Photon Path Research Articles

NaI cubic detector full-energy peak efficiency, including coincidence and self-absorption corrections for rectangular sources using analytical method

Low activities of radionuclides in environmental and occupational samples demand for the lower detection limits of the measuring system, which can be achieved by minimizing the source-to-detector distance. Analytical technique to calculate full-energy peak efficiency and total efficiency, self-absorption of sources and a coincidence factor of the NaI cubic scintillation detector with rectangular cavity for rectangular source have been derived. The photon path length of the volumetric sources calculated and determined source self-absorption. The photon attention by rectangular sources and detector cap materials is also calculated. In the experiments gamma aqueous source containing Eu-152 radionuclide covering range from 121 to 1408 keV was used. By comparison analytical method for calculating the full energy peak efficiency and the corrected experimental efficiency values are in good a agreement.

The Quantum Efficiency and Diffractive Image Artifacts of Si:As IBC mid-IR Detector Arrays at 5–10 μm: Implications for the JWST/MIRI Detectors

Arsenic doped back illuminated blocked impurity band (BIBIB) silicon detectors have advanced near and mid-IR astronomy for over thirty years; they have high quantum efficiency (QE), especially at wavelengths longer than 10 μm, and a large spectral range. Their radiation hardness is also an asset for space based instruments. Three examples of Si:As BIBIB arrays are used in the Mid-InfraRed Instrument (MIRI) of the James Webb Space Telescope (JWST), observing between 5 and 28 μm. In this paper, we analyze the parameters leading to high quantum efficiency (up to ∼60%) for the MIRI devices between 5 and 10 μm. We also model the cross-shaped artifact that was first noticed in the 5.7 and 7.8 μm Spitzer/IRAC images and has since also been imaged at shorter wavelength (≤10 μm) laboratory tests of the MIRI detectors. The artifact is a result of internal reflective diffraction off the pixel-defining metallic contacts to the readout detector circuit. The low absorption in the arrays at the shorter wavelengths enables photons diffracted to wide angles to cross the detectors and substrates multiple times. This is related to similar behavior in other back illuminated solid-state detectors with poor absorption, such as conventional CCDs operating near 1 μm. We investigate the properties of the artifact and its dependence on the detector architecture with a quantum-electrodynamic (QED) model of the probabilities of various photon paths. Knowledge of the artifact properties will be especially important for observations with the MIRI LRS and MRS spectroscopic modes.

Effect of scattering anisotropy on the properties of photon density waves.

The frequency characteristics of spherical photon density waves excited in media with different degrees of scattering anisotropy are studied. Statistical modeling of the frequency and phase responses of the spatial irradiance of the light field emitted by a point-sized isotropic source were performed employing the Monte Carlo technique. The scattering anisotropy of the medium was determined by the Henyey-Greenstein phase function with different values of the mean scattering cosine. It is shown that the scattering anisotropy factor determines the frequency range, in which the effect of the photon path length distribution on the magnitude of the photon density wave dispersion is maximal. In media with quasi-isotropic scattering, dispersion effects are manifested at lower frequencies as compared to those for anisotropic media. The simulation results are compared with the analytical solution for the asymptotic regime of the light field in an isotropically scattering medium.

Structural, physical and radiation attenuation properties of tungsten doped zinc borate glasses

For the x WO3 (40 – x) ZnO 50B2O3 10K2O, (0 ≤ x ≤ 20 wt%) glass system. optical, structure, gamma and neutron radiation shielding aspects were examined comprehensively. The mass attenuation coefficients of gamma-rays, the mean free photon path (MFP), and the effective atomic number (Zeff) have been determined experimentally at photon energies 238, 662,911, 1173, 1332 and 2614 keV. The results obtained were compared with the corresponding theoretical data, which were found to be dependent on glass components and energy. Moreover, the calculated ƩR shows that increasing the removal cross section increases with increasing the WO3 concentration. The molar volume of the glasses has been derived from density measurements and studied as a function of composition. FTIR spectral results revealed that the glass network matrix is sequentially formed by BO3, BO4, ZnO4, WO4 and WO6 structural groups. The optical transmission was done on these glasses and the absorbance was increased as WO3 increased. Moreover, the peak shifted to a longer wavelength as WO3 increased and a decreasing behavior of the bandgap. The obtained results have been analyzed in the light of various oxidation states of tungsten ions in the glass matrix. All results pointed out that these glasses have potential applications in radiation shielding.

An Improved Efficiency by Surface Modification Using Pulse Laser for Partial Transparent Bifacial Solar Cell

Bifacial solar cell has symmetrical configuration contacts on front and rear surface that eliminate expansion mismatch, decrease metal usage and improves photon absorption. The limitation of the reflector at the back of bifacial solar panel able to be eliminated by developing special designed partially transparent bifacial solar cell to optimize light trapping on rear surface. Therefore, the partial transparent silicon (Si) wafers were developed to increase light transmission to rear surface. Surface modification on Si wafer was conducted to form partial transparent Si wafer. Surface modification was employed by pulsed laser interaction to create dot marking array on Si wafer. Two pulsed laser power applied were 25.5W and 39.6W to produce pattern, then immersed in 10% KOH solution to etch laser-induced structure and debris to form partial transparent Si wafer. Low power laser was induced 80-85 μm depth of micro-hole, while high power was induced 140-145 μm. KOH treatment was conducted to etch laser region which to form deeper and wide micro-holes. The bifacial solar cells have been fabricated using partial transparent Si wafer and the current-voltage of the devices were tested. The front surface efficiency obtained for both partial transparent bifacial solar cells were 4.36% and 5.59%, while rear surface achieved 1.23% and 1.16%. Fabricated conventional bifacial solar cell has an efficiency of 2.39% for front and 0.64% for rear. The surface modification enhanced the efficiency due to the photon path length transmission to rear surfaces, micro-hole’s dimension and optical absorption in the near-infrared region.

Explanation of Photon Navigation in the Mach-Zehnder Interferometer

Photons in interferometers manifest the functional ability to simultaneously navigate both paths through the device, but eventually appear at only one outlet. How this relates to the physical behaviour of the particle is still ambiguous, even though mathematical representation of the problem is adequate. This paper applies a non-local hidden-variable (NLHV) solution, in the form of the Cordus theory, to explain photon path dilemmas in the Mach–Zehnder (MZ) interferometer. The findings suggest that the partial mirrors direct the two reactive ends of the Cordus photon structures to different legs of the apparatus, depending on the energisation state of the photon. Explanations are provided for a single photon in the interferometer in the default, open-path, and sample modes. The apparent intelligence in the system is not because the photon knows which path to take, but rather because the MZ interferometer is a finely-tuned photon-sorting device that auto-corrects for randomness in the frequency phase to direct the photon to a specific detector. The principles also explain other tunnelling phenomena involving barriers. Thus, navigation dilemmas in the MZ interferometer may be explained in terms of physical realism after all.

Development and Application of HECORA Cloud Retrieval Algorithm Based On the O2-O2 477 nm Absorption Band

In this paper, we present the Hefei EMI Cloud Retrieval Algorithm (HECORA), which uses information from the O2-O2 absorption band around 477 nm to retrieve effective cloud fraction and effective cloud pressure from satellite observations. The retrieved cloud information intends to improve the atmospheric trace gas products based on the Environment Monitoring Instrument (EMI) spectrometer. The HECORA method builds on OMCLDO2 and presents some evolutions. The Vector Linearized Discrete Ordinate Radiative Transfer (VLIDORT) model has been used to produce the Top of the Atmosphere (TOA) reflectance Look-up Tables (LUT) as a function of the cloud fraction and cloud pressure. Applying the Differential Optical Absorption Spectroscopy (DOAS) technique to the synthetic reflectance LUT, the reflectance spectra can be associated with O2-O2 geometrical vertical column densities (VCDgeo) and continuum reflectance. This is the core of the retrieval method, since there is a one-to-one relationship between O2-O2 VCDgeo and continuum reflectance, on the one hand, and effective cloud fraction and effective cloud pressure, on the other hand, for a given illumination and observing geometry and given surface height and surface albedo. We first used the VLIDORT synthetic spectra to verify the HECORA algorithm and obtained good results in both the Lambertian cloud model and the scattering cloud model. Secondly, HECORA is applied to OMI and TROPOMI and compared with OMCLDO2, FRESCO+, and OCRA/ROCINN cloud products. Later, the cloud pressure results from TROPOMI observations obtained using HECORA and FRESCO+ are compared with the CALIOP Cloud Layer product. HECORA is closer to the CALIOP results under low cloud conditions, while FRESCO+ is closer to high clouds due to the higher sensitivity of the O2 A-band to cloud vertical information. Finally, HECORA is applied to the TROPOMI NO2 retrieval. Validation of the tropospheric NO2 VCD with ground-based MAX-DOAS measurements shows that choosing HECORA cloud products to correct for photon path variations on the TROPOMI tropospheric NO2 VCD retrievals has better performance than using FRESCO+ under low cloud conditions. In conclusion, this paper shows that the HECORA cloud products are in good agreement with the well-established cloud products and that they are suitable for correcting the effect of cloud in trace gas retrievals. Therefore, HECORA has the potential to be applied to EMI.

Plasmon-Enhanced Greenhouse Selectivity for High-Temperature Solar Thermal Energy Conversion.

The greenhouse effect arises when thermal radiation is forced to undergo absorption and re-emission many times before escaping, while sunlight transmits largely unimpeded. Although this effect is responsible for global warming, it is generally weak in solid-state materials because radiation can be easily overpowered by other modes of heat transfer. Here, we report on the use of infrared plasmonic nanoparticles to enhance the greenhouse effect in transparent mesoporous materials. Local surface plasmon resonances in transparent conducting oxide nanoparticles (TCO NPs) selectively shorten the mean free path of thermal photons while maintaining high solar transmittance. The addition of a small amount of TCO NPs (<0.1% by volume) nearly halves the heat losses at 700 °C. This leads to an experimentally demonstrated effective thermal emittance of ∼0.17 at 700 °C, which is the lowest reported value to date, among all selective surfaces and transparent insulating materials measured at 650 °C or above. Our results show that plasmon-enhanced greenhouse selectivity (PEGS) is a promising mechanism for spectral control of radiative heat transfer, and more specifically, for conversion of minimally concentrated sunlight into high-temperature heat.

A strong no-go theorem on the Wigner’s friend paradox

Does quantum theory apply at all scales, including that of observers? New light on this fundamental question has recently been shed through a resurgence of interest in the long-standing Wigner's friend paradox. This is a thought experiment addressing the quantum measurement problem -- the difficulty of reconciling the (unitary, deterministic) evolution of isolated systems and the (non-unitary, probabilistic) state update after a measurement. Here, by building on a scenario with two separated but entangled friends introduced by Brukner, we prove that if quantum evolution is controllable on the scale of an observer, then one of 'No-Superdeterminism', 'Locality' or 'Absoluteness of Observed Events' -- that every observed event exists absolutely, not relatively -- must be false. We show that although the violation of Bell-type inequalities in such scenarios is not in general sufficient to demonstrate the contradiction between those three assumptions, new inequalities can be derived in a theory-independent manner, that are violated by quantum correlations. This is demonstrated in a proof-of-principle experiment where a photon's path is deemed an observer. We discuss how this new theorem places strictly stronger constraints on physical reality than Bell's theorem.

Interferometric transmission probing with coded mutual intensity

We introduce a new interferometric imaging methodology that we term interferometry with coded mutual intensity, which allows selectively imaging photon paths based on attributes such as their length and endpoints. At the core of our methodology is a new technical result that shows that manipulating the spatial coherence properties of the light source used in an interferometric system is equivalent, through a Fourier transform, to implementing light path probing patterns. These patterns can be applied to either the coherent transmission matrix, or the incoherent light transport matrix describing the propagation of light in a scene. We test our theory by building a prototype inspired by the Michelson interferometer, extended to allow for programmable phase and amplitude modulation of the illumination injected in the interferometer. We use our prototype to perform experiments such as visualizing complex fields, capturing direct and global transport components, acquiring light transport matrices, and performing anisotropic descattering, both in steady-state imaging and, by combining our technique with optical coherence tomography, in transient imaging.

Stochastic radiative transfer in random media: Pure absorbing cases.

We study stochastic radiation transport through random media in one dimension, in particular for pure absorbing cases. The statistical model to calculate the ensemble-averaged transmission for a binary random mixture is derived based on the cumulative probability density function (PDF) of optical depth, which is numerically simulated for both Markovian and non-Markovian mixtures by Monte Carlo calculations. We present systematic results about the influence of mixtures' stochasticity on the radiation transport. It is found that mixing statistics affects the ensemble-averaged intensities mainly due to the distribution of cumulative PDF at small optical depths, which explains well why the ensemble-averaged transmission is observed to be sensitive to chord length distribution and its variances. The effect of the particle size is substantial when the mixtures' correlation length is comparable to the mean free path of photons, which imprints a moderately broad transition region into the cumulative PDF. With the mixing probability increasing, the intensity decreases nearly exponentially, from which the mixing zone length can be approximately estimated. The impact of mixed configuration is also discussed, which is in line with previous results.

Hydrodynamic Response of the Intergalactic Medium to Reionization

Abstract The intergalactic medium is expected to clump on scales down to M ⊙ before the onset of reionization. The impact of these small-scale structures on reionization is poorly understood despite the modern understanding that gas clumpiness limits the growth of regions. We use a suite of radiation-hydrodynamics simulations that capture the Jeans mass of unheated gas to study density fluctuations during reionization. Our simulations track the complex ionization and hydrodynamical response of gas in the wake of ionization fronts. The clumping factor of ionized gas (proportional to the recombination rate) rises to a peak value of 5–20 approximately Δt = 10 Myr after ionization front passage, depending on the incident intensity, redshift, and degree to which the gas had been preheated by the first X-ray sources. The clumping factor reaches its relaxed value of ≈3 by Δt = 300 Myr. The mean free path of Lyman-limit photons evolves in unison, being up to several times shorter in unrelaxed, recently reionized regions compared to those that were reionized much earlier. Assessing the impact of this response on the global reionization process, we find that unrelaxed gaseous structures boost the total number of recombinations by ≈50% and lead to spatial fluctuations in the mean free path that persist appreciably for several hundred million years after the completion of reionization.

Disembodiment of arbitrary number of properties in quantum Cheshire cat experiment

The quantum Cheshire cat is an effect demonstrated within the framework of weak measurement aided with post-selection scenario where the property (say, grin) of a quantum particle (the cat) can be found in a spatially separated location from its position. In this work, we first propose interesting variants of quantum Cheshire cat where disembodiment of two different properties of a `cat' is demonstrated, so that, the \emph{grin} and the \emph{meowing} of it can be found in two different paths on an interferometer while the cat is in another path. We further extend this proposal for three-qutrit and $d$-qudit systems of a single particle. We provide sketches of the experimental proposals for testing our scheme by using the path, spin and energy degrees of freedoms of a single neutron and the path, polarization and orbital angular momentum of a single photon.

Evolution of transmitted depolarization in diffusely scattering media.

We performed Mueller matrix Monte Carlo simulations of the propagation of optical radiation in diffusely scattering media for collimated incidence and report the results as a function of thickness and the angle subtended by the detector. For sufficiently small thickness, a fraction of the radiation does not undergo any scattering events and is emitted at zero angle. Thus, for a very small detector angle, the measured signal will indicate mostly the attenuation of the coherent contribution, while for larger angles, the diffuse scattering radiation will contribute significantly more. The degree to which the radiation is depolarized thus depends on the angle subtended by the detector. A three-stream model-where the coherent radiation, the forward diffusely scattered radiation, and the backward scattered radiation are propagated according to the differential Mueller matrix formalism-is introduced and describes the results from the Monte Carlo simulations and the results of measurements well. This scatter-based model for depolarization in diffusely scattering media is an alternative to that based upon elementary fluctuation theory applied to a single propagation stream. Results for average photon path length, determined from the Monte Carlo simulations, suggest that applying fluctuation theory to photon path length may unify the two approaches.

Remitted photon path lengths in human skin: in-vivo measurement data.

The remitted photon path lengths in human skin can be estimated by modelling; however, there are very few experimental data available to validate the simulations. This study exploited the photon time of flight method where picosecond laser pulses at seven wavelength bands in the spectral range 560-800 nm were launched into in-vivo forearm skin of 10 volunteers via an optical fiber. The pulses of back-scattered light were detected via another optical fiber placed at variable distance (1, 8, 12, 16 or 20 mm) from the input fiber, with subsequent analysis of their shapes for all 35 spectral-spatial combinations. Using a deconvolution algorithm, the distribution functions of remitted photon arrival times after infinitely narrow input pulse were calculated and transformed into distributions of skin-remitted photon path lengths. Nearly linear dependences of the remitted photon mean path length on inter-fiber distance were obtained for all wavelength bands, while the spectral dependences at fixed inter-fiber distances showed more complicated character, most probably due to absorption of the dermal hemoglobin.

Towards simultaneous observation of path and interference of a single photon in a modified Mach–Zehnder interferometer

Classical wisdom of wave–particle duality regulates that a quantum object shows either the particle or wave nature but never both. Consequently, it would be impossible to observe simultaneously the complete wave and particle nature of the quantum object. Mathematically the principle requests that the interference visibility V and which-path distinguishability D satisfy an orthodox limit of V 2 + D 2 ≤ 1 . The present work reports a new wave–particle duality test experiment using single photons in a modified Mach–Zehnder interferometer to demonstrate the possibility of breaking the limit. The key element of the interferometer is a weakly scattering total internal reflection prism surface, which exhibits a pronounced single-photon interference with a visibility of up to 0.97 and simultaneously provides a path distinguishability of 0.83. Apparently, the result of V 2 + D 2 ≈ 1.63 exceeds the orthodox limit set by the classical principle of wave–particle duality for single photons. We expect that more delicate experiments in the future should be able to demonstrate the ultimate limit of V 2 + D 2 ≈ 2 and shed new light on the foundations of contemporary quantum mechanics.

Dual-Wavelength Diffuse Optical Tomographic System for Direct Concentration Measurement

This article presents a promising dual-wavelength continuous wave (CW) diffuse optical tomography (DOT) system for direct estimation of concentrations and hemodynamic parameters for potential application in detection of rheumatoid arthritis (RA). The generalized curved-beam reconstruction technique is modified for direct estimation of hemodynamic parameters. The Rosenbrock’s function is fit to estimate the photon path as curved one followed by majority photons that enabled the use of modified Beer–Lambert law (MBLL) in differential form with assumption that unknown absorption coefficient ( $\mu _{a}$ ) varies from one path to another. The $\mu _{a}$ values are calculated and back-projected along the photon paths for image reconstruction without solving the inverse problem. Thus, stability is not an issue in image reconstruction. Also, there is no need for baseline measurement and prior information on perturbation, unlike the iterative methods used for dynamic imaging. The reconstructed images of the distal interphalangeal (DIP) and proximal interphalangeal (PIP) joints of a healthy male volunteer showed good consistency and are used for direct optical estimation of the physiological parameters. A novel application of optical imaging beyond biomedical applications is demonstrated by imaging the gradual dispersion of viscous Indian ink and glycerin mixture in turbid water with encouraging results.

Gamma ray shielding characteristics of Sn-20Bi and Sn-20Bi-0.4Cu lead-free alloys

As a result of the expansion in the different uses of gamma ray sources and as a result of the harmful effects of radiation exposure, scientific research remains in need of finding and developing materials used as radiation shields. In the present study, shielding parameters of Sn-20Bi (SB) and Sn-20Bi-0.4Cu (SBC) lead-free alloys solidified with and without the effect of a rotating magnetic field (RMF) have been studied. Gamma ray mass attenuation coefficient (μt/ρ) was measured experimentally for the studied alloys at photon energy of 356, 511, 662, 1173, 1274, and 1332 KeV. The experimental μt/ρ values were compared with the calculated values by using the WinXCom and MCNP5 programs for alloys solidified without RMF. Besides, WinXCom and MCNP5 were used to calculate μt/ρ for gamma ray photons of energy range of 10−3-102 MeV. The atomic and electronic cross sections (σa and σe) and hence the effective atomic number (Zeff) and effective electron density (Neff) were calculated. The mean free path (MFP) of photons was calculated and introduced to MCNP5 input file to calculate the gamma ray energy buildup factor (EBF). The results of μt/ρ are shown to be highly compatible between the theoretical WinXCom and simulated MCNP5 programs and with the experimental values. The results of the shielding parameters confirm that the alloys under study are good shielding materials against gamma rays.

Accurate 3-D radiative transfer simulation of spectral solar irradiance during the total solar eclipse of 21 August 2017

Abstract. We calculate the variation of spectral solar irradiance in the umbral shadow of the total solar eclipse of 21 August 2017 and compare it to observations. Starting from the Sun's and Moon's positions, we derive a realistic profile of the lunar shadow at the top of the atmosphere, including the effect of solar limb darkening. Subsequently, the Monte Carlo model MYSTIC (Monte Carlo code for the phYSically correct Tracing of photons In Cloudy atmospheres) is used to simulate the transfer of solar radiation through the Earth's atmosphere. Among the effects taken into account are the atmospheric state (pressure, temperature), concentrations of major gas constituents and the curvature of the Earth, as well as the reflectance and elevation of the surrounding area. We apply the model to the total solar eclipse on 21 August 2017 at a position located in Oregon, USA, where irradiance observations were performed for wavelengths between 306 and 1020 nm. The influence of the surface reflectance, the ozone profile, the mountains surrounding the observer and aerosol is investigated. An increased sensitivity during totality is found for the reflectance, aerosol and topography, compared to non-eclipse conditions. During the eclipse, the irradiance at the surface not only depends on the total ozone column (TOC) but also on the vertical ozone distribution, which in general complicates derivations of the TOC from spectral surface irradiance. The findings are related to an analysis of the prevailing photon path and its difference compared to non-eclipse conditions. Using the most realistic estimate for each parameter, the model is compared to the irradiance observations. During totality, the relative difference between model and observations is less than 10 % in the spectral range from 400 to 1020 nm. Slightly larger deviations occur in the ultraviolet range below 400 and at 665 nm.

Vector-light quantum complementarity and the degree of polarization

The dual wave–particle nature of light and the degree of polarization are fundamental concepts in quantum physics and optical science, but their exact relation has not been explored within a full vector-light quantum framework that accounts for interferometric polarization modulation. Here, we consider vector-light quantum complementarity in double-pinhole photon interference and derive a general link between the degree of polarization and wave–particle duality of light. The relation leads to an interpretation for the degree of polarization as a measure describing the complementarity strength between photon path predictability and so-called Stokes visibility, the latter taking into account both intensity and polarization variations in the observation plane. It also unifies results advanced in classical studies by showing that the degree of polarization can be viewed as the ability of a light beam to exhibit intensity and polarization-state fringes. The framework we establish thus provides novel aspects and deeper insights into the role of the degree of polarization in quantum-light complementarity and photon interference.