate that active functional high-performance integrated photonic devices can be realized on the thin-film Ta2O5 platform.

We demonstrate a versatile bismuth-doped fiber pulse source that is seeded by a mode-locked fiber laser operating in different regimes with different net dispersions in the same cavity, including the square-wave noise-like pulse regime with anomalous net dispersion at 1331 nm and the multi-pulse soliton regime with normal net dispersion at 1320 nm. The versatile pulse evolutions and the multi-pulse dynamics in these two regimes are investigated under different pump powers or polarization states. The seed pulses are then amplified by a bismuth-doped fiber amplifier, which boosts the pulse energy to 21 nJ with a slope efficiency of 21.3% without power saturation and is anticipated to be useful for practical applications.

We presented a repetition-rate tunable Yb-doped fiber laser system, which used a chirped fiber Bragg grating as a fiber stretcher designed to match the second- and third-order dispersion of the transmission grating compressor. The system delivered 1-µJ, 143-fs pulses at a 2 MHz repetition rate and 10-µJ, 157-fs pulses at a 200 kHz repetition rate, respectively. The pulse repetition rate can be tuned from 200 kHz to 2 MHz while the pulse duration maintains <180 fs. This compact fiber laser source was built for applications in ophthalmology, such as corneal flap cutting and tissue vaporization. Furthermore, it can be applied in micro-machining applications, such as laser marking, scribing, and drilling.

A high-quality 1% (atom fraction) Ho3+:BaF2 crystal was successfully grown using the temperature gradient technique (TGT). The optical properties of the crystal were investigated, and continuous-wave (CW) laser operation of Ho3+ ions in the 2 µm range was successfully demonstrated for the first time in the BaF2 crystal, to the best of our knowledge. Spectral parameters such as Ωt (t = 2, 4, 6) and radiative lifetimes were calculated and studied by the Judd–Ofelt (J–O) theory. The quality factor was calculated to be Q = 6.60 × 10-20 cm2·ms, and the full width at half-maximum (FWHM) was fitted to be 134.5 nm, indicating that the Ho:BaF2 crystal has a low laser threshold and broadband tunability. A maximum output power of 1.5 W and a slope efficiency of 29.3% were achieved by the 1908 nm fiber laser as the pumping source, with a relatively low threshold of 399 mW. Additionally, the Ho:BaF2 crystal achieved a tunable laser output with a bandwidth of 166.4 nm, which is the widest as reported for other 2 µm band Ho-doped fluoride crystals to the best of our knowledge. These results suggest that the Ho:BaF2 crystal has the potential to achieve femtosecond ultrafast pulse laser output through mode-locking operation.

We propose a method for generating an all-fiber cylindrical vector beam (CVB) using a fiber Bragg grating (FBG) inscribed in a ring core fiber (RCF). The FBGs are inscribed using the femtosecond laser phase mask scanning technique, chosen for its large ring core diameter and low photosensitivity of the RCF. Additionally, a lateral offset splicing spot is introduced to couple the fundamental mode to the second-order modes. Switchable LP01 and LP11 mode lasers can be achieved. Meanwhile, azimuthally and radially polarized CVBs are successfully realized by adjusting the polarization controllers.

In this paper, an all-optical tuning scheme of a multi-walled carbon nanotube (MWCNT)-coated microcavity is introduced, achieving high-speed precise resonance control across the free spectral range (FSR). A modulation laser input through the microcavity tail fiber adjusts the resonance peak position, achieving a tuning efficiency of 107.3 pm/mW below 15 mW, with a maximum range exceeding one FSR and a response time of ∼20 ms. Combined with a fixed-wavelength pump, this scheme can precisely control the microcomb states. The scheme offers high tuning efficiency, simple fabrication, and low cost, making it suitable for applications in microcomb control and optical filters.

In this Letter, we propose and experimentally demonstrate, to the best of our knowledge, a novel compact power-equalized multi-wavelength laser (MWL) source for optical I/O technology. This multi-wavelength distributed feedback (DFB) laser array is used to achieve simultaneous emission of multiple wavelengths with balanced output power and stable single-mode operation. The reconstruction equivalent chirp technique is used to design and fabricate the π-phase shifted DFB laser array to achieve precise wavelength spacing. The power equalizers (PEs) are monolithically integrated in front of the laser unit to equalize the output power. The experimental results show that the wavelength spacing of the proposed eight-channel MWL is 100 G ± 4.38 G, and the maximum deviation of the intensity (MDOI) is 1.00 dB under a 25°C working environment. Compared with the traditional MWL structure, the wavelength spacing error is reduced from 0.32 to 0.035 nm, and the MODI is reduced from 3.8 to 1.0 dB. The output power exceeds 25 mW when the current injected into the semiconductor optical amplifier (SOA) is 150 mA. Besides, the relative intensity noise (RIN) of all wavelengths is below -138 dB/Hz, and clear 25 Gb/s non-return-to-zero (NRZ) eye diagrams are obtained for the eight wavelengths with the external lithium-niobate Mach–Zehnder modulator. The superior performance of the proposed MWL makes it a promising method for low-bit-error optical I/O links and high-density chip interconnection systems.

The nonlinear Schrödinger equation (NLSE) is extensively used to numerically study pulse evolution dynamics in ultrafast fiber lasers. Yet, the computational speed of the NLSE is relatively slow, restricting its applications in systems that rely on real-time computation for dynamic control and operation. In this work, we propose and demonstrate a deep learning approach for the prediction of Stokes pulses’ evolution in a Raman fiber amplifier based on nonlinear optical gain modulation (NOGM). A four-layer fully connected neural network is developed to predict the spectral evolution of the first-order Stokes light in fiber amplifiers using different types of Raman gain fibers. The model achieves high prediction accuracy with normalized root mean square errors below 0.1, while providing up to 86 times faster computation compared to conventional NLSE methods. The network demonstrates reliable generalization capability for parameter combinations beyond the training dataset.

In order to balance the suppression of stimulated Raman scattering (SRS) and transverse mode instability (TMI) in high-power fiber lasers, in this Letter, a new type of spindle-shaped ytterbium-doped fiber (YDF) with asymmetric longitude distribution was designed and produced, which had a small-sized input end, large-sized transmission section, and moderate output end, enabling a good fit with a seed laser and mitigating SRS as well as TMI effects. A counter-pumped fiber laser amplifier was established using this YDF, and two kinds of laser diodes (LDs) were adopted for increasing the TMI threshold. Finally, the maximum output power reached 6 kW, and the beam quality (M2 factors) indicated near-single-mode output. The SRS suppression ratio under 6 kW output power was 36 dB, and no dynamic TMI was observed, which revealed that further enhancement of output power was limited only by pump power.

The acousto-optic modulator (AOM) plays an important role in heterodyne interferometric sensing, and it is always regarded as an ideal optical frequency shifter. In this paper, we compare the effects of its residual zero-order diffraction in different AOM configurations. The theory shows that using double AOMs can effectively solve the same frequency crosstalk problem caused by zero-order perturbation without worsening the noise floor. The interferometer employs a photonics-assisted mmWave composed of two comb lines from an electro-optical frequency comb as the optical source, which results in the laser frequency noise cancellation in the difference. Experimentally, a dither with a peak-to-peak value of 0.15 ps in the single AOM configuration can be effectively suppressed to below the noise floor through double AOMs, which shows the potential to achieve high sensing accuracy.

A microwave photonic subsampling digital receiver (MPSDR) is proposed and experimentally demonstrated for target detection with a sampling rate of 10 MSa/s. Stepped and pseudo-random frequency-hopping signals with frequencies across the K band are both used for target detection and can be captured by the MPSDR. The range profiles of the targets are then derived using a compressed sensing algorithm, and precise target position estimation is achieved by changing the measurement position of the antenna pair. The results demonstrate that the estimation accuracy remains comparable even when the pseudo-random frequency-hopping signal utilizes only 12.5% of the frequency points required by the stepped frequency-hopping signal. This highlights the efficiency and potential of the proposed MPSDR in processing complex signals while maintaining high accuracy.

It has long been a challenging task to improve the light collection efficiency of conventional image sensors built with color filters that inevitably cause the energy loss of out-of-band photons. Here, we demonstrate a pixelated spectral router based on a sparse meta-atom array, which can efficiently separate incident R (600–700 nm), G (500–600 nm), and B (400–500 nm) band light to the corresponding pixels of a Bayer image sensor, providing over 56% signal enhancement above the traditional color filter scheme. It is enabled by simple compound Si3N4 nanostructures, which are very suitable for massive production. Imaging experiments are conducted to verify the router’s potential for real applications. The complementary metal-oxide-semiconductor (CMOS)-compatible spectral router scheme is also found to be robust and can be freely adapted to image sensors of various pixel sizes, having great potential in building the new generation of high-performance image sensing components.

Light-beam shifts accompanied by propagation between two media show potential in applications such as optical sensing, optical communication, and optical computing. However, existing work tends to focus on the static response of the device, i.e., the beam shift when the structural parameters and incident conditions are fixed. Here, we analyze the dynamics of beam shifting via photonic crystal slabs under refractive index variation. On the one hand, we investigate the trend of cross-polarized phase gradient under small changes in refractive index. Simulation results show that the direction of the beam shift can change by more than 50° for a refractive index change of only 0.06. On the other hand, we study the interaction of incident light with the far-field polarizations of bound states in the continuum in the presence of a refractive index jump in the phase-change material. In this case, simulation results show that the large change in the Pancharatnam–Berry phase gradient causes the beam to move widely, with a change in beam direction of 61.30° and a change in beam displacement of 15 µm. Furthermore, all displacement amounts are comparable to the radius of the incident beam (∼8 µm). Our work provides a new perspective on the study of beam shifts, which can advance practical applications of beam shift in sensing, intelligent detecting, and beam control.

We fabricated a three-dimensional nonlinear photonic crystal in a Sr0.61Ba0.39Nb2O6 (SBN) crystal using femtosecond laser direct writing of ferroelectric domain structures. The crystal features three layers of fork-shaped gratings, each oriented differently. These gratings convert an incident vortex beam into a second-harmonic Gaussian beam in specific directions. By altering the vortex beam’s topological charge, we can control the emission direction of the second-harmonic Gaussian beam, enabling flexible all-optical switching and manipulation. This work provides a foundation for controlling photon angular momentum in nonlinear optical frequency-conversion processes.

In classical linear optics, when light shines upon a grating in the normal configuration where the incident plane of light is perpendicular to the optical axis of the grating, ordinary Bragg diffraction will occur. However, when light is incident in the general conical configuration where the incident plane of light is oblique to the optical axis of the grating, the Bragg diffraction becomes much more complicated. What happens to the nonlinear diffraction of a laser beam by a nonlinear grating? In this Letter, we wish to answer this interesting and fundamental question in the realm of nonlinear optics. We shine a Ti:sapphire femtosecond pulse laser beam (with a central wavelength at 800 nm) upon a periodically poled lithium niobate (PPLN) thin plate nonlinear grating and systematically investigate the Raman–Nath nonlinear diffraction (NRND) pattern of a second-harmonic generation (SHG) laser beam in various “conical” (or off-plane) incidence configurations characterized by both the polar angle α and azimuthal angle φ. By analyzing the diffraction characteristic and uncovering the underlying mechanisms of conical NRND nonlinear diffraction, we have provided a comprehensive understanding of its spatial behavior. The study of conical nonlinear diffraction enriches the understanding of the complicated interaction between the pump laser beam and the structured nonlinear medium and broadens the arena of nonlinear optics.

Gallium oxide (Ga2O3), a promising candidate in ultraviolet photodetection, suffers significant limitations in its optoelectronic performance owing to the challenge of achieving p-type doping. To address this challenge, we designed a type-I heterostructure photodetector (PD) by depositing two-dimensional Bi films on Ga2O3 using the pulsed laser deposition technique. Under the illumination intensity of 0.1 µW/cm2, this PD exhibits a remarkable responsivity of up to 200 mA/W and a detectivity of 8.58 × 1011 Jones, demonstrating its excellent low-light detection ability. In addition, due to the built-in electric field of the heterojunction, the device can effectively suppress the dark current and has the performance of self-powered detection.

Polarimeter is a vital precision tool used for measuring optical parameters through polarization variations. Among the wide range of application fields, the precise measurement of photosensitive materials is an unavoidable task but faces immense obstacles due to the excessive input photons. Facing this situation, introducing a quantum source into the classical precision measurement system is a feasible way to enhance the detection accuracy under the low illumination regime. In this work, we employ polarization-entangled photon pairs in the classical polarimeter to precisely detect the relative phase retardance of uniform anisotropic media. The experimental results show that the accuracy can reach the nanometer scale at extremely low input intensity, and the stabilities are within 0.4% for all samples. Our work paves the way for polarization measurement at low incident light intensity, with potential applications in measuring photosensitive materials and remote monitoring scenarios.