Mirror Distance Research Articles

Mirror-coupled toroidal dipole bound states in the continuum for tunable narrowband perfect absorption

Metasurfaces have received a significant amount of attention in recent years as they offer novel ways for wave front control, subwavelength light focusing, and flat optics. Here, we employ sharp resonances in metasurfaces originated from the physics of bound states in the continuum (BICs) for both engineering and enhancing the absorption of light. Specifically, using temporal coupled-mode theory and numerical simulations, we demonstrate that an all-dielectric metasurface, of which the meta-atom consists of narrow-gap Si dimers with a monolayer graphene, can perfectly absorb the incident near-infrared light through critical coupling to the mirror-coupled toroidal dipole BIC. Due to unique loss engineering capabilities of the mode, multiple tuning knobs, including the narrow gap, meta-atom–mirror distance, and geometrical scaling factor, can be utilized for control over the coupling condition and the electric-field enhancement at the critical coupling condition. These results suggest that our platform could promise in on-chip optoelectronic applications.

Gonadotropin inhibitory-hormone modulates neurosteroids-synthesizing enzymes expression and aggressive behavior in male sea bass, Dicentrarchus labrax

Neurosteroids are involved in the regulation of multiple behavioral and physiological processes and metabolic activities in the vertebrate brain. However, central mechanisms of how neurosteroid synthesis is regulated is far to be understood. Gonadotropin-inhibitory hormone (GNIH) is a hypothalamic neuropeptide that negatively regulates gonadotropin secretion but also inhibits sexual and aggressive behaviors in birds and mammals by modulating aromatase enzyme and neuroestrogen synthesis. In a previous study performed in male sea bass, we reported that Gnih inhibited the reproductive axis by acting at the three levels of the brain-pituitary-gonad axis. Moreover, the presence of Gnih cells and fibers in the telencephalon, mesencephalon and rhombencephalon suggests a role of Gnih in regulating other important brain functions in sea bass, including behavior. In this study, we have analyzed the effects of the intracerebroventricular (icv) injection of sbGnih-2 on the brain and pituitary expression of the main neurosteroids-synthesizing enzymes (stAR, cyp17, 3β-hsd, 17β-hsd, cyp19b, cyp7b), as well as on estrogen and androgen receptors (erα, erβ1, erβ2, ar). A combination of immunohistochemistry and in situ hybridization was also used to identify putative interaction of Gnih- and aromatase-positive cells. We also performed a mirror test study as a proxy to measure aggression levels and agonistic behavior after icv injection of sbGnih-2. Central administration of sbGnih-2 at different doses reduced the transcript levels of 3β-hsd and 17β-hsd, and increased the expression of cyp19b (brain aromatase) in the sea bass brain. Neuroanatomical results suggest that paracrine and neuroendocrine actions could mediate Gnih effects on aromatase expression. Central administration of sbGnih-2 also decreased the pituitary expression of 17β-hsd and estrogen receptors (erβ2). The mirror test analysis showed that sbGnih-2 affected the agonistic/aggressive behavior of sea bass as revealed by the decreased interaction with the mirror, lower time spent in the mirror zone, increased latency to establish contact with the mirror and higher mean distance to the mirror zone. In contrast, locomotor activity parameters measured were not affected by sbGnih-2 injection. Taken together, our results showed for the first time in fish that Gnih inhibits social-aggressive behavior and affects the gene expression of neurosteroid-synthesizing enzymes giving rise to neuroandrogens and neuroestrogens in the sea bass brain.

Linking Methanogenesis in Low-Temperature Hydrothermal Vent Systems to Planetary Spectra: Methane Biosignatures on an Archean-Earth-like Exoplanet.

In this work, the viability of the detection of methane produced by microbial activity in low-temperature hydrothermal vents on an Archean-Earth-like exoplanet in the habitable zone is explored via a simplified bottom-up approach using a toy model. By simulating methanogens at hydrothermal vent sites in the deep ocean, biological methane production for a range of substrate inflow rates was determined and compared to literature values. These production rates were then used, along with a range of ocean floor vent coverage fractions, to determine likely methane concentrations in the simplified atmosphere. At maximum production rates, a vent coverage of 4-15 × 10-4 % (roughly 2000-6500 times that of modern Earth) is required to achieve 0.25% atmospheric methane. At minimum production rates, 100% vent coverage is not enough to produce 0.25% atmospheric methane. NASA's Planetary Spectrum Generator was then used to assess the detectability of methane features at various atmospheric concentrations. Even with future space-based observatory concepts (such as LUVOIR and HabEx), our results show the importance of both mirror size and distance to the observed planet. Planets with a substantial biomass of methanogens in hydrothermal vents can still lack a detectable, convincingly biological methane signature if they are beyond the scope of the chosen instrument. This work shows the value of coupling microbial ecological modeling with exoplanet science to better understand the constraints on biosignature gas production and its detectability.

Non-Markovianity of an atom in a semi-infinite rectangular waveguide

We investigate the non-Markovianity (NM) of a waveguide QED with a two-level atom as the system and a semi-infinite rectangular waveguide as the environment, where the transverse magnetic (TM mn ) modes define the quantum channels of guided photons. The perfect mirror imposed by the finite end exerts a retarded feedback mechanism to allow for information backflow, which leads to NM dynamics. For the energy separation of the atom far away from the cutoff frequencies of transverse modes, the delay differential equations are obtained with single-excitation initial in the atom. Our attention is focused on the effects of multiple quantum channels involved in guiding photons on the degree of non-Markovian behavior. An asymptotic value of the non-Markovianity can be found as the atom–mirror distance is large enough, however, the asymptotic value of of the atom interacting with the effective double-modes is lower than that of the atom interacting with the effective single-mode. We also show that is a constant, and the analytical expression for is related to the parameters associated with the modes, which is related to the interference of the two modes.

Ground-based gravitational wave detection and its implications

A bit of historical review is given for the concept of gravitational waves and detection experiments. In the presence of gravitational waves, it is frequently asked whether the laser light gets stretched and shrunk in the same way as the mirror distances in the interferometer so that gravitational waves cannot be measured. To answer this question, we have reviewed the interaction between light and gravitational waves carefully in both the transverse-traceless (TT) gauge and the proper detector or locally Lorentz frame. In the TT frame, the laser light directly interacts with gravitational waves, its frequency gets modified, but mirrors remain at rest to the linear order of a gravitational wave perturbation. In the detector frame, on the other hand, the frequency of light does not change while “distances” between the beam splitter and the mirrors get modified. Recent results for gravitational wave observations up to the first half of the third observation run in the advanced LIGO and the advanced Virgo are briefly summarized. Tests of general relativity based on gravitational wave data observed during O1 and O2 are described. These tests include residual and inspiral–merger–ringdown signal consistency tests, parameterized deviations in the waveform model, and constraint on the speed of gravitational waves by comparisons with the propagation of the electro-magnetic counterpart observed in the binary neutron star merger event. Some interesting events observed during O3a are also discussed.

Solar Fresnel modelling, geometry enhancement and 3D ray tracing analysis devoted to different energy efficiency definitions and applied to a real facility

Despite their few installations, Linear Fresnel Collectors (LFC) represent a very promising technology for efficient solar energy exploitation at medium to high temperatures thanks to their lowest land area per electric energy ratio. Their first appearance was in the ’60, thanks to Professor Giovanni Francia realizations at the University of Genova, Italy. This research aims to determine the performance of a LFC and perform parametric studies through 3D ray-tracing simulations. The in-house developed code accounts for all geometrical parameters of the mirrors and receiver assembly, including mirror dimensions, curvature and distance, primary mirror optical errors, receiver aperture area and elevation, secondary mirror compound parabolic shape. The present study includes a detailed investigation on shading, blocking and end effect issues while introducing 6 different different optical and energy efficiency definitions. A parametric analysis is applied to the distance between mirrors and the receiver height. After the code validation against Tonatiuh, the calculations are performed to analyse in details the performance of a real LFC plant in Morocco. The peak optical efficiency of the test case plant has been estimated up to 87% but it is demonstrated the selection of the efficiency definition is crucial for performing successful geometry optimizations.

Structure of Multiple Mirror System From Kaleidoscopic Projections of Single 3D Point.

This paper proposes a novel algorithm of discovering the structure of a kaleidoscopic imaging system that consists of multiple planar mirrors and a camera. The kaleidoscopic imaging system can be recognized as the virtual multi-camera system and has strong advantages in that the virtual cameras are strictly synchronized and have the same intrinsic parameters. In this paper, we focus on the extrinsic calibration of the virtual multi-camera system. The problems to be solved in this paper are two-fold. The first problem is to identify to which mirror chamber each of the 2D projections of mirrored 3D points belongs. The second problem is to estimate all mirror parameters, i.e., normals, and distances of the mirrors. The key contribution of this paper is to propose novel algorithms for these problems using a single 3D point of unknown geometry by utilizing a kaleidoscopic projection constraint, which is an epipolar constraint on mirror reflections. We demonstrate the performance of the proposed algorithm of chamber assignment and estimation of mirror parameters with qualitative and quantitative evaluations using synthesized and real data.

Representation in Cognitive Science

<i>Representation in Cognitive Science</i>

Design of tunable liquid laser based on presence of the conjugated-polymer counter influencing the spectral properties of the oligomer

Abstract In this paper, we studied the optical properties, lasing properties, and time-resolved spectroscopy (TRS) dynamics of the energy transfer between the conjugated oligomer (CO) 1,4-bis(9-ethyl-3-carbazo-vinylene)-9,9-dihexyl-fluorene (BECV-DHF) and conjugated-polymer (CP) influencer poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) in a toluene environment. The oligomer 1,4-bis(9-ethyl-3-carbazo-vinylene)-9,9-dihexyl-fluorene (BECV-DHF) exhibits single amplified spontaneous emission (ASE) in a solution for a wide variety of concentration and solvent environment, but it produces dual ASE under the influence of MEH-PPV. The dual ASE of the oligomer is due to the interaction between these two laser materials, and it is studied using various spectroscopic techniques. The TRS showed that the presence of the CP in the CO solution does not change the excited state dynamics of the CO, and the fluorescence of the CO is quenched, and the fluorescence of CP is enhanced simultaneously; hence, the underlying mechanism could be modulation of the absorption band at specific wavelength region (460 ± 10 nm). Under an optical cavity (100%–60% reflectivity plane mirrors and with internal grating), a tunable laser with a 6 nm full width at half maximum (FWHM) from 560 nm to 580 nm and attenuation from 600 to 650 nm was observed. Spectrally narrow peaks were obtained at various wavelengths by changing the cavity mirror distance. This strategy of obtaining a laser tunable from 560 to 580 nm, in addition to dual ASE (436 nm and 464 nm), from a CP and CO blend could potentially facilitate the development of an efficient, low-cost laser.

The gap angle as a design criterion to determine the position of linear Fresnel primary mirrors

A common choice for Linear Fresnel Reflector primary mirrors is the so-called uniform configuration, in which a constant value of mirror width – and their relative distances – is used. Often, it results in large relative mirror distances, leading to significant losses of etendue and concentration due to the light lost between the mirrors. In this paper a method to optimize the position of primary mirrors is presented with the goal of producing a more continuous primary optic, eventually closer to the theoretical limits of solar concentration. This calculation was done for two Linear Fresnel Reflector concentrators with uniform configurations, exploring how this method can improve the performance of such systems. This paper analyses the impact of such modifications on the overall optical performance of the collector, through the calculation of Concentration-Acceptance Product, Incidence Angle Modifier curves and an estimation of the total amount of collected energy for a specific location, Faro (Portugal). For the analyzed cases, the simulation results show that the proposed method produces denser primary fields, with an increase up to 21% in mirror area and collecting up to 14% more energy.

A novel hyperspectral line-scan imaging method for whole surfaces of round shaped agricultural products

The present study has developed a novel line-scan technique for hyperspectral imaging (HSI) of the whole surface of a round object. The developed system uniquely incorporates an external optical assembly of four mirrors to view a rotating round object from two opposite sides and project a combined two-view image onto the aperture of line-scan HSI camera. This allows imaging of the whole surface of the round object to detect defects located on any part of that surface. For obtaining the two side views that include the areas around the poles, the design of the optical path requires consideration of the distance from the inside mirrors to the outside mirrors, and the inclination angles of the outside mirrors. The optimum mirror distance of 171.6 mm and mirror angle of 13.24° was determined by sequential quadratic programming (SQP). The system was first calibrated using four wooden spheres of various sizes and was demonstrated for potential whole-surface imaging of round-shaped fruits by scanning 101 apples each marked with six simulated defects at known positions across the fruit surface. By using 3D reconstruction images, the system was able to accurately detect all six dots on 78% of the apples, but detected 5 dots (undercounted) and 7 dots (overcounted) on 4% and 18% of the apples, respectively. The image processing algorithm investigated in this study will be used to develop real-time multispectral systems for whole-surface quality evaluation of rounded objects in the agro-food sector.

Testing of the ITER plasma position reflectometry high-field side in-vessel antenna assembly prototype.

The ITER plasma position reflectometry diagnostic aims to provide measurements of the edge plasma to correct or supplement the magnetics for plasma position control. It consists of five reflectometers, two of which have components installed inside the vessel. One of these systems probes the plasma from the high-field side using a bistatic array of small pyramidal horns located in the gap between two blankets. Electromagnetic simulations have shown that the blankets shape the radiation pattern and need to be considered as part of the antenna. Full-wave plasma simulations have confirmed these results and have also shown that the first-wall geometry may induce measurement errors above the required margin. To further address these issues, we manufactured a prototype of the high-field side antenna, which includes a mock-up of the blanket modules. Here, we present the results of the prototype tests, with and without the blankets, using a metallic mirror as a target. The signals reflected from the mirror are used to derive the mirror distance and assess the precision of the measurements under different arrangements. The sensitivity to the blankets' installation tolerances is also assessed by changing the antennas' position with respect to the blankets' surfaces and cut-outs.

Efficient Plasmonic Gas Sensing Based on Cavity-Coupled Metallic Nanoparticles

Here, we demonstrate the gas sensing ability of cavity-coupled metallic nanoparticle systems, comprising gold nanoparticles separated from a gold mirror with a polymer spacer. An increase in relative humidity (RH) causes the spacer to expand, which induces a significant reduction of nanoparticle scattering intensity, as the scattering is highly dependent on the cavity–nanoparticle coupling that closely relates to the nanoparticle–mirror distance. With high structural tolerance, i.e., no requirement for high-precision nanoparticle geometry, this lithography-free system enables a remarkable average sensitivity at 0.12 dB/% RH and 0.25 dB/% RH over a wide RH range (45–75%) and full reversibility with much faster response time than the commercial electrochemical sensors, possessing the characteristics to be used for notable gas sensing.

Optimization of group delay dispersion measurement by Gires–Tournois interferometer

In this paper the group delay dispersion (GDD) of some laser mirrors is measured by a Gires–Tournois interferometer (GTI). The GTI is constructed with a partially reflective non-dispersive mirror and a highly reflective dispersive mirror. The GDD of the dispersive mirrors is calculated by determining the spectral position of the minima in the reflection light of the GTI. The previous GDD measurement equation is modified by introducing a correction coefficient. An appropriate level of accuracy is obtained by optimizing the Gires–Tournois mirror distances in our simple and inexpensive practical setup.

Enhancing steady-state entanglement via vacuum-induced emitter–mirror coupling in a hybrid optomechanical system

We investigate a hybrid optomechanical system consisting of an ensemble of quantum emitters inside a standard optomechanical cavity with a moving end mirror, in which the motion of the mirror changes the transition rate of each emitter and therefore leads to a direct coupling between the internal state of the quantum emitter and the mechanical mode. We analyzed the steady-state characteristics of the optomechanical system and found that the bistability of the system depends strongly on the distance between the emitter ensemble and the mirror. Further, we also analyze in detail the influences of the distance and other system parameters, i.e., the effective detunings, the driving power, the decay rates of the cavity, and the emitter ensemble and the thermal phonons on the steady-state entanglement by considering fluctuation of the mechanical oscillator, the cavity field, and the emitter ensemble. It is found that the degree of the steady-state entanglement can be greatly enhanced in a certain range of parameters by increasing the vacuum-induced emitter–mirror coupling, which can be realized by decreasing the emitter–mirror distance and increasing properly the free-space spontaneous emission rate of the emitter.

Optimization of the geometrical stability in square ring laser gyroscopes

Ultra-sensitive ring laser gyroscopes are regarded as potential detectors of the general relativistic frame-dragging effect due to the rotation of the Earth. Our project for this goal is called GINGER (gyroscopes in general relativity), and consists of a ground-based triaxial array of ring lasers aimed at measuring the rotation rate of the Earth with an accuracy of . Such an ambitious goal is now within reach, as large-area ring lasers are very close to the required sensitivity and stability. However, demanding constraints on the geometrical stability of the optical path of the laser inside the ring cavity are required. Thus, we have begun a detailed study of the geometry of an optical cavity in order to find a control strategy for its geometry that could meet the specifications of the GINGER project. As the cavity perimeter has a stationary point for the square configuration, we identify a set of transformations on the mirror positions that allows us to adjust the laser beam steering to the shape of a square. We show that the geometrical stability of a square cavity strongly increases by implementing a suitable system to measure the mirror distances, and that the geometry stabilization can be achieved by measuring the absolute lengths of the two diagonals and the perimeter of the ring.

Development of a 4-mirror optical cavity for an inverse Compton scattering experiment in the STF

To obtain high-brightness quasi-monochromatic X-rays via inverse Compton scattering (ICS), an optical cavity for intensifying laser beams was designed and implemented in a new beam line at the KEK Superconducting RF Test Facility (STF) accelerator. The optical cavity adopts a planar configuration consisting of 4 mirrors. This confocal type resonator provides stable laser storage even with a long mirror distance, enabling head-on collision with the electron beams. To overcome the well-known astigmatism problems of the planar-type optical cavity, two forcibly bendable cylindrical mirrors were introduced instead of flat mirrors. With this new function for laser profile adjustment, an almost round laser profile at the waist point in the accelerator environment was successfully achieved. Estimated waist sizes were 43.7μm for the horizontal and 50.8μm for the vertical dimensions. The feedback control of this 4-mirror optical cavity worked with a stiff plate supporting all 4 mirrors. 1.7×103 finesse and 2.8-kW stored power for a 1-ms duration with 5Hz were achieved.

Experimental Design Affects Social Behavior Outcomes in Adult Zebrafish Developmentally Exposed to Lead

Lead (Pb(2+)) affects neuronal and endocrine systems that influence social interactions. By providing potential hiding locations, spatial heterogeneity may affect Pb(2+)-induced behavioral outcomes. Therefore, a test chamber was designed into which a refuge could be inserted. The refuge allowed test subjects to escape from the mirror image that stimulated agonistic interactions. Behaviors with a mirror were compared with baseline activity patterns without a mirror. Adult (12-month old) male and female zebrafish, exposed to Pb(2+) (0-10 μM) as embryos (2-24 hours post fertilization), were tested individually for 5 min in each chamber design within 2 h of feeding. Behaviors were evaluated for % time in mirror zone, distance traveled (=activity level), and attacks on the mirror image. When there was no refuge, significant concentration-dependent increases occurred in male % time in mirror zone, activity level, and number of attacks. Increases in these variables were less pronounced in females. When there was a refuge, there were significant differences for males only in activity level and attacks at the higher developmental exposure concentrations; % time in mirror zone followed a similar pattern and level as without refuge. Females displayed Pb(2+)-induced behavioral changes only for attacks on mirror. Since the presence of refuges that is, environmental enrichment, reduced Pb(2+)-induced agonistic behavior in both sexes, experimental spatial design can be considered an important factor when interpreting behavioral outcomes.

The impact of rear-view mirror distance and curvature on judgements relevant to road safety

We report two experiments that investigate the impact of rear-view mirror distance and curvature on distance, spacing, and time-to-contact (TTC) judgements. The variation in mirror distance had a significant effect on TTC judgements, but only marginally influenced distance and spacing estimations. As mirror distance increased, TTC was overestimated, which is potentially dangerous. Control conditions with identical visual angles across different mirror distances revealed that effects were not solely caused by variation in visual angle. The impact of mirror curvature moderated the effect. While observers were unable to compensate for the mirror distance effect, they could do so for the distortions generated by non-planar mirrors, at least up to a certain degree of distortion. Implications for vehicle design and national guidelines are discussed. Practitioner Summary: Regulations regarding rear-view mirrors are vastly different between countries. For instance EU regulations encourage convex driver-side mirrors, whereas US regulations allow them merely on the passenger's side. The use of a dynamic TTC paradigm puts the human factors designer in a position to evaluate the existing regulations and to design safer mirrors.

Jet-cooled infrared spectra of molecules and complexes with a cw mode-hop-free external-cavity QCL and a distributed-feedback QCL

The coupling of quantum cascade lasers (QCLs) with an off-axis cavity enhanced absorption (CEA) spectrometer and an astigmatic multiple pass absorption (MPA) spectrometer are described in this paper. A continuous wave (cw) liquid nitrogen cooled distributed-feedback QCL at 5.7 μm and a cw room temperature mode-hop-free external-cavity QCL at 6.1 μm were employed as the light source. For the CEA spectrometer, the effects of mirror size and laser scan rate were evaluated. For the MPA spectrometer, a pair of astigmatic mirrors with a 55 cm mirror distance was aligned to the 366-pass configuration. The jet-cooled samples were generated using a homemade pulsed slit jet nozzle assembly. Two LabVIEW programs were written to automate and synchronize the timing of the laser scan, the pulsed slit jet molecular expansion, and the data acquisition. Infrared spectra of jet-cooled methyl lactate and the Ar–H2O complex and room temperature N2O and NH3 samples were measured using both the rapid scan and the wavelength modulation methods to evaluate the sensitivity and resolution of the CEA and MPA spectrometers. The combination of the MPA spectrometer with the external-cavity QCL using the rapid scan method was found to be the best suited combination to measure high resolution jet-cooled infrared spectra.