In this paper, we demonstrate a three-point-supported 2D optical scanner designed to enhance the field of view (FoV) and optical scanning angles, and facilitate the development of large mirrors (>10 ). By integrating fused deposition modeling (FDM) 3D printing with electromagnetic driving, we present a cost-effective, large-sized scanning mirror with two-dimensional scanning capabilities. The mirror has an area of 144 , enabling greater light capture for enhanced scanning performance. Under DC driving, the maximum optical scanning angles are 5.99° in the x direction and 12.61° in the y direction. For AC driving, the resonant scanning frequencies are 18.2 Hz for the x scan and 19 Hz for the y scan, with maximum scanning angles of 7.87° for the x scan and 7.19° for the y scan.

This paper presents a comprehensive cryptoanalysis of a multiple-image encryption scheme based on amplitude truncation (AT) and phase truncation (PT) in the Fourier domain. In contrast to the conventional single-image cryptosystem based on phase-truncated Fourier transform (PTFT), the enhanced PTFT-based cryptosystem was proposed to encode multiple images efficiently and to augment the security strength by expanding the key space. Nevertheless, we found that the amplitude key exhibits low sensitivity, which has a restricted impact on the security enhancement and makes the scheme vulnerable. Moreover, the two random phase masks (RPMs) employed as private keys are uncorrelated with the plaintexts, which can be recovered through a devised known-plaintext attack (KPA). Once these additional private keys are recovered, the number of unknown keys is reduced to two, making it possible to recover plaintext information encrypted by this advanced PTFT-based cryptosystem using an iterative attack without any knowledge of the private keys. Based on these findings, a hybrid attack consisting of two cascaded KPAs and chosen-ciphertext attacks (CCAs) is proposed to successfully crack the improved PTFT-based cryptosystem. Numerical simulations have been performed to validate the feasibility and effectiveness of the proposed hybrid attack.

This study investigates the enhancement of the microwave (MW) electric (E) field due to the Fabry-Perot (FP) effect in cubic cells of varying sizes, and it is confirmed that the lower limit of MW power can be measured. Theoretical simulations and empirical validations are conducted for three vapor cells of different sizes. At a MW frequency of 23.904 GHz, the FP effect in the 10 mm cell is found to significantly enhance the MW E-field relative to larger cells (20 and 25 mm). The results show that, due to the existence of the FP effect, the lower limit of MW power can be measured in the cubic atomic vapor cells with different sizes. These findings contribute to the advancement of the vapor cell design for quantum accuracy measurements and the development of future atomic MW communication technologies.

This paper describes an optoelectronic oscillator (OEO) capable of accepting CW light as input and providing radio-frequency (RF) carriers as output. To the best of our knowledge, we are the first to describe an easy-to-assemble and low-cost OEO that uses visible LED sources with a standard 1 mm diameter plastic optical fiber as part of the oscillation ring. The gain is solely provided by a transimpedance pre-amplifier integrated with a photodetector. Self-oscillations occurred. Fundamental frequencies in the 7.7-26.5 MHz range were generated, since the length of the fiber and the bias current feeding the LED are both correctly tuned. A comprehensive approach is used to explain the operation of the OEO. The proposed OEO may be didactically useful for use in research or teaching laboratories by untrained people.

The popularity of focus tunable lenses has increased in the last decade. In this study we present an experimental optical characterization of a commercially available manually tunable lens to describe its behavior regarding optical aberrations, expressed in terms of Zernike coefficients, under different laboratory conditions. Measurements were performed by using a Shack-Hartmann aberrometer, and four different experiments were carried out in order to assess 1) the lens stability in time for a given temperature, 2) the temporal response of the lens, 3) the behavior of the lens when changing the room temperature, and 4) the possible influence of gravity on the lens performance according to its mounting orientation. The main conclusion we outlined states that the properties of the tunable lens stay steady over time as long as room temperature remains constant, making it a good option for ophthalmologic and optometric eye-care applications.

The main function of the dynamic scan and stare imaging system is to quickly and continuously search a large area and perform high-resolution imaging. To eliminate image motion during the scanning process, this paper proposes an image motion compensation control method with dual-channel control. First, an improved model-assisted active disturbance rejection control is proposed, in which an auxiliary model is integrated into the algorithm to improve the control accuracy and response speed of the rotation rate of the platform. Second, a fast steering mirror (FSM) is introduced into the control system to compensate for the scanning speed and multiple disturbances. By adopting the amplitude frequency characteristics of the tracking differentiator, a parallel tracking differentiator filter is designed to suppress the interference of gyroscope noise on the FSM. When the system is disturbed by multiple frequency disturbances, the residual error of the image motion compensation is less than the spatial angular resolution of one pixel through the dual-channel stable control of the platform and the FSM. In the scan imaging experiment results, the average value of the grayscale variance function for the compensated images is close to 90% that of the static reference images.

Aimed at addressing the problem of azimuth measurement of a short-range target with a pulsed laser, a new, to our knowledge, azimuth measurement method based on a single-pulse laser beam expanding mechanism is proposed based on the research of the pulse laser dynamic/static azimuth detection method. The echo power equation of single-pulse laser beam expanding short-range detection is derived theoretically. Combined with the spatial geometric distribution of the optical path and the normalized sum-difference angle measurement algorithm of the four-quadrant detector, a single-pulse laser short-range azimuth angle calculation model is established. Monte Carlo theoretical simulation and laboratory static measurement experiments are carried out. The influence mechanism of laser emission power, beam expanding reflection cone angle, and target projection size on the probability distribution of azimuth measurement is studied. The results show that with the increase of transmission power and target projection size, the half-width of azimuth measurement distribution decreases, the peak value increases, and the detection accuracy improves. With the increase of the cone angle of the reflected light, the half-width of the azimuth measurement distribution increases, the peak value decreases, and the detection accuracy decreases. As the spot is far away from the coordinate center, it will lead to an increase in the half-width of the azimuth measurement probability distribution, a decrease in the peak value, and a decrease in the detection accuracy.

We present several nonlinear wavefront sensing techniques for few-mode sensors, all of which are empirically calibrated and agnostic to the choice of wavefront sensor. The first class of techniques involves a straightforward extension of the linear phase retrieval scheme to higher order; the resulting Taylor polynomial can then be solved using the method of successive approximations, though we discuss alternate methods such as homotopy continuation. In the second class of techniques, a model of the WFS intensity response is created using radial basis function interpolation. We consider both forward models, which map phase to intensity and can be solved with nonlinear least-squares methods such as the Levenberg-Marquardt algorithm, as well as backwards models, which directly map intensity to phase and do not require a solver. We provide demonstrations for both types of techniques in simulation using a quad-cell sensor and a photonic lantern wavefront sensor as examples. Next, we demonstrate how the nonlinearity of an arbitrary sensor may be studied using the method of numerical continuation, and apply this technique both to the quad-cell sensor and a photonic lantern sensor. Finally, we briefly consider the extension of nonlinear techniques to polychromatic sensors.

Bound states in the continuum (BIC) refers to waves that are entirely confined within the continuous spectrum of radiation waves without interacting with them. In our study, we attempted to construct a waveguide satisfying BIC conditions by forming a polymer layer on a 4H-SiC substrate, positioned on an insulator. By fine-tuning the waveguide parameters, we minimized losses to the substrate continuum and determined that the lowest loss meeting BIC conditions occurs when the HSQ width is 1.82 µm and the 4H-SiC thickness is 440 nm. Subsequently, we investigated the supercontinuum generation (SCG) in this waveguide. First, we analyzed the primary linear and nonlinear effects in the SCG process, introducing well-established theoretical frameworks such as the generalized nonlinear Schrödinger equation (GNLSE) for pulse propagation in nonlinear media. We then studied the influence of waveguide parameters on SCG, observing the variations in SCG with different HSQ widths and 4H-SiC thicknesses. Our results indicate that optimal spectral broadening and conversion efficiency are achieved with an HSQ width of 1.82 µm and a 4H-SiC thickness of 440 nm. In our simulations, the waveguide length was set to 1 cm, and the pump pulse was modeled as a Gaussian pulse with a width of 100 fs and a peak power of 8 W.

This paper introduces and analyzes a theory for a paraxial design of a hybrid catadioptric optical system with variable focal length, which uses focus tunable optical components. Compared to the conventional zoom lens system, the proposed hybrid optical system can be designed with a smaller length and weight than a lens system of similar characteristics. The hybrid system does not need the movement of individual elements for zooming. All necessary relations for the calculation of the paraxial parameters and the third-order spherical aberration of the hybrid optical system are derived. The presented theory helps to find out the optical power distribution of individual optical elements of the whole hybrid zoom system considering the requirement on the spherical aberration of the system. In addition, the procedure for the calculation of basic design parameters of such an optical system is shown by examples.

Direct current biased optical orthogonal frequency division multiplexing (DCO-OFDM) is widely used in blue light-emitting diode (LED)-based underwater optical wireless communication (UOWC), but the limited LED bandwidth leads to nonlinear distortions at higher frequencies. Using experiments, this paper proposes and validates a differential pre-emphasis (DPE) scheme for OFDM signal transmission in underwater channels to mitigate LED modulation bandwidth-induced nonlinearity, therefore improving transmission system performance. It is shown that the optimum DPE value leads to shorter rise time and fall time of the received signal and also avoids over- and under-shoots. The DPE scheme is validated through numerical simulations for QPSK, 16-QAM, and 64-QAM at symbol rates of 10 MS/s, 20 MS/s, and 25 MS/s, respectively, with an LED bandwidth of 8 MHz. The bit error rate (BER) performances are estimated at different values of the DPE factor for each modulation format and symbol rate. The simulation results indicate an optimized modulation format and symbol rate-dependent DPE factor for achieving minimum BER values. We further validate the DPE scheme on QPSK, 16-QAM, and 64-QAM-based OFDM transmissions in a 2.5 m tap water UOWC experimental setup. Results confirm that the optimized DPE factor depends on the modulation format and symbol rate for achieving the best BER performance. Experimental results show that the DPE scheme improves BER performance significantly, providing over 4 orders of BER improvement for all modulation formats at their respective maximum symbol rates. Successful transmissions of the OFDM signal at data rates of 24.09 Mb/s for QPSK, 48.19 Mb/s for 16-QAM, and 72.28 Mb/s for 64-QAM using an 8 MHz blue-LED-based transmitter in the presence and absence of air-bubble-induced turbulence in the water channel are experimentally demonstrated in this paper.

Event-based cameras offer unique advantages over traditional cameras, such as high dynamic range, absence of motion blur, and microsecond-level latency. This paper introduces an innovative approach to visual odometry, to our knowledge, by integrating the newly proposed Rotated Binary DART (RBD) descriptor within a Visual-Inertial Navigation System (VINS)-based event visual odometry framework. Our method leverages event optical flow and RBD for precise feature selection and matching, ensuring robust performance in dynamic environments. We further validate the effectiveness of RBD in scenarios captured by a large field-of-view (FoV) fisheye event camera under high dynamic range and high-speed rotation conditions. Our results demonstrate significant improvements in tracking accuracy and robustness, setting what we believe to be a new benchmark for event-based visual odometry. This work paves the way for advanced applications in high-speed, high dynamic range, and large FoV visual sensing.

Small-sized parabolic trough collectors are a promising solution for renewable heat supply, meeting the industrial demand for thermal energy up to 250°. In this manuscript, a novel, to our knowledge, optical design hybridizing parabolic trough concentrators with photovoltaic generators is introduced, incorporating actionable photovoltaic slats in the aperture plane. This configuration allows efficient operation under diffuse irradiance and improves electricity production when direct irradiation is insufficient. Optical simulations using OTSunWebApp software demonstrate that the inclusion of photovoltaic slats does not significantly reduce optical efficiency. The hybrid collector allows simultaneous or exclusive production of thermal and photovoltaic energy, adapting to various energy demand conditions.

This paper proposes a novel seawater temperature sensor, to the best of our knowledge, that utilizes an optical microfiber coupler combined with a reflective silver mirror (OMCM). The sensor's sensitivity and durability are enhanced by encapsulating it in polydimethylsiloxane (PDMS). Additionally, a specially designed metal casing prevents the OMCM from responding to pressure, thus avoiding the challenge of multi-parameter demodulation and increasing its adaptability to harsh environments. The paper analyzes the advantages of the new sensor structure and evaluates its performance in terms of temperature sensitivity and compressive strength through experiments. Finally, the paper employs machine learning demodulation methods. Compared with traditional demodulation methods, the particle swarm optimization support vector regression (PSO-SVR) algorithm demonstrates a substantial reduction in the demodulation error. Specifically, the mean absolute percentage error (MAPE) relative to the full scale drops from 2.16% to 0.157%. This paper provides an effective solution for high-precision monitoring of the ocean environmental temperature.

We have realized for the first time, to the best of our knowledge, a 2 µm nanosecond solid-state passive Q-switched Tm:YAP laser based on a / heterojunction saturable absorber. At an incident pump power of 12.69 W, the Tm:YAP laser produces stable laser pulses with a minimum pulse width of 818 ns, a maximum single-pulse energy of 15.48 µJ, and a peak power of 18.93 W at a repetition rate of 79.44 kHz. The comparison results show enhanced saturable absorption performance compared to single (1 µs, 70.32 kHz) and single (1.31 µs, 71.97 kHz). The experimental results confirm that the / heterojunction is a promising saturable absorption material that can be used to realize high-performance mid-infrared pulsed lasers. The resulting nanosecond 2 µm Q-switched pulsed laser will play an important role in atmospheric monitoring, lidar, and other fields, and can provide a strong driving force.

Soft matter research often involves studying correlation functions such as the intermediate scattering function. Wave scattering experiments or digital Fourier microscopy are usually used to obtain this function, generating large amounts of data that must be analyzed to obtain reliable information. However, this process can be time-consuming and requires an optimized data analysis procedure to minimize calculations while ensuring statistical validity. To address this issue, we have developed an algorithm that uses an efficient sampling technique to reduce the number of calculations needed for fast statistical convergence in digital Fourier microscopy. Our algorithm provides information equivalent to traditional analysis but in a much shorter time frame, up to 2 orders of magnitude faster.

The curvilinear mask has received much attention in recent years due to its better lithography imaging fidelity than the Manhattan mask. As a significant part of computational lithography techniques, the curvilinear OPC optimally designs the mask contour represented by parametric curves to generate a curvilinear mask structure. However, the current curvilinear OPC process is computationally intensive and contains redundant data. In this paper, a curvilinear OPC method using the non-uniform B-spline curve, together with a knot removal process, is proposed to improve the optimization efficiency and reduce the mask file size. The non-uniform B-spline curve is used to characterize curvilinear mask structure without a complex splicing process, which can effectively reduce the computation complexity. To our best knowledge, knot removal theory is for the first time applied to solve the redundant data problem in curvilinear OPC. Simulations and comparisons verify the superior optimization efficiency and data reduction (DRON) rate of the proposed method.

Measuring the linear polarization signal in extreme-ultraviolet (EUV) spectral lines, produced by the Hanle effect, offers a promising technique for studying magnetic fields in the solar corona. The required signal-to-noise ratio for detecting the Hanle polarization signals is on the order of 10 (off-limb) to 10 (disk center). Measuring such low signals in the photon starved observations demands highly efficient instruments. In this paper, we present the design of an instrument, (SPOLEO), which utilizes reflective components with suitable mirror coatings and thicknesses to minimize the throughput losses. We analyze the system performance within the spectral range from 740 to 800 Å. The K-mirror-based polarimeter model provides a polarizing power of 20%-40% in this wavelength range. Based on the system throughput and polarizing power, we discuss various possibilities for achieving the required signal-to-noise ratio, along with their limitations. Due to lack of facilities for fabrication and testing in the EUV, we have calibrated a prototype of the reflection-based polarimeter setup in the laboratory at the visible wavelength of 700 nm.

High-flux solar furnaces are valuable tools for applied research and development in solar energy. However, misalignment of concentrator facets can produce optical losses and lower the concentration ratio of these systems. This study proposes a practical method to align a faceted solar furnace. The optical method uses a computer projector that illuminates the facets with a well-defined light pattern to quantitatively and qualitatively determine any misalignment associated with the mirrors. Through the Monte Carlo ray-tracing technique, the complete solar furnace, projector, and observation plane are optically modeled for the development of the methodology. A theoretical sensitivity analysis of the technique is reported, along with the experimental validation of the determined mirror misalignments, which results in a detection accuracy of 0.32 mrad.

With current polishing methods, it is hard to guarantee roughness uniformity between the edge and inner regions of the surface. Hence, this paper develops a sub-aperture polishing method based on chemical mechanical action to remove turning periodic marks and improve surface roughness uniformity. A compliant polishing pad with a rigid tool holder is proposed to ensure that the pressure in the contact area remains constant when the polishing tool moves out the edge of the workpiece. The optimal process parameters were investigated in the full aperture polishing experiment. Numerical simulation was implemented to analyze the relationship between the overhang ratio and removal uniformity and optimize the polishing trajectory parameters. The polishing experiments with aluminum alloy mirrors reveal that the impurities inside the aluminum alloy restrict the further improvement of surface roughness. The average surface roughness is improved from 8.82 nm to 1.71 nm, and the peak and valley roughness value is reduced from 2.51 nm to 0.71 nm, which indicates the proposed sub-aperture polishing method can improve the surface roughness uniformity.

The opto-mechanical system of optical whispering-gallery mode (WGM) microcavities confines resonant photons in micro-scale resonators for a long time, which can strongly enhance the interaction between light and matter, making it an ideal platform for various sensors. To measure the slim optical pressure in the interaction between the laser and matter, a silica microdisk cavity sensor with metal film is designed in this paper. In this study, the finite element method was employed to investigate the opto-mechanical coupling mechanism in a microdisk cavity. From the aspects of optics and mechanics, the structural parameters of the sensor were optimized and the performance was simulated. The simulation results show that at 1550 nm, the sensor's optical quality factor () can reach ∼10, the free spectral range is ∼5.3 , the sensing sensitivity is 5.32 / , and the optical force resolution is 6.61×10 , which is better than the thin-film interferometry and optical lever method.