Guest Editors Nick Takaki, Alexander Lin, Fatima Toor, and Matthew E.L. Jungwirth introduce the Special Section on Education and Training in Optical Instrumentation and Lens/Illumination.

We discuss oblique spherical aberration, its balance, and its control. Several ways to mitigate this aberration are listed and some lens design examples are presented. The variation of oblique spherical aberration as a function of index of refraction and the shape factor of a thin lens is also presented. It is argued that controlling the amount and distribution of spherical aberration propagating in a lens system can be an important mechanism for mitigating oblique spherical aberration. The control of oblique spherical aberration is illustrated with a double Gauss lens, with lenses for microlithography, and with a lens for mobile phones.

Computer-based simulation tools can be an effective component in the teaching of aberrations, interferometry, and optical testing, as part of an educational strategy that includes classroom fundamentals and hands-on laboratory practice. At the University of Rochester, a MATLAB-based simulation graphical user interface (GUI) has been incorporated into both the undergraduate and graduate curricula. Users specify aberrations using either primary Seidel aberration coefficients or Zernike coefficients and the simulation GUI produces a broad array of displays including wavefront and transverse ray aberration representations, imaging-system performance metrics, interferometry simulation, including lateral shearing interferometry, Shack–Hartmann sensing simulations, and Foucault knife-edge and wire tests. We describe the simulation GUI and discuss how aspects of it are used to enhance classroom instruction at both the undergraduate and graduate levels.

This article introduces a streamlined method for ray-tracing Gaussian laser beams in optical systems, drawing from traditional matrix optics and J. A. Arnaud’s complex rays. It provides an intuitive tool for optical engineers, accommodating arbitrary initial beam curvatures and spot radii for versatile system analyses. Examples, including beam focusing, mode matching, and zoom lens systems, demonstrate its applicability. We present a user-friendly Microsoft Excel tool for simulations and optimization, along with a Python-coded 3D beam propagation model. This method enhances understanding and equips professionals with practical tools for various optical configurations. This work also explores the application to 3D virtual reality.

The U.S. Air and Space Forces require optical expertise among their personnel. The Air Force Institute of Technology offers a graduate optics curriculum, which includes a three-course sequence to educate students in the optical concepts of radiometry and radiometric instrumentation. We find radiometry is often a deceptively difficult concept for students to master. To address this, we have developed an experiment in our optics-laboratory coursework to help them gain this mastery. A Fourier-transform infrared spectrometer (FTS) is used to collect spectral data from an unknown sample. FTS calibration and data collection are discussed here, as are the two specific samples used, one with specular reflectance properties, the other with diffuse. The analysis methodology used on the data is also discussed. This is a good radiometry exercise to reveal to the student what can be learned about an unknown material’s optical properties in a remote-sensing scenario and is the basis upon which the limiting simplifications of this initial experiment may be generalized to address more difficult, but more realistic, remote-sensing analyses.

The Institute of Optics at the University of Rochester (UofR) launched a program in the fall of 2020 for students interested in earning an MS in optics. The program is referred to as the hybrid optics master’s education (HOME). The HOME system of coursework allows working individuals to take classes remotely either synchronously with in-person MS students through Zoom or asynchronously guided by the professor. Courses are structured to be inclusive to the online learner through group projects and discussion with other in-person/online students and one-on-one interaction with the professor and teaching assistant. Each course has specific learning objectives and may incorporate a variety of technology platforms to engage the online student and create an active learning environment. The degree requirements for the MS HOME and in-person Optics MS are identical; only the form of curriculum delivery is modified. Optics faculty were enrolled in a specific course through the UofR’s Warner School of Education to develop their online curriculum. In the three short years since the program’s inception, we have gathered data on what makes a successful online master’s student in optics and how to keep the online student engaged in the classroom and connected to their professors as well as other students in the program.

Public educational outreach is critical for introducing students to the field of optics. Video-sharing platforms, including YouTube and TikTok, are powerful tools for introducing optics to young students, especially as video consumption rates continue to rise. The proliferation of short, casual videos shot vertically on a cell phone on these applications and other social media platforms has greatly reduced the barriers to entry for educating through video. This work will cover the strategies and tactics used by Edmund Optics in recent years to establish and rapidly scale up a video-based outreach program that now reaches up to 13 million views per month. While this scale may at first seem unattainable, short-form video on social media provides a low-cost, low-time-requirement method for achieving this level of reach. In addition to practical guidance for educational video creation, the benefits of such an effort to the company or institution who sponsors it and tips to get buy-in from organizational leadership will be shared. A digital video-based optics outreach program can serve as the foundation for a larger outreach effort that develops the future photonics workforce.

There is a shortage of trained optical engineers in our industry, particularly a shortfall of optical design engineers. One way to create more optical designers is through a cultivation strategy. This work discusses the current optical design education process and describes a possible strategy to cultivate engineers into real working optical design engineers based on the mentorship program used by Hughes Aircraft Company in the 1980s. The process used by Hughes Aircraft Company is discussed and a possible structure for implementing something similar is based on today’s toolset and requirements. The design process is broken into 12 blocks, each of which consists of four one hour classes with four hours of homework for each. Using a layered approach, the homework can accommodate students with diverse backgrounds and skills and can be taught using any of the existing optical design codes. The document includes a detailed structure of 48 lessons for a possible mentoring program, which can be customized as necessary for specific groups of students or companies. The mentoring program has been refined over the past five years, with more than 30 participants to date in seven countries and a dozen companies with great success.

Optics and photonics have become integral components of undergraduate and postgraduate curricula due to their extensive applications in physics, biology, and engineering, particularly in fields such as sensing and communication. Diffraction and interference phenomena are building blocks for understanding principles of optics and photonics based technologies. As a result, these concepts are taught to students at various educational levels in colleges and universities. However, many students currently face challenges in grasping the fundamental principles of light diffraction and interference. To address this issue, there is a need for an experimental setup that can effectively and visually explain these principles to students. We present a single-beam experimental setup. This setup is well suited for conducting a range of experiments related to the diffraction and interference of light. Through the utilization of this setup, we are able to showcase the experiments involving diffraction patterns produced by circular apertures, knife-edge diffraction, single slit, wire diffraction, as well as intriguing phenomena, such as the Poisson spot and spatial frequency filtering.

Optics is an excellent complement to undergraduate study in fields such as mechanical, electrical, or biomedical engineering. Applications in those disciplines are also a great motivation for deeper learning in optics. One area in particular where optics and engineering intersect that is worthy of more attention is three-dimensional (3D) printing (3DP). I describe how optics concepts relevant to 3DP enhance the usual introductory discussion as well as how 3DP can be beneficial to the humbly stocked optics lab. The work concludes with some practical examples of capabilities that have been made possible in our instructional labs through 3DP.

This communication analyzes the potential for immersive virtual reality (IVR) to improve efficiency in optics education. We first critically review the common motivations to use IVR in education. Second, we highlight the two capabilities of IVR that distinguish it from the other visualization technologies that can be used in education: immersion and analysis of the learner’s movement. Then, we identify four characteristics of situations in which IVR can efficiently support optics learning: large equipment, operating with distraction, security training, and feedback for motor skills. We illustrate these findings with 11 concrete examples.

We present practical laboratory work for master’s students in photonics. The laboratory session is based on the construction of a telescope, emulating the one used by Galileo Galilei and analyzing the effect of aberrations and other practical limitations on the quality of the image. Different situations and configurations are analyzed, and the recreation of historical observations is carried out to generate a debate on the limitations of real telescopes with the students. The impact on the learning procedure of the students is analyzed by means of the results they have obtained during several academic years.

This research aimed to compare physics syllabi on the diffraction concept implemented in Indonesian, Malaysian, and International schools. This research used a qualitative approach with document analysis and interview methods. The analysis showed that the syllabi used in the three schools exhibit significant differences even though both neighboring countries use similar instructional languages. The differences are highlighted in concept usage terms, students’ ages, and the concept delivery flow. The interview findings showed that the teachers developed their teaching and learning activities based on the students’ circumstances and the availability of teaching aids and practicum instruments.

Digital and remote education is of growing interest for internationalized education programs that combine state-of-the-art training programs including hybrid and blended elements. Particularly, but not limited to optics and photonics, hands-on experiences in training laboratories are key ingredients of modern academic education programs that cannot easily be replaced adequately. We propose a versatile platform for remote-controllable experiments with a focus on a flexible implementation. We present a toolbox called Extended Reality Twin Lab, which enables teachers and lecturers in academia with a personal commitment to advance and innovate education methods and learning outcomes to build their own remotely controllable optics and photonics experiments. An open-source GitHub repository includes source codes for the server, the respective web applications, and the included microcontrollers. It also contains the 3D printable models used to create the attachments for optical components often used in scientific labs. All parts are modularly designed to enable individual adaptation to a variety of experiments. We exemplify our approach by presenting a fully remote-controllable Michelson interferometer that was readily implemented in an ongoing international master’s degree curriculum. With this implementation, international students are now able to attend the course and acquire specific optical knowledge and lab training regardless of their actual physical location. Reviewing this running field experiment, we also discuss students’ learning outcomes with respect to optical principles, experimentation, and instruments.

The optics industry, essential for innovations such as smartphones and defense technologies, is transforming daily life. Optics technicians, key in manufacturing and quality control, contribute significantly to these advancements, so development of the current and next-generation optics manufacturing workforce is vital. To meet this growing demand for skilled optics technicians, Monroe Community College’s Optical Systems Technology Program created the Defense Engineering Education Program in Optics initiative to increase the national precision optics technician workforce. The program has consistently grown enrollment and graduation rates over the last several years through the following strategies: (1) offering innovative training; (2) recruiting and retaining underrepresented populations; and (3) fostering partnerships with industry and educators. We describe how Monroe Community College has become a national model for building a successful precision optics technician training program, thus reinforcing the United States’ capabilities in both technology and national security.

Objective based surface plasmon resonance microscopy (SPRM) is a label free technique, which is suitable for observing chemical and biological activities at metal-dielectric interfaces in real-time, with high resolution. Recently, digital holographic techniques have been combined with the SPRM to further increase its sensitivities. In SPRM and SPR digital holographic microscope (SPR-DHM) setups, cube beam splitters (BS) are commonly used to direct light onto the back focal plane (BFP) of the microscope objective. However, SPRs feature very strong absorptions, and the intensity of the unwanted reflections from the BS could be of the order of the SPR image intensity. These unwanted reflections will produce strong interference noise in both SPRM and SPR-DHM. The fringes thus generated have to be removed. The illumination being convergent, the reflections would focus in the direction opposite to the BFP. We propose to block them by inserting a 3D fabricated hard knife-edge filter set at that focus, in such a way as not to stop the SPR waves from forming images of interest. Experiments and simulations show that the filter can significantly improve the image quality by reducing the root mean square of the unwanted fringes from 12.6 to 0.500 in terms of gray levels.

We propose a modified residual neural network (ResNet) to quickly and accurately detect the particle quantity from raw reconstructed images of a high-density particle solution in digital holography. The raw reconstructed image is fed into the modified ResNet to obtain the particle quantity. Then, the quantity and particle concentration in the captured volume are calculated. The metrological challenge is modeled as a regression problem in deep learning. The average relative error of the holograms in the test dataset is less than 10% even when predicting the particle quantities untrained by the model. Hence, an accurate particle quantity is obtained even when the raw reconstructed images are not denoised, thereby reducing the processing time.

Digital image correlation (DIC) has the advantages of non-contact, high accuracy, and full-field visibility, making it a prevalent tool for structural health monitoring of stratospheric airship skins. However, real applications need to be run on mobile and embedded devices, and the high computational resource requirement of the DIC method poses a challenge to its implementation. To this end, a lightweight digital image correlation network (LW-DIC-Net) is proposed specifically for DIC applications with limited computational resources. First, we utilize the depth separable convolution to reduce the model complexity. Then, we design an attention module named efficient convolutional block attention module, which is an enhancement of convolutional block attention module adopting the efficient channel attention instead of the general channel attention to guarantee prediction accuracy. Experiments demonstrate that our method achieves a 43.04% reduction in the number of parameters and a 44.75% decrease in floating-point operations per second compared to the original DIC-Net while maintaining the measurement accuracy. With these improvements, the LW-DIC-Net proves to be exceptionally suitable for complex stratospheric environments and resource-constrained mobile and embedded devices, providing an efficient and accurate method for stratospheric airship skin deformation measurements.

In prior research, Jamali et al. demonstrated the efficacy of a 20-mm aperture liquid crystal (LC) tunable lens for both accommodation-convergence mismatch correction and presbyopia correction. This lens employed a concentric ring electrode-based LC design with a segmented phase profile, enabling a larger aperture size without affecting switching speed. However, for near-eye application, a high optical quality LC lens with larger than 20-mm aperture size is a requirement to allow large field of view. Therefore, we report here a 50-mm aperture LC lens with incorporated solutions to minimize haze that results due to the large aperture size. Due to its large aperture size, fast switching speed, compact size, and low voltage operation, the reported 50 mm LC lens is a practical option for near-to-eye applications and other tunable lens applications. The objective of this paper is to provide a comprehensive detail on the design, modeling, fabrication, and characterization of the optical quality of the developed 50 mm LC lens. Quantitative assessments of the lens’s optical quality are presented across the entire aperture, with a particular focus on near-eye applications.

Digital micromirror devices (DMDs), owing to their rapid refresh rates, are among the most commonly used spatial light modulators in holographic three-dimensional near-eye displays. However, the modulation of DMD is typically confined to binary amplitude modulation, resulting in a noticeable presence of zero-order and conjugate noise, which significantly occupies the spatial bandwidth of the display optics and reduces the quality of optical reconstruction. To address these issues, we propose a computational framework of generating optimized binary computer-generated holograms for DMD-based holographic near-eye displays. Our work employs an iterative-based optimization strategy within a band-limited diffraction computation, thereby enhancing the display quality while achieving a considerable field of view by eliminating zero-order and conjugate noise. The proposed method is verified experimentally by displaying true three-dimensional images with low speckle noise and high contrast, opening a path towards next-generation of virtual reality/augmented reality display devices.

Tomato is an important vegetable that is rich in antioxidants, vitamins, and minerals and has significant economic and health value. In this study, hyperspectral images in the wavelength range of 370 to 1715 nm were first preprocessed to improve the data quality and comparability. Subsequently, the tomatoes were chemically destroyed, and the average activities of peroxidase enzyme, phenylalanine ammonia-lyase enzyme, and α-amylase enzyme were 5.108 mU/g, 7.347 U/g, and 35.856 U/g, respectively. Then, two spectral selection algorithms, the genetic algorithm (GA) and the successive projection algorithm, were used to extract effective wavelength bands from high dimensional spectral data. And the extracted effective wavelength variables were combined with partial least squares (PLS) regression to build the optimal spectral selection model GA-PLS. Finally, three additional spectral prediction models were created by combining the GA-selected spectra with three other algorithms: support vector machine, particle swarm optimization-backpropagation neural network, and random forest. After comparing the predictive performance of four models, it was found that the GA-PLS model had the highest prediction accuracy and stability. Furthermore, compared with tomato stems, the near infrared (NIR) bands of tomato leaves were more accurate in predicting the enzyme content of tomato plants. It was found that the GA-PLS model had a better prediction performance for the three enzymes in the NIR band of leaves with R¯p (average coefficient of determination for the three enzymes) and RMSEP¯ (average root means square error of the three enzymes) of 0.815 and 1.659, respectively. This provides an effective method for phytochemical composition analysis using hyperspectral imaging.

Projector calibration is crucial for the structured light three-dimensional measurement system. However, the projector is unable to capture images like a camera, thus the accuracy of projector calibration is determined by the mapping relationship between the pixel coordinate system of a camera and that of a projector. The goal of optimizing projector calibration is to find a more accurate mapping relationship. We propose a sub-pixel mapping method based on blob detection to find the corresponding projector pixel coordinates of the marker points of a calibration target and then realize sub-pixel level projector calibration. This method can reduce eccentric error and is also suitable for the projectors with different pixel arrangements. Besides, it is independent of the results of camera calibration. Experimental results demonstrate that our proposed mapping method can achieve good projector calibration performance: its re-projection error is about 10% less than the existing methods and the accuracy of measurement with the calibrated results is also higher.

This article presents a comprehensive analysis of the dispersion characteristics of virtually imaged phased array (VIPA) based on the principle of paraxial dispersion. It proposes a calculation equation for the Brillouin shift specifically designed for a single-stage VIPA-based Brillouin scattering measurement system. To capture Brillouin scattering images of water and anhydrous glycerol, a Brillouin scattering measurement system is constructed. The Brillouin shift of both substances is calculated using the proposed method in this article as well as the methods proposed by Giuseppe Antonacci and Pei-Jun Wu. The comparison of the three calculation results with the theoretical values confirms the accuracy and reliability of the proposed method. Moreover, this study addresses practical challenges in Brillouin image processing and introduces a precise method for extracting Brillouin spectra from the images. Additionally, a spectral calibration program is developed using MATLAB, guaranteeing accurate spectral extraction while greatly streamlining the spectral processing workflow.

In a smoke environment, smoke-suspended particles scatter and absorb laser photons. Smoke not only attenuates the target echo signal but also forms backward scattering. It interferes with the extraction and recognition of the target signal and brings great difficulties to the laser fuze detection. This article establishes a simulation model of the echo of a linear frequency modulation (LFM) pulse laser fuze in a smoke environment based on an improved Monte Carlo and multi-layer perceptron method. While ensuring the simulation accuracy, the echo simulation speed is greatly improved. Meanwhile, the precise ranging of the LFM pulse laser fuze was achieved using the pulse compression Butterworth filter signal extraction algorithm. In low concentration smoke interference environments, the backward scattering interference signal of smoke can be completely removed. The target signal is completely attenuated in interference environments with smoke concentrations greater than 1.4 mg/m3. Smoke interference is present but has a small amplitude and can be excluded by an appropriate threshold. The LFM pulsed laser regime outperforms the pulsed regime in high concentrations of smoke. The research results provide important support for the application of an LFM laser instead of a pulse laser in the field of fuze.

We generate a zero-order Bessel beam with a laser beam focused onto an elastomeric replica of a weevil carapace scale. Carapace surface structures are imprinted on an elastomeric cast via soft lithography. The output Bessel beam exhibits the expected properties of non-diffraction over a propagation range of 30 cm. The width of the central spot at a propagation distance of 25 cm is 296.8 μm, corresponding to a replicated weevil scale with a diameter of 64.3 μm acting as an annular slit. Self-healing of the beam after encountering a wire obstruction is also observed.

Based on our original development of a new laser absorption spectroscopy chamber (LASC) system, we further report ammonia emission concentration measurement using the LASC system based on deep belief networks (DBNs), aiming to present an effective approach for the retrieval of the gas concentration to increase the measurement accuracy of the LASC system and expand its application to monitoring ammonia emission in farmland. Surrounding the LASC system, an experimental system was constructed, and a DBN algorithm was introduced for gas concentration retrieval. The absorption spectroscopy obtained by the experimental system was first pretreated by an empirical wavelet transform algorithm and principal component analysis method, which greatly improved the signal-to-noise ratio of the signal and reduced the dimensionality of the processed signal to meet the need of the training of DBN model. The results showed that the measured gas concentrations were close to true values with small errors, and the mean relative error obtained by the DBN algorithm (0.37%) was much smaller than those obtained by the back-propagation neural network algorithm (0.97%) and absorbance peak method (2.37%) in a wide range of NH3 standard concentrations. Field experiments verified the effectiveness and reliability of the LASC system when it was applied to ammonia emission measurement in farmland with the concentration retrieval based on the DBN algorithm, which is of importance for its applications in air pollution detection.

The purpose of this work is to design and manufacture low cost, efficient terahertz (THz) diffraction gratings using a 3D printing technique. We performed theoretical modeling and numerical simulations to determine the components’ optimal parameters; then, we proceeded to 3D printing and final production of the desired component. Experimental characterization has shown that the components that we manufactured offer very satisfactory performances despite their insignificant cost, which is promising for providing THz components with a very high quality/price ratio.

This paper presents the results of wave-optics simulations predicting losses due to the effects of atmospheric optical turbulence on laser communication (lasercom) space-to-ground downlinks. Power in the aperture, tilt-corrected Strehl, and phase-corrected Strehl are reported. These may be used by engineers evaluating design trades and developing link budgets. Results are reported for a variety of scenarios at both the 1.55 and 1.06 μm lasercom bands. Zenith angles from 0 to 80 deg and aperture diameters of 0.1 to 1.0 m are modeled. Height of the receiver’s aperture above ground is considered and found to make only a small difference in link turbulence loss. Both 1 and 3 times the well-known Hufnagel-Valley 5/7 turbulence profile are used in the simulations. For each scenario, 4800 statistically independent instances were run. This paper reports the results of the cumulative probability tails of fade at 2.5×10−3. On links where errors are dominated by turbulence-induced fades, with proper interleaving and a good forward error correction code, this probability of channel fade can translate to a user bit error rate orders of magnitude lower.

In this numerical study, we examined solid-state lasers that comprise side pumping with a blue light-emitting diode (LED) and a Ce:Nd:YAG lasing medium, utilizing the Monte Carlo photon tracing technique. We designed and modeled new cavities for LED side-pumped solid-state lasers. As a precondition for the experimental realization of these proposed cavities, we investigated trapezoidal and hexagonal shapes from the family of planar structures, along with parabolic and double parabolic shapes from the family of curved structures. Exploring a range of cavity parameter spaces, we determined the optimized parameters for the proposed cavities. Notably, the double parabolic cavity exhibited the highest efficiency in terms of laser performance. We calculated laser outputs by considering model parameters, such as pumping efficiency and absorption distributions, using space-dependent rate equations. Our study demonstrates the potential to achieve an output higher than 30 W with a 10% optical-to-optical efficiency for a blue-LED pumped Ce:Nd:YAG laser, and an even higher output, ∼40 W, with a slightly improved 13% efficiency for a near-infrared LED pumped Nd:YAG laser

The metasurface is composed of a large number of sub-wavelength unit structures, which has received wide attention in the fields of holographic display and functional encryption due to its smaller structure size and more flexible modulation capability. And it has been extended to a more elaborate design for the increasingly demanded information-carrying capability. In this work, a dual-band four-channel reflective metasurface that operates simultaneously in the visible and near-infrared light is designed using heterogeneous meta-atoms and polarization-multiplexed holography. Hydrogenated amorphous silicon (a-Si: H) and Au are interleaved in the same plane, and the properties of the composite phase modulation determine the dimensional parameters of the two materials, which modulate the polarization distribution of the holograms using an optimized Gerchberg-Saxton algorithm based on quadratic phases. The designed dual-band multi-channel metasurface may provide a new avenue for device integration and enhancement of anti-counterfeiting technology.

This article describes the design of an optical system using multi-wavelength illumination and dispersion principle to achieve iris recognition imaging with a large depth of field in noncooperative environments. Through the use of optical design software, the iris acquisition imaging system was designed with the modulation transfer function (MTF) curve serving as the evaluation criteria for this system. It was found that at different object distances, the MTF value at a spatial frequency of 100 lp/mm is greater than 0.33, indicating that the iris acquisition imaging system has a significant depth of field. To further validate the performance of the system, we set up an actual optical platform based on the parameters designed by the optical design software for the iris acquisition imaging system and conducted iris image acquisition experiments at different object distances, obtaining iris images of three different individuals. We performed algorithm verification on the iris recognition of the three sets of iris images and found that the average interclass matching result was 0.44, while the average intraclass matching result was 0.30, demonstrating a high level of accuracy in iris recognition. This indicates that the iris images obtained by the system have a high resolution, thereby confirming the feasibility of depth extension using multi-wavelength illumination and lens chromatic aberration imaging principle. It is worth mentioning that this method is not only applicable to iris recognition but also holds reference value in other biometric recognition fields.

We present a numerical investigation of the generation of an ultra-broadband optical similariton spectrum in a photonic crystal fiber (PCF) with a carbon disulfide core through Raman amplification. The proposed PCF has an extremely high nonlinear coefficient of 4519 W−1km−1 at a telecommunication wavelength of 1550 nm and exhibits near-zero ultraflattened normal dispersion of −1.5(ps/nm/km) as well as low confinement loss of about 10−9 dB/m at 1550 nm. The numerical study was conducted using full vectorial finite-element method with a circular perfectly matched layer as a boundary condition. The similariton generated in the proposed PCF has an ultra-broadband and flat spectrum centered at 1550 nm, which spans from 1383 to 1719 nm via 14 mW input peak power and over a fiber length of only 83 cm. This continuum spectrum covers both C and L bands and can be divided into several narrow bands centered at the wavelengths of the wavelength division multiplexing channels.

Facing integration and intelligence requirements of the contemporary magnetic field sensing, a highly sensitive compact magnetic field sensor based on magnetofluid-infiltrated dual-core photonic crystal fiber with gold layer is proposed and analyzed. The mature finite element method is employed to implement optical property investigation. The simulation results demonstrate that when the large hole diameter d1 is 1.80 μm, the small hole diameter d2 is 1.20 μm, the lattice constant Λ is 2.00 μm, the major axis length of the elliptical holes a is 1.875 μm, the minor axis length of the elliptical holes b is 0.75 μm, and gold layer thickness t is 50 nm; the sensor operates near 1.55 μm and the optimal sensing performance can be achieved. Within the detected magnetic field range of 43.00 to 522.60 Oe, this sensor possesses a minimum length of 0.872 mm, a maximum sensitivity of 0.149 nm/Oe with the corresponding magnetic field resolution of 0.0067 Oe and a high linearity of 0.9994. What’s more, the fabrication scheme is also discussed. It is believed that the proposed sensor includes multiple advantages of compactness, high-sensitivity, high-linearity, and ease of manufacture, making it an ideal candidate for magnetic field detection in power systems, oilfield exploration, and aerospace.

An active quenching circuit in 0.35 μm bipolar complementary metal oxide semiconductor (BiCMOS) technology with a high quenching slew rate is introduced. Quenching transients of an integrated single-photon avalanche diode (SPAD) measured by means of an integrated mini-pad are shown. An NPN transistor as quenching switch enables an active quenching time of 350 ps from an excess bias voltage of 6.6 V and a quenching slew rate of 15 V/ns. Active resetting of the SPAD can be achieved in 550 ps. The power consumption of the BiCMOS quenching circuit is 8.6 mW at 40 Mcounts/s and 3 mW in the idle state.

We perform shape optimization of anti-resonance fiber (ARF) structures using a particle swarm optimization algorithm, achieving the lowest confinement loss of 2.4347×10−5 dB/m at 1.07 μm based on a single-layer tubing structure. Different from the existing design approaches that focus on size optimization and stacking of tubes, this research employs algorithm-driven point iteration and reconstruction to explore new structures for ARFs. This approach enhances the design flexibility and provides a new perspective for the design of ARFs. Furthermore, it was discovered that adding an additional tubing can effectively control the bending loss. This method enables the optimization of tubing shapes that are difficult to achieve through parameter analysis and supports local optimization of tubing structures. This method is capable of discovering higher-performance ARF structures based on existing classical designs, which is a significant inspiration for the design of non-uniform waveguides.

We propose a broadband bismuth-erbium co-doped fiber amplifier (BEDFA) that utilizes a bismuth-erbium co-doped fiber (BEDF) as the gain medium. The amplifier utilizes a simple bidirectional pumping configuration and a shorter length of BEDF to achieve signal amplification in the C+L band. The BEDFA achieves signal amplification within a 90 nm bandwidth, spanning from 1530 to 1620 nm, with an input signal power of −30 dBm, and achieves a maximum gain of 23.261 dB at 1555 nm. In summary, our proposed BEDFA demonstrates significant potential for telecommunication applications in cost-effective and compact fiber amplifiers, as well as high-capacity fiber transmission system.

A reflective dual-function beam splitter with bilayer trapezoidal structure is presented, which exhibits two standalone functionalities under normal incidence at 1550 nm. The performance of the bilayer trapezoidal structure is thoroughly investigated using simulated annealing algorithm and rigorous coupled-wave analysis, with validation conducted through finite element method. The findings demonstrate that this grating possesses exceptional characteristics, offering a wide incident bandwidth and manufacturing tolerance. The grating demonstrates a consistent three-port output with an efficiency of 32.36% for ±2nd order and 33.02% for 0th order at transverse electric polarization. By the same token, for transverse magnetic polarization, the grating is capable of achieving similar five-port output, exhibiting efficiencies of 19.98%, 19.51%, and 19.37% for the 0th, ±1st, and ±2nd diffraction orders, individually. Therefore, this proposed splitter has a high reference value in the research of optical communication, laser, optical imaging, and other fields.

The performances of a red, green, and blue (RGB) combiner are crucial for the future development of laser beam scanning display systems. In this work, we conduct a comparative study on RGB combiners designed with silicon nitride (SiN), gallium nitride (GaN), and SU8 to reveal their comparative advantages, such as refractive index difference, dispersion characteristic, single-mode condition, transmission efficiency, and light field distribution. Our findings indicate that GaN devices exhibit the largest refractive index difference between the core and cladding, the smallest single-mode cutoff size, and the device length of 2000 μm, and SU8 devices have the smallest refractive index difference between the core and cladding, the largest single-mode cutoff size, and a device length of 3600 μm. In addition, the RGB average transmission efficiency of SiN, GaN, and SU8 devices are 78%, 55%, and 91%, respectively. It is worth mentioning that the optimized ultra-compact GaN multimode interference-based integrated RGB waveguide combiner is suitable for application in micro-miniature integrated projection systems, while its SU8 counterpart holds great value in deformable systems owing to flexibility. These devices will serve as the technical foundation for the development of optical projection systems that prioritize microminiaturization and high transmission efficiency.

Visible light (VL) indoor positioning offers significant advantages, such as low cost, high durability, and environmental protection. In this work, a phase difference-based VL positioning (VLP) system is presented. It uses the fast Fourier transform to accelerate the computation of the phase differences between the received signals. Furthermore, unlike most similar published works, it addresses the crucial issue of synchronization that arises in any system based on the time difference of arrival or phase difference and it proposes a technique to solve it. Compared with current indoor positioning methods using light-emitting diode (LED) light, our method has the advantage of having a high positioning accuracy, while being simple to implement and low cost. By means of simulations, we studied the impact on its performance of the choice of its design parameters, such as the values of frequencies assigned to different LEDs, the sampling frequency, the power of noise, and the lack of synchronization. The obtained results show that an appropriate choice of these parameters achieves high-accuracy positioning. Using only three LEDs, an average error of 0.59 cm could be achieved over a testing area of 100 cm×100 cm×160 cm, for a signal-to-noise ratio equal to 15 dB.

Vortex beams have a broad application prospect in the fields of information modulation, detection, and identification of targets because they carry orbital angular momentum. First, the related theories of vortex beam and bidirectional reflection distribution function are introduced. Differential surface element method is a numerical calculation method that discretizes the problem domain into small panels, approximates the properties of the problem, and transforms it into a system of algebraic equations. The expression for the backscattered intensity of a vortex beam illuminating a typical target (sphere, cylinder, cone, and dome) is derived by combining the scattering theory and the differential surface element method, and simulations are carried out. Finally, the theoretical analysis was verified by the experiments. The results show that: for different targets, the difference between the backscattered power curves of the vortex beam is larger, which is conducive to target identification; for the same target, the peak range of the backscattered power curve of the vortex beam is wider, which is conducive to the detection of multiple angles; when the typical target is a sphere and the material is different, the peak value of the backscattered power curve of the vortex beam changes with the change of the material but the trend of the change is basically the same.

Because of the pseudo phase conjugation effect (PPCE) of the micro corner-cube reflector array (MCCRA), the turbulence-induced fading in the modulating retroreflector (MRR) free-space optical (FSO) system using the MCCRA can be considerably reduced to improve the system performance. We first describe the achievement of double-pass wave-optics simulation for the MCCRA-based MRR FSO channel. Then, the channel fading of the MCCRA-based MRR FSO system is statistically analyzed together with that of the CCR-based MRR FSO system. The composite channel models based on double Lognormal (LN) and double Gamma-Gamma (GG) distributions are considered, and it is verified by the simulations that the double LN model could be acceptable for describing the MCCRA-based MRR FSO channel under the weak-to-strong turbulence conditions. On the other hand, the fading correlation between the double-pass channels is relatively high and will impact the performance improvement originating from the PPCE. Hence, bit error rates of the MCCRA- and CCR-based MRR FSO systems are analyzed and compared to illustrate the performance gain of the use of the MCCRA. Finally, the experimental measurements of double-pass channel fading are carried out in an indoor atmospheric chamber, and the experimental results show the applicability of the double LN model and the turbulence suppression of the MCCRA.

We present a detailed study on the behavior of two cascaded injection-locked (IL) single-loop optoelectronic oscillators (OEOs). We develop a mathematical model based on the previously reported analytical theory of injection-locking of a single-loop OEO under the influence of a sinusoidal radio frequency (RF) signal. We provide formulas for the locking-range of the two individual IL-OEOs and two cascaded IL-OEOs. The frequency response characteristics of the two individual IL-OEOs and two cascaded IL-OEOs are investigated by considering amplitude perturbation. The closed-form expressions for the stability of the individual IL-OEO and the two cascaded IL-OEOs are derived using Routh’s stability criteria. The influence of the injection-locking on the phase noise performance of the two cascaded IL-OEOs is investigated. Experimental results are provided to validate the conclusions. It is found that our analytical model describes the injection-locking behavior of two cascaded IL-OEOs accurately.

Underwater optical wireless communication (UOWC) is an emerging technology designed to enable advanced high data rate applications, such as environmental monitoring, underwater exploration, and secure communication for military and defense purposes. Accordingly, a high-capacity UOWC system utilizing dual-polarization states and 16-quadrature amplitude modulation with orthogonal frequency-division multiplexing is proposed. The system leverages a single laser diode operating at 532 nm to generate orthogonally polarized signals that are transmitted along the X and Y polarization axes, achieving an independent data rate of 40 Gbps per polarization state with a total capacity of 80 Gbps. The performance of the proposed system is evaluated through the bit error rate (BER), error vector magnitude (EVM), and constellation diagrams for 10 distinct waterbodies. The findings demonstrate that water types with lower attenuation, such as pure water, Jerlov I, clear ocean, and Jerlov IA, enable longer transmission distances of 13.93, 13, 10, and 10 m, respectively, at a BER below the threshold limit (3.8×10−3) and an EVM of less than 16%. Conversely, higher attenuation in Harbor I and Jerlov III waters leads to shorter achievable ranges of 3 m at the same BER and EVM values.

Erratum corrects the omission of a reference from the published paper.