Angular Acceptance Research Articles

Broadband high-contrast visible optical switches based on a spin-crossover material.

Visible optical switches embedding a spin-crossover thin film and exploiting the frustrated total internal reflection operation principle are studied and optimized numerically with a view to obtain broadband high-contrast devices. A practical implementation using uncoated SF11 prisms embedding a 1-µm-thick layer of iron-triazolyl-borate complex as the thermo-active phase-change material is shown to support p-polarized modulation with contrast in excess of 90% over a spectral bandwidth greater than 270nm and over an angular acceptance bandwidth of 0.45°, surpassing the performance achievable with optically resonant devices.

220 nm deep-UV coherent source based on fifth-harmonic generation in ADP and DKDP crystals

Based on the 1.1 μm laser radiation obtained by parametrically amplifying Yb:YAG laser using frequency doubling of Nd:YAG laser, a 220 nm deep-UV coherent source was systematically presented via the efficient fifth-harmonic generation (FiHG) in NH4H2PO4 (ADP) and KD2PO4 (DKDP) crystals. In ADP crystals, noncritical phase-matching (NCPM) fourth-harmonic generation (FHG) and FiHG were realized at 109.4 and 31.6 °C, respectively. For DKDP crystals, we demonstrated the critical phase-matching FHG at 57.5 °C and verified that NCPM FiHG can be achieved at 38.7 °C, which was the first demonstration of the FiHG using the DKDP crystal to our knowledge. The energy-dependent conversion efficiencies, angular acceptances, and temperature acceptances of these nonlinear processes were systematically measured. The highest total conversion efficiencies from 1.1 μm to the fifth harmonic in ADP and DKDP crystals were 17.5% and 23.6%, respectively. Owing to the large-aperture availability of KDP-family crystals, this work paves the way for the generation and application of high-energy and high-peak-power deep-UV laser radiation.

Design of the High Rigidity Spectrometer at FRIB

A High Rigidity Spectrometer (HRS) has been designed for experiments at the Facility for Rare-Isotope Beams (FRIB) at Michigan State University (MSU). The HRS will allow experiments to be performed with the most exotic neutron-rich isotopes at high beam energies (≳100MeV/u). The HRS consists of an analysis beamline called the High-Transmission Beamline (HTBL) and the spectrometer proper called the Spectrometer Section. The maximum magnetic rigidity of the HRS is 8Tm, which corresponds to the rigidities at which rare-isotope beams are optimally produced at FRIB. The resolving power, angular acceptance, and momentum acceptance are set to match the anticipated scientific program. An ion-optical design developed for the HRS is described in detail, along with the specifications of the associated magnet and detector systems.

DOME: Discrete Oriented Muon Emission in GEANT4 Simulations

The simulation of muon tomography requires a multi-directional particle source that traverses a number of horizontal detectors of limited angular acceptance that are used to track cosmic-ray muons. In this study, we describe a simple strategy that can use GEANT4 simulations to produce a hemispherical particle source. We initially generate random points on a spherical surface of practical radius by using a Gaussian distribution for the three components of the Cartesian coordinates, thereby obtaining a generating surface for the initial position of the particles to be tracked. Since we do not require the bottom half of the sphere, we take the absolute value of the vertical coordinate, resulting in a hemisphere. Next, we direct the generated particles into the target body by selectively favoring the momentum direction along the vector constructed between a random point on the hemispherical surface and the origin of the target, thereby minimizing particle loss through source biasing. We also discuss a second scheme where the coordinate transformation is performed between the spherical and Cartesian coordinates, and the above-source biasing procedure is applied to orient the generated muons towards the target. Finally, a recipe based on restrictive planes from our previous study is discussed. We implement our strategies by using G4ParticleGun in the GEANT4 code. While we apply these techniques to simulations for muon tomography via scattering, these source schemes can be applied to similar studies for atmospheric sciences, space engineering, and astrophysics where a 3D particle source is a necessity.

Pr:LGSB as a new nonlinear optical crystal: Czochralski growth and optical characterization

Herein, we report on the Czochralski growth and optical characterization of Pr:LGSB as a new nonlinear optical (NLO) and laser crystal. Single crystals of Pr:LGSB were grown by the Czochralski method, for the first time to the best of our knowledge, from the starting melt compositions La 0.656 Pr 0.022 Gd 0.572 Sc 2.75 (BO 3 ) 4 and La 0.651 Pr 0.027 Gd 0.572 Sc 2.75 (BO 3 ) 4 . The crystal growth parameters were optimized and two Pr:LGSB crystals with good optical quality were obtained. The chemical compositions of the grown crystals were determined to be La 0.750 Pr 0.020 Gd 0.450 Sc 2.780 (BO 3 ) 4 and La 0.743 Pr 0.025 Gd 0.452 Sc 2.780 (BO 3 ) 4 corresponding to a Pr 3+ ions concentration in the crystals of 2.0 at% and 2.5 at%, respectively. The spectroscopic properties were investigated and the obtained results show that the 2.5 at% Pr:LGSB is a promising laser crystal emitting in the orange spectral range at ~ 603 nm. The refractive indices were measured and the phase-matching curves for type I and type II SHG were determined. The walk-off angle, the external angular acceptance, and the nonlinear coefficient d 11 for type I SHG of 603 nm fundamental wavelength were also evaluated. This work shows that the 2.5 at% Pr:LGSB crystal could be a new promising candidate for obtaining laser sources in the UV range (~ 301.5 nm) in SFD configuration. • Pr:LGSB crystal were grown by the Czochralski method for the first time. • Spectroscopic and NLO properties of the 2.5 at% Pr:LGSB crystal are presented. • 2.5 at% Pr:LGSB has promising properties for laser emission in the orange domain. • Phase-matching curves for type I and type II SHG are determined. • Preliminary prospects for SFD in the UV domain were analyzed.

Requirements and R&D for detectors at the future Electron–Ion Collider

The Electron–Ion Collider’s (EIC’s) ability to collide high-energy electron beams with high-energy ion beams will provide access to those regions in the nucleon and nuclei where their structure is dominated by gluons. Moreover, polarized beams in the EIC will give unique access to the spatial and spin structure of gluons and sea-quarks in the proton and light nuclei.The EIC will be an unprecedented collider with luminosities 2–3 orders of magnitude higher than previous e + p colliders over a very wide range of center-of-mass energies, from 20 to 140 GeV, while accommodating highly polarized electron and nucleon beams. Equally demanding are the requirements for the detector(s) that will be needed to carry out the physics program: hermetic coverage in tracking, calorimetry and particle ID within a wide pseudorapidity range, substantial angular and momentum acceptance in the hadron-going direction, as well as high quality hadronic calorimetry among others.This paper gives a brief overview of the detector requirements, current general-purpose detector concepts, and the ongoing EIC detector R&D efforts.

Noncritical phase-matching fourth- and fifth-harmonic generation of 1077 nm laser using KDP-family crystals.

We systematically demonstrated the angular and temperature acceptances of noncritical phase-matching (NCPM) fourth- and fifth-harmonic generation (FHG and FiHG) of a 1077 nm laser in NH4H2PO4 (ADP), KH2PO4 (KDP), and KD2PO4 (DKDP) crystals. In this work, a new, to the best of our knowledge, laser frequency with a wavelength of 1077 nm was generated by optical parametric amplification, in which the pump light (526.3 nm) was generated by the frequency doubling of a Nd:YLF laser (1052.7 nm), and the signal light was a Yb:YAG laser (1029.5 nm). Subsequently, the 1077 nm laser was used as the fundamental wave for FHG and FiHG to obtain a deep-ultraviolet laser source. For ADP and DKDP crystals, NCPM FHG of a 1077 nm laser was realized at 74.0∘C and 132.5∘C, respectively, and large angular acceptances of 59.8 and 61.6 mrad were measured. For the FiHG, NCPM was realized in a KDP crystal at 48.5∘C with an angular acceptance of 56.4 mrad. The results pave the way for high-energy and high-power deep-ultraviolet laser generation using KDP-family crystals under noncryogenic conditions.

Top quark effective couplings from top-pair tagged photoproduction in pe− collisions

We present a detailed study, at the fast detector simulation level, of top-pair photoproduction in semileptonic mode at the Large Hadron-electron Collider (LHeC) and Future Circular Collider (FCC-he). We work in full tree-level QED, not relying on the equivalent photon approximation, taking into account the complete photoproduction kinematics. This allows us to define three photoproduction regions based on the angular acceptance range of the electron tagger. Those regions provide different degrees of sensitivity to top quark effective couplings. We focus on the $t\overline{t}\ensuremath{\gamma}$ dipole couplings and the left-handed vector $tbW$ coupling for which we determine limits at both energies and in different photoproduction regions. We find that the LHeC and FCC-he will yield tight direct bounds on top dipole moments, greatly improving on current direct limits from hadron colliders, and direct limits on the $tbW$ coupling as restrictive as those expected from the HL-LHC. We also consider indirect limits from $b\ensuremath{\rightarrow}s\ensuremath{\gamma}$ branching ratio and $CP$ asymmetry, that are well known to be very sensitive probes of top electromagnetic dipole moments.

Diffuse Solar Micro‐Concentrators Using Dielectric Total Internal Reflection with Tunable Side and Top Profiles

Solar technology candidates for building‐integrated photovoltaics and mobile power applications suffer from difficulty in fabricating large‐area, defect‐free solar cells, high materials costs, and small angular acceptance for incoming radiation. Solar concentrators collecting non‐normal‐incidence radiation and diffuse light while retaining high concentration ratios are therefore an enticing technology for high‐efficiency‐low‐cost photovoltaic systems. Here, a novel implementation of dielectric total internal reflection concentrators (DTIRCs) utilizing a piecewise smooth sidewall profile with an intermediate segment is developed. Coupled with a turning point in the entrance surface, this design allows for a tunable phase shift between the two sidewall segments, thereby allowing both the concentration ratio at normal incidence and the maximum acceptance angle to be increased, and the limit imposed by etendue conservation to be potentially exceeded under specific conditions. Scalable fabrication techniques are used to produce flexible DTIRCs, and their performance is verified with high‐efficiency commercial solar cells. Moreover, the collectible sun power over the course of a year is calculated, demonstrating that the new design receives more total power compared to traditional direct solar concentrators and standard DTIRC designs in realistic conditions, making it a good candidate for scalable micro‐concentrator systems that can be integrated directly into a solar cell package.

Broadband Time-Delay and Chirp Compensator for X-ray Pulses

A new type of aberration-corrected time-delay compensating monochromator (TDCM) for soft X-rays is presented. Composed of two identical reflection zone plates (RZPs) on spherical substrates and an intermediate flat mirror for band-pass selection, the TDCM can operate in a wide energy range of about ±20% around the design energy of 410eV. Assuming a source size of 50μm and an angular acceptance of 1 mrad, the spectral resolving power may reach 6×102, at a pulse length as short as 4.3femtoseconds(fs). In the case of μm-sized sources, the resolution can be better than 0.1eV and the sub-fs regime could become accessible. The overall transmission efficiency varies within (4.2–6.0)% across the energy range (310–510) eV. In the complementary mode, chirped-pulse compression works as well. Depending on the properties of the source, simulations predict an up to 9-fold reduction in pulse duration, whereas ≤50% of the peak intensity is maintained.

In-flight production of an isomeric beam of 16N

An in-flight beam of 16N was produced via the single-neutron adding (d,p) reaction in inverse kinematics at the recently upgraded Argonne Tandem Linear Accelerator System (ATLAS) in-flight system. The amount of the 16N beam which resided in its excited 0.120 MeV Jπ=0− isomeric state (T1/2≈5 μs) was determined to be 40(5)% at a reaction energy of 7.9(3) MeV/u, and 24(2)% at a reaction energy of 13.2(2) MeV/u. The isomer measurements took place at an experimental station ≈30 m downstream of the production target and utilized an Al beam-stopping foil and a HPGe Clover detector. Composite 16N beam rate determinations were made at the experimental station and the focal plane of the Argonne in-flight radioactive ion-beam separator (RAISOR) with Si ΔE-E telescopes. A Distorted Wave Born Approximation (DWBA) approach was coupled with the known spectroscopic information on 16N in order to estimate the relative 16N isomer yields and composite 16N beam rates. In addition to the observed reaction-energy dependence of the isomer fraction, a large sensitivity to the angular acceptance of the recoils was also observed.

Widely tunable long-wave infrared difference frequency generation with a BaGa4Se7 crystal.

We report an experimental study of long-wave infrared difference frequency generation based on BaGa4Se7 crystal. The sources of two input wavelengths were the fundamental output of a Nd:YAG laser and its second-harmonic pumped ∼1.2µmKTiOPO4 optical parametric oscillator. A wide tuning range of 7.9-17.5 µm (>1.14 octave) was achieved, which reached the upper limit of the BaGa4Se7 transparency region. The spectra and pulse widths, input-output relationship, beam profile, wavelength tolerance, and angular acceptance of the phase-matching were characterized in detail. This presented coherent source can potentially be applied in multiple gas analyses and spectral imaging.

A recoil ion momentum spectrometer for probing ionization, e-capture, and capture-ionization induced molecular fragmentation dynamics.

The development of a recoil ion momentum spectrometer (RIMS) along with a post-collision projectile charge state analyzer (CSA) and its performance for carrying out studies of molecular fragmentation following direct ionization, electron-capture, and capture-ionization have been demonstrated here. This is a two-stage Wiley-McLaren type spectrometer with slight modification introduced by adding a lens to achieve higher momentum resolution as well as larger angular acceptance. Along with the time and position sensitive detector, it can measure all the three momentum components of singly charged recoil ions of energy up to 10 eV emitted in all directions. The CSA assembly is designed for separating out any neutral or singly or doubly charged post-collision projectiles typically of keV energy. The RIMS with initial trigger ("start") from CSA or an ionized electron can uniquely determine the dynamics of molecular fragmentation following different electron-capture or direct ionization events, respectively. To check the performance of the setup, we carried out an experimental study of the fragmentation of N2 molecules under the impact of 250 keV protons. Apart from the single-electron-capture channel, we could clearly identify three more capture-ionization channels, which lead to fragmentation. The essential features of the momentum distributions and the kinetic energy release distributions of all three fragmentation channels are discussed in detail. These results are compared with the findings from the ionization induced fragmentation experiments and with the available results from theoretical calculations as well as high resolution experiments. The branching ratios of these fragmentation channels are determined.

Angle-Multiplexing Nonlinear Holography for Controllable Generations of Second-Harmonic Structured Light Beams

Nonlinear multiplexing holography emerges as a powerful tool to produce structured lights at new wavelengths. In this work, we propose and experimentally demonstrate an angle-multiplexing nonlinear holography in an angular noncritical phase-matching configuration. In experiment, various types of structured light beams, such as vortex beam, Airy beam and Airy vortex beam, are simultaneously output at second-harmonic waves along different paths. Because of the large angular acceptance bandwidth of noncritical phase-matching, one can achieve high conversion efficiency of angle-multiplexing nonlinear holography. Our method has potentially applications in high-capacity holographic storage and security encryption.

Unique surface sensitivity to ferro- and antiferromagnetic phases by polarization analysis in synchrotron Mössbauer reflectivity

Polarization analysis of the reflected radiation has been performed in Mössbauer reflectivity measurements with a Synchrotron Mössbauer Source (SMS). Effective π→σ′ polarization selection is attained with LiF crystal ((6 2 2) 90o-reflection for 14.4 keV radiation, angular acceptance ∼ 100``) capable of high π→π′ suppression. Basic features of the reflectivity with the rotated π→σ′ polarization are revealed in the experiment with the [57Fe(10 ML)/V(20 ML)]20 multilayer. Selection of π→σ′ polarization component in Mössbauer reflectivity allows to exclude nonresonant electronic scattering, besides Mössbauer π→σ′ reflectivity spectra (R-spectra) contain only contributions from magnetized along the beam ferromagnetic phases. The antiferromagnetic iron oxides do not contribute to π→σ′ R-spectra (dichroic component is compensated). Therefore, in the Mössbauer reflectivity experiment supplemented by polarization analysis the data interpretation becomes more certain and gives information about depth position for ferromagnetic layers selectively. With this new technique we locate antiferromagnetic iron phases in the very top layer of [57Fe(10 ML)/V(20 ML)]20 multilayer and ascertain the ferromagnetic ordered iron layers in the remaining part of the structure. This new approach in Mössbauer reflectivity has interesting perspectives for investigations of hyperfine interactions for iron complexes on the surface, ultrathin layers and multilayers with complicated magnetic structures.

Ultra-broadband perfect absorber based on nanoarray of titanium nitride truncated pyramids for solar energy harvesting

A metamaterial perfect absorber working in the ultraviolet to near-infrared band is proposed based on a triple-layer structure composed of titanium nitride (TiN) periodic nanoarray, dielectric film, and TiN bottom layer. Each unit cell of the nanoarray is a truncated pyramid structure with its width tapered linearly from the bottom to the top. The physical mechanism of the absorber was explained by analyzing the electric field distributions at different wavelengths, and the absorption performance was simulated as a function of its geometric parameters and the angle and polarization of incident light as well. Optimal geometric parameters are presented. The absorber implemented using the optimal parameters would display an excellent performance with almost perfect absorption (above 99%) over the entire spectral region from 300 to 2500 nm. The ultra-broadband perfect absorption behavior is attributed to the localized surface plasmon resonance effect of the TiN pyramid, the intrinsic loss of the TiN material and the coupling of resonance modes between two adjacent pyramids. Besides, the absorber also exhibits a polarization-independent feature at normal incidence and good angular acceptance capability of incident light. The reported ultra-broadband metamaterial absorber shows great application prospects in the solar energy harvesting industry and solar thermophotovoltaic systems.

A new cylindrical borehole detector for radiographic imaging with muons

Muon radiography is a methodology which enables measuring the mass distribution within large objects. It exploits the abundant flux of cosmic muons and uses detectors with different technologies depending on the application. As the sensitive surface and geometric acceptance are two fundamental parameters for increasing the collection of muons, the optimization of the detectors is very significant. Here we show a potentially innovative detector of size and shape suitable to be inserted inside a borehole, that optimizes the sensitive area and maximizes the angular acceptance thanks to its cylindrical geometry obtained using plastic arc-shaped scintillators. Good spatial resolution is obtained with a reasonable number of channels. The dimensions of the detector make it ideal for use in 25 cm diameter wells. Detailed simulations based on Monte Carlo methods show great cavity detection capability. The detector has been tested in the laboratory, achieving overall excellent performance.

Modelling the visual world of a velvet worm.

In many animal phyla, eyes are small and provide only low-resolution vision for general orientation in the environment. Because these primitive eyes rarely have a defined image plane, traditional visual-optics principles cannot be applied. To assess the functional capacity of such eyes we have developed modelling principles based on ray tracing in 3D reconstructions of eye morphology, where refraction on the way to the photoreceptors and absorption in the photopigment are calculated incrementally for ray bundles from all angles within the visual field. From the ray tracing, we calculate the complete angular acceptance function of each photoreceptor in the eye, revealing the visual acuity for all parts of the visual field. We then use this information to generate visual filters that can be applied to high resolution images or videos to convert them to accurate representations of the spatial information seen by the animal. The method is here applied to the 0.1 mm eyes of the velvet worm Euperipatoides rowelli (Onychophora). These eyes of these terrestrial invertebrates consist of a curved cornea covering an irregular but optically homogeneous lens directly joining a retina packed with photoreceptive rhabdoms. 3D reconstruction from histological sections revealed an asymmetric eye, where the retina is deeper in the forward-pointing direction. The calculated visual acuity also reveals performance differences across the visual field, with a maximum acuity of about 0.11 cycles/deg in the forward direction despite laterally pointing eyes. The results agree with previous behavioural measurements of visual acuity, and suggest that velvet worm vision is adequate for orientation and positioning within the habitat.

Performance evaluation for the dielectric asymmetric compound parabolic concentrator with almost unity angular acceptance efficiency

This paper proposes a systematic design and formation process for the asymmetric compound parabolic concentrator taking the angular acceptance range as the target function and a dielectric asymmetric compound parabolic concentrator (DACPC) that presents almost unity angular acceptance efficiency is got. Ray-tracing simulation and experimental characterization study were conducted to reveal the optical performance of the DACPC. It was found that the DACPC with the geometric concentration ratio of 2.4 increased the short-circuit current and the maximum power by 87.0% and 96.6% averagely within the incidence angels of 0°–85° as compared with the non-concentrating photovoltaic cell. Corresponding average simulation and actual optical efficiency of it are 93.3% and 77.9%. The angular acceptance efficiency is proposed to evaluate the annual performance potential and regional applicability for optical concentrators, which indicates that the angular acceptance efficiency of the DACPC can be up to 97.7% for simulation results and 94.4% for experiment results. The outdoor experiments on 25th June when the projected incidence angle lied in the range of 60°–89° for the DACPC were conducted. It was found that the DACPC can still increase the short-circuit current and maximum power of the photovoltaic cell by average factors of 57% and 76% respectively.

Video-Rate Identification of High-Capacity Low-Cost Tags in the Terahertz Domain.

In this article, we report on video-rate identification of very low-cost tags in the terahertz (THz) domain. Contrary to barcodes, Radio Frequency Identification (RFID) tags, or even chipless RFID tags, operate in the Ultra-Wide Band (UWB). These THz labels are not based on a planar surface pattern but are instead embedded, thus hidden, in the volume of the product to identify. The tag is entirely made of dielectric materials and is based on a 1D photonic bandgap structure, made of a quasi-periodic stack of two different polyethylene-based materials presenting different refractive indices. The thickness of each layer is of the order of the THz wavelength, leading to an overall tag thickness in the millimetre range. More particularly, we show in this article that the binary information coded within these tags can be rapidly and reliably identified using a commercial terahertz Time Domain Spectroscopy (THz-TDS) system as a reader. More precisely, a bit error rate smaller than 1% is experimentally reached for a reading duration as short as a few tens of milliseconds on an 8 bits (~40 bits/cm2) THID tag. The performance limits of such a tag structure are explored in terms of both dielectric material properties (losses) and angular acceptance. Finally, realistic coding capacities of about 60 bits (~300 bits/cm2) can be envisaged with such tags.