Abstract Narrow-linewidth vertical-cavity surface-emitting lasers (VCSELs) are key enablers for chip-scale atomic clocks and quantum sensors, yet conventional designs suffer from short cavity lengths and excess spontaneous emission, resulting in broad linewidths and degraded frequency stability. Here, we demonstrate a monolithically integrated VCSEL operating at the cesium D1 line (894.6 nm) that achieves intrinsic linewidth compression to ~1 MHz, without requiring external optical feedback. This performance is enabled by embedding a passive cavity adjacent to the active region, which spatially redistributes the optical field into a low-loss region, extending photon lifetime while suppressing higher-order transverse and longitudinal modes. The resulting device exhibits robust single-mode operation over a wide current and temperature range, with side-mode suppression ratio (SMSR) > 35 dB, orthogonal polarization suppression ratio (OPSR) > 25 dB and a beam divergence of ~7°. Integrated into a Cesium vapor-cell atomic clock, the VCSEL supports a frequency stability of 1.89 × 10–12 τ-1/2. These results position this VCSEL architecture as a compact, scalable solution for next-generation quantum-enabled frequency references and sensing platforms.
Efficient operation of light-to-pressure transducers and flexible fabrication on demand are key factors for the use of photoacoustic devices in various biomedical disciplines. Graphene layers can be grown at wafer scale and transferred to any surface geometry, providing a versatile approach for the development of photoacoustic emitters with a large and nearly uniform thermal interface. Here we report the picosecond excitation of a photoacoustic emitter consisting of a large-area, 10-layer graphene grown by chemical vapour deposition and encapsulated with a polydimethylsiloxane. The theoretical and experimental studies address the generation of broadband ultrasounds upon excitation with nanosecond and picosecond laser pulses, showing how the multilayer graphene can serve as an ultrafast nanoheater to drive efficient expansion of the adjacent polymer layer in the picosecond regime. The picosecond excitation results in a sharper acoustic waveform, and the pressure evolution time is twice as short with a 30 ps excitation as with a 6 ns pulse, thus satisfying the thermal and stress confinement conditions, while energy loss occurs with nanosecond excitation. We experimentally observed that the 10-layer graphene/polydimethylsiloxane generates a high-frequency photoacoustic wave with a bandwidth of about 110 MHz at −6 dB, increasing to 250 MHz at −20 dB, due to stress confinement, increased thermal interface, and ultrafast dynamics. The peak pressure of 0.85 MPa in 3.4 nm thick graphene multilayers (∼20 % absorption of 40 mJ cm–2) is remarkably high, demonstrating its potential as a photoacoustic material and the advantages of combining picosecond excitation with large-area graphene in wave transmission technologies.
Rhegmatogenous retinal detachment (RRD) is an ophthalmic emergency characterized by the separation of the neurosensory retina from the retinal pigment epithelium due to retinal breaks. Scleral buckling is a conventional surgical treatment for this condition. This case series aims to illustrate the application of a novel surgical technique—illuminated scleral depressor-assisted scleral buckling for precise break localization—in clinical practice and to evaluate long-term postoperative outcomes in patients.
Abstract The identification of individual cells is crucial for advancements in single-cell analysis. Optically readable barcodes provide a means to distinguish and track cells through repeated, non-destructive measurements. Traditional fluorophore-based methods are limited by the finite number of unique barcodes they can produce. Laser particles (LPs), which emit narrowband peaks over a wide spectral range, have emerged as a promising technology for single-cell barcoding. Here, we demonstrate the use of multiple LPs to generate combinatorial barcodes, enabling the identification of a vast number of live cells. We introduce a theoretical framework for estimating the number of LPs required for unique barcodes and the expected identification error rate. Additionally, we present an improved LP-tagging method that is highly effective across a variety of cell types and evaluate its biocompatibility. Our experimental results show successful barcoding of several million cells, closely matching our theoretical predictions. This research marks a significant step forward in the scalability of LP technology for single-cell tracking and analysis.
Abstract Optical neural networks are emerging as a competitive alternative to their electronic counterparts, offering distinct advantages in bandwidth and energy efficiency. Despite these benefits, scaling up on-chip optical neural networks for end-to-end inference is facing significant challenges. First, network depth is constrained by the weak cascadability of optical nonlinear activation functions. Second, the input size is constrained by the scale of the optical matrix. Herein, we propose a scaling up strategy called partially coherent deep optical neural networks (PDONNs). By leveraging an on-chip nonlinear activation function based on opto-electro-opto conversion, PDONN enables network depth expansion with positive net gain. Additionally, convolutional layers achieve rapid dimensionality reduction, thereby allowing for an increase in the accommodated input size. The use of a partially coherent optical source significantly reduces reliance on narrow-linewidth laser diodes and coherent detection. Owing to their broader spectral characteristics and simpler implementation, such sources are more accessible and compatible with scalable integration. Benefiting from these innovations, we designed and fabricated a monolithically integrated optical neural network with the largest input size and the deepest network depth, comprising an input layer with a size of 64, two convolutional layers, and two fully connected layers. We successfully demonstrate end-to-end two-class classification of fashion images and four-class classification of handwritten digits with accuracies of 96% and 94%, respectively, using an in-situ training method. Notably, performance is well maintained with partially coherent illumination. This proposed architecture represents a critical step toward realizing energy-efficient, scalable, and widely accessible optical computing.
This work explores water-to-air optical wireless communication (W2A-OWC) transmission schemes and realizes a prototype of real-time W2A-OWC system based on field programmable gate array. This prototype comprises underwater nodes, aerial nodes, and transmitter-receiver hardware circuits. The real-time system employs multiple-input multiple-output technique and the low density parity check (LDPC) code of 5G-new radio for dynamic W2A-OWC. Additionally, the impact of background radiation is mitigated through spatial optical filtering. To validate the practical feasibility of the system, experiments are conducted in both indoor water tank and outdoor deep pool under strong background radiation. The frame error rate of the real-time system is tested under different LDPC code rates and transmitter-receiver configurations. The experimental results verify the feasibility of the realized W2A-OWC system.
In recent years, space-division multiplexing (SDM) technology, which involves transmitting data information on multiple parallel channels for efficient capacity scaling, has been widely used in fiber and free-space optical communication systems. To enable flexible data management and cope with the mixing between different channels, the integrated reconfigurable optical processor is used for optical switching and mitigating the channel crosstalk. However, efficient online training becomes intricate and challenging, particularly when dealing with a significant number of channels. Here we use the stochastic parallel gradient descent (SPGD) algorithm to configure the integrated optical processor, which has less computation than the traditional gradient descent (GD) algorithm. We design and fabricate a 6×6 on-chip optical processor on silicon platform to implement optical switching and descrambling assisted by the online training with the SPDG algorithm. Moreover, we apply the on-chip processor configured by the SPGD algorithm to optical communications for optical switching and efficiently mitigating the channel crosstalk in SDM systems. In comparison with the traditional GD algorithm, it is found that the SPGD algorithm features better performance especially when the scale of matrix is large, which means it has the potential to optimize large-scale optical matrix computation acceleration chips.
A novel compact optical fiber concentration sensing system based on machine learning was proposed and experimentally demonstrated in this paper. The Michelson interferometer (MI) was realized by multiple arc discharge performed on the end of a section of bent bare single-mode fiber (SMF). To improve the stability and accuracy of demodulation, machine learning based on long short-term memory (LSTM) was employed and it provided an accuracy of 97.5%, which is more stable and accurate than conventional peak wavelength tracking due to the fact that LSTM can avoid the effects of dip selection, wavelength sampling rate and spectral noise on the peak wavelength tracking. Furthermore, the proposed sensing system has the advantages of compact size, low cost, high robustness, and ease of fabrication.
The suggested work emphasizes the benefits of employing positively charged gold nanoparticles to detect negatively charged E.coli cells by electrostatic attraction without the need of any identification elements. As a result, a simple, label-free colorimetric biosensor for detecting E.coli, a well-known food contaminant, was developed. Initially, the Taguchi approach was used to synthesis small, stable, and positively charged Au NPs in orthogonal array L8 by optimizing 5 critical parameters such as pH, capping agents, temperature, Sonication duration, and Au/LE ratio. Based on the Maximum wavelength (λ max) values and ANOVA, Trail 3 (T3) a Polyallyl amine hydrochloride capped Au NPs (PAH-Au NPs) along with D-Mannose was chosen to be employed in detecting E.coli. It functions as a colorimetric sensor in both sol and paper coated forms. Based on the sensing technique, we discovered that the LOD in sol is (1*105CFU/mL), which is significantly higher than the sensor based on paper (1*102 CFU/mL).
Cooperative quantum magnetism One of the earliest and most intensively studied problems in quantum optics is the interaction of a two-level system (an atom) with a single photon. This simple system provides a rich platform for exploring exotic light-matter interactions and the emergence of more complex phenomena such as superradiance, which is a cooperative effect that emerges when the density of atoms is increased and coupling between them is enhanced. Going beyond the light-matter system, Li et al. observed analogous cooperative effects for coupled magnetic systems. The results suggest that ideas in quantum optics could be carried over and used to control and predict exotic phases in condensed matter systems. Science, this issue p. 794 Cooperatively enhanced coupling, similar to that of light-matter interactions, is generalized to a coupled spin system. The interaction of N two-level atoms with a single-mode light field is an extensively studied many-body problem in quantum optics, first analyzed by Dicke in the context of superradiance. A characteristic of such systems is the cooperative enhancement of the coupling strength by a factor of N. In this study, we extended this cooperatively enhanced coupling to a solid-state system, demonstrating that it also occurs in a magnetic solid in the form of matter-matter interaction. Specifically, the exchange interaction of N paramagnetic erbium(III) (Er3+) spins with an iron(III) (Fe3+) magnon field in erbium orthoferrite (ErFeO3) exhibits a vacuum Rabi splitting whose magnitude is proportional to N. Our results provide a route for understanding, controlling, and predicting novel phases of condensed matter using concepts and tools available in quantum optics.
Blue/green light-emitting diodes (LEDs) have been studied extensively in medium/short-distance underwater optical wireless communication (UOWC), while available commercial bandwidth-limited LEDs cannot support the increased capacity. In this work, a 175-µm blue mini-LED with a high 3 dB modulation bandwidth of 580 MHz was designed and employed to implement a high-speed UOWC system to improve the bandwidth while maintaining high emitting optical power. As a result, we achieve the data rate of 3.8 Gb/s and the rate-distance product of 7.6 Gb/s·m of the PAM-4 signal with the 3.7e-3 bit error rate (BER) over the 2-m underwater channel by using a single-pixel 175-μm GaN-based mini-LED and an avalanche photodiode (APD). To the best of our knowledge, it is the highest rate-distance product among the UOWC systems based on a single-pixel LED and a single APD. In addition, we design multiple sets of comparison experiments to provide a comprehensive investigation regarding channel loss, transmission capacity, and computation complexity between the UOWC system with and without water.
A silicon photomultiplier (SiPM) contains an array of microcells that can each detect individual photons. Consequently, it can arguably result in the most sensitive receiver in visible light communication (VLC). However, each microcell needs a period of several nanoseconds to recover after detecting a photon. This creates a non-linear response and introduces a unique form of inter-symbol interference. In this paper, we first show that this interference splits each element of the received signal constellation into multiple clusters. This observation motivates the investigation into the use of a Radial Basis Function Neural Network (RBFNN) to deal with the impact of the nonlinearity. Both the training procedures and the performance of the RBFNN are explained and discussed in detail. The influence of the number of the RBFNN centers, the widths of the centers, the constellation size and the period of the transmitted signal samples on the system performance are investigated. In addition, two different RBFNN-based data demodulation methods are introduced. The simulation results suggest that the new RBFNN-aided receivers reduce the negative impacts of the SiPM nonlinearity and can result in lower bit error rates (BERs) for a wide range of irradiances on the SiPM.
Ernest Teye, Charles L. Y. Amuah, Kofi Atiah
et al.
The rise in population growth worldwide requires efficient management of agricultural lands through the correct determination of authentic fertilizers. In this current study, a rapid on-site detection technique was developed by using portable NIR spectroscopy in the wavelength range of 740–1070 nm together with optimum multivariate algorithms to identify fertilizer integrity (unexpired, expired, and adulterated) as well as quantify the levels (10–50%) of adulteration. NIR models were built based on support vector machine (SVM) and random forest (RF) for identification, while different types of partial least square regression (PLS, iPLS, Si-PLS, and GaPLS) were used for quantification purposes. The models were evaluated according to identification rate (Rt), coefficient of correlation in prediction (Rpre2), and root mean square error of prediction (RMSEP). For the identification of the integrity of the fertilizer, among the mathematical pretreatments used, the first derivative (FD) together with SVM gave above 99.20% identification rate in both calibration and prediction sets. For the quantification of the adulterants, Si-PLS was found to be superior and showed an excellent predictive potential of Rpre2 = 0.95–0.98 and RMSEP = 0.069–0.11 for the two fertilizer types used. The overall results indicated that a handheld NIR spectrometer together with appropriate algorithms could be employed for fast and on-site determination of fertilizer integrity.
The field of hybrid optical fibers is one of the most active research areas in current fiber optics and has the vision of integrating sophisticated materials inside fibers, which are not traditionally used in fiber optics. Novel in‐fiber devices with unique properties have been developed, opening up new directions for fiber optics in fields of critical interest in modern research, such as biophotonics, environmental science, optoelectronics, metamaterials, remote sensing, medicine, or quantum optics. Here the recent progress in the field of hybrid optical fibers is reviewed from an application perspective, focusing on fiber‐integrated devices enabled by including novel materials inside polymer and glass fibers. The topics discussed range from nanowire‐based plasmonics and hyperlenses, to integrated semiconductor devices such as optoelectronic detectors, and intense light generation unlocked by highly nonlinear hybrid waveguides.
Gil Bashan, Hilel Hagai Diamandi, Yosef London
et al.
Abstract Opto-mechanical interactions in guided wave media are drawing great interest in fundamental research and applications. Forward stimulated Brillouin scattering, in particular, is widely investigated in optical fibres and photonic integrated circuits. In this work, we report a comprehensive study of forward stimulated Brillouin scattering over standard, panda-type polarization maintaining fibres. We distinguish between intra-polarization scattering, in which two pump tones are co-polarized along one principal axis, and inter-polarization processes driven by orthogonally polarized pump waves. Both processes are quantified in analysis, calculations and experiment. Inter-modal scattering, in particular, introduces cross-polarization switching of probe waves that is non-reciprocal. Switching takes place in multiple wavelength windows. The results provide a first demonstration of opto-mechanical non-reciprocity of forward scatter in standard fibre. The inter-polarization process is applicable to distributed sensors of media outside the cladding and coating boundaries, where light cannot reach. The process may be scaled towards forward Brillouin lasers, optical isolators and circulators and narrowband microwave-photonic filters over longer sections of off-the-shelf polarization maintaining fibres.
A cascaded liquid crystal polymer-based miniature angle magnifier is demonstrated to enable high-efficiency, wide-range, and high-precision beam steering for light detection and ranging (LiDAR) applications.
We consider the statistical properties of different mosaic filters. We demonstrate that in Pitiev's morphology, the measure of shape complexity is directly related to the shape simplicity measure based on morphological correlation coefficient (MCC). Based on MCC, we introduce the normalized morphological simplification index (NMSI). Using NMSI, we show that the simpler the mosaic shape, the more shape simplification is provided by the corresponding Pyt'ev projector. For the examples of mean and median mosaic filters, we address the problem of different operator comparison. In this context we introduce the concept of statistically simplifying morphological operators. Morphological correlation of mosaic shape and diffusion mosaic operator is considered. We prove that the NMSI for the diffusion mosaic operator is not related to the complexity for the corresponding diffusion shape kernel. Thus, a principal qualitative difference in the relationship between relational and operator models for diffuse and projective mosaic linear filters is demonstrated.