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Silicon carbide (SiC) ceramic lattice structures (CLSs) hold significant potential for use in structural components and optical mirrors in space exploration due to their light weight, high strength, and excellent dimensional stability. However, they face challenges such as poor curing performance and weak mechanical strength during the digital light processing (DLP) additive manufacturing process. In this study, SiC@Al 2 O 3 powder was prepared, resulting in a 21 % reduction in absorptivity compared to bare SiC powder. The ceramic paste derived from this powder achieved a curing thickness of up to 80 μm, exhibited a reduced over-curing width, and demonstrated a 75 % improvement in stability compared to bare SiC paste. Consequently, high-quality triply periodic minimal surfaces (TMPS) structured SiC@Al 2 O 3 CLSs green bodies were successfully fabricated. By integrating precursor impregnation pyrolysis with the reaction melting infiltration (PIP-RMI) post-treatment densification method, SiC@Al 2 O 3 /Si CLSs were produced, exhibiting superior mechanical properties with low dimensional shrinkage. At 30 % volume fraction, the specific compressive strength of the primitive-TPMS SiC@Al 2 O 3 /Si CLSs reached 24.79 MPa. This study presents an effective method for fabricating SiC-based CLSs and establishes a foundation for the optimization of SiC ceramic fabrication processes. [ABSTRACT FROM AUTHOR]

This paper presents an innovative piezo-actuated fast-steering mirror (FSM) that integrates control design and system operation to improve the tracking performance of laser beam steering (LBS) systems. The proposed piezoelectric FSM is centered on two pairs of stacked actuators functioning in the tip-tilt direction via novel flexible hinges with strain-gauge sensors for position measurement. The suggested flexible hinge scheme allows the first fundamental resonance mode with the optical mirror to exceed 400 Hz while achieving an actuation range of ±5 mrad. Thus, the design offers a wider mechanical actuation range than conventional piezoelectric FSMs. Moreover, LBS systems that use fast-steering motion controllers should be robust against dynamic disturbances, such as periodic external vibrations. Such disturbances, inherently associated with the operating conditions for LBS systems, typically reduce the stability of the tip-tilt motion. To attenuate the effects of such disturbances, a high-precision control system is necessary for the tip-tilt motion. Therefore, a control method integrating a proportional–integral controller with an adaptive feedforward control (AFC) algorithm is outlined to enhance tip-tilt tracking performance during high-speed scanning, compared with conventional LBS systems. Based on experimental findings, the AFC algorithm boosted control performance under dynamic disturbances, such as sinusoidal vibrations with multiple frequencies. [ABSTRACT FROM AUTHOR]

Compensating for the pitch error in the scanning movement is a fundamental issue when conducting large-scale surface shape measurements with deflectometric profilers. This paper presents a new long trace profiler employing a shearing measurement technique. In this setup, the optical head and the mirror under test are mounted on two independent parallel movable air-bearing carriages to enable shearing and scanning movements separately. The distance between the optical head and the tested mirror remains fixed, effectively minimizing the influence of system errors resulting from imperfections in optical devices. Simulation studies show that the double shear measurement method with a low-spatial-frequency filtering process can effectively mitigate high-frequency angular measurement errors introduced by the instability of the air-bearing stage. Experimental tests conducted on flat mirrors demonstrated a precision of less than 50 nrad rms, thereby confirming the robustness of the system. [ABSTRACT FROM AUTHOR]

A carbon dioxide (CO2) gas sensor based on non-dispersive infrared (NDIR) technology has been developed and is suitable for use in portable devices for high-precision CO2 detection. The NDIR gas sensor comprises a MEMS infrared emitter, a MEMS thermopile detector with an integrated optical filter, and a compact gas cell with high optical coupling efficiency. A dual-ellipsoid mirror optical system was designed, and based on optical simulation analysis, the structure of the dual-ellipsoid reflective gas chamber was designed and optimized, achieving a coupling efficiency of up to 54%. Optical and thermal simulations were conducted to design the sensor structure, considering thermal management and light analysis. By optimizing the gas cell structure and conditioning circuit, we effectively reduced the sensor's baseline noise, enhancing the overall reliability and stability of the system. The sensor's dimensions were 20 mm × 10 mm × 4 mm (L × W × H), only 15% of the size of traditional NDIR gas sensors with equivalent detection resolution. The developed sensor offers high sensitivity and low noise, with a sensitivity of 15 μV/ppm, a detection limit of 90 ppm, and a resolution of 30 ppm. The total power consumption of the whole sensor system is 6.5 mW, with a maximum power consumption of only 90 mW. [ABSTRACT FROM AUTHOR]

Optical Wireless Communication (OWC) technology has gained significant attention in recent years due to its potential for providing high-data-rate wireless connections through the large license-free bandwidth available. A key challenge in OWC systems, similar to high-frequency Radiofrequency (RF) systems, is the presence of dead zones caused by obstacles like buildings, trees, and moving individuals, which can degrade signal quality or disrupt data transmission. Traditionally, relays have been used to mitigate these issues. Intelligent Reflecting Surfaces (IRSs) have recently emerged as a promising solution, enhancing system performance and flexibility by providing reconfigurable communication channels. This paper presents an overview of the application of IRSs in OWC systems. Specifically, we categorize IRSs into two main types: mirror array-based IRSs and metasurface-based IRSs. Furthermore, we delve into modeling approaches of mirror array-based IRSs in OWC and analyze recent advances in IRS control, which are classified into system power or gain optimization-oriented, system link reliability optimization-oriented, system data rate optimization-oriented, system security optimization-oriented, and system energy optimization-oriented approaches. Moreover, we present the principles of metasurface-based IRSs from a physical mechanism perspective, highlighting their application in OWC systems through the distinct roles of light signal refraction and reflection. Finally, we discuss the key challenges and potential future directions for integrating IRS with OWC systems, providing insights for further research in this promising field. [ABSTRACT FROM AUTHOR]

Electromagnetic metasurfaces have been playing exotic roles in the construction of ultracompact and versatile metadevices for wave–matter interactions. So far, multiple metasurfaces cascaded with intercouplings have been intensively investigated for extraordinary wavefront control and broadband spectral regulations. However, most cases face high structural complexity and little attention is paid to cascaded metasurfaces without interlayer couplings. In this paper, we demonstrate one type of terahertz Bragg mirror with ideally high reflectivity and ultra-broad bandwidth by simply resorting to decoupled metasurfaces. Cascaded metasurfaces with decoupled mode control prove practically straightforward for analytical design and easy to fabricate for engineering purpose in our scheme. Essentially, by flexibly tuning the decoupled metasurface mode, the middle Fabry–Perot mode that behaves like a defect mode inside the reflective passband can be eliminated for substantial band expanding. Fundamental analyses and rigorous calculations are performed to confirm the feasibility of our metasurface-based THz Bragg mirror with scalable bandgap. In comparison, our meta-mirror provides superior spectral performance of a larger bandgap and higher in-band reflectivity over that composed by ten layers of alternate dielectrics (Rogers 3003 and 3005). Finally, our analytical methodology and numerical results provide a promising way for the rapid design and fabrication of a Bragg mirror in the optical regime. [ABSTRACT FROM AUTHOR]

Optical bistability is investigated for optomechanical system composed of an ensemble of inhomogeneously broadened two-level atoms embedded between the two mirrors of the optical cavity, that is subjected to two input (strong and probe) fields. We consider two types of inhomogeneous broadened distributions, namely, Lorentzian and Gaussian line shapes. The first order harmonic components of the output fields (due to the presence of probe field) show reversed and knotted bistability shapes simultaneously with the standard bistable shape of the fundamental component of the field at frequency ω c . The inhomogeneous broadened line width for both Lorentzian and Gaussian distribution affects the dispersive switching of the system, as well as the bistable behavior. Locations of the maxima of photon numbers associated with higher harmonics of the output fields are identified with respect to the probe field frequency. [ABSTRACT FROM AUTHOR]

The optical properties of an off-axis integrated cavity system are influenced by both structural deformation and thermal deformation. In this paper, the finite element simulation and analysis software COMSOL multiphysics was used to numerically simulate the optical system. By coupling geometric optics, solid mechanics, and solid heat transfer and conducting parametric temperature scanning, a multiphysics simulation of the off-axis integrated cavity optical sensing system was achieved. The effects of different temperature conditions on the stress field, displacement field, and optical mirrors were analyzed, and changes in optical properties were assessed using ray trajectories and point diagrams. Additionally, optical simulation software was used to simulate and optimize the experimental optical path, obtaining the distribution of light spots on the detector surface. This provides a theoretical basis for the subsequent optimization of the off-axis integrated cavity optical system. [ABSTRACT FROM AUTHOR]

This research takes the optical mirror polishing robot as the research object. The optical mirror polishing robot receives complex forces during the grinding process. Operational accuracy can be affected by gravity and movement of the parallel manipulator. In addition, the parallel manipulator is a nonlinear system with more variables, more parameters, and strong coupling. Therefore, trajectory tracking control of the parallel manipulator is analyzed and studied. The extended state observer based sliding mode control method is used for trajectory tracking control, and the non-singular terminal sliding surface is designed. The extended state observer not only realizes high-precision trajectory tracking control, but also ensures the rapid response performance of the system. [ABSTRACT FROM AUTHOR]

In this study, we design an ultra-low self-heating radiation long-wave infrared laser communicationoptical system, which mainly includes aperture stop, primary mirror, secondary mirror, three-mirror,field stop, four-mirror, window glass, detector light shield, and image plane. The system enters apupil diameter of 280 mm, a field of view angle of 1×1°, a system focal length of 840 mm, and awavelength of 8 − 12 μmkm; the off-axis four-fold anti-structure is adopted. The optical mirror andstructural components of the material are Aluminum, the system's own thermal radiation equivalent toa black-body temperature of 171 K. The equivalent black-body temperature of the system is measuredin a vacuum chamber. The temperature of the spacer is 100 – 120 K, the temperature of the coldplate is 85 – 87 K, and the integration time is 550 – 800 μs. At this time, the measured equivalentblack-body radiation temperature of the system is 172.9K; it is consistent with the simulation value.The design scheme solves the technical problems of low signal-to-noise ratio, poor image contrast, andshort detection distance of infrared laser communication system. [ABSTRACT FROM AUTHOR]

Perfect magnetic mirrors are important optical devices for the development of novel optical detectors, solar cells, and imaging devices. They have the property of only reversing the magnetic field of a light wave upon reflection, for instance, in functional optical metasurfaces. To design an optical magnetic mirror, high-refractive-index dielectric nanostructures that support strong magnetic dipole (MD) response in the optical wavelength range are used. However, the spectral overlap between the MD and electric dipole in dielectric resonators degrades the magnetic mirror reflection. Here, we propose and demonstrate a perfect optical magnetic mirror metasurface that totally reflects an incident wave without electric field phase change. In this perfect magnetic mirror, the electric dipole radiation is completely suppressed by the radiation of the anapole mode in the spectral range where the destructive interference between the electric dipole and toroidal dipole occurs. By fine-tuning the size parameters of the dielectric resonators, we show near-perfect MD scattering as a result of the spectral overlap between MD resonance and anapole mode. The optical magnetic mirror can be tuned from the visible to near-infrared range by scaling the sizes of the resonators. The MD scattering resonators promote the perfect magnetic mirror, a promising platform for designing photodetectors, biological sensors, and reflected waveplates. [ABSTRACT FROM AUTHOR]

In order to study the damage behaviors of optical mirrors induced by film defects (as film bumps, film pits and film contaminants) in high-power CW laser, a simulation study was carried out, which considered temperature, thermal stress and thermal deformation in results. The results show that the bumps of the film will primarily absorb laser energy, and its temperature, thermal stress and thermal deformation will become extremely high, which is easy to damage the film; similarly, the film pits will also absorb laser energy for its temperature rise, and the pits will expand to the inwards. The larger the size of the pits, the larger the expansion of melting range will be, and eventually damage the film layer; after absorbing the laser energy, the temperature of the film contaminants is very high (for film contaminants size of 150 μm, its maximum temperature reaching 900 K), even exceeding the damage temperature (523 K) that the film can withstand, and finally causing the film to be ablated. [ABSTRACT FROM AUTHOR]

This paper presents a two-axis AlScN-based water-immersible MEMS mirror fabricated in an 8-inch MEMS process. Compared with other studies, this device has a larger optical aperture 10 mm in diameter. The resonant frequencies of the device are 1011 Hz in air and 342 Hz in water. The scanning angle reaches ±5° and ±2° at resonant frequencies in air and water, respectively. The cavitation phenomenon is observed when the device is operating in water, which leads the device to electrical failure. To address this issue, a device with reduced resonant frequencies—246 Hz and 152 Hz in air and water—is characterized, through which the bubbles can be effectively prohibited. This MEMS mirror could potentially be used in ultrasound and photoacoustic microscopy applications. [ABSTRACT FROM AUTHOR]

Increasing the efficiency of photocatalysis is an extremely important basic problem with applications in chemistry, biology, pharmacology, and medicine. A possible way to increase the efficiency of photocatalysis is to use the effect of strong light–matter coupling, a specific physical phenomenon that has been at the forefront of research in basic and applied physics and chemistry in recent years. One of the most intriguing characteristics of the strong coupling effect is the possibility of controlling the selectivity and yield of chemical reactions and increasing manyfold the efficiency of catalysis, which is ensured by the appearance of the upper polariton, a higher-energy electron level, upon splitting of the original electron level of the catalyst or substrate. Here, a flow-through microfluidic photocatalytic reactor has been designed, which contains a microcavity providing strong light–matter coupling and operating in the microfluidic mode with a throughput in the range of 0.01–0.1 mol/h. The design is based on the integration of a photocatalyst (functionalized porous matrix of boron nitride) into the space between the mirrors of an optical microcavity located in the microfluidic cell. It is assumed that the new technology will significantly increase the rates of photocatalytic reactions in the working volume of the reactor irradiated with visible light. [ABSTRACT FROM AUTHOR]

Featured Application: The primary and secondary mirror misalignment errors and the bending and sinking compensation method proposed in this paper can be applied to the mounting and observation of large telescopes. Cassegrain telescopes with larger apertures suffer significant optical pupil shifting errors caused by gravity and temperature gradients. This study constructs an optical model of a large Cassegrain telescope and a method to calculate and compensate its shifting error. First, the optical structure is simplified by incorporating only the most relevant telescope components, and the system optics is modeled using ray tracing. A computer-aided mounting-based method for calculating the misalignment error of primary and secondary mirrors is proposed, with the spatial position change of secondary mirrors as the input. Next, a compensation method based on the coma-free point theory of the Cassegrain system is proposed, with the main mirror's optical axis as the reference. Finally, using a 4 m aperture telescope as an example, the gravity- and thermal-deformation-induced shifting error is simulated. Based on this simulation, the secondary mirror position is adjusted using a secondary mirror-adjustment mechanism Hexapod platform to compensate for the misalignment error. Both gravity and temperature are major causes of shift in the pupil position, with a maximum shift of 18 mm. After compensation, this shift is controlled within 1 mm. The modeling method and the simulation process mentioned in this research can also be used in the other relevant fields. [ABSTRACT FROM AUTHOR]

A computer simulation was conducted using Optics Software for Layout and Optimization (OSLO) to design a Cassegrain telescope system for on-axis rays. In order to establish such a telescope, the two mirrors of the optical system were designed as spherical surfaces: a concave mirror and a convex mirror. The obscuration ratios of the Cassegrain telescope's secondary mirror were examined using different values, which ranged between 0.1 and 0.3, to determine the best obscuration ratio. This work adopted three criteria to decide which obscuration ratio is the best for the Cassegrain telescope. The first criterion was the number of rays that reached the final image. The second criterion was calculating the modulation transfer function (MTF). The third criterion was calculating the point spread function (PSF) and Strehl ratio (SR). Finally, the result showed that the best obscuration ratio of the telescope’s secondary mirror was found at D2/D1=0.116-0.166, where D1=0.76 m for the primary mirror and D2=0.09 – 0.125m for the secondary mirror. [ABSTRACT FROM AUTHOR]

Statistical analysis of the properties of single microparticles, such as cells, bacteria or plastic slivers, has attracted increasing interest in recent years. In this regard, field flow cytometry is considered the gold standard technique, but commercially available instruments are bulky, expensive, and not suitable for use in point-of-care (PoC) testing. Microfluidic flow cytometers, on the other hand, are small, cheap and can be used for on-site analyses. However, in order to detect small particles, they require complex geometries and the aid of external optical components. To overcome these limitations, here, we present an opto-fluidic flow cytometer with an integrated 3D in-plane spherical mirror for enhanced optical signal collection. As a result, the signal-to-noise ratio is increased by a factor of six, enabling the detection of particle sizes down to 1.5 µm. The proposed optofluidic detection scheme enables the simultaneous collection of particle fluorescence and scattering using a single optical fiber, which is crucial to easily distinguishing particle populations with different optical properties. The devices have been fully characterized using fluorescent polystyrene beads of different sizes. As a proof of concept for potential real-world applications, signals from fluorescent HEK cells and Escherichia coli bacteria were analyzed. [ABSTRACT FROM AUTHOR]

Analytical and finite-difference methods have been used to analyze the thermo-stressed state of an uncooled deformable mirror. Assessments have been made of temperatures and movements of the optical surface of the mirror both in assigning a uniform intensity of the heat flux and in the presence of global and local nonuniformities. A conclusion has been drawn about the possibility of using simplified analytical computational methods in design analysis. [ABSTRACT FROM AUTHOR]

The heaters-based thermal-compensated adaptive adjustment of a reflection mirror at Shanghai high repetition rate X-ray Free-Electron Laser and extreme light facility (SHINE) is presented here based on finite element analysis. The correction performance of different control algorithms [singular value decomposition and gradient descent (GD)] is analyzed and compared. This study has demonstrated that a significant control algorithm can further improve the surface shape accuracy of the mirror. After optimizing the mirror control algorithm, the calculated slope errors and height errors of the mirror are reduced to nearly less than 50 nrad rms and 0.5 nm rms, respectively. The optimization result indicates that the GD control algorithm based on the Hessian matrix exhibits superior performance and practicality compared to the control algorithm before optimization. [ABSTRACT FROM AUTHOR]

Micro-cutting processes, such as single-point diamond turning, are required for selective laser melting (SLM)–fabricated AlSi10Mg to machine optical mirrors. During the SLM process, cross contamination can often introduce the different metal particle into the AlSi10Mg workpiece, inducing various surface defects (concaves and scratches) on the micro-cutting machined surface. To find the micro-cutting mechanism of SLM AlSi10Mg containing the inside metal particle, the micro-cutting process was simulated using finite element analysis (FEA). The surface morphology formation mechanisms of the SLM AlSi10Mg containing the inside metal particle during the micro-cutting process were investigated. A scratch was created on the AlSi10Mg surface when the tool was at the upper part of the inside metal particle. A concave was formed due to the entire removal of the inside metal particle when the tool acted at the lower part of the particle. The proposed model was proven efficient and accurate by verifying the above mechanism with the machined surface morphologies. This paper provides a FEA example for the micro-cutting process of alloy matrix containing the inside metal particle. [ABSTRACT FROM AUTHOR]

Complex silicon carbide (SiC) ceramic components are difficult to fabricate due to their strong covalent bonds. Binder jetting (BJ) additive manufacturing has the outstanding advantages of high forming efficiency and no thermal deformation, especially suitable for printing complex structure SiC components. This study tried to obtain low silicon content silicon carbide ceramics by binder jetting followed by phenolic resin impregnation and pyrolysis (PRIP) and liquid silicon infiltration (LSI). BJ was used for the SiC green parts fabrication, and the highest compressive strength (7.7 ± 0.3 MPa) and lowest dimensional deviations (1.2–1.6 mm) were obtained with the printing layer thickness of 0.15 mm. Subsequently, PRIP treatments were introduced to increase the carbon content for the following LSI process. As the number of PRIP cycles increased, the carbon density of SiC/C preform increased and the porosity decreased. After the LSI treatment, the final Si-SiC composites processed with 2 PIRP cycles reached the highest flexural strength (257 ± 14.26 MPa) and the best wear resistance. This was attributed to the low residual silicon content (10.2 vol%) and almost no residual carbon. Furthermore, several complex structural components were fabricated using these methods. The preparation of complex components verifies the feasibility of BJ and LSI for manufacturing high-strength and high-precision SiC ceramics. Besides, this work hopes to provide technical guidance for the preparation of complex SiC composites in the future. • Si-SiC composites were fabricated by the binder jetting and liquid silicon infiltration. • The ultimate flexural strength and wear resistance were enhanced simultaneously. • Several representative complex structures (optical mirror, turbine disc, and topology) were fabricated. [ABSTRACT FROM AUTHOR]

Nonlinear optical loop mirrors (NOLMs) are used in modern fiber optic devices and optical communications. In this study, we present numerical analyses of the multiple variables involved in the operation of an NOLM in low- and high-power transmissions. The Jones matrix formalism was used to model linear and circular polarization inputs. We used three-dimensional (3D) plots to identify the characteristics required in the experimental operation of the NOLM. These characteristics, including the critical power, low- and high-power transmission, and dynamic range, depend on parameters such as the fiber loop length, input power, angle of retarder plate, and input polarization. A standard single-mode fiber (SMF-28) with high twist loop lengths of 100, 300, and 500 m and input powers of 0–100 W was simulated. Three-dimensional surface graphics provided a comprehensive view of the NOLM transmission and considerably enhanced the optimal transmission by manipulating adjustable device components including the power and polarization control plates. Optimal transmission facilitates its use in integrating ultrafast pulse generation, optical signal processing, optical communication systems, and photonic integrated circuit applications. [ABSTRACT FROM AUTHOR]

Following the advent of petawatt (PW)-class lasers already capable of achieving light intensities of 10 23 W/cm 2 , high-field science now aims at solving a major challenge of modern physics: can we produce extreme light intensities above 10 25 W/cm 2 beyond which yet unexplored strong-field quantum electrodynamics (SF-QED) regimes would dominate light–matter or even light–quantum vacuum interactions? As the required intensities are orders of magnitude higher than the present record held by a 4 PW laser, solving this major question with the current generation of lasers requires conceptual breakthroughs that we strived to address at CEA-LIDYL over the last 5 years. To break this barrier, we proposed to revive an old concept called the 'Curved Relativistic Mirror' (CRM). Assuming a perfectly reflective and aberration-free CRM, reflecting a high-power laser on such a moving mirror could in principle boost its intensities by several orders of magnitude through Doppler effect. The major obstacle with this simple concept is its actual implementation: how to produce a curved and highly reflective relativistic mirror of excellent optical quality in experiments? This has remained an open question so far, which has resisted all experimental attempts. In this article, we present the theoretical and numerical efforts that we have carried out to answer this question, starting from the development of the 3D kinetic code WarpX-PICSAR in strong collaboration with the team of Dr. Jean-Luc Vay at Berkeley Lab, up to the very first numerical experiments of CRM designs performed with the code at very large scale. Leveraging on these first results, we show that high-power PW lasers, boosted by a relativistic plasma mirror, can increase SF-QED signatures by orders of magnitude, potentially giving access to new physics at existing laser facilities. [ABSTRACT FROM AUTHOR]

The emergence of new materials and fabrication techniques provides progress in the development of advanced photonic and communication devices. Transition metal dichalcogenides (e.g., molybdenum disulfide, MoS2) are novel materials possessing unique physical and chemical properties promising for optical applications. In this paper, a metasurface composed of particles made of bulk MoS2 is proposed and numerically studied considering its operation in the near‐infrared range. In the bulk configuration, MoS2 has a layered structure being a uniaxial anisotropic crystal demonstrating an optical birefringence property. It is supposed that the large‐scale and uniform MoS2 layers are synthesized in a vertical‐standing morphology, and then they are patterned into a regular 2D array of disks to form a metasurface. The natural anisotropy of MoS2 is utilized to realize the splitting of electric and magnetic dipole modes of the disks while optimizing their geometric parameters to bring the desired modes into overlap. At the corresponding resonant frequencies, the metasurface behaves as either an electric or a magnetic mirror, depending on the polarization of incident light. Based on the extraordinary reflection characteristics of the proposed metasurface, it can be considered an alternative to traditional mirrors and optical splitters when designing compact and highly efficient metadevices, which provide polarization and phase manipulation of electromagnetic waves on a subwavelength scale. [ABSTRACT FROM AUTHOR]

Catastrophic optical mirror damage (COMD) and catastrophic optical bulk damage (COBD) are the main factors that affect the reliability of semiconductor lasers. In this paper, we characterize the COMD and COBD failure modes by examining the voltage changes at the current point where failure occurs, as well as by using the electroluminescent technique. Our study reveals that the voltage has an increase at the failure current point for COMD samples, in which failure occurs due to the damage to the facet mirrors; for COBD samples, in which failure occurs inside the laser cavity, the voltage exhibits a decrease and the amount of voltage decrease is roughly proportional to the size of the damaged area. [ABSTRACT FROM AUTHOR]

Modern studies have confirmed the possibility of making atomic mirrors using quadrupole-active atomic transition evanescent waves. The reflection process has been shown to be enhanced to approach specular behavior in several ways. In this study, we considered the atomic mirror due to the optical quadrupole potential generated by two counter-propagating optical Gaussian beams. This arrangement provides good enhancement for the evanescent field in the vacuum above the surface, which can be used as an atomic mirror. A high-quality atomic mirror should reflect the atoms specularly while maintaining the coherence of the de Broglie wave function. We focused on a particular atomic transition in Cs, which is a dipole-forbidden but quadrupole-allowed transition. We illustrate the optical quadrupole potential and suggest that quadrupolar transitions generally ignored in atom optics exist for exploitation. This study investigated the conditions facilitating atomic mirrors using typical experimentally accessible parameters. [ABSTRACT FROM AUTHOR]

In a Cassegrain optical system, the surface precision of the primary mirror is an important factor in the quality of the image. The design of a lightweight primary mirror with a high-quality optical surface is crucial. In this thesis, an integrated mirror light engine design optimization process is proposed for an aviation optoelectronic device. It is based on the Kriging surrogate model and nests the topology optimization algorithm, which constructs the mirror RMS value response surface and obtains the dominant relationship between mirror structure and surface accuracy. The optimal surface figure lightweight structure of the mirror is obtained by optimizing the surrogate model with an additive criterion and multi-objective optimization analysis. The root mean square value (RMS) of the corresponding primary mirror is 10.41 nm, which is better than 1/40 λ (λ = 632.8 nm). This meets the optical design specifications. The optimal primary mirror structure is analyzed by using the finite element method, which verifies the precision of the Kriging surrogate model. It has an error of 0.28%. The kinetic analysis of the primary mirror shows that the primary mirror does not yield to plastic deformation or even failure under a three-way 20 g acceleration load. This meets the environmental suitability requirements. [ABSTRACT FROM AUTHOR]

Tunable multiwavelength fiber lasers based on semiconductor optical amplifiers (SOA) have received attracting interest due to their wide prospective applications in dense division multiplexing (DWDM) systems and optical sensing. Using an SOA in a nonlinear optical loop mirror (NOLM), we demonstrate up to 13 lasing peaks by controlling the pump current and the polarization controller. At maximum pump current (450 mA), the emitted multiwavelength is between 1550 nm and 1572 nm with a wavelength spacing of 1.87 nm and 3 dB output linewidth of 0.8 nm with an output power of −7 dBm and 27 dB optical signal-to-noise ratio (OSNR). The multiwavelength output power and multiwavelength peak stability are investigated, and it was found that the power fluctuation of each multiwavelength line is less than 0.2 dB. In addition, by adjusting the polarization controllers (PCs) and SOA temperature, we obtained a tunable multiwavelength emission. The proposed fiber laser offers advantages such as simple structure, low loss, and long-time stable and multiwavelength emission. [ABSTRACT FROM AUTHOR]

The intravacuum mirrors used in the systems of optical plasma diagnostics on fusion installations are subject to contamination and require periodic cleaning. It is proposed to clean the mirrors by ion sputtering of the impurity from the reflective surface in a gas discharge. In this work, results are presented from experimental studies of the possibility of controlling the mirror cleaning process in the glow discharge localized inside a grid hollow cathode and controlled by direct current (DC) or mid-frequency pulsed direct current (MDC). Three independent methods of control were studied: measurements of the voltage of the cleaning discharge at a fixed current, measurements of the frequency of the appearance of microarc couplings in the presence of dielectric contaminants, and emission spectroscopy studies of the cleaning discharge. Separately, to verify the cleaning effect, results were presented from measuring the reflection spectrum of the mirror. It was shown that all three methods can be used in the cleaning systems. The first of the discussed methods appears to be the most promising since it does not require additional detectors and uses only the data obtained from the discharge power supply unit, and it is applicable to cleaning mirrors from both current-conducting and thin dielectric contaminations. The control based on measuring the frequency of appearance of microarc couplings can be used when one alternates between the PDC and the DC regimes in the presence of layered metal–dielectric contaminations and cleaning the local dielectric contaminations resulting from emergencies. The spectroscopic control method provides the highest sensitivity and allows one to determine the composition of the contaminants, yet it also has higher requirements for the recording equipment. The considered methods can be used to automate the processes of removing the contamination in the systems for plasma cleaning of the input diagnostic mirrors of fusion installations and to control the finishing treatment of substrates before vacuum deposition of coatings. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR) is a common and useful measurement technique to perform fast and sensitive optical detection. SPR instrumentations usually comprise optical systems of mirrors and lenses which are quite expensive and impractical for point-of-care applications. In this work, we presented a novel and compact SPR device called SPECTRA, designed as a spectrophotometer add-on with a grating coupling configuration. The device is conceived as a marketable solution to perform quick SPR measurements in grating configuration without the requirement of complex instrumentation. The device can be customized either in a vertical structure to reach lower incident light angles, or in a horizontal configuration, which is suitable for SPR analysis using liquid solutions. The SPECTRA performance was evaluated through SPR measurements in typical applications. The vertical SPECTRA system was employed to detect different functionalization molecules on gold 720 nm-period grating devices. Meanwhile, the horizontal SPECTRA configuration was exploited to carry out fluid-dynamic measurements using a microfluidic cell with glycerol solutions at increasing concentrations to account for different refractive indexes. The experimental tests confirmed that the SPECTRA design is suitable for SPR measurements, demonstrating its capability to detect the presence of analytes and changes in surface properties both in static and dynamic set-ups. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate a tunable and switchable low-threshold multi-wavelength erbiumdoped fiber pulsed laser. It is based on a composite structure of Lyot filter and nonlinear optical loop mirror. At a threshold of 30 mW, single-wavelength and dual-wavelength states can be obtained with a tuning range of 5 nm for the single wavelength and 1 nm for the dual wavelength. By adjusting the pump power and polarization controllers, the laser can achieve at most eightuple-wavelength operation. We use the nonlinear optical loop mirror as a saturable absorber to realize stable pulse output. The pulse sequences begin to appear when the pump power is 100 mW. The pulse repetition rate corresponding to the dual-wavelength is 40.52 kHz, and the pulse width is 144 ns. Due to its abundant range of wavelengths and significant pulse phenomenon, the proposed laser is widely used in fiber sensing and other fields. [ABSTRACT FROM AUTHOR]

Pancake lens structure offers a promising solution to compact formfactor for near-eye displays. However, utilizing a half mirror to triple the optical path length causes a dramatic optical loss. The theoretical maximum optical efficiency is only 25%. To balance the tradeoff between compact formfactor and optical efficiency, here we propose a new folded optical structure with a doubled efficiency and doubled optical path length, using two polarizationselective cholesteric liquid crystal reflectors. Simulation results agree with the experiment reasonably well. Two display configurations are established to evaluate the imaging performances of the proposed pancake lens structure. [ABSTRACT FROM AUTHOR]

Airborne one-point to multiple-point laser communication terminal is an important node in laser communication networking. In order to meet the requirements of miniaturization and lightweight of the optical transceivers, we simplify several gyroscopes of the optical transceiver and shared the strapdown stable information with only one gyroscope. According to the position relationship between mirrors on the optical transceiver, we establish a series of new mirror coordinate systems. Based on these coordinate systems, we extend the application of the concepts of projection transformation and Euler angle, and supply the mathematical model of attitude stability of multi-mirror with single gyro. In the process of deducing the mathematical model, we notice that the arc tangent function can only solve the function values in the range of ( - 90 ∘ , 90 ∘ ), but can not satisfy the full-cycle motion calculation of yaw attitude. Through the analysis of the elements in the attitude transformation matrix, we found the model modification methods of mirrors in different positions, which can expand the range of yaw attitude calculation. We simulate four mirrors mounted at 0 ∘ , 90 ∘ , 180 ∘ and - 90 ∘ positions of the optical transceiver and give the calculation curves of yaw attitude. The results show that the maximum calculation range of the yaw attitude of each mirror is (- 90 ∘ , 90 ∘) before adopting the modification methods. As the pitch attitude decreases, the calculation range also shrink. After adopting the modification methods, the calculation range is increased to (0 ∘ , 360 ∘) . The mathematical model and modification methods provide theoretical support for multi-attitude stabilization system with single gyro and greatly reduce the burden of airplane. [ABSTRACT FROM AUTHOR]

A common problem in deformable mirror assembly is that the adhesion of actuators to an optical mirror face sheet introduces unwanted topography due to large local stresses generated at the adhesive joint. A new approach to minimizing that effect is described, with inspiration taken from St. Venant's principle, a fundamental precept in solid mechanics. It is demonstrated that moving the adhesive joint to the end of a slender post extending from the face sheet largely eliminates deformation due to adhesive stresses. A practical implementation of this design innovation is described, using silicon-on-insulator wafers and deep reactive ion etching. Simulation and experiments validate the effectiveness of the approach, reducing stress-induced topography on a test structure by a factor of 50. A prototype electromagnetic DM using this design approach is described, and its actuation is demonstrated. This new design can benefit a wide range of DMs that rely on actuator arrays that are adhesively bonded to a mirror face sheet. [ABSTRACT FROM AUTHOR]

The surface accuracy and quality of the mirror blank determine the performance of the optical mirror, so it is essential to explore a simple and effective way to process the mirror blank. Gas jet forming is a simple and efficient way of forming optical surfaces. However, the key to accurately forming mirror blanks is establishing the relationship between the gas jet parameters and the resulting surface shape. Therefore, several experiments were carried out in this study to develop the relevant models to investigate the above issues. The experimental data analysis found that the surface tension of the viscous fluid being processed impacts the shape of the surface formed by the gas jet. Therefore, the new model for predicting the surface shape of gas jets was developed by refining the Blanks and Chandrasekhara model by adding surface tension. The prediction error of the new model for the depth of the surface formed by the gas jet is in the range of 0.0497–0.833 mm, much smaller than the uncorrected model. [ABSTRACT FROM AUTHOR]

A frequency comb generator (FCG) based on dual-cavity Brillouin random fiber lasing oscillation in the 1.5 μm telecon spectral window is established and experimentally demonstrated. In the half-open main cavity of the dual cavity, the stimulated Brillouin scattering in highly nonlinear fiber (HNLF) and Rayleigh scattering in single-mode fiber are employed to provide sufficient Brillouin gain and the randomly distributed feedback, respectively, for random mode resonance. The sub-cavity includes an Er-doped fiber amplifier to couple back and boost lower-order Stokes and anti-Stokes light for the cascade of stimulated Brillouin scattering to generate multiple higher-order Stokes and anti-Stokes light. Meanwhile, efficient four-wave mixing is stimulated in the HNLF-based main cavity, further enhancing the number and intensity of the resonant Stokes and anti-Stokes light. By taking advantages of the unique transmission characteristics of nonlinear optical loop mirrors, the power deviation between Stokes and anti-Stokes lines is further optimized with 17 orders of stable Stokes lines and 15 orders of stable anti-Stokes lines achieved within the 10 dB power deviation, with maximum optical signal-to-noise ratio (OSNR) of ~22 dB and ~17 dB and minimum OSNR of ~10 dB and ~7.5 dB for Stokes and anti-Stokes lines, respectively. In addition, the dynamic characteristics of the proposed FCG have been experimentally investigated. Such an FCG with fixed frequency spacing will find promising applications in fields of optical communication, microwave, optical sensing, etc. [ABSTRACT FROM AUTHOR]

As an essential part of nanoparticle‐on‐mirror (NPoM) plasmonic nanocavities, metal mirrors play an important role not only in determining the optical response of the nanocavities but also their application performance. Here the effect of mirror quality on the optical response of nanosphere‐on‐mirror (NSoM) and nanocube‐on‐mirror (NCoM) nanocavities is experimentally studied. Polycrystalline sputtered gold films (SGFs), template‐stripped gold films (TSGFs), and single‐crystalline gold microflakes (GMFs) are investigated and compared. Due to the great improvement in the surface roughness that can minimize fluctuations in the gap morphology, NSoM and NCoM nanocavities formed on smooth TSGFs and GMFs have a better cavity‐to‐cavity homogeneity in the scattering spectrum than those formed on comparably rougher SGFs. In addition, there is an obvious change in the spectral positions of the resonance modes of NSoM and NCoM nanocavities formed on SGFs due to the variation in the gap morphology, which is reproduced very well by theoretical calculations based on measured dielectric functions of the gold films. Finally, due to the reduction in electron scattering losses from SGFs to TSGFs and GMFs, an increase in the quality factors and scattering intensities of the resonance modes is observed for nanocavities formed on the corresponding films. [ABSTRACT FROM AUTHOR]

The surface accuracy and quality of the mirror blank determine the performance of the optical mirror after coating; therefore, it is crucial to seek a simple and effective method for mirror blank processing. The gas jet forming provides a new idea, which employs a gas jet to impinge on a liquid pool, forms a specific curved surface and solidifies it. However, due to the interface instability that occurred with a specific range of jet velocity, periodical fluctuations appear on the interface and affect the forming of the mirror blank. In this study, the amplitude and transfer period of surface waves in the air gas/dimethyl silicone oil system are taken as the research objects. After conducting orthogonal experiments, this study uses a high-speed camera to record the generation of the surface wave and the fluctuation of the gas–liquid interface during its transfer. Subsequently, this study analyses the influences of jet velocity and viscosity of dimethyl silicone oil on the amplitude and transfer period of the surface wave. In the following experiments, multiple groups of parameters were selected in the range of jet velocity of 11~13 m/s and dimethyl silicone oil viscosity of 500~2000 Pa·s. This study measures the interface morphology with different parameters using the method of image recognition. Finally, using the measured data, this study establishes the calculation model of surface wave amplitude and transfer period, realizing the study of the characteristics of surface waves on the unstable interface. This research can be used to enhance the forming accuracy of the gas jet-forming method. [ABSTRACT FROM AUTHOR]

In this paper, we experimentally investigated the mode configuration of an excited-state quantum dot laser (ESQDL) under concave mirror optical feedback, and the influences of the feedback strength on the mode characteristics were analyzed. The results showed that after introducing concave mirror optical feedback, some longitudinal modes of the excited-state (ES) existing in a free-running ESQDL could be suppressed. When the feedback strength increased to a certain extent, the ground-state (GS) emission occurred and co-existed with the ES emission. By further increasing the feedback strength, all the longitudinal modes of the ES emission were suppressed, and only the longitudinal modes of the GS emission could be observed. As a result, the emission-state switching from the ES to GS emission was realized. When the ESQDL was biased at a larger current, the feedback strength required to achieve emission-state switching was stronger. [ABSTRACT FROM AUTHOR]

In this paper, a different Fiber Loop Mirror (FLM) configuration with two circulators is presented. This configuration is demonstrated and characterized for sensing applications. This new design concept was used for strain and torsion discrimination. For strain measurement, the interference fringe displacement has a sensitivity of (0.576 ± 0.009) pm‧με−1. When the FFT (Fast Fourier Transformer) is calculated and the frequency shift and signal amplitude are monitored, the sensitivities are (−2.1 ± 0.3) × 10−4 nm−1 με−1 and (4.9 ± 0.3) × 10−7 με−1, respectively. For the characterization in torsion, an FFT peaks variation of (−2.177 ± 0.002) × 10−12 nm−1/° and an amplitude variation of (1.02 ± 0.06) × 10−3/° are achieved. This configuration allows the use of a wide range of fiber lengths and with different refractive indices for controlling the free spectral range (FSR) and achieving refractive index differences, i.e., birefringence, higher than 10−2, which is essential for the development of high sensitivity physical parameter sensors, such as operating on the Vernier effect. Furthermore, this FLM configuration allows the system to be balanced, which is not possible with traditional FLMs. [ABSTRACT FROM AUTHOR]

Abrasive machining has been used for inner surface processing of various hollow components. In this study, we applied an in-air fluid jet as a precision machining method for the inner surface of an axisymmetric x-ray mirror whose inner diameter was less than 10 mm. We employed an abrasive with a polyurethane@silica core–shell structure, which has a low density of about 1.2 g/cm3 and a relatively large particle size of about 15 µm. By using this abrasive, a practical removal rate and a smooth machined surface were simultaneously obtained. We performed figure corrections for an axisymmetric mirror and improved the circumferential figure accuracy to a sub-10 nm root mean square level. To evaluate the machining performance in the longitudinal direction of the ellipsoidal surface, we also performed periodic figure fabrication on the inner surface of a 114 mm-long nickel ellipsoidal mirror. X-ray ptychography, an optical phase retrieval method, was also employed as a three-dimensional figure measurement technique of the mirror. The wavefield of the x-ray beam focused by the processed ellipsoidal mirror was observed with the ptychographic system at SPring-8, a synchrotron radiation facility. The retrieval calculations for the wavefront error confirmed that a sinusoidal waveform with a period of 12 mm was fabricated on the mirror surface. These experimental results suggest that a nanoscale figure fabrication cycle for the inner surface consisting of jet machining and wavefront measurement has been successfully constructed. We expect this technique to be utilized in the fabrication of error-free optical mirrors and various parts having hollow shapes. [ABSTRACT FROM AUTHOR]

Here, we introduce ultrafast tunable MEMS mirrors consisting of a miniature circular mirrored membrane, which can be electrostatically actuated to change the mirror curvature at unprecedented speeds. The central deflection zone is a close approximation to a parabolic mirror. The device is fabricated with a minimal membrane diameter, but at least double the size of a focused optical spot. The theory and simulations are used to predict maximum relative focal shifts as a function of membrane size and deflection, beam waist, and incident focal position. These devices are demonstrated to enable fast tuning of the focal wavefront of laser beams at ≈MHz tuning rates, two to three orders of magnitude faster than current optical focusing technologies. The fabricated devices have a silicon membrane with a 30–100 μm radius and a 350 nm gap spacing between the top and bottom electrodes. These devices can change the focal position of a tightly focused beam by ≈1 mm at rates up to 4.9 MHz and with response times smaller than 5 μs. [ABSTRACT FROM AUTHOR]

This paper proposes a method with an off-axis interferometer and an ensemble deep learning (I-EDL) hologram-classifier to interpret noisy digital holograms captured from the tissues of flawed biological specimens. The holograms are captured by an interferometer, which serves as a digital holographic scanner to scan the tissue with 3D information. The method achieves a high success rate of 99.60% in identifying the specimens through the tissue holograms. It is found that the ensemble deep learning hologram-classifier can effectively adapt to optical aberration coming from dust on mirrors and optical lens aberrations such as the Airy-plaque-like rings out-turn from the lenses in the interferometer. The deep learning network effectively adapts to these irregularities during the training stage and performs well in the later recognition stage without prior optical background compensations. The method does not require an intact sample with a full outline shape of the specimens or the organs to understand the objects' identities. It demonstrates a new paradigm in object identification by ensemble deep learning through a direct wavefront recognition technique. [ABSTRACT FROM AUTHOR]

The Advanced Virgo Plus project aims to increase the sensitivity of the Virgo gravitational-wave detector, given the forthcoming O4 Observing Run. One of the major upgrades is the addition of the Signal Recycling Mirror in the optical layout. This additional mirror will provide a broadband improvement to the sensitivity curve of the instrument, but poses significant challenges in the acquisition and operation of the detector's working point. The process which brings the main optical components from the uncontrolled state to the final working point, which ensures the best detector sensitivity, is called lock acquisition: the lock acquisition is made by moving through increasingly more complex configurations toward the full control of all the interferometer's longitudinal degrees of freedom. This paper will focus on the control of the Dual-Recycled Michelson Interferometer (DRMI, the central part of the Virgo interferometer), presenting a comprehensive study of the optical simulations used in the design and the commissioning of this configuration. Treated topics include: the characterization of optical fields, powers, and error signals for the controls; the development of a trigger logic to be used for the lock acquisition; the study of the alignment sensing and control system. The interdependence between the three items has also been studied. Moreover, the validity of the studied techniques will be assessed by a comparison with experimental data. [ABSTRACT FROM AUTHOR]

The steering mirrors and the focusing mechanisms are the key components of the optical system. Traditional steering mirrors driven by voice coil actuator or piezoelectric stack actuator have the disadvantages of short stroke, self-locking difficulty and poor structural reliability. These defects limit the performance of the steering mirrors and make it difficult to be compatible with the focusing mechanism. As a result, additional focusing devices are required in the optical system, which significantly increases the complexity of the system. To simplify the optical system, a large stroke three-degree-of-freedom (3-DOF) piezoelectric steering mirror (PSM) which can realize both light path adjustment and focus adjustment is proposed in this study. Two rotational degrees of freedom of the PSM are used to adjust the light path, and a translational degree of freedom is used to adjust the focus. The screwed-typed piezoelectric actuators (STPAs) are designed to drive the PSM by exciting the travelling wave. The feasibility of the operating principle and reliability of the proposed PSM have been verified by finite element simulation. A prototype of the PSM is fabricated and tested. The experimental results show that the PSM achieves rotational degrees of freedom around the x -axis, y -axis and translational degree of freedom along the z -axis with maximum ranges of ±0.17 rad, ±0.17 rad, and ±10 mm, respectively, meeting the application requirements of the optical systems. The resolutions of the two rotary motions of the PSM are 28 μrad, and 21 μrad, respectively, and that of the translational motion is 0.5 μm. Finally, the position adjustment and focusing operations of the image are demonstrated to validate the potential application of PSM in optical systems. [Display omitted] • A large-stroke high-precision fast-response screwed-typed piezoelectric actuator (STPA) is designed in this study. • A novel 3-DOF piezoelectric steering mirror is proposed to realize the light path adjustment and focusing functions. • The proposed PSM is verified to adjust the image position adjustment and focus adjustment. [ABSTRACT FROM AUTHOR]

Optical tilt mirrors (OTM) enable the mirrors to achieve high precision posture adjustment, playing a significant role in various optical system applications in the fields such as active optics, adaptive optics, satellite communications and biomedicines. However, the rapid development of modern technologies has brought new challenges to OTM in terms of their dimension, operating space and dynamic performance. Herein, a novel biaxial optical flexible tilt mirror (OFTM) driven by four simple bonded-type thin sheet piezoelectric actuators was proposed, where the OFTM was designed based on the flexible bending motions of composite piezoelectric beams. Particularly, OFTM is mainly composed of PZT sheet and stainless steel substrate, and shows a dimension of 42 mm × 42 mm × 0.2 mm. A theoretical model of OFTM was established to accurately describe the relationship between input electric field and output pose based on elastic beam theory, where the relationship was verified by both finite element analysis and experimental results. Finally, an OFTM prototype was fabricated and presented good performance on motion behaviors. Compared with traditional fast steering mirror (FSM) and MEMS mirror, the developed OFTM shows low cost, small size and simple manufacturing process, which greatly extends the applications of OFTTM in emerging fields. [Display omitted] • A novel biaxial optical flexible tilt mirror (OFTM) driven by four bonded-type piezoelectric actuators was developed. • A model was established to describe the relationship between static characterictics and structural parameters of OFTM. • Static and dynamic test results demonstrated the feasibility of OFTM in beam steering at closed-loop working conditions. [ABSTRACT FROM AUTHOR]

The study delves into the characteristics and dynamics of vector square waves in an erbium-doped fiber laser employing a nonlinear optical loop mirror (NOLM). Through experimental investigation, the laser's operational modes, namely stable and periodic pulsating states, are achieved by manipulating polarization controllers (PCs). Within these states, the generation of two square waves with distinct peak power is observed. The vector properties of the pulses are authenticated using a polarized beam splitter (PBS). Furthermore, meticulous adjustment of the PCs reveals phenomena such as multi-pulse periodic breathing and prolonged fluctuations in pulse intensity. • Two orthogonally polarized vector square waves with different group velocities are generated. • The pulsating mode-locking operation is accompanied by dispersive wave radiation. • The pulse breathing and energy transfer are driven by the dispersive waves. • The periodic pulsation of pulse intensity and the associated temporal offset are observed. [ABSTRACT FROM AUTHOR]

The imaging performance of segmented optical telescopes depends on the positional assembly accuracy of segmented mirrors. In this paper, we present a novel method for measuring the piston and tip/tilt errors of segmented mirrors based on optical vortex polarization phase-shifting interferometry. The functional relationships between piston error or tip/tilt error and phase distribution in the image plane are derived. To validate the correctness of the relationships, we established an optical system model in the non-sequential mode of OpticStudio. The phase information is acquired by the least squares method as well as the Hough transform, whereby the piston or tip/tilt errors can be retrieved by the functional relationships. The results of simulations and experiments validated the feasibility of the proposed method. It shows excellent efficiency because the analysis process is computationally non-intensive. The method has an extended measurement range and high accuracy, bypassing the demanding hardware requirements and providing a novel approach for measuring co-phase errors in a segmented primary mirror. • Can be applied to segmented primary mirrors with any shape to achieve fast and efficient measurement of co-phase errors. • High precision, high efficiency, good vibration resistance. • Simple principle and implementation, avoiding the use of difficult-to-manufacture optical components. [ABSTRACT FROM AUTHOR]

• Comprehensive analysis of generation and separation of both frequency degenerate and non-degenerate FWM twin beams in an OPLM which consists of an optical coupler with adjustable splitting ratio, a nonlinear fiber, a dispersion element, and two tunable attenuators placed at different positions in the loop is demonstrated. • With the splitting ratio of the coupler being 1:1 and no loss in the loop, both the frequency degenerate and non-degenerate twin beams can propagate through different ports completely by introducing proper dispersion, and switching between phase-sensitive and phase-insensitive amplification can be realized by changing the dispersion within the loop. • When the beam splitting ratio of the coupler deviates from 1:1, adjusting the loss in the loop can partially compensate for the asymmetry of the beam splitting ratio and promote the separation of signal and idler beams. • Our research is of great significance for the preparation of twin beams and the creation of switchable phase-sensitive amplifiers by Sagnac fiber loop. We theoretically demonstrate the propagating performance of twin beams generated in a Sagnac fiber loop by developing a practical model of optical parametric loop mirror consisting of an optical coupler with adjustable splitting ratio, a nonlinear fiber, a dispersion element, and two tunable attenuators placed at different positions in the loop. Two situations of frequency degenerate and frequency non-degenerate four-waving mixing are considered and various of factors including dispersion conditions, internal losses in the loop, and splitting ratios of the coupler are investigated in detail. When the splitting ratio of the coupler is 1:1 and no loss is in the loop, both the frequency degenerate and non-degenerate twin beams can propagate from different ports completely by introducing proper dispersion, and switching between phase-sensitive and phase-insensitive amplification can be realized by changing the dispersion within the loop. In general, the propagation of signal and idler beams at the two output ports of the fiber loop are influenced by both the splitting ratio of the coupler and the internal loss within the loop. Adjusting the internal loss can partially compensate for the asymmetry of the splitting ratio of the coupler, facilitating spatial separation of the signal and idler beams. Our research is useful for the generation of twin beams using Sagnac fiber loop and the realization of switchable phase-sensitive amplifiers. [ABSTRACT FROM AUTHOR]