Double Photon Research Articles

Atomic-like Autler–Townes splitting controlled by destructive and constructive natural non-Hermitian quantization in Eu3+: BiPO4

We report atomic-like Autler–Townes splitting controlled by destructive and constructive natural non-Hermitian quantization in Eu3+: BiPO4. For the first time, we explored destructive and constructive AT splitting in different regions. Fluorescence (FL), spontaneous four-wave mixing (SFWM), and shot noise signals exhibit different kinds of AT splitting. FL signal exhibits three level dip AT splitting through destructive quantization, SFWM signals exhibit peak and multi-dip AT splitting through constructive quantization, and shot noise signals exhibit a two-level dip AT splitting. These kinds of AT splitting originate through single photon dressing and double photon–phonon dressing, which can be controlled by adjusting experimental parameters. Our atomic-like Autler–Townes-splitting technique is useful for making a spectral router.

Echoes of massless scalar field induced from hairy Schwarzschild black hole

A hairy Schwarzschild black hole describes the deformation of Schwarzschild black hole with an exponent correction due to the introducing of additional sources. Inspired by the novel feature that the hairy Schwarzschild black hole can have double photon spheres for certain parameters space, in this paper we study the echo signals of a massless scalar field from this hairy Schwarzschild black hole by calculating its time evolution. We mainly analyze how the hairy parameters and scalar field's angular momentum affect the echo waveform of the perturbing scalar field. Additionally, we roughly evaluate the time delay of echoes. We find that the hairy parameters have significant influences on the echo signals.

Search for Dark Photon in e+e− → A′A′ Using Future Collider Experiments

The Standard Model (SM) does not provide an information for 26% of dark matter of the universe. In the dark sector, dark matter is supposed to be linked with the hypothetical particles called dark photons that have similar role to photons in electromagnetic interaction in the SM. Besides astronomical observation, there are studies to find dark matter candidates using accelerators. In this paper, we searched for dark photons using future electron-positron colliders, including Circular Electron Positron Collider (CEPC)/CEPC, Future Circular Collider (FCC-ee)/Innovative Detector for Electron-positron Accelerator (IDEA), and International Linear Collider (ILC)/International Large Detector (ILD). Using the parameterized response of the detector simulation of Delphes, we studied the sensitivity of a double dark photon mode at each accelerator/detector. The signal mode is double dark photon decay channel, e+e− → A’A’, where A’ (dark photon with spin 1) decaying into a muon pair. We used MadGraph5 to generate Monte Carlo (MC) events by means of a Simplified Model. We found the dark photon mass at which the cross-sections were the highest for each accelerator to obtain the maximum number of events. In this paper we show the expected number of dark photon signal events and the detector efficiency of each accelerator. The results of this study can facilitate in the dark photon search by future electron-positron accelerators.

Evaluation of osseointegration by resonance frequency analysis in patients with different bone mineral density: clinical and biomechanical aspects

The method of resonance frequency analysis was used to compare the stability of dental implants in patients with normal bone tissue condition, osteopenia and osteoporosis. The indicators allow obtaining information on the state of the implants and determining the permissible biomechanical load using an orthopedic structure. The measurement method allows observing the dynamics of the osteointegration process, and, if necessary, make timely adjustments to the functional load.Material and methods: comprehensive examination and treatment of 690 patients who applied to the clinic for dental flaw removal by dental implantation. Among them, 547 were (79.3%) women and 143 (20.7%) men. In preparation for dental implantation operations, all patients, except for the standard examination, were also densitometrically examined by double X-ray photon absorptiometry, which revealed systemic changes in bone mineral density. Stability of dental implants and osteointegration were monitored by resonance frequency analysis.Results: the overall value of the resonance-frequency analysis, regardless of the region of implants installed in patients with normal bone tissue, differed from those of the osteopenia and osteoporosis group, and was respectively higher by 7.1% (p < 0.001) and 10.1% (p < 0.001). The overall rate in the osteopenia group was higher, and differed from such a group of patients with osteoporosis by 5.7% (p < 0.001).Conclusion: the results of the resonance-frequency analysis provide significant information about the state of the implant-bone interface at different stages of treatment and at control examinations of patients. The measurement method allows observing the dynamics of the osteointegration process, and, if necessary, make timely adjustments to the functional load. Resonance frequency analysis is an important method for documenting the clinical outcome of implantation.

Study of cLFV with ℓiℓjγγ effective vertex

In this work we analyze cLFV processes using a low-energy EFT that induces the effective interaction between two charged leptons of different flavor and two photons. We compute ℓi → ℓjγ, ℓi → ℓjγγ decays and ℓi → ℓj conversion in nuclei. We derived indirect upper limits on the double photon decays, which turned out to be below current experimental bounds. Our prediction for ℓ → τ conversion in nuclei is below the expected sensitivity of the NA64 experiment

Optical Router and 4 × 1 Multiplexer of Coexisting Crystal Field and Non‐Hermitian Autler‐Townes Splitting Controlled by Photon–Phonon Dressing in Eu3+: BiPO4

AbstractFor the first time, the Autler Townes‐splitting dependency on parity‐time symmetry breaking is investigated. The first‐, second‐, and third‐order splitting in spectral domain outputs obtained through different phase transitions of Eu3+: BiPO4 are explored. First‐order splitting corresponds to pure crystal field splitting attributed to the shifting of energy levels and the inherent effect of the crystal field. Second/third‐order splitting results from the coexistence of crystal field and non‐Hermitian spectral Autler Townes (SAT)‐splitting caused by single‐photon dressing coupled with the interaction of phonon and double photon–phonon dressing. It is further explored the relationship between spectral and temporal‐domain splitting obtained through the different phases of Eu3+: BiPO4 by changing the laser detuning. It is authenticated that the contributions of crystal field, photon, and phonon dressing interactions can only be individually distinguished in the spectral domain. Moreover, the experiment results suggest the analogy of an optical 4 × 1 multiplexer with a channel spacing contrast of ≈91% and an optical router with a channel equalization ratio of ≈93%.

The Evolution of Population III and Extremely Metal-poor Binary Stars

Numerical simulations have now shown that Population III (Pop III) stars can form in binaries and small clusters and that these stars can be in close proximity to each other. If so, they could be subject to binary interactions such as mass exchange that could profoundly alter their evolution, ionizing UV and Lyman–Werner photon emission and explosion yields, with important consequences for early cosmological reionization and chemical enrichment. Here we investigate the evolution of Pop III and extremely metal-poor binary stars with the MESA code. We find that interactions ranging from stable mass transfer to common envelope evolution can occur in these binaries for a wide range of mass ratios and initial separations. Mass transfer can nearly double UV photon yields in some of these binaries with respect to their individual stars by extending the life of the companion star, which in turn can enhance early cosmological reionization but also suppress the formation of later generations of primordial stars. Binary interactions can also have large effects on the nucleosynthetic yields of the stars by promoting or removing them into or out of mass ranges for specific SN types. We provide fits to total photon yields for the binaries in our study for use in cosmological simulations.

Optimization of BiVO4 coatings for high yield photoelectrochemical production of reactive chlorine species

Photoelectrochemical (PEC) synthesis of valuable chemicals, such as hydrogen and oxidants, is widely studied as a potential alternative to replace conventional synthesis processes with high carbon footprint. In the present study two different approaches were used to improve photoelectrochemical activity of BiVO4 coatings, i.e. doping with molybdenum and heterostructuring with BiOCl. Crystalline structure, chemical composition and morphology of the coatings were characterized using X-ray diffraction, energy-dispersive spectroscopy and scanning electron microscopy techniques. Performance of the photoelectrodes was tested in the solutions of Na2SO4 and NaCl. PEC activity was found to increase in the sequence BiVO4 < Mo_BiVO4 < Mo_BiVO4/BiOCl and the enhancement was much more pronounced in chloride medium. Mo doping was found to double incident photon to current conversion efficiency (from 5% to 10%) as well as Faradaic efficiency of photoinduced generation of reactive chlorine species (RCS) (from an average of 36% to 78%). Formation of hypochlorite and chlorite (ClO− and ClO2−) was determined experimentally. Construction of heterojunction between Mo_BiVO4 and BiOCl promoted separation of photogenerated electrons and holes and led to significant enhancement of photocurrent. Moreover, presence of BiOCl layer was found to catalyze photooxidation of ClO− to ClO2−. Findings of the study demonstrate the potential of BiVO4-based coatings for photoelectrochemical production of RCS via saline water splitting.

Improvement of double photon emission Compton imaging using angular and polarization correlations in cascade photons

A Compton camera is a gamma ray imaging system that produces images by superposing Compton cones calculated from Compton kinematics. However, the reconstructed images exhibit a high background. In this study, the angular correlation and polarization correlation were used to decrease the background. 111In, which emits 171 keV and 245 keV cascade gamma rays, was imaged using Compton camera modules in the ring structure. The 3D list-mode ordered subset expectation maximization method was used to reconstruct the images. Probability modeling of events reflecting angular and polarization correlations was applied to the image-reconstruction algorithm. The results were compared with those of a typical Compton camera method using only 245 keV Compton cones. The sensitivity of the proposed method was 1.03% of that of the typical method. However, compared to the typical method, the application of angular and polarization correlations improved the signal-to-background ratio. The proposed method is expected to be useful in capturing low-background images wherein a ring-type Compton camera and cascade photon-emitting nuclides can be used.

Measurement of angular correlation changes in double-photon emission nuclides using ultrasound irradiation

Our group has been developing DPECT (Double Photon Emission CT) to enhance nuclear medicine diagnostics using cascade nuclides that emit multiple gamma rays simultaneously. It is possible to detect the local environment around the nuclide by examining the angular correlation of the emitted cascade gamma-rays. In this study, with the goal of developing a new imaging method combining ultrasound and nuclear medicine, we investigated the effect of ultrasound on cascade gamma-ray emission and found that the angular correlation could be changed by a micro-electric field around 111In in an aqueous solution caused by ultrasound irradiation. Using 8 × 8 array of GAGG scintillators as a detector and Hamamatsu Photonics 8 × 8 MPPCs as a photomultiplier, eight detectors were used and arranged in a ring shape to surround the point source 111In from 360° direction. For the readout system, using a dynamic ToT board, read out its channel information, energy information as ToT signal, and detection time information simultaneously and independently concerning gamma-ray detection. We measured the angular correlation change with four types of ultrasound intensities of 0.05 V, 0.10 V, 0.15 V, and 0.20 V input voltage, and found that the gamma-ray emission angle distribution decreased by about up to 5% around the 90° direction and increased by about up to 5% around 0° and 180° for an ultrasound with an input voltage of 0.15 V or higher.

A broadband high-brightness quantum-dot double solid immersion lens single photon source

High-brightness single photon sources (SPSs) are key components for practical quantum information processing systems. Although the performances of recently reported high-brightness SPSs are excellent, it remains challenging to match the emission wavelength of a quantum dot (QD) to the cavity since the high-Q cavity structures have narrow spectral bandwidths. Here, we propose a highly bright and broadband QD SPS that can be deterministically fabricated with a simple yet precise method. The optimized GaAs-polymer double solid immersion lens structure is capable of a brightness of 88% at 0.5 NA and has an operation band of 65 nm with a brightness of over 80% from numerical simulations. Experimentally, we achieved a brightness of 51.6% ± 2% and pure single photon emission [g(2)(0) = 0.029 ± 0.005] at saturation. We believe that our result can pave the way to a practical high-brightness QD SPS, considering its simple QD geometry together with its low cost and precise deterministic fabrication without using expensive and complicated e-beam lithography and dry etching processes.

Multi-molecule imaging and inter-molecular imaging in nuclear medicine

Abstract Multi-molecule imaging and inter-molecular imaging are not fully implemented yet, however, can become an alternative in nuclear medicine. In this review article, we present arguments demonstrating that the advent of the Compton positron emission tomography (Compton-PET) system and the invention of the quantum chemical sensing method with double photon emission imaging (DPEI) provide realistic perspectives for visualizing inter-molecular and multi-molecule in nuclear medicine with MeV photon. In particular, the pH change of InCl3 solutions can be detected and visualized in a three-dimensional image by combining the hyperfine electric quadrupole interaction sensing and DPEI. Moreover, chemical states, such as chelating, can be detected through angular correlation sensing. We argue that multi-molecule and chemical sensing could be a realistic stream of research in future nuclear medicine.

A double photon coincidence detection method for medical gamma-ray imaging

Abstract Cascade nuclides emit two or more gamma rays successively through an intermediate state. The coincidence detection of cascade gamma rays provides several advantages in gamma-ray imaging. In this review article, three applications of the double photon coincidence method are reviewed. Double-photon emission imaging with mechanical collimators and Compton double-photon emission imaging can identify radioactive source positions with their angular-resolving detectors, and reduce the crosstalk between nuclides. In addition, a novel method of coincidence Compton imaging is proposed by taking coincidence detection between a Compton event and a photopeak events. Although this type of coincidence Compton imaging cannot specify the location, it can be useful in multi-nuclide Compton imaging.

Osteointegration assessment by the resonant frequency analysis method in patients with different bone mineral density (clinical and biomechanical aspects): prospective study

BACKGROUND: Dental implant stability depends on the mechanical bone properties in the area of the planned surgical intervention and the correctness of the implant embedded in the bone tissue. A significantly decreased bone tissue mineral density of the jaws was found in patients with osteoporosis, which complicates or even prevents the restoration of the integrity of the dentition by the dental implantation method.&#x0D; AIM: This study aimed to conduct a comparative assessment of the effectiveness of the treatment of dentition defects by dental implantation in patients with a normal state of bone tissue, osteopenia, and osteoporosis, to assess the stability of the installed implants using the resonance frequency analysis.&#x0D; MATERIALS AND METHODS: All patients underwent a densitometric study using double X-ray photon absorptiometry, in addition to the basic examination, in dental implantation operation preparation, which made it possible to identify systemic and regional changes in bone mineral density. Dental implant stability and osseointegration were controlled by the resonant frequency analysis method.&#x0D; RESULTS: The parameters of resonance frequency analysis in patients with normal bone mass, osteopenia, and osteoporosis vary depending on the area where the implants are installed when studying the implant stability in patients with different bone mineral densities. The overall index of resonance frequency analysis values differed from those of the group with osteopenia and osteoporosis, regardless of the area of implants installed in patients with normal bone tissue, and was respectively higher by 7.1% (p 0.001) and 10.1% (p 0.001), respectively. The overall index in the group with osteopenia was higher and differed from that in the group with osteoporosis by 5.7% (p 0.001).&#x0D; CONCLUSION: The resonance frequency analysis results provide significant information about the state of the implant-bone interface at different treatment stages and during follow-up examinations of patients. The measurement technique makes it possible to observe the dynamics of the osseointegration process, and, if necessary, make timely adjustments to the functional load. Resonance frequency analysis is an important method for documenting the clinical outcome of implantation. This is of particular importance from a medical-legal point of view.

Measuring Hot-Spot Interaction Length in Single-Strip SNSPD

Superconducting nanowire single photon detectors (SNSPD) functionality is based on the local suppression of the superconducting order parameter upon photon absorption, causing a change in resistance which can be detected as a DC voltage pulse. Finding the size and the profile of the superconducting order parameter suppression area (the so-called “hot-spot”) experimentally is a challenging task. Here, we report the results of a quantum detector tomography on micron-length SNSPDs. The high internal detection efficiency of our SNSPDs allowed us to extract single and double photon efficiencies from the count rate vs radiation power dependence and extract hot-spot interaction length. We investigated a series of SNSPD samples made of NbN films with different sheet resistance and a MoSi film, with various widths of the stripe. The experimental results confirmed that regardless of the material or the film resistance, the hot-spot interaction length coincides with the strip width which is a promising feature for making a 2-photon counter with high fidelity.

Search for gamma-ray line signals around the black hole at the galactic center with DAMPE observation

The adiabatic growth of a black hole (BH) may enhance the dark matter (DM) density surrounding it, causing a spike in the DM density profile. The spike around the supermassive BH at the center of the Milky Way may lead to a dramatic enhancement of the gamma-ray flux of DM annihilation from the galactic center (GC). In this work, we analyze the gamma-ray data of the innermost region (i.e., the inner 1$^\circ$) of the GC to search for potential line-like signals from the BH spike. Such line-like signals could be generated in the process of DM particles annihilating into double photons. We adopt the gamma-ray data from the Dark Matter Particle Explorer (DAMPE). Although the DAMPE has a much smaller effective area than the Fermi-LAT, the gamma-ray line search can benefit from its unprecedented high energy resolution. No significant line-like signals are found in our analysis. We derive upper limits on the cross section of the annihilation based on this non-detection. We find that despite the DAMPE's small effective area for photon detection, we can still place strong constraints on the cross section ($\left<\sigma v\right>\lesssim10^{-27}\,{\rm cm^3\,s^{-1}}$) in the spike scenario due to the very bright model-expected flux from the spike. Our results indicate that either DM does not annihilate primarily through the $\gamma\gamma$ channel in the mass range we considered or no sharp density spike is present at the GC.

Light ring images of double photon spheres in black hole and wormhole spacetimes

The silhouette of a black hole having a critical curve (an unstable bound photon orbit) when illuminated by an optically thin accretion disk whose emission is confined to the equatorial plane shows a distinctive central brightness depression (the shadow) whose outer edge consists of a series of strongly lensed, self-similar rings superimposed with the disk's direct emission. While the size and shape of the critical curve depend only on the background geometry, the pattern of bright and dark regions (including the size and depth of the shadow itself) in the image is strongly influenced by the (astro)physics of the accretion disk. This aspect makes it difficult to extract clean and clear observational discriminators between the Kerr black hole and other compact objects. In the presence of a second critical curve, however, observational differences become apparent. In this work we shall consider some spherically symmetric black hole and wormhole geometries characterized by the presence of a second critical curve, via a uniparametric family of extensions of the Schwarzschild metric. By assuming three toy models of geometrically thin accretion disks, we show the presence of additional light rings in the intermediate region between the two critical curves. The observation of such rings could represent a compelling evidence for the existence of black hole mimickers having multiple critical curves.

Double photon coincidence crosstalk reduction method for multi-nuclide Compton imaging

Compton imaging based on Compton scattering kinematics has the potential to visualize multi-nuclides by discriminating the total energy of Compton scattering and photoelectric absorption events. This feature enables us to perform multi-tracer imaging that reflects different functional information in nuclear medicine, resulting in a definitive diagnosis and being useful for biological and medical research. One of the challenges with multi-nuclide imaging is the crosstalk artifacts caused by scattered photons of higher energy gamma-rays. In this study, we investigated the potential benefits of the double photon coincidence detection as a drastic crosstalk reduction method. Coincidence detection of successive gamma-rays can differentiate nuclides and reduce the background caused by other nuclides' gamma-rays because some nuclides emit two or more gamma-rays in rapid succession. In this study, we focused on the coincidence detection of a Compton event and a photoelectric absorption event, and we showed simultaneous double photon emitter imaging of 111In and 177Lu with a ring-type Compton imaging system. The artifacts caused by other nuclides' gamma-rays were reduced by extracting Compton events coincident with photoelectric absorption events. The coincidence Compton images demonstrated a signal-to-background ratio improvement of 1.1–1.7 times over the one of no-coincidence Compton images, despite a drop in intrinsic detection efficiency of the order of 10-2. This strategy of directly reducing crosstalk will be useful in other combinations imaging such as of 111In (or 177Lu) and a positron emission tomography nuclide.

A Study of Double Dark Photons Produced by Lepton Colliders using High Performance Computing

The universe is thought to be filled with not only Standard Model (SM) matters but also dark matters. Dark matter is thought to play a major role in its construction. However, the identity of dark matter is as yet unknown, with various search methods from astrophysical observartion to particle collider experiments. Because of the cross-section that is a thousand times smaller than SM particles, dark matter research requires a large amount of data processing. Therefore, optimization and parallelization in High Performance Computing is required. Dark matter in hypothetical hidden sector is though to be connected to dark photons which carries forces similar to photons in electromagnetism. In the recent analysis, it was studied using the decays of a dark photon at collider experiments. Based on this, we studies double dark photon decays at lepton colliders. The signal channels are e+e– → AʹAʹ and e+e– → AʹAʹγ where dark photon Aʹ decays dimuon. These signal channels are based on the theory that dark photons only decay into heavily charged leptons, which can explain the muon magnetic momentum anomaly. We scanned the cross-section according to the dark photon mass in experiments. MadGraph5 was used to generate events based on a simplified model. Additionally, to get the maximum expected number of events for the double dark photon channel, the detector efficiency for several center of mass (CM) energy were studied using Delphes and MadAnalysis5 for performance comparison. The results of this study will contribute to the search for double dark photon channels at lepton colliders.

Suppressed charge carrier trap states and double photon absorption in substitutional Ta-doped TiO2-NT array

Anatase-TiO2 nanotubes (A-TiO2 NTs) represent a great opportunity for the electron transport materials used in perovskite solar cells because of several intrinsic advantages, e.g. an improved light trapping effect, an inherent ion-blocking layer, a directed electron transmission channel without interfacial random scattering. Nevertheless, its severe double-photon absorption and charge carrier trap states badly jeopardize the stability and electron transport of the perovskite active layers (PALs) under visible light, representing a major obstacle for practical applications. In this paper, we introduce Ta to substitute Ti position in A-TiO2 NTs lattice through a simple fluorination process, and reveal its underneath mechanism on suppresing the abovementioned limiting factors of charge carrier trap states and double-photon absorption. Moreover, we use the effect of double-photon absorption of studied NTs to excite the photogenerated carriers under a modulated sinusoidal visible light with small amplitude, which can perturb the transport dynamics of photo-induced charge carriers and simulate the dynamic process of charge carriers at the interface between electron transport layer (ETL) and PALs in real time. These achievements highlight the unique potential of substitutional Ta doping for interfacing engineering of perovskite solar cells.