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• Development of cantilever magnetometer and its validation. • Estimation of magnetostriction of FeGa thin films up to 10-6 order. • Utilization of N-(3-dimethylaminopropyl)-N0 -ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS) bio-markers for detection of BSA. • Detection of BSA up to 1 mg/mL. Detection of bovine serum albumin (BSA) is important to comprehend the severity of a certain diseases. Here, we report on the remote detection of bovine serum albumin (BSA) using modified cantilever beam magnetometery (CBM). A magnetostrictive Fe 70 Ga 30 cantilever in combination with optical detection technique allowed us to detect BSA concentration up to 1 mg/mL in a remote way. Essentially, a position sensitive detector (PSD) is used to detect reflected light from cantilever without any optical mirrors. Apart from the above, magnetostriction of Fe 70 Ga 30 cantilever estimated as 80 ppm at 180 mT. We ascertain that our method is easy and efficient in estimating the magnetostriction of thin films up to 10-6 order. We believe that CBM technique that we developed would be helpful in estimating magnetostriction of bulk and thin films apart from the detection of bio – molecules. [ABSTRACT FROM AUTHOR]

A tunable and switchable multi-wavelength random fiber laser (MW-RFL) is proposed and experimentally demonstrated in this work, which consists of a random distributed feedback mechanism, an improved Lyot filter, and a nonlinear optical loop mirror (NOLM). The theoretical derivation and simulation analysis of the improved Lyot filter are carried out by using the transfer matrix theory. The results show that by adjusting the polarization controller (PC) in the filter, not only the channel interval can be switched between 0.9 and 0.45 nm, but also the extinction ratio (ER) of the transmission spectrum can be adjusted and the wave peak position can be moved. The feedback mechanism of the proposed laser is provided by the randomly distributed backward Rayleigh scattering generated in the single-mode fiber. By changing the pump laser power, the number of output laser channels will be linearly increased. When the channel interval is kept constant, the wavelength can be tuned within a certain range by carefully adjusting the PC3 in the NOLM. When the channel interval of the spectrum is 0.9 nm, the wavelength tuning ranges of the three and four laser channels are 3.6 and 3.5 nm, respectively. When the channel interval of the spectrum is 0.45 nm, the wavelength tuning ranges of the three and four laser channels are 2.8 and 2.77 nm, respectively. Then the variations of the output spectrum when using 25 km single-mode fiber (SMF) are studied. It is observed that the linewidth and side mode suppression ratio (SMSR) of the laser channel are significantly increased. Finally, the stability of the random laser is discussed, and the maximum central wavelength drift and peak power fluctuation measured at room temperature are 0.05 nm and 0.34 dB, respectively. The average peak power and SMSR are maintained at −4.47 dBm and 34.6 dB, respectively, which confirms that the laser has good stability. [ABSTRACT FROM AUTHOR]

• We propose a switchable and tunable multi-wavelength random distributed feedback fiber laser based on a parallel Lyot filter; • This laser's channel spacing can be changed among of 0.88 nm and 0.46 nm by changing the PMF length; • The proposed laser has good flexibility in channel interval switching and large tuning range, when the wavelength interval is 0.88 nm, the wavelength tuning ranges of the three and four laser channels are 4.4 nm and 3.7 nm, respectively. When the wavelength interval is 0.46 nm, the wavelength tuning ranges of the three and four laser channels are 3.7 nm and 4 nm, respectively; • The side mode suppression ratio is greater than 34.5 dB. A switchable and tunable multi-wavelength random distributed feedback fiber laser based on a parallel Lyot filter is designed, and the transmission characteristics of the filter are deduced in detail by using the transmission matrix theory. The randomly distributed backward Rayleigh scattering generated in single-mode fiber (SMF) serves as a feedback mechanism. The number of output wavelength increases linearly with the increase of pump power. By adjusting the polarization controller (PC) to control the polarization state of the beam into the polarization maintaining fiber (PMF), laser channels with wavelength interval of 0.88 nm or 0.46 nm can be output. Where the wavelength interval depends on the wavelength phase difference caused by the corresponding branch PMF. The intensity-dependent loss (IDL) caused by the nonlinear optical loop mirror (NOLM) in the experimental structure is not only used to suppress the intense mode competition caused by EDF, but also to control the spectral range of the output wavelength to achieve tunable laser output. When the wavelength interval is 0.88 nm, the wavelength tuning ranges of the three and four laser channels are 4.4 nm and 3.7 nm, respectively. When the wavelength interval is 0.46 nm, the wavelength tuning ranges of the three and four laser channels are 3.7 nm and 4 nm, respectively. Subsequently, the influence of using different lengths of SMF on the output wavelength is analyzed. It is found that longer SMF can increase the linewidth of the laser channel, and the side mode suppression ratio (SMSR) will be improved to 39 dB. In addition, the output power fluctuation of the laser is less than 0.32 dB within 30 min, and the power amplitude and SMSR are stable at −4.47dBm and 34.5 dB, respectively, indicating that the laser can achieve flat and stable multi-wavelength output at room temperature. [ABSTRACT FROM AUTHOR]

• In terms of adjusting the splitting ratio f and cavity length L of the NOLM, self-similar pulse (SSP), soliton molecule (SM), DSR, DS and dissipative soliton pair (DSP) can be obtained in such fiber laser system. • Found that the parameter P max defined by us is the main factor that determines the type of solitons generated in the laser. • Investigated the nonlinear dynamics in the process of the transformation between these solitons. • Discussed the mechanisms and characteristics of these solitons. The properties of the saturable absorber are critical to the soliton dynamics in the all-normal dispersion Yb-doped mode-locked fiber laser based on the nonlinear optical loop mirror (NOLM). In this paper, it is found that by adjusting the splitting ratio f and cavity length L of the NOLM, self-similar pulse (SSP), soliton molecule (SM), dissipative soliton resonance (DSR), dissipative soliton (DS) and dissipative soliton pair (DSP) can be obtained in such fiber laser system. In addition, the mechanisms and characteristics of these solitons are discussed. These findings will facilitate the in-depth understanding of the characteristics of nonlinear pulses generated by NOLM-based all-normal dispersion Yb-doped mode-locked fiber laser. [ABSTRACT FROM AUTHOR]

A method for fabrication of a concave spherical mirror made of crystalline quartz is proposed and X-ray optical properties of the mirror are studied. The radius of curvature is 1630 mm. The shape of the mirror surface is studied using an interferometer with a diffraction reference wave. In the entire processing region, the maximum deviation from the nearest sphere is about 0.2 μm and the rms is 34 nm, so that high quality of imaging is provided with an angular error of about 2″ (angular seconds). Reflection coefficient (about 7%) and lower bound limit of spectral selectivity (λ/δλ ≈ 1775) are determined in the vicinity of a wavelength of λ = 0.834 nm, which is close to the working wavelengths of the MgXII doublet (λ = 0.8418 and 0.8423 nm). Position of the Bragg peak and spectral selectivity remain unchanged upon bending of the crystal mirror within measurement accuracy. [ABSTRACT FROM AUTHOR]

• Mechanism of nonlinear optical loop mirror used to achieve mode-locking operation. • First demonstration of an all-PM Tm-doped mode-locked fiber laser based on NOLM. • Stable linearly polarized pulse with a duration of 732 fs centered at 1996.6 nm. • Amplification of the subpicosecond pulses to an energy over 11 nJ. • Demonstration of soliton splitting during amplification in a fiber amplifier. We report on a self-starting, anomalous dispersion mode-locked Tm-doped fiber laser based on all polarization maintaining (PM) fiber components. The oscillator, which is based on a nonlinear optical loop mirror, generates stable, linearly polarized sub-picosecond solitons at a repetition frequency of 11.78 MHz, centered at 1996.6 nm with a spectral width of 7.12 nm. Amplification of the pulses in a single-stage thulium-doped fiber amplifier resulted in an increase of the pulse energy to over 11 nJ at which soliton splitting process was demonstrated. [ABSTRACT FROM AUTHOR]

Lightweight optical mirrors usually play key roles in aerospace and optical structural systems applied to space telescopes, radars, solar collectors, communication antennas, etc. Due to their high flexibility and low damping properties, external excitations such as orbital maneuver may induce unexpected oscillations and thus reduce their working performance. Active vibration control is therefore essential for the lightweight optical mirror systems. In this spirit, a lightweight mirror structronic system with a linear quadratic optimal controller is presented. The mirror is modeled as a membrane plate with pretension and distributed polyvinylidene fluoride sensors and actuators. The sensing sensitivity of the piezoelectric (PVDF) sensors and the modal actuation factor of the PVDF actuators are derived. The state-space equations are established and the feedback control gains between sensing and control signals are obtained. Sensor and actuator of different shape, size, and position are employed to actively control the first four natural modes of the mirror. The influences of mode order, pretension, and the two weighting factors Q and R on the control performance are also investigated. Analytical results in this paper could guide the design and layout of the PZT sensor and actuator on lightweight membrane plate mirrors. [ABSTRACT FROM AUTHOR]

The first mirrors of optical diagnostics in ITER are exposed to high radiation and fluxes of particles which escape the plasma, in the order of 1020 m−2s−1. At the position of the mirror, the flux may still reach about 1018 m−2s−1. First mirrors are thus the most vulnerable in-vessel optical components, being subject to erosion, esp. by fast charge-exchange neutrals, or to deposition of impurities at flux rates which can reach 0.05 nm/s. The material selected for the reflecting surface must combine a high optical reflectivity in a wide spectral range and a sufficient resistance to physical sputtering during normal operation and during mirror cleaning discharges, if any is installed. Rhodium (103 Rh) was identified early as a possible or even promising candidate. It combines several attractive properties, for instance a mass which leads in most cases to low sputtering yields together with an optical reflectance (R Rh ≈ 75 %) which is much higher than of some other options. R Rh is insensitive to large temperature changes. Rhodium is fairly inert and its low oxidation is an appreciable advantage in case of steam ingress events. The core-plasma CXRS diagnostic in ITER (UPP 3) have now turned to Rh as a baseline. The aim is to procure monocrystalline rhodium (SC-Rh) to mitigate the increase of the diffuse reflection with the damage due to physical sputtering. [ABSTRACT FROM AUTHOR]

The WEST platform aims at testing ITER like W divertor targets in an integrated tokamak environment. To operate long plasma discharges, IR thermography is required to monitor the main plasma facing components by means of real time surface temperature measurements, while providing essential data for various physics studies. To monitor the new divertor targets, the WEST IR thermography protection system has been deeply renewed, to match the new tokamak configuration. It consists of 7 endoscopes located in upper ports viewing the whole lower divertor and the 5 heating devices. Electronic devices and computers allow data storage of ≈3 Gb/s IR images and real time video frames processing at 50 Hz rate, to ensure the protection of the main plasma facing components during plasma discharges by a feedback control of the power injected by the heating systems. Each endoscope provides 2 views covering 2 divertor sectors of 30° (toroidally) and 1 view of a heating antenna. Each optical line is composed of a tight entrance window followed by a head objective which forms an image transported through the endoscope by a series of 4 optical relays and mirrors, up to a camera objective. Finally, 12 IR cameras specially developed for WEST environment capture the thermographic data, at the wavelength of 3.9 μm, with a 640 × 512 pixels frame size. The paper describes the design constraints and diagnostic technologies: optics, mechanics, electronics, hard & software, cameras. Tvhe laboratory characterization procedures (Modulation Transfer Function, slit response, calibration), and the measurement performance results are given (spatial resolution, temperature threshold). Finally, first results obtained during experimental campaigns in WEST are presented. [ABSTRACT FROM AUTHOR]

One of the important aspects of the service life of the first and second optical mirrors (FM and SM) in ITER UWAVS diagnostics is to understand the influence of plasma cleaning on materials re-deposition and optical surface quality after multiple cleaning cycles. The capacitively coupled RF 30–60 MHz system is a candidate for the UWAVS mirror cleaning. It generates ion fluxes of tens of electron-volts, sputtering contaminants as well as construction materials. In the present report, we discuss materials re-deposition after cleaning with 30–60 MHz discharges inside the prototype of the front-end vacuum compartment. Typical ion energies were below 100 eV at the RF electrode and 20–30 eV at the grounded wall. Materials sputtered from the FM were deposited at various locations and on the SM. The deposition rates were estimated as 0.05 nm/hour or lower. The experiments showed advantages of Molybdenum as a plasma facing construction material due to lower sputtering. Traces of Fluorine were found, which may indicate cable damage at higher powers. The single-crystal Mo-mirror mock-up was etched at 0.5–1 nm/hr. rate. The mirror reflectivity showed satisfactory results after 60 h of exposure, with 50–60 nm removed. The overall effect on the reflectivity considering full service time is yet to be investigated. [ABSTRACT FROM AUTHOR]

• Conservative estimation of DT and Be neutral fluxes on the first mirrors of H-alpha and Visible spectroscopy in stationary modes of ITER was done. • Zemax software was used for calculation of attenuation factors in real geometry of equatorial port-plugs. • Optical area of the first mirror will remain clean being occupied by erosion-dominated zone. • Contamination of the first mirror edges will not affect the diagnostics performance. • In-situ mirror cleaning system will be used in case of eventual contamination of the optical area. The first mirrors of all optical diagnostics in ITER will be exposed to the fluxes of neutrals, mainly D, T and Be. This can lead to formation of erosion and deposition zones on the mirror surface. In this work, the fluxes of neutral D, T and Be on the first mirror of H-alpha diagnostics in the equatorial ports were analyzed with Zemax OpticStudio software. Only stationary modes of ITER were considered. The geometry of viewing cutouts in diagnostic shielding modules (DSM) and the model of the first mirror units (FMU) were taken from the ENOVIA database. It is shown that the net erosion is dominating in major part of the first mirror zone with erosion rate ≈100 nm/year. The net deposition zone is located on the edges of the mirror, where deposition rate reaches up to 900 nm/year. Being made of single crystal molybdenum, the mirrors will keep their optical properties under erosion over the whole ITER lifetime. The contaminated edges are not important for the light collection and imaging of the SOL emission in the areas of interest at the ITER first wall within the selected field-of-view. The DC plasma discharge mirror cleaning system will be used to recover FM performance in case of eventual contamination. [ABSTRACT FROM AUTHOR]

Each of the 4 ITER Electron Cyclotron Heating Upper Launcher (ECHUL) features 8 transmission lines used to inject microwave power of up to 1.31 MW per line (at the FCS diamond window), into the plasma at a frequency of 170 GHz. The millimetre waves are guided through a quasi-optical section consisting of three fixed mirror sets (M1, M2 and M3) and the front steering mirror set (M4). The M2 mirror set is composed of an upper and lower part, each reflecting 4 Gaussian beams coming from the M1 passing to the M3 mirror, which ultimately will reach the M4 steering mirror that will aim at the correct location in the plasma for suppression of the Neoclassical Tearing Modes (NTMs) that occur at the q = 3/2 and q = 2/1 rational surfaces. Reflecting mm-wave power generates heat by ohmic dissipation, reaching a peak power density of approximately 4 MW/m2 on each of the 4 beam centre spots of the M2 mirror, and totaling 19.4 kW of absorbed power. EPFL-SPC has developed a novel water cooled mirror design concept which is able to dissipate such high heat loads (with up to 60,000 thermal cycles) and also to resist the applied external loads and dynamic displacements arising from plasma disruptions and seismic events, while complying with material and space restrictions. This study describes the main design features of the upper M2 mirror, its design conformity in accordance to thermal and structural integrity, as well as its compliance with the Essential Safety Requirements for nuclear in-vessel components. [ABSTRACT FROM AUTHOR]

This article gives a condensed review of the MEMS actuators that have seen light in the past three decades. Since the electrostatic drive comes almost natural when creating mechanical devices with the available MEMS technology, greater importance is highlighted. Nevertheless, by introducing more non-IC related materials, other devices are presented, and range from magnetic and piezo-electric drive, to applications based on hydraulics and pneumatic actuation. [ABSTRACT FROM AUTHOR]

We propose a novel optical setup to project a flat plane onto a spherical surface. Our proposed method employs putting a curved mirror in the optical path of the projection optics. The curved mirror is placed at the initial image plane formed by a relay lens. This initial image is then re-imaged at the spherical surface. Thus, our optical setup enables having a focused image on a spherical surface. To determine the radius of the curved mirror at the initial image position, we calculated it by paraxial equation. The result is confirmed by optical simulations and demonstrated with a prototype optical system. [ABSTRACT FROM AUTHOR]

Active optics technology eases the requirements for the fabrication and stability of mirrors. Optical replication techniques make it possible to fabricate a mirror of optical quality rapidly and inexpensively. Combining the advantages of these two methods, we designed a lightweight unimorph mirror with a diameter of 160 mm based on an Al-SiC passive layer. A finite element model was established to predict the performance of this mirror and to optimize relevant parameters. A spherical prototype mirror was fabricated and tested to measure its shape-correction capability, thermal stability, and surface roughness; this prototype has been used in an innovation project on lightweight active mirrors from the Chinese Academy of Sciences. [ABSTRACT FROM AUTHOR]

A hybrid quantum optomechanical system is an interface made from coupling between photons, excitons and mechanical oscillations. We use the quantum Langevin approach to study a hybrid optomechanical system which contains a single undoped semiconductor quantum well placed inside a cavity as well as one mirror of the optical resonator linear coupled to the cavity fields. A decorrelation method is employed to get a closed set of coupled equations. Furthermore, we have used these solutions to discuss squeezing dynamics for the coupled mode quadratures of the cavity field and the semiconductor quantum well exciton. We have illustrated that squeezing dynamics can be controlled by appropriate choice of physical parameters present in our hybrid optomechanical system. [ABSTRACT FROM AUTHOR]

Summary: Thermochromic manganite represents a promising energy‐saving material individualizing tunable emittance via external stimuli to manipulate thermal radiation and automatically regulate temperature. However, the ceramics fabricated from the manganite are commonly hard and brittle, which make the fabrication of their flexible device very difficult. Here, large‐scale thermochromic foils (TFs) prepared via manganite nanoparticles (NPs) and polyimide (PI) is flexible with thermal emittance self‐adjusting from 0.31 to 0.77 upon heating, which the emittance is enhanced by 148%. Especially, the emittance increases dramatically with temperature till 293 K, followed by a leveling off. It is suggested that the PI transparency and the filling ratio of NPs are two important parameters to optimize the thermochromic properties of TFs. Our experiment demonstrated that TFs fabricated with the fluorinated PI can save at least 61% energy consumption versus the existed optical surface mirror at low temperature. The flexible TFs has good prospects for application in smart thermal management. [ABSTRACT FROM AUTHOR]

The micro-displacement measurement system with 2D/3D has become increasingly important in the field of scientific research and technology application. In order to explore the application of an optical surface in micro-displacement measurement, a novel and simple 2D micro-displacement measurement method based on the elliptical paraboloid was designed and subjected to experiment. The measurement system takes advantage of the elliptical paraboloid instead of a plane mirror in the optical structure of an autocollimator which has been ameliorated to adapt to curved surface measurement. Through the displacement of the light spot on the CCD (Charge Coupled Device) detector, the displacement of the target could be measured with a linear correlation coefficient of 0.9999. The accuracy of the system is about ± 0.3 μm in a wide range in two dimensions. The results were in good agreement with the theoretical analysis and indicated the potential applicability of the proposed system in the detection of geometric errors of CNC (Computerized Numerical Control) machine tools. [ABSTRACT FROM AUTHOR]

Highlights • Holograms binarization for displays, media characterization, optical encryption. • 12 local and 18 global thresholding techniques were analyzed. • Optically recorded off-axis digital holograms were binarized. • The highest quality was achieved using clustering-based thresholding methods. Abstract Binary digital and computer-generated holograms are used in a number of digital micromirror device (DMD) applications, including holographic displays, media characterisation, optical encryption, and others. Binarisation is one of the most simple and efficient methods of hologram compression. In this paper, 12 local and 18 global thresholding techniques of different groups were analysed and compared based on attribute similarity, clustering, entropy, histogram shape, and local adaptive factors. Optically recorded off-axis digital holograms of different objects were binarised using these methods. The amplitude quality of the obtained reconstructed images was compared using PSNR and SSIM values. The clustering-based methods achieved the highest quality. The results of binarisation by global and local methods were comparable on average. [ABSTRACT FROM AUTHOR]

Abstract A single platform multifunctional fiber optic filter is presented. The filter is based on a Michelson–Gires–Tournois Interferometric (MGTI) structure, which makes use of high dynamic range fiber loop mirrors (FLM) for the tunability of the required reflectance. Path length control is another degree of freedom which provide the multifunctionality in the optical transfer function of the filter. The optical filter can be configured to suppress optical side bands, shape the amplitude of optical combs, or perform spectral slicing for signal processing. Rectangular pass-band transfer functions (TF) with tunable center frequency (tens of GHz) and tunable frequency bandwidth (BW) with side lobe suppression of more than 20 dB and ripple of < 0.2 dB is obtained. Modifications in the resonator reflectance (>99%) and optical paths can change the TF to notch type with 250 MHz bandwidth. Further reflectance modification (<99%) leads to TF with linear portions, where the slope can be adjusted by adjusting the resonator reflectance. Finally, sinusoidal transfer function of varying period completes the set of obtainable TF using a dual Gires–Tournois cavity MGTI configuration in a single photonic platform. Highlights • Single platform multifunctional fiber-optic filter based on fiber-optic Michelson–Gires–Tournois Interferometer. • Potential transfer functions include rectangular , notch, ramp and sinusoidal. • Transfer function tunability is obtained by fiber loop mirror reflectivity control and path length adjustments. [ABSTRACT FROM AUTHOR]

Highlights • Proposal of a novel image processing algorithm for the testing of optical focusing mirrors. • Computing of accurate wavefront gradient estimations from a single defocused "bironchigram" sample. • Complete and valid indirect measurement optical technique featuring an accuracy akin to interferometry. Abstract Since its proposal the Ronchi "ruling" test has been considered as the most remarkable technique of the Schlieren family. Despite being based on fringe pattern generation and commonly interpreted in a qualitative way, it was capable of achieving outstanding results in the detection of aberrations in optical surfaces. Given its theoretical straightforwardness, experimental simplicity and economic affordability in comparison to other methodologies in the field, in the present work is addressed the lingering issue of how to extract quantitative information from digital captures of this test. Such task was accomplished taking advantage of the improved Ronchi test with a square grid, from which it was possible to develop a mathematical model with foundation in the Fourier theory to describe its observations. Thereupon, it was devised a novel iterative algorithm grounded in Fourier phase measuring able to compute fairly accurate wavefront gradient estimations from a single "bironchigram" sample with grid defocus. This procedure is complemented by a mandatory integration algorithm that is based on the regularization theory. The overall proposed methodology was put to test in a large aspherical mirror, estimating a surface aberration profile with a P–V (peak to valley) ratio of 155 nm, value well in accord with the one reported by the commercial interferometric system used for validation. [ABSTRACT FROM AUTHOR]

Forschungszentrum Jülich and partners are developing the ITER core charge exchange spectroscopy (cCXRS) hosted by upper port plug#3 (UPP). The system should withstand loading due to the plasma transients resulting in electromagnetic (EM) forces acting on the UPP and its onboard components. On the other hand, the eddy currents and shock dynamic EM loads occur in the vacuum vessel (VV) and make it vibrate. As a result, it excites the UPP and, consequently, its onboard components. The computational problem is a superposition of these solutions: 1) the deterministically calculated time-history UPP response to the applied EM forces and 2) the UPP response to the VV excitations that are specified as floor response spectra (FRS) at the port stub (attachment to the VV). On the top of this, the EM loads should be combined with the seismic ones which are also specified as an FRS. This paper considers a potential methodology for combining plasma transients with seismic events. A numerical modeling of the UPP hosting a specific cCXRS component is presented. This methodology gives a direct and transparent engineering way to estimate the mechanical strength of the UPP onboard components. The analysis uses port stub FRS input and does not depend on a spectra-to-spectra recalculation procedure (from VV to component attachment) that is well established for the seismic-type response spectra but is not validated for the FRS due to the plasma transients. [ABSTRACT FROM AUTHOR]

A low-power three-degree-of-freedom scanning micromirror is presented. The 2- × 2-mm mirror is a gimbaless structure, directly supported by single-crystal microsprings. It is actuated by Lorentz force and is able to tilt about two axes and has linear motion in a third-axis. The transient and frequency responses of the micromirror are analyzed. The Lagrange's equations of motions describing the dynamic behavior of the system are presented and show a good agreement with the experimental results. The fabricated microelectromechanical system mirror demonstrates a tilt angle of 22.8 deg at 247.5 Hz about y-axis, and 13.3 deg at 292.7 Hz about x-axis, in a 0.1 T magnetic field and 20-mA current on the mirror. Power consumption is 2.6 mW of power in tilting motions in resonant operation. With a total DC-drive current of 110 mA, 232-µm linear motion is achieved. [ABSTRACT FROM AUTHOR]

This study investigates the nonlinear dynamics and hysteresis phenomena in a figure-of-9 fiber laser. The laser cavity consists of an Erbium doped nonlinear amplifying loop mirror (NALM) containing a Dispersion Compensation Fiber (DCF) segment, coupled to a nonlinear optical loop mirror (NOLM). A lumped-element model is developed for the laser cavity accounting for bi-directional light propagation. The model is based on the modified nonlinear Schrödinger equation (NLSE) with coefficients directly related to the parameters of each cavity segment. Gain saturation is taken into consideration for stable laser operation. The numerical results show that self-starting passive mode-locking and self-structuration of soliton lattices occur in the cavity of the laser. The soliton structuring is based on the concept of dissipative solitons, which requires a balance between dispersion-nonlinearity and gain-loss. The gain-loss parameters influence both the temporal pulse interactions and the NALM's transmission, leading to a large variety of single and multiple breathing dissipative soliton dynamics. In that context, riveting studies of the transition dynamics from breathing single pulses to high-order multiple breathing dissipative solitons and hysteresis with respect to unsaturated amplifier gain in a figure-of-9 all-fiber laser are explored. [Display omitted] • Investigates nonlinear dynamics and hysteresis in figure-of-9 fiber laser. • lumped-element model used based on the modified nonlinear Schrödinger equation. • Model considers bi-directional light propagation and gain saturation. • Studies transition from single to high-order multiple breathing dissipative solitons. • Explores hysteresis with respect to unsaturated amplifier gain. [ABSTRACT FROM AUTHOR]

The integrated design and manufacturing of aerospace metal optical mirrors can be challenging for rapid manufacturing with traditional techniques while maintaining mechanical integrity and meeting mass limitations. Hybridized additive/ultra-precision machining process is a promising approach to fabricate optical surfaces on AlSi10Mg alloy to meet the optical demands and mechanical performances. However, the fundamental investigation of ultra-precision machining of optical surfaces on additively manufactured AlSi10Mg alloy is still lacking, delaying the application of this technology. In this study, the microstructure, mechanical properties, and machinability of AlSi10Mg alloys produced by laser powder bed fusion (LPBF) were investigated, including the effect of heat treatment. A superior surface finish was achievable on the as-built alloy due to the unique fine cellular microstructure that aided the cutting process. Surfaces with roughness of ∼4 nm Ra and excellent mechanical properties with tensile strength of up to ∼491 MPa were obtained. In contrast, the large silicon particles that formed during heat treatment led to the deterioration of machined surface quality with an achievable roughness of ∼9 nm Ra along with the reduction in tensile strength to ∼283.5 MPa. Subsurface TEM analysis on the machined as-built sample indicated that the nano-scale silicon particles in the cellular microstructure boundary of the alloy and the semi-coherent relationship between silicon particles and the aluminum matrix avoided the generation of machined surface damages. New insights into the relationships between the additive manufacturing process, microstructure, and machinability are detailed to highlight the potential of hybrid manufacturing technology for high-strength and high-surface-quality parts. [ABSTRACT FROM AUTHOR]

The preparation of a non-absorption window (NAW) through impurity-free vacancy disordering (IFVD) induced quantum well intermixing (QWI) in 915 nm GaInAsP/GaAsP semiconductor lasers is aimed at enhancing the catastrophic optical mirror damage (COMD) threshold and output power of semiconductor lasers. A process for the fabrication of high-power semiconductor lasers has been explored through the intermixing study of primary epitaxial wafers. In the experimental procedure, the epitaxial layers at the front and rear facets were first selectively etched, followed by the deposition of a 200 nm SiO2 dielectric layer on their surfaces. Additionally, a 100 nm TiO2 dielectric layer is applied to suppress QWI in the gain emission region. A NAW is achieved through a rapid thermal annealing process at 830°C for 180 s under atmospheric pressure. In the wafer-scale fabrication process, wide-stripe single-tube devices are produced with a light-emitting region width of 200 μm and a cavity length of 4000 μm. Test results reveal that conventional single-tube devices typically experience COMD at an input current of ∼20 A, with power output at around 19 W. In contrast, the single-tube devices with the NAW reach a continuous output power of 27.7 W at an input current of 30 A, representing a power enhancement of ∼45.8 %. No optical catastrophic damage is observed, and characteristics, such as slope efficiency and threshold current, remain unaltered. This research demonstrates that IFVD combined with the wafer-scale fabrication can effectively enhance the COMD threshold of 915 nm GaInAsP/GaAsP semiconductor laser devices, offering valuable insights into the study of high-power semiconductor lasers. [ABSTRACT FROM AUTHOR]

Next-generation gravitational wave detectors, including the Einstein Telescope [1] [2] , aim to achieve amplitude-spectral-density strain sensitivities on the order 10 − 24 m / Hz [3]. In the low-frequency band such sensitivities can only be obtained when thermal noise, mainly stemming from the mirror coating, is reduced by employing cryogenic cooling techniques for the mirrors. The optical surface of the mirror should not vibrate with strain noise amplitude spectral densities above 10 − 20 m / Hz for the cryogenic mirrors in the Einstein Telescope [3]. The ETpathfinder research facility [4] [5] , aims to facilitate the development and testing of critical new technologies required for the design and operation of future gravitational wave detectors. A key enabling technology for the design and operation of such advanced interferometers is the cryogenic system that cools the main optics to a temperature of approximately 10 K. Given the stringent requirements on vibrational noise for these optics, the cryogenic cooling under continuous operation should be essentially vibration free. Joule-Thomson cryocoolers using sorption compressors are known to generate an absolute minimum of vibrational noise during operation. We propose a modular cryochain design comprised of a system of sorption compressors and Joule-Thomson cold stages fitting the ETpathfinder project requirements. In this paper, we present the conceptual design of the cooler chain that is based on a parallel cascade arrangement of a 40 K neon stage, a 15 K hydrogen stage and a 8 K helium stage. The operating parameters of the sorption-based cooler chain are selected via a hybrid modeling workflow, aiming to optimize performance and other design considerations within an envelope of acceptable design parameters. • Novel cryochain design for the ETpathfinder using sorption compressors and J-T cold stages. • Hybrid simulation workflow enables efficient optimization and performance evaluation. • Cryochain attributes: 40 K neon, 15 K hydrogen, 8 K helium stages for 10 K optics cooling. • Sensitivity analysis highlights design robustness under parameter variations. • Paves the way for vibration-free cooling developments in next-generation gravitational wave detectors. [ABSTRACT FROM AUTHOR]

A single-mode (SM) vertical-cavity surface-emitting laser (VCSEL) constructed using a multi-oxidation structure was demonstrated. With the help of an undoped bottom mirror for reduction of optical absorption, the SM-VCSEL possessed a threshold current of 0.6 mA. A pure single mode is observed at an operating current of 4 mA. For back-to-back transmission, the maximum bandwidth is 26.6 GHz, and the highest bit-rate is 48 Gb/s for on-off keying modulation. Under single-mode operation, 40 Gb/s error-free transmission up to 500 m in OM4 fiber was achieved in this work. [ABSTRACT FROM AUTHOR]

We propose a biaxial scanning mirror with a large rotation angle and low resonance frequency for a compact and low-power-consuming LIDAR. The scanning mirror in LIDAR, which is driven by a rotating motor, requires a wide field of view and a low working frequency. To achieve these requirements, we develop an electromagnetic actuator for a biaxial scanning mirror that consists of two pairs of coils, one yoke with a cross shape, one rare-earth permanent magnet, and one gimbal structure frame. The gap distance between the permanent magnet and yoke is adjusted to find the optimum condition. The overall size of the developed system is 20 mm × 20 mm × 12 mm (width × depth × height) with a gap distance of 3 mm. Experiments and simulations are performed with various gap distances. The experimental results indicate that the maximum rotation angle is ± 51° at 37 Hz when the gap distance is 3 mm and the applied voltage is ± 5 V. [ABSTRACT FROM AUTHOR]