Axis Of Mirror Research Articles

Alignment of Fabry–Pérot Cavities for Optomechanical Acceleration Measurements

The wave optics processes in a Fabry–Pérot cavity with a length of about tens of millimeters are considered. Such cavities are used, among other applications, in optomechanical accelerometers for precise measurement of displacement of moving elements. A Fabry–Pérot cavity formed by a spherical and flat mirror is considered. The influence of parameters characterizing the alignment of the Fabry–Pérot cavity mirrors and the laser beam on the appearance of the higher order modes is investigated using numerical modeling. It is shown that the angle of inclination of the flat mirror of the cavity greatly affects the occurrence of higher order modes in addition to the fundamental mode. The levels of displacement of the axis of a spherical mirror in the vertical direction which do not cause the emergence of higher order modes is shown. The influence of the degree of displacement of the laser beam axis in the vertical direction relative to the symmetry axis of the Fabry–Pérot cavity is also investigated.

Distinct learning, retention, and generalization patterns in de novo learning versus motor adaptation

People correct for movement errors when acquiring new motor skills (de novo learning) or adapting well-known movements (motor adaptation). While de novo learning establishes new control policies, adaptation modifies existing ones, and previous work have distinguished behavioral and underlying brain mechanisms for each motor learning type. However, it is still unclear whether learning in each type interferes with the other. In study 1, we use a within-subjects design where participants train with both 30° visuomotor rotation and mirror reversal perturbations, to compare adaptation and de novo learning respectively. We find no perturbation order effects, and find no evidence for differences in learning rates and asymptotes for both perturbations. Explicit instructions also provide an advantage during early learning in both perturbations. However, mirror reversal learning shows larger inter-participant variability and slower movement initiation. Furthermore, we only observe reach aftereffects following rotation training. In study 2, we incorporate the mirror reversal in a browser-based task, to investigate under-studied de novo learning mechanisms like retention and generalization. Learning persists across three or more days, substantially transfers to the untrained hand, and to targets on both sides of the mirror axis. Our results extend insights for distinguishing motor skill acquisition from adapting well-known movements.

Angle-resolved transport non-reciprocity and spontaneous symmetry breaking in twisted trilayer graphene.

The identification and characterization of spontaneous symmetry breaking is central to our understanding of strongly correlated two-dimensional materials. In this work, we utilize the angle-resolved measurements of transport non-reciprocity to investigate spontaneous symmetry breaking in twisted trilayer graphene. By analysing the angular dependence of non-reciprocity in both longitudinal and transverse channels, we are able to identify the symmetry axis associated with the underlying electronic order. We report that a hysteretic rotation in the mirror axis can be induced by thermal cycles and a large current bias, supporting the spontaneous breaking of rotational symmetry. Moreover, the onset of non-reciprocity with decreasing temperature coincides with the emergence of orbital ferromagnetism. Combined with the angular dependence of the superconducting diode effect, our findings uncover a direct link between rotational and time-reversal symmetry breaking. These symmetry requirements point towards exchange-driven instabilities in momentum space as a possible origin for transport non-reciprocity in twisted trilayer graphene.

Determination of in-plane surface directions in scanning probe microscopy images.

We describe an approach to determine the in-plane crystallographic surface directions in scanning probe microscopy (SPM) images. This method is based on a one-time characterization of the SPM instrument with an appropriate test sample and is exemplified by the analysis of non-contact atomic force microscopy (NC-AFM) images on surfaces whose natural cleavage occurs along {111} planes. We introduce a two-dimensional rotation matrix relating the crystallographic surface directions known from an analysis of the macroscopic crystal to the directions in the NC-AFM images. The procedure takes into account rotations and mirror axes resulting from sample mounting, the SPM scanner rotation, the choice of scan direction, as well as data processing, storage, and display. We demonstrate the practicability of the approach by determining the [112̄] direction in topographic images of a CeO2(111) film grown on a Si(111) wafer and atomic resolution images of CaF2(111) with an instrument based on the beetle-type scanner.

Analysis of Error Sources in the Lissajous Scanning Trajectory Based on Two-Dimensional MEMS Mirrors

Deviations or distortions in the trajectoy of MEMS-based Lissajous scanning imaging platforms might be detrimental to imaging quality. These deviations often arise from differences in MEMS mirror frequency response characteristics and asymmetry in parameters within the measurement and control circuit. This study concentrated on the measurement and control circuit unit as it identified and analyzed four error sources: the MEMS mirror frequency response error, the AD acquisition synchronization error, the drive source error, and the cross-coupling error between the MEMS mirror axes. This study constructed a Lissajous trajectory test platform based on oscilloscopes and a position sensitive detector. Consequently, its experimental results guided the error processing methods to access the feasibility of the compensation methods by combining measured trajectories. Overall, regarding MEMS-based Lissajous scanning platforms for biomedical imaging, this study could provide quantitative numerical references for error analysis, image reconstruction, and aberration correction.

Second Harmonic Generation in Exfoliated Few‐Layer ReS2

AbstractThe second harmonic generation (SHG) is systematically investigated in mechanically exfoliated, few‐layer ReS2 samples. The stacking orders are identified as (AA)nA and (ABy)nA for (2n+1)‐layer samples and (AA)n and (ABy)n for 2n‐layer samples. The layer structure A stands for that of a monolayer, and the layer structure By is mirror to A followed by a one‐tenth unit cell translation along the mirror axis, that is, the b‐axis of the crystal. Only the even‐layer samples with (ABy)n stacking order are SHG active. After carefully extracting the effective bulk susceptibility for SHG, it is found that the spectra are greatly enhanced as the fundamental photon energy matches exciton levels. The polarization dependence is strongly anisotropic, and each susceptibility component shows very different wavelength dependence. The results demonstrate that few‐layer ReS2, with its unique SHG, can be considered as an ideal platform for fundamental research in anisotropic nonlinear optics.

Research on high precision testing method for mirror optical axis of two-sided community aspheric mirror (invited)

Research on high precision testing method for mirror optical axis of two-sided community aspheric mirror (invited)

Using mathematical ideas from carpet and carpet-weavers as a context for designing mathematics tasks

In this study, the mathematics of carpet will be introduced by presenting the lifestyle of two expert carpet-weavers from Kerman, Iran, who work for many years in carpet-weaving activities through an explanation of carpet weavers’ culture. This explanation reveals that carpet weavers can do mathematics and solve related real-world problems without academic education in mathematics according to their needs through practical activities. The main purpose of this study is to investigate the mathematical ideas in the art of carpet weavers, and the ethnography approach is used as a methodological framework. Our findings showed that there are many mathematical concepts in the carpet weaving process, such as mirror axes, parallel and diagonal lines, geometric shapes, ratio, and measurement which can be used as context for developing enrich and meaningful mathematical tasks.

Cavity design with single-mirror THz frequency tuning for polariton lasers.

We demonstrate a new, to the best of our knlowledge, cavity design for terahertz (THz) lasers based on stimulated polariton scattering (SPS). The design simplifies the angle tuning of these lasers, which require non-collinear cavity fields at fundamental and Stokes wavelengths to cross in an SPS crystal with adjustable crossing angle. A mirror shared by both the fundamental and Stokes cavities ensures stationary overlap of the fields within the crystal, with the angle between the fields tunable by adjustment of one axis of a single mirror. We demonstrate the design for an intracavity SPS laser using a rubidium titanyle phosphate (RTP) crystal, and achieve single-mirror tuning of the THz output in bands between 3 and 5.8 THz, with a maximum output of 78 μW at 4.08 THz.

Низкоорбитальные космические аппараты высокодетального наблюдения с длительным сроком существования на рабочих орбитах высотой ниже четырехсот километров

The paper analyzes mass-dimensional design parameters of the optical-electronic equipment for Earth’s remote sensing from heights in the range of 300...400 km. Within the research, we carried out the synthesis of a mirror-lens telescopic complex with an additional rotary mirror tilted to the optical axis of the main mirror and selected the design parameters from the conditions for ultra-high spatial resolution satellite images. Furthermore, we analyzed the mass-dimensional parameters of the spacecraft as a whole, the parameters allowing for the smaller effect of the Earth’s upper atmosphere on the evolution of the parameters of the working orbit. To maintain the radius of the low working orbit of the spacecraft for seven years, an electric propulsion system is proposed. To compensate for the aerodynamic drag force in the investigated range of heights and in any conditions of the upper atmosphere, a thrust force of no more than 18 milliNewtons is sufficient. The reserves of the mass of the working body for the operation of the electric propulsion system depend on the design-ballistic parameters of the spacecraft and the required lifetime in a given working orbit.

Spatially-resolved electronic structure of stripe domains in IrTe2 through electronic structure microscopy

Phase separation in the nanometer- to micrometer-scale is characteristic for correlated materials, for example, high temperature superconductors, colossal magnetoresistance manganites, Mott insulators, etc. Resolving the electronic structure with spatially-resolved information is critical for revealing the fundamental physics of such inhomogeneous systems yet this is challenging experimentally. Here by using nanometer- and micrometer-spot angle-resolved photoemission spectroscopies (NanoARPES and MicroARPES), we reveal the spatially-resolved electronic structure in the stripe phase of IrTe2. Each separated domain shows two-fold symmetric electronic structure with the mirror axis aligned along 3 equivalent directions, and 6 × 1 replicas are clearly identified. Moreover, such electronic structure inhomogeneity disappears across the stripe phase transition, suggesting that electronic phase with broken symmetry induced by the 6 × 1 modulation is directly related to the stripe phase transition of IrTe2. Our work demonstrates the capability of NanoARPES and MicroARPES in elucidating the fundamental physics of phase-separated materials.

Magnetically collimated relativistic charge-neutral electron–positron beams from high-power lasers

We report the observation of charge-neutral MeV electron–positron beams from magnetically collimated laser-driven pair-production experiments. Relativistic pairs of electrons were generated from laser–solid interactions in an external 13-T mirror field. The pairs were subsequently confined, deflected, or collimated depending on the particle energy and field strength and measured by a magnetic particle spectrometer. Equal quantities of positrons and electrons were measured in the collimated beams with an energy around 13 MeV along the magnetic mirror axis.

Adjustment of a catadioptric objective with an eccentric pupil for the infrared spectral range

A method for the adjustment of a wide-angle catadioptric collimating objective for the infrared spectral range with an eccentric pupil designed according to the Cassegrain scheme with a prefocal lens compensator is proposed. The approach combines interference methods for determining the position of the axis of the aspherical main mirror and the position of the secondary mirror with an autocollimating method for the centering of the compensator lenses. All the adjustment procedures are performed in a standard objective housing without reference to the geometric bases of the optical elements. An analysis of the adjustment errors and the testing results of the manufactured objective are presented.

Circular Truncated Conical Mirror with Cavity Shape and Inner Reflection for Concentrating Diffused Light to Collector Mouth from a Half Celestial Sphere

In this study, we designed a circular truncated conical mirror to concentrate diffused light to the collector mouth from a half celestial sphere and evaluated its performance. The conical mirror has a circular truncated cone-shaped cavity, which reflects light on the cavity’s inner surface. The top of the truncated cone shape is the incident mouth, the bottom is the collector mouth, and the sides are the mirror surfaces. The incident mouth size is smaller than the collector mouth size. All light incident on the incident mouth is either reflected or not reflected on the mirror surface to reach the collector mouth. Light incident at a shallow angle to the central axis of the conical mirror is not reflected on the mirror surface, while light incident at a deep angle is reflected on the mirror surface. The conical mirror can concentrate all diffused light incident at the incident mouth from a half celestial sphere of 360◦ in the horizontal direction and 180◦ in the vertical direction to the collector mouth. A coordinate system is established for the conical mirror, and a design method is proposed. Using our design method, the conical mirror is manufactured from the determined design values. A plane mirror, concave mirror, compound parabolic mirror, and Fresnel lens, comprising the conical mirror, are used as the measured objects to compare the manufactured conical mirror performance. An experimental setup is constructed to evaluate the performance of the measured objects. Using the constructed experimental setup, diffused light is irradiated to the measured objects as scattered light. The illuminance of the light concentrated in the collector mouth of the measured objects is measured for the irradiated diffused light. The measured illuminance is then used to compare and evaluate the light-concentrating efficiency of the measured objects.

Terahertz time-domain spectral imaging using telecentric beam steering and an f-θscanning lens: distortion compensation and determination of resolution limits.

We report on the development and performance characterization of a telecentric terahertz spectroscopic scanner using an f-θ objective lens and a single gimballed scanning mirror for image formation. We derived a beam steering transform to compensate for the intercoupling of the gimballed mirror axes and the distortions caused by an imperfect scanning lens. We characterize the optical performance of the system in both the time and spatial domains, demonstrating a constant diffraction-limited imaging resolution over the entire field of view. Finally, given the large depth of focus of the objective lens, we demonstrate the broadband imaging capability at different depths using a Boehler star target. This imaging setup has the potential to be miniaturized into portable form factors for field-deployable scenarios.

Development of a Pepper Pot probe to measure the Four-dimensional emittance of low energy beam of electron cyclotron resonance ion source at IMP

The ion beams extracted from an Electron Cyclotron Resonance (ECR) ion source always exist strong transverse coupling effect that is caused by the field of the axis mirror magnets and the extraction solenoid. In order to obtain the four-dimensional (4D) characteristic matrix with coupling elements, a Pepper Pot probe was developed and used to obtain the full 4D transverse phase space distribution of the low energy beam extracted from the ECR ion source at IMP. This paper describes the detailed design and image processing procedure of Pepper Pot probe, especially the analysis results verification compared to another type emittance meter. The first 4D transverse phase space distribution measurement data of oxygen beams from the LECR4 experimental platform are presented and discussed.

Metastable Self‐Assembly of Theta‐Shaped Colloids and Twinning of Their Crystal Phases

AbstractAnisotropic colloids self‐assemble into different crystal structures compared to spherical colloids. Exploring and understanding their self‐assembly behavior could lead to creation of new materials with hierarchical structures through a bottom‐up process. Herein, we report metastable self‐assembly of theta‐shaped SiO2 colloids interacting with a depletion force in a quasi‐two‐dimensional space and we demonstrate that both a metastable “prone” crystal phase and a stable “standing” crystal phase can be formed, depending on the self‐assembly path. Path selection stems from an interplay between particle–particle interactions and particle–wall interactions. In particular, a twinning of the metastable crystals was observed and two twinning mirror axes were found. A variety of complex twinned crystals were formed by each individual mirror axis or their combinations.

Metastable Self-Assembly of Theta-Shaped Colloids and Twinning of Their Crystal Phases.

Anisotropic colloids self-assemble into different crystal structures compared to spherical colloids. Exploring and understanding their self-assembly behavior could lead to creation of new materials with hierarchical structures through a bottom-up process. Herein, we report metastable self-assembly of theta-shaped SiO2 colloids interacting with a depletion force in a quasi-two-dimensional space and we demonstrate that both a metastable "prone" crystal phase and a stable "standing" crystal phase can be formed, depending on the self-assembly path. Path selection stems from an interplay between particle-particle interactions and particle-wall interactions. In particular, a twinning of the metastable crystals was observed and two twinning mirror axes were found. A variety of complex twinned crystals were formed by each individual mirror axis or their combinations.

Calculation of the Optical Telescope Mirror

This work considers the problem of bending a thick annular plate of variable thickness on point supports under the action of its own weight. The problem describes the stress-strain state of the primary mirrors of large optical telescopes when the mirror axis is directed to the zenith. The main feature of this problem is the transverse displacements of the plate reference surface, which coincides with the rear flat base of the plate where the supports are located, and the front surface from which the incident light is reflected. Errors of the wavefront of the reflected light, including the standard deviation and the magnitude of the wavefront, are associated with the transverse displacement. The problem is solved with the use of two nonclassical theories of plates, the Timoshenko-Reissner theory of plates and the Palii-Spiro theory of mean thickness shells. The case of the optimal location of the supports corresponds to the smallest values of the deviation of the wavefront magnitude and the standard deviation. Calculations according to the Timoshenko-Reissner and the Palii-Spiro theories gave the same optimal location of the supports. The Palii-Spiro theory, which takes into account the variation of the transverse displacement along the thickness of the plate, is preferable for calculating the distortion of the reflecting surface of the primary mirrors of optical telescopes.

Interocular Symmetry of Fixation, Optic Disc, and Corneal Astigmatism in Bilateral High Myopia: The Shanghai High Myopia Study.

PurposeWe investigate the interocular symmetry of fixation, optic disc, and corneal astigmatism in bilateral high myopia, and evaluate the predictive relationships between them.MethodsWe enrolled 202 cases with bilateral high myopia. Fixation, in terms of the bivariate contour ellipse area (BCEA), was evaluated with the Macular Integrity Assessment microperimetry. Optic disc features, including orientation, tilt, and rotation, were evaluated with ultrawide-field retinal photographs. Corneal topography was performed with Pentacam. Interocular symmetry of fixation, optic disc, and corneal astigmatism was assessed, and the predictive relationships between these parameters were investigated.ResultsAxial length differences between the two eyes were: ≥0 to ≤1 mm, 67.8%; 1 to ≤2 mm, 20.3%; 2 to ≤3 mm, 9.4%; and >3 mm, 2.5%. Axial length, 95% BCEA, and magnitude of corneal astigmatism showed good interocular symmetry, whereas the optic disc tilt, rotation, and axis of corneal astigmatism (mirror axes) showed less symmetry (all P < 0.05). No interocular symmetry was observed in the direction of the fixation ellipse. In both eyes, the corneal steep meridian more often was consistent with the optic disc orientation than inconsistent (right eye [OD], P < 0.001; left eye [OS], P = 0.029).ConclusionsAs different parameters presented different degrees of symmetry, cautions are needed when including both eyes or only one lateral eye in cases of bilateral high myopia for clinical investigations. The optic disc orientation, to some extent, may indicate the steep meridian of the cornea.Translational RelevanceOur study provided evidences for selection of eye laterality in clinical investigations of highly myopic eyes.