Reflective Mirror Research Articles

The nanophotonic machinal cavity and its hydrogen sensing application

Hydrogen, a clean energy carrier, possesses great potential to be an alternative fuel in the future. However, it also has a reputation for being explosive and dangerous. Thus, in the realization of hydrogen energy utilization, hydrogen safe storage and transport are the main issues which currently need to be solved at present. For safety, hydrogen leaks or concentration variations should be monitored accurately and timely during storage or transport. Among the many sensors, the optical hydrogen sensor can satisfy demands of safety, online detection, undisturbed surrounding, and lack of spark. Hence, a fiber-based nanophotonic machinal cavity (NPMC) is proposed and proved that it can be used for hydrogen sensing. This cavity is composed of two mirrors: One is fiber-air interface, another is gold (Au)/palladium (Pd) hybrid nanofilm, herein, Au film with low elastic modulus is employed as a reflective mirror and support substrate of Pd component. Since Pd-hydrogen reactions can induce deformation on this hybrid nanofilm, which will change the resonant characteristics of the cavity, Pd functions as hydrogen-sensitive nanomaterial. Experimentally, Au/Pd hybrid nanofilm-based NPMCs are prepared and used to demonstrates the feasibility of hydrogen sensing. The experimental results reveal that this proposed NPMC maintains advantages of reusable, durable, fast response/recovery (12/1s), low limit of detection (0.1%) and widely linear detection range (1–3.5%) in hydrogen sensing application. This intrinsically safe, miniaturized fiber optic device can be used in space constrained and hazardous environments.

Diamond mirrors for high-power continuous-wave lasers

High-power continuous-wave (CW) lasers are used in a variety of areas including industry, medicine, communications, and defense. Yet, conventional optics, which are based on multi-layer coatings, are damaged when illuminated by high-power CW laser light, primarily due to thermal loading. This hampers the effectiveness, restricts the scope and utility, and raises the cost and complexity of high-power CW laser applications. Here we demonstrate monolithic and highly reflective mirrors that operate under high-power CW laser irradiation without damage. In contrast to conventional mirrors, ours are realized by etching nanostructures into the surface of single-crystal diamond, a material with exceptional optical and thermal properties. We measure reflectivities of greater than 98% and demonstrate damage-free operation using 10 kW of CW laser light at 1070 nm, focused to a spot of 750 μm diameter. In contrast, we observe damage to a conventional dielectric mirror when illuminated by the same beam. Our results initiate a new category of optics that operate under extreme conditions, which has potential to improve or create new applications of high-power lasers.

Hybrid Integration of VCSEL and 3-μm Silicon Waveguide Based on a Monolithic Lens System

We design an optical interface system for vertical coupling between vertical-cavity surface-emitting lasers (VCSELs) and 3-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> silicon waveguides. The system includes a photoresist lens and a total internal reflection mirror, which allows for passive alignment and flip-chip bonding (FCB) of VCSELs. The simulated coupling loss is 0.7 dB, in optimal conditions, which increases to 1 dB when 3- and 20-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> alignment tolerances are considered in lateral and longitudinal directions, respectively. The system is built by post-processing lens and metallic wiring on the backside of a 3-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> silicon photonic platform. After FCB and embedding of the VCSELs, the system performance is characterized, and VCSEL-to-waveguide coupling efficiency of &#x2212;7.5 dB is obtained.

Disordered mullite grains in a sapphire-derived fiber for high-temperature sensing.

In this study, a sapphire-derived fiber (SDF)-based Fabry-Pérot interferometer (FPI) is proposed and experimentally demonstrated as a high-temperature sensor using the arc discharge crystallization process, forming a region with disordered mullite grains. This shows that the disordered mullite grains are related to the gradual temperature distribution during the arc discharge process, which results in a larger refractive index (RI) modulation of the SDF near the fusing area, forming a reflection mirror. An FPI was obtained by combining the optical fiber end facet. Considering the high-temperature resistance of the fiber, the fabricated FPI was used for high-temperature sensing. This shows that the device can operate at temperatures of up to 1200°C with a sensitivity of 15.47 pm/°C, demonstrating that the proposed devices have potential applications in high-temperature environments.

High energy widely tunable narrow-linewidth Ti:sapphire laser using combined-cavity configuration.

A high-energy narrow-linewidth Ti:sapphire laser with widely tunable wavelength was investigated. The Littman cavity was seeded by an extended prism cavity, and they were coupled together by sharing a partial reflection mirror. The widely wavelength tunability of the prism cavity and the linewidth compression of Littman cavity were incorporated together, which resulted in a significantly increased tunable wavelength range from 720 nm to 884 nm with linewidth of less than 100 MHz. The coupling effect and the synchronization between the two cavities in temporal and spectral domain were discussed. The narrow-linewidth laser centered at 786 nm was further amplified to 36 mJ and frequency-doubled to 393 nm with pulse energy of 18.8 mJ while maintaining the narrow linewidth at a repetition rate of 10 Hz. This widely tunable narrow-linewidth laser is a promising light source for high-resolution fluorescence spectroscopy.

A new joint reverse time migration method to improve vertical seismic profile image quality

Vertical seismic profile (VSP) data have the advantage of higher data quality than surface seismic data. Using VSP data has become a powerful technology to achieve accurate recognition of fine structures. Conventional VSP seismic migration methods mainly use up-going waves (reflection waves) for imaging and often treat down-going waves (multiple waves) as a kind of noise to be suppressed and eliminated. The up-going waves (reflection waves) only provide a narrow subsurface coverage near the receiver well. However, the down-going waves (multiple waves) also carry underground medium information and can provide much wider subsurface illumination than the up-going waves (reflection waves). The imaging quality can be improved by using reflection and multiple waves simultaneously. Therefore, we developed a new joint reverse time migration (JRTM) method to use both the up-going and down-going waves simultaneously based on the mirror principle. The up- and down-going data can be simultaneously placed at the reflection positions and mirror reflection positions as the boundary conditions and initial conditions for wavefield reverse time extrapolation. Some numerical examples from the graben, the modified Marmousi, and the modified HESS models show that the proposed new JRTM method can jointly use and image multiple and reflection waves simultaneously. In addition, the newly proposed JRTM method also has a higher imaging quality than reflection wave migration and multiple wave migration from VSP data in complex structures. High-quality imaging results from our proposed JRTM can be further used to improve the accuracy of subsequent oil and gas reservoir characterization and seismic inversion of VSP data.

Panoramic/Dual-Surface Digital Image Correlation Measurement Using a Single Camera.

We propose a cost-effective and simple-to-implement mirror-assisted single-camera panoramic digital image correlation (DIC) method for panoramic/dual-surface profile and deformation measurement. Specifically, two planar mirrors and a single camera attached with a four-mirror adapter are used to capture stereo images of the front and rear surfaces of a test object. These stereo images can be processed by regular stereo-DIC to retrieve shape and kinematics fields of each surface. Further, with the speckle patterns prefabricated on the mirrors, reflection transformation matrices are obtained and applied to transform all reconstructed surfaces into a common world coordinate system. As such, panoramic/dual-surface shape and deformation measurements can be realized. For validation, a high-resolution smartphone camera and an industrial camera were, respectively, used to construct mirror-assisted single-camera panoramic DIC systems. Real experiments, including panoramic shape measurement of an aluminum cylinder, dual-surface shape measurement of an aluminum plate and uniaxial tensile tests of aluminum sheet specimens, were performed, confirming the feasibility and accuracy of the method. Since only a single camera and a few auxiliary reflective mirrors are required, the proposed method provides a cost-effective and convenient way for taking panoramic/dual-surface shape and deformation measurements of regular-sized cylindrical and bar samples.

Influence of Deposition Conditions on Properties of Ta2O5 Films Deposited by Ion Beam Sputtering Coating Technique

Investigation of deposition conditions on structural, optical, and surface properties of Tantalum pentaoxide (Ta2O5) thin films deposited without assisted ion beam (Single Ion Beam Sputtering technique, SIBS) and with assisted ion beam (Dual Ion Beam Sputtering technique, DIBS) is carried out. For both SIBS and DIBS identical coating process conditions are applied for deposition of Ta2O5 films onto highly polished and clean, fused silica substrates. Estimation of deposition rates of Ta2O5 with identical beam energies and coating chamber conditions is done. Benefits of O2 assist beam on the behavior of structural, optical, and surface properties of thin films deposited are studied. The films are characterized with an ellipsometer, optical profilometer, XRD, FE-SEM, and XPS techniques to bring the merits films coated of Ion Beam Sputtering deposition with and without assist Ion Beam. Configuration of ion sources and targets in the coating chamber for DIBS of oxide targets is carried out in the present work are useful for multi-layer coatings for high reflectivity mirrors for electro-optical instruments like ring laser-based rotation sensors.

Optical-feedback cavity-enhanced absorption spectroscopy for OH radical detection at 2.8 µm using a DFB diode laser.

We report the development of an optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS) instrument for OH detection at 2.8 μm using a DFB diode laser. Two different approaches, symmetry analysis and wavelength modulation, were performed to achieve laser frequency locking to the cavity mode. Compared with the symmetry analysis method, the wavelength modulation method continuously locked the laser frequency to the cavity mode and eliminated decoupling the laser from the cavity mode. A detection sensitivity of 1.7×10-9 cm-1 was achieved in a 25 s sampling time and was about 3 times better than that of the symmetry analysis method. The corresponding OH detection limit was ∼ 2×108 molecule/cm3. Further improvement can be achieved by using higher reflectivity mirrors and other high-sensitivity approaches, such as frequency modulation spectroscopy and Faraday rotation spectroscopy.

Incoherent broadband cavity-enhanced absorption spectroscopy for sensitive measurement of nutrients and microalgae.

Incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) can achieve sensitive measurements at trace concentrations for liquid phase marine samples. The IBBCEAS system consists of a cavity-enhancement module (CEM) and a transmission hyperspectral module (THM). The CEM has cavity-enhancement factors up to 78 at 550 nm. Measurements were obtained over a wide wavelength range (420-640 nm) with a halogen lamp, and the optical cavity was formed by two concave highly reflective mirrors (R=0.99). The minimum detectable absorption coefficient αmin of 7.3×10-7cm-1 at 550 nm corresponds to a limit of detection for nutrients of 780 pM. The spectral resolution of the THM is 3 nm in the wavelength range of 400 to 750 nm. We performed the IBBCEAS measurements for biological and chemical substances, including nutrients, microalgae, and Cy5 dye. The concentrations of nutrients in a deionized water environment and artificial seawater environment were measured at nanomolar levels; the concentration of microalgae phaeocystis was detected with 3.46×104/mL, and fluorescence substances such as Cy5 dye could be measured at 0.03 mg/L. Experimental results show that the IBBCEAS system has the capability for sensitive measurements of biological and chemical substances and has strong potential forin situ ecological marine environmental monitoring function.

EFFECT OF ELECTROMAGNETIC FIELD ON THE THERMAL EFFICIENCY OF CONCENTRATED SOLAR COLLECTOR (EXPERIMENTAL STUDY)

In this work, the effect of electromagnetic field on thermal performance of concentrated parabolic trough solar collector is studied experimentally. A two-axis tracking parabolic trough collector formed of a reflector (mirror tapes matrix), of (2m *1m), and an absorber copper tube (receiver) is designed. Water and water-based magnetic iron oxide (Fe3O4) nanofluid are used as heat transfer fluid in the collector. Three volume concentrations (0.3%, 0.5%, and 0.9%) of nanoparticles are investigated under a magnetic flux of (3.2, 4.3, 6.2, and 7.9*103 Gauss), which is installed at absorber inlet, middle, and exit. The three coils are connected to a DC-generator to control the electromagnetic field. The electromagnetic field effect on water flow in the absorber is found weak. A significant thermal improvement is figured when utilizing ferrofluid as a heat transfer fluid in the absorber. It is represented by higher temperature distributions in the absorber and higher solar collector efficiency compared with base fluid.

Использование активной системы терморегулирования для создания рефлектора антенного комплекса космического базирования

The article considers a variant of using carbon heating elements for increasing the thermal stability of space-based radar satellite antenna. The effectiveness of such a variant is justified. The radiative-conductive heat transfer of the reflector structure was simulated as part of a flight in a low Earth orbit using carbon heating elements, which showed a decrease in the level of thermal displacements of the reflector mirror from 1.8 to 0.4 mm. The effect of the power and the layout of carbon heating elements on the temperature state of the reflector has been studied. The dimensional stability of its structural elements was assessed.

Modulation Response of Monolithically Integrated External Optical Injection-Locking Semiconductor Ring Laser Based on PPR Effect

The modulation response of monolithically integrated external optical injection-locking (EOIL) semiconductor ring lasers based on photon-photon resonance effect was systematically analyzed. The simulation results show that the modulation response of the EOIL laser is strongly dependent on the internal loss of the ring laser. Assuming that the waveguide was loss-free, the modulation bandwidth of as high as 67.5 GHz was predicted. However, due to the excessive loss associated with the bending waveguide of the circular-shaped ring laser, the modulation performance of such EOIL laser has no any advantage over its free-running counterpart. Instead, use of rectangular-shaped ring laser as the slave laser is proposed to circumvent the issue associated with the excessive waveguide loss, since the internal loss, in this case, is only dependent on the reflectivity of the total reflection mirrors. Simulation shows the modulation bandwidth of at least 38 GHz is achievable in such EOIL laser, provided the reflectivity of the total reflection mirrors is greater than 96&#x0025;. It is believed that this theoretical study will facilitate the future experimental demonstration of the monolithically integrated EOIL lasers.

Sub-Nanometer Accuracy Combination Processing Technology for Nickel-Phosphorus Modified Surfaces Based on Aluminum Reflector Mirror.

The surface of metal mirrors is often polished by electroless coating with a Ni–P modified layer after single-point diamond turning. In practice, however, improvements in mirror quality are closely related to the polishing environment, polishing medium, and polishing force. If not adequately controlled, processing defects such as visible scratches can lead to the deterioration of surface roughness. Based on the Ni–P modified surface of a metal reflector mirror, this study optimizes the configuration of magnetorheological figuring (MRF) fluid and polishing process parameters so that MRF high-efficiency surface modification can be realized and the scratch problem can be resolved. The processing method of a high-performance metal mirror is developed by studying the high-efficiency and high-precision processing technology based on small head smoothing. The surface roughness achieved by the proposed method was better than Ra = 0.39 nm. The ultrasonic cleaning process effectively improved the surface roughness after processing. According to the combined processing technology developed in this study, the modified layer of the parabolic mirror with a diameter of 370 mm was processed, and the surface quality was increased from RMS = 338.684 nm to RMS = 21.267 nm.

2 ng/√Hz-resolution optomechanical accelerometer employing a three-dimensional MEMS interferometer

A portable and high-resolution optomechanical accelerometer employing a deformable grating-based micro-electro-mechanical system (MEMS) interferometer is presented in this Letter. The movable reflective mirror of this interferometer is realized by a low-frequency vertical sensing structure with a three-dimensional (3D)-spring construction, which, to the best of our knowledge, is first proposed and fabricated in this work. All the components of the sensor are packaged in a metal case with a compact size of 4cm×6cm×3.15cm. The micrometer-scale springs permit the device to have a high mechanical sensitivity of 893.23 µm/g and a resultant self-noise below 2 ng/H z from 2 to 7 Hz. Meanwhile, the measured voltage responsivity is as high as 15,874 V/g, demonstrating it is one of the most sensitive accelerometers reported to date.

Recent Progress in Nonlinear Frequency Conversion of Optical Vortex Lasers

Optical vortices are optical fields that possess a helical phase and orbital angular momentum, which have found the application in micromanipulation, optical communication, orbital angular momentum entanglement, super-resolution imaging, metrology, etc. The urgent need for the wide spreading applications of vortex lasers is to increase the wavelength versatility. In this study, the nonlinear frequency conversion of vortex lasers with a focus on sum frequency generation stimulated Raman scattering, and optical parametric oscillators were meticulously reviewed. The characteristics of the topological charge transfer and output beam profiles of different frequency conversion were discussed. As the precise tuning of optical fields in both temporal and spatial domains shall be the trend of future studies, it is our hope that this review shall serve as a reference for future research. Combining these techniques with the streaming methods to produce optical vortices, i.e., annular pump, off-axis pump, reflection mirror with defect spots, spherical aberration, and birefringence, it is advisable to expand the wavelength and fill the wavelength gap in the ultraviolet, visible, and infrared bands.

Identification of Railway Power Supply Voltage Sag Source Using Optical Fiber Voltage Sensor

With the construction of the smart grid and the continuous improvement of voltage levels, the traditional voltage sensor can no longer meet the development needs of the modern power system. There is an urgent need for a new high-quality voltage sensor to replace it. Aiming at the problems of complex structure, difficult adjustment, poor temperature stability, large optical power loss and inconvenient voltage introduction of the existing optical fiber voltage sensor, an optical fiber voltage sensor based on full polarization state detection without polarizer and analyzer is proposed. The sensor only contains three main components: Grin Lens, BGO crystal and total reflection mirror. It has few devices, simple structure and easy alignment. Moreover, the polarization state evolution and high voltage on the transmission line of Pockels effect of BGO crystal are analyzed. The voltage sag simulation model of the electrified railway is established. The sample data of different disturbance sources are obtained with the assistance of the designed optical fiber voltage sensor. S-transformation and Radial Basis Function (RBF) neural networks are introduced and combined with the prototype of electrified railway power quality detection and analysis device to identify voltage sag sources. The designed optical fiber voltage sensor is suspended. There is no electrode or grounding on the sensor, which saves expensive insulators and increases the sensor’s measuring range. The sensor has a good linear relationship in the power frequency AC voltage range of 0~10 kV at room temperature. It is proved that the design is effective. The working condition analysis of the actual railway power supply reveals that it can detect the voltage sag amplitude and disturbance time, and identify the type of voltage sag disturbance source.

Design and Performance of Ultraviolet 368-nm AlGaN-Based Flip-Chip High-Voltage LEDs with Epitaxial Indium Tin Oxide/Al Reflective Mirror and Symmetry Electrode Arrangement

In this letter, we describe the design and fabrication of high-power AlGaN-based ultraviolet (UV) flip-chip high-voltage light-emitting diodes (LEDs) operating at 368 nm with an epitaxial indium tin oxide (ITO)/Al reflecting mirror and symmetry electrode layout. Metal-organic chemical vapor deposition (MOCVD) was used to grow an ITO thin film as a transparent electrode on the LED surface. At 365 nm, epitaxial ITO thin films exhibited a transmittance of up to 93.6%. Additionally, the epitaxial ITO/Al reflective mirror has a reflectance of 81.2% at 365-nm. To investigate the electrical characteristics, four types of HV-LED micro-cells were constructed with varying n-type mesa structures and p-type interconnect electrodes. We demonstrated a forward voltage (Vf) of 7.86 V at 350 mA with a 2 × 2 mico-cells high-voltage ultraviolet 368-nm flip-chip LED after optimising electrode structure and device process.

A potential way of detecting circulating tumor cells via laser scanning

Circulating tumor cells (CTCs) are generally considered as seeds for metastases, serving as a clinical biomarker for cancer diagnosis. Due to their low content in the blood, detection of CTCs normally requires an antibody-mediated biological enrichment process, which is rather complicated and time-consuming. In this work, we demonstrate a potential, fast, and cost-effective way of detecting CTCs. That is, CTCs are physically isolated by size using filtration and imaged optically via laser scanning. The filtered and stained blood sample, which is placed on a moving and spinning stage, is illuminated by a 405 nm diode laser. Scattered optical signals are collected by using an ellipsoidal reflective mirror for dark-field imaging. Then CTCs in dark-field images are screened and counted by the clustering algorithm. Our method possesses the advantages of antibody-free and low cost, holding great promise for early diagnosis and prognosis prediction of cancer patients.

Pengaruh Material Reflektor Terhadap Kinerja Kompor Energi Surya

The use of solar energy in Indonesia is the right choice as an alternative energy for energy needs in industry or to meet daily energy needs in households. To utilize solar energy for cooking purposes, a solar cooker can be used. Factors that affect the performance of this solar cooker in addition to the length of time it shines and the intensity of thermal radiation from the sun are the reflexivity of the collector material, the surface area of ​​the collector, the geometric shape and location of the focal point of the collector, the normal direction of the collector surface to the incoming sunlight, and the amount of heat loss to the surroundings. The materials used as reflectors in the research on this solar cooker are zinc (aluminum and galvanized) AL-Zn and black paint back ground mirror glass. This material is re-glued on top of a ready-made parabolic dish from the market. Then look for the focal point that corresponds to the diameter of the parabola. From the results of the study, it can be concluded that the back ground mirror glass material with black paint is better to use than the AL-Zn zinc plate if it is used as a raw material for the surface material (reflector) of solar cooker. Likewise, the efficiency of the solar oven in terms of the amount of heat that is converted into energy for heating the pot is better for a solar oven than a reflector with black paint back ground mirror glass material. And the efficiency of the solar cooker from the black paint back ground mirror on the first day is 16.4% to 25.7% on the second day, while the efficiency of the solar cooker from the AL-Zn zinc plate on the first day is 16.4% to second day 22.8%. The emissivity of the solar stove with AL-Zn zinc plate reflector on the first day was 0.02906 and on the second day 0.02892, while the emissivity of the solar cooker with black paint back ground mirror reflector on the first day was 0.01812 and the second day was 0 0.02544.