Reflective Mirror Research Articles

Low loss directly etched uniform grating couplers on thin film lithium niobate platform

We report a low-loss uniform grating coupler (GC) directly etched on a thin film lithium niobate (TFLN) platform. The GC is characterized to have a low coupling loss of 3.2 dB around 1550 nm and a 3-dB bandwidth of 76 nm. Fabrication of such GC employs just a single-step etching process without any complex grating structure, mirror reflector, or incorporation of hybrid materials. Our work demonstrates that directly etched uniform GCs can realize high coupling efficiency on the TFLN platform by optimizing the fiber coupling angle, grating parameters, and upper cladding thickness, holding the potential to benefit a wide range of applications across diverse fields such as high-speed transmitters, frequency combs, and hybrid integration.

Narrow-Pulse-Width, Straight-Type-Cavity, All-Solid-State Laser at 228.5 nm

Deep-ultraviolet (DUV) lasers operating at a wavelength of 228 nm offer distinct advantages in Raman spectroscopy and analysis, demonstrating significant potential in the field of surgical medicine. This paper details the development of a high-repetition-rate, narrow-pulse-width, short-cavity laser system functioning at 228.5 nm, which is based on Barium Borate (BBO) electro-optic Q-switching. The system utilizes a double-concave resonator structure and a pressure-applied electro-optic Q-switching technique, incorporating Lithium Borate (LBO) and BBO as frequency-doubling crystals. A low-concentration Nd:YVO4 crystal, measuring 4 mm × 4 mm × 5 mm, serves as the gain medium, with a high-reflectivity coating applied to its left end face to function as the total reflection mirror within the resonant cavity. Upon achieving a pump power of 37 W at a repetition rate of 12 kHz, the system produced a maximum average power of 32 mW, with a pulse width varying from 2.48 ns to 2.70 ns and a central wavelength of 228.5 nm, which is effectively applicable for deep-ultraviolet spectral detection.

High-sensitivity ocean temperature sensor usinga reflective optical microfiber coupler andmachine learning methods.

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.

Research on vehicle-mounted measurement of NO2 based on cavity ring-down spectroscopy

Nitrogen dioxide (NO2) is a significant atmospheric pollutant with notable impacts on the environment and human health. The measurement of NO2 concentration is crucial for gas phase analysis in atmospheric chemistry, assessment of regional pollution levels, and improvement of data management systems. In this paper, a highly sensitive cavity ring-down spectroscopy (CRDS) technique has been used to measure the concentration of NO2. The CRDS system utilizes a diode laser and high reflectivity mirrors (over 99.99 %) at 405 nm, achieving a minimum detection limit of 43 ppt (1σ, 40 s) and 92 ppt (1σ, 10 s) as determined by Allan variance. In order to improve the measurement accuracy and stability, the Kalman filtering has been used to process the background ring-down time and ring-down time, and the minimum detection limit can be increased by about 2.06 times to 45 ppt (1σ, 10 s), while preserving temporal response and reducing noise. Under the condition of atmospheric NO2 measurement, a comparative experiment was carried out in Hefei with the CEAS system. The linear fitting slope was 1.033±0.017, and the correlation coefficient reached about 92 %. The CRDS device was integrated for vehicle-mounted measurements of NO2 concentrations in suburban, urban, and industrial areas of Maanshan City. The experimental result has demonstrated that this system can achieve high-precision, high-sensitivity, and stable measurements of NO2.

MULTI-SENSOR CAMERA MODEL FOR CONTROLLING COORDINATES OF POINTS ON THE SURFACE OF TELESCOPES

A new optoelectronic system for measuring the reflective mirror surface distortion of large telescopes is discussed in this study. This system comprises a multi-matrix structure of CMOS sensors, each sensor responsible for capturing an image of a control point on the mirror surface through a common objective. Simulation and calculation studies show that during operation, the position of the multi-sensor camera on the supporting ring is determined by control points on the telescope surface. The more control points, the higher the accuracy of the calculations. Simulation results indicate that the camera position error falls within acceptable limits when using 5 or more control points. Experimental results show that when calculating simultaneously with 3 control points, the error in determining the angular position of the camera reaches a value of  = 0.302 arc minutes, which is 2 - 2.5 times smaller than when calculating with only one control point.

Enhancement of PV and concentered PV panels using evaporative cooling during summer and winter seasons: A case study in Egypt

Numerous efforts are made to comprehend the performance evolution of photovoltaic (PV) panels. The elevated surface temperature causes a deterioration in PV panels' performance, hindering the expected increase in harvested energy associated with integrating solar reflectors. In this context, the year-round efficacy of cooling PV panels supported by reflective mirrors is investigated to assess the effectiveness of solar reflector implementation. A conventional PV panel, a CPV (cooled PV panel), and a CCPV (concentrated cooled PV panel) were compared side-by-side to determine their relative performance and energy productivity. Evaporative cooling pads are utilized to chill the two modified PV systems by varying the coolant flow rate during the summer and winter seasons of 2022 and 2023, respectively, in the environmental conditions of the Tenth of Ramadan City, Egypt. The findings indicate that the average daily power increment ratio (PIR) for CPV ranges from 4.7 % up to 7.4 %, while CCPV ranges from 6.7 % to 12 % for different climate conditions year-round. Finally, changing the setup configuration from CPV to CCPV increased the (PIR) 1.5 times during the summer tests and 1.7 times during the winter tests.

The Design of Highly Reflective All-Dielectric Metasurfaces Based on Diamond Resonators

All-dielectric metasurfaces offer a low-loss alternative to plasmonic metasurfaces. We proposed the configuration for high-reflectivity all-dielectric metasurfaces based on single-crystal diamond (SCD) resonators on fused silica substrate and conducted simulations to optimize and analyze such a configuration via the FDTD solver. We utilized GMR as the design principle to select the configuration and the substrate material, and analyzed the scattering properties of a single SCD resonator by multipole decomposition. Then, we demonstrated that both the cylindrical resonators in square lattice and frustum-shaped resonators in hexagonal lattice can achieve near-unity reflectivity (>99.99%) and ultra-low absorption (<0.001%) at 795 nm, the typical alkali-metal laser wavelength. Additionally, we demonstrated that such a design is quite tolerant of fabrication errors and further supports its potential for realistic applications. To expand the functionality of such devices across multiple wavelengths, dual-band high-reflectivity metasurfaces at 744 nm and 828 nm were also designed. Our work is quite useful for designing diamond-based highly reflective mirrors, paving the way for low-loss all-dielectric reflective metasurfaces in high-power laser applications.

Precise Reflectance/Transmittance Measurements of Highly Reflective Optics with Saturated Cavity Ring-Down Signals

In this paper, a data processing approach was developed to accurately extract the ring-down time and amplitude of the saturated cavity ring-down (CRD) signal; both were utilized to determine simultaneously the high reflectance and residual transmittance of highly reflective (HR) mirrors with a dual-channel CRD configuration. The influence of saturation was eliminated by deleting the beginning saturated data points of the saturated CRD signal and fitting the remaining non-saturated CRD signal to a single-exponential function. By comparing the reflectance/transmittance measurement results of HR samples obtained via data processing of saturated CRD signals and via single-exponentially fitting non-saturated CRD signals with utilization of neutral density filter(s) to eliminate saturation, it was found that the reflectances obtained with both methods were in excellent agreement, while the residual transmittance obtained with the saturated CRD signal was more accurate than that obtained with the neutral-density-filter-attenuated non-saturated CRD signal. The proposed data processing method eliminated the need to use the neutral density filters, therefore avoiding the adding of the optical density error to the uncertainty of residual transmittance measurement and improving the measurement accuracy. The proposed data processing method also extended the dynamic range of the dual-channel CRD scheme for simultaneous measurement of reflectance, transmittance and optical loss.

Enhancing the efficiency of wavelength-shift fiber-based detectors for optical wireless communications

A wavelength-shift fiber-based optical detector promises to revolutionize the deployment of optical wireless communication (OWC) due to its inherent advantages over traditional receivers. These advantages include a flexible structure, a wide field of view (FOV), and a large active area. Despite progress in previous studies, there remains a gap in optimizing the re-utilization of unabsorbed light within wavelength-shift fiber (WSF) and maximizing the efficiency of light focusing onto photodetectors. To address these challenges, this study explores three novel, to the best of our knowledge, approaches to enhance the light conversion and detection efficiency of WSF-based optical detectors. First, a reflective mirror is employed behind the WSF array to increase the light absorption and re-emission probability. Second, a reflective mirror is placed at one end of the WSF array to direct the light toward the opposite end. Third, a tightly bundled WSF array configuration focuses the emitted light onto the photodetector’s active area. Experimental results demonstrate that each approach significantly improves the peak-to-peak voltage. This work presents an optical detector design featuring a large active area of 0.4cm×20cm, based on a blue-to-green color-converting WSF and achieving a high 3-dB bandwidth of up to 48 MHz. This design enables real-time data transmission at rates of 275 Mbps using non-return-to-zero on-off keying (NRZ-OOK) modulation over a distance of 1 m. Additionally, the transmission link operates at over 250 Mbps, with bit error rates (BERs) below the forward error correction (FEC) limit, under a wide FOV of 60°. This work opens exciting possibilities for revolutionizing photodetection schemes in non-line-of-sight free-space optical communications.

Thermal analysis of a reflection mirror by fluid and solid heat transfer method.

High-repetition-rate free-electron lasers impose stringent requirements on the thermal deformation of beamline optics. The Shanghai HIgh-repetition-rate XFEL aNd Extreme light facility (SHINE) experiences high average thermal power and demands wavefront preservation. To deeply study the thermal field of the first reflection mirror M1 at the FEL-II beamline of SHINE, thermal analysis under a photon energy of 400 eV was executed by fluid and solid heat transfer method. According to the thermal analysis results and the reference cooling water temperature of 30 °C, the temperature of the cooling water at the flow outlet is raised by 0.15 °C, and the wall temperature of the cooling tube increases by a maximum of 0.5 °C. The maximum temperature position of the footprint centerline in the meridian direction deviates away from the central position, and this asymmetrical temperature distribution will directly affect the thermal deformation of the mirror and indirectly affect the focus spot of the beam at the sample.

Exploring Miracles and Wonders in Pre-Modern Korean Society through the Samguk yusa

Samguk yusa 三國遺事 (Memorabilia of the Three Kingdoms), compiled by Iryŏn 一然 (1206–1289), a prominent Buddhist monk in Koryŏ, stands as one of Korea’s most valued historical classics. This classic weaves together a collection of captivating and unconventional narratives—marked by their peculiarity, miracles, and wonder—diverging from the usual societal norms. Unlike traditional historical chronicles such as Samguk sagi 三國史記 (Histories of the Three Kingdoms), Samguk yusa presents a diverse mosaic woven with historical anecdotes, legends, and folklore, especially emphasizing connections to Buddhism. The tales of miraculous events hold historical significance, serving as reflective mirrors that not only shaped the beliefs of pre-modern Korean Buddhists but also influenced the wider population of that era in Korea. This paper delves into the cultural significance and societal roles of miracles and wonders within pre-modern Korean society, particularly through a thorough exploration of narratives and accounts within the Samguk yusa. Through these miraculous stories, the Samguk yusa not only validates the spiritual power of Buddhism but also redefines concepts like filial piety and national protection by integrating them into the Buddhist framework. This ensured Buddhism’s enduring significance in Silla society and reinforced the importance of the supernatural as an integral part of a holistic view of history and culture.

Darwinian Philosophy as Optimization Method for Design High Reflection Mirror Include New Merit Function

In this paper we proposes the philosophy of the Darwinian selection as synthesis method called Genetic algorithm ( GA ), and include new merit function with simple form then its uses in other works for designing one of the kinds of multilayer optical filters called high reflection mirror. Here we intend to investigate solutions for many practical problems. This work appears designed high reflection mirror that have good performance with reduction the number of layers, which can enable one to controlling the errors effect of the thickness layers on the final product, where in this work we can yield such a solution in a very shorter time by controlling the length of the chromosome and optimal genetic operators . Result shows that the construction of multilayer high reflection mirror using in this approach can be considered as a master stone for design another type of filters with most complicated performance, and it is difficult designing in other approach The experiment results demonstrate that our approach is a powerful technique. It is enable to locate the global optimum optimal automatically with high confidence without need for a good starting design.

PMMA light channels facilitate the additive manufacturing of complex-structured SiC reflector mirrors

The rapid manufacturing of lightweight SiC reflector mirrors has always posed a formidable challenge. We have successfully solved the problem of SiC slurry’s difficulty in vat photopolymerization by using highly transparent organic particles to construct the light channels for the first time. Through the integration of digital light processing with reaction sintering, we manufactured complex-structured SiC/Si reflector mirrors. Utilizing the light channels constructed with PMMA, ultraviolet light can effectively penetrate SiC slurry, thereby significantly enhancing the curing depth. During subsequent reaction sintering, PMMA particles induce the formation of numerous spherical silicon through dissolution-precipitation mechanism, alleviating stress concentration in the matrix and enhancing the flexural strength of SiC/Si ceramics. The method achieves significantly higher curing depth for SiC slurry and greater flexural strength for ceramic compared to similar materials. Extending the success above further, we have demonstrated their potential as high-quality products for practical applications.

Designing and Manufacturing a Solar Center for Water Heating and Changing the Specifications Involved in its Manufacture

In this paper, the design and development of an equivalent dish (center) for heating water using available materials was presented. Comparative studies were conducted for reflective and absorbent surfaces, and the best of them was chosen to form the solar concentrator unit. Solar concentrator units were installed in the College of Science, Al-Ajilat - Libya, and center variables such as two temperatures were measured. The entry and exit of water, the intensity of direct radiation on the center opening, and the environmental variables surrounding the center such as ocean temperature and wind speed, and the flow rate was fixed at “L/h 15” The period of measuring the variables lasted for 6 months, and the available energy, the extracted energy, and the instantaneous, hourly, and daily efficiency of the solar center were calculated. At every quarter hour of the measurement hours, it became clear from the measured quantities that the variables change with the change in the intensity of the solar radiation falling directly on the center, where it takes the value. The maximum is at noon. It was also noted that the average efficiency for the day for a moving center was (29)%, compared to the fixed center, which was (6)%, and as for a glass-coated pipette, the efficiency was (39)% Compared to the absorbent without a coating, which was (30)%, and the absorbent coated with epoxy (49%), compared to the other types of coatings, which were (45,39,28) respectively, and for the mirror reflector, the efficiency was (58)%, and compared to the following reflectors, which were ( (47.41%). It was also noted that the temperature of the hot water reached (100℃), and from the results, in order for the center to give the largest amount of heat, it must follow the movement of the sun, and the absorber must be surrounded by a glass casing, and painted with a selective paint such as epoxy. Keywords: water heating, reflective and absorbing surfaces, solar concentrators, solar motion, water temperature.

Modelling П-Shaped Concentrating Optics for Lcpv Solar Cells Using Fresnel Lens

Abstract Most concentrating optics do not show good performance at higher incidence angles and have low acceptance angles and, therefore, they require a high-accuracy solar tracking system, which is costly. In this study, by detailed investigation of optics of the proposed П-shaped concentrating optics, it was found that system remained high in terms of optical efficiency and its concentration ratio at certain higher incidence angles. During the work, ray path through the concentrating optics, width of the light spot at different incidence angles were calculated. Optical efficiency, geometrical concentration ratio, concentration ratio at different incidence angles were found by the results of COMSOL Multiphysics calculations. It was found that the system had a high optical efficiency of approximately 95% and its concentration ratio of 3x-5x was at the range of ±0-20 degrees of incidence angle, and it could reduce the work of a solar tracking system. As well, an increase in the optical efficiency could be seen from 0 to 5 degrees of the incidence angle and an increase in the concentration ratio could be seen from 0 to 12 degrees of the incidence angle in terms of the reflective mirrors which helped redirect the rays to the solar cells. Optical systems with such a high incidence angle could reduce the performance of the solar tracker system, and it reduced the overall cost and energy consumption of the LCPV.

The Image of the Negative Man in the Folk Tale (Qalat Hamida & Qalat Ajibiya) is a Model A Study According to the Descriptive Analytical Approach

The folk tale or Popular tale, as a popular prose art, is transmitted orally from one generation to another. Therefore, the folk tale has occupied a prominent place among other literary genres, due to its characteristics and features that have made it present to various nations and peoples. It expresses the hopes and dreams of those peoples who have taken It is a way to have fun...and get rid of the harsh reality. These folk tales included different images of that life, as they represented the image of the negative man, and the traits of betrayal and weakness that characterized him. The folk tale is one of the means that preserve cultural heritage and consolidate cultural identity. It is one of the most important forms of expression. It is a summary of the experiences of generations, formulated in an interesting narrative form, full of lessons and noble values. It is a creation of the imagination in which the wisdom of society is revealed. It is a reflective mirror of the society in which it grew, so that the story is considered Folklore is one of the genres of popular literature that is beloved by adults and children, due to the elements it contains that attract, excite, and enrich the imagination, in addition to the positive values it contains. It is the ancient, common art of spontaneous speech, passed down from generation to generation, linked to customs and traditions. The story is the backbone of popular heritage, and it is what we metaphorically call popular literature. Among the studies of the folktale in which the researcher invested the importance of the folktale is a study by M. Furqan Abdel Kadhim Katyou Hammadi, tagged with (the popular story in the book of Qalat Ajibiya, Tihami Myths, Structure and Function).

Polarization-Independent Perfect Absorption in Monolayer Black Phosphorus Metasurfaces at Terahertz Frequencies via Critical Coupling.

Two-dimensional (2D) materials, which possess rich underlying physical properties that can provide the potential for designing more efficient and compact optoelectronic devices, have attracted great interest among scientists. Due to the atomic-scale thickness and the anisotropy of in-plane conductivity, 2D black phosphorus (BP) exhibits a polarization-dependent absorption spectrum with low absorption, which limits its further development in polarization-independent applications such as light absorbers and sensors. In this paper, a polarization-independent perfect absorber in the terahertz band is proposed, which is composed of a patterned BP monolayer deposited on a lossless photonic crystal (PC) slab with a back reflection mirror. The absorption of the patterned BP monolayer can reach 100% at resonant frequencies through the critical coupling mechanism of guided resonance. Moreover, the absorber exhibits polarization-independent absorption characteristics for vertically incident light, which are attributed to the 4-fold rotational symmetry of the PC substrate and the patterned BP monolayer deposited on it. This work opens up the possibility of fabricating optically polarization-independent devices based on single-layer 2D anisotropic materials.

Narrow linewidth optical feedback vertical cavity surface emitting lasers based on cholesteric liquid crystal

Abstract In this paper, we present a narrow linewidth vertical cavity surface emitting laser (VCSEL) based on cholesteric liquid crystal (CLC). We investigated the impact of incorporating optical feedback into the external cavity on the linewidth of VCSELs, and successfully utilized CLC film as the reflector for the external cavity. This enabled us to achieve mode control and linewidth compression in VCSELs through optical feedback. The linewidth of the optically feedbacked VCSEL was measured at different driving currents and oxidation apertures. Under the same oxidation aperture, when the driving current is 1.2 mA, the linewidth is compressed from 120.9 MHz to 55.97 MHz; when the driving current is 0.8 mA, the linewidth is compressed from 22.87 MHz to 12.68 MHz. When the driving current remains constant, the linewidth is compressed from 169.31 MHz to 72 MHz when the oxidation aperture is 7 μm; and from 39.13 MHz to 10 MHz, when the oxidation aperture is 3 μm. By validating the feasibility of employing CLC film as an external cavity reflector mirror, our findings offer new insights towards achieving narrow-linewidth external cavity systems, thereby laying an experimental foundation for subsequent high-quality and highly integrated LC optical feedback VCSELs.

Automated line scan profilometer based on the surface recognition method

Existing high-precision measurement devices face numerous challenges when dealing with complex surfaces, including high manual involvement, low measurement efficiency, and high costs. It is even more difficult to obtain complete surface data, particularly when confronted with unknown surfaces. This paper combines a fringe projection sensor with a high-precision line-structured light sensor to construct a line scan profiler. It proposes a surface recognition measurement method to overcome these challenges. This method fully leverages the fringe projection sensor's wide-field advantage to identify the object's surface shape and pose quickly. Subsequently, through the point cloud extraction and path planning algorithms proposed in this paper, efficient and complete line scan measurement paths are automatically generated, thus achieving the automation of the measurement process. Experimental measurements of aspherical lenses, freeform reflective mirrors, and artificial knee joint models validate the advantages of this method over existing methods in terms of measurement efficiency, automation capability, and applicability.

Circularly polarized lasing from chiral metal-organic frameworks

Circularly polarized lasers play a pivotal role in classical optics, nanophotonics, and quantum optical information processing, while their fabrication remains complex. This article begins with examining the interactions between stimulated emission and chiral matter, outlining a simple strategy for producing circularly polarized lasing from chiral metal-organic frameworks (MOFs), such as the zeolitic imidazolate framework (ZIF), embedded with achiral laser dyes (L/D-ZIF⊃dyes). It is found that the stimulated emission threshold and intensity are influenced by the interplay between the chiral polarization of the pump light and the inherent chirality of the MOF nanoparticles. We further present the design of a chiral vertical-cavity surface-emitting laser (VCSEL), comprising an L/D-ZIF⊃dyes solid-state film sandwiched between a high-reflectivity distributed Bragg reflector (DBR) mirror and a silver film. The cavity-based lasing exhibits higher asymmetry between emitting left-handed and right-handed polarized light compared to chiral spontaneous emission (SE) and amplified spontaneous emission (ASE), with an asymmetry value g lum of approximately ±0.31. This value is nearly four-fold greater than that of SE and twice that of ASE. Our findings reveal a new approach to amplify chiral signals, promoting the comprehension and application of chiral–matter interactions, and offering a simple yet effective strategy to fabricate chiral lasers.