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Colloidal quantum dots (QDs) based on CdS were directly incorporated into a sol to fabricate solid rods. Various characterization techniques were employed to study the properties of the composite rod. A comparison between the absorption, emission, and excitation spectra of the QDs in the solid rod and in solution revealed their significant and stable nature in the solid state. SEM image shows that QD particles are well interacted with the sol gel environment. The observed particle size of QDs was heteronomous approximately from 5 to 10 nm. The XRD pattern of QDs illustrates their crystalline nature. The significant spontaneous emission (SE) signal was enhanced from QDs composite rod under the excitation of a 355 nm Pico second laser source. These findings suggest that further improvements in the integration of QDs into sol gel rods could be achieved by employing a higher density of QDs in the solid rod. The fabrication of QDs composite rods with a high concentration holds the potential for testing stimulated or amplified spontaneous emission in future studies.

Spontaneous emission is one of the most fundamental out-of-equilibrium processes in which an excited quantum emitter relaxes to the ground state due to quantum fluctuations. In this process, a photon is emitted that can interact with other nearby emitters and establish quantum correlations between them, e.g., via super and subradiance effects. One way to modify these photon-mediated interactions is to alter the dipole radiation patterns of the emitter, e.g., by placing photonic crystals near them. One recent example is the generation of strong directional emission patterns – key to enhancing super and subradiance effects – in two dimensions by employing photonic crystals with band structures characterized by linear isofrequency contours and saddle points. However, these studies have predominantly used oversimplified toy models, overlooking the electromagnetic field's intricacies in actual materials, including aspects like geometrical dependencies, emitter positions, and polarization. Our study delves into the interaction between these directional emission patterns and the variables mentioned above, revealing the untapped potential to fine-tune collective quantum optical phenomena. [ABSTRACT FROM AUTHOR]

It is important to elaborate on versatile strategies for achieving the perfect nonreciprocal reflection amplification, which is the key technology of high-quality nonreciprocal photonic devices. In this work, we ingeniously design a coherent four-level N-type atomic system to harness the nonreciprocal light amplification, in which the uniform distribution of atoms is driven by two strong coupling fields and a weak probe field. In our regime, the strength of the two control fields is designed with linear variation along the x direction to destroy the spatial symmetry of the probe susceptibility, leading to the nonreciprocity of the reflection. In particular, the closed-loop transitions to amplify the probe field are due to the combined effect of the control fields and spontaneous emissions. The numerical simulation indicates that the perfect nonreciprocal reflection amplification can be realized and modulated by the appropriate settings of the control fields and the detuning, Δ c . Our results will open a new route toward harnessing nonreciprocity, which can provide more convenience and possibilities in experimental realization. [ABSTRACT FROM AUTHOR]

Analytical expressions for spontaneous emission probability in the vicinity of nanowire for the emitter oriented in axial, radial and azimuthal direction in respect to the nanowire axis, has been obtained. Directionality of emission and probability of emission have been calculated for various positions of emitter. Enhancement of the spontaneous emission probability by one order of magnitude, and formation of the sharp directionality diagram has been demonstrated. [ABSTRACT FROM AUTHOR]

[Display omitted] Optical metasurfaces, i.e., subwavelength planar nanostructures, have attracted increasing attention due to their unprecedented capabilities of molding classical light and revolutionized conventional optics by replacing bulky optical components with ultrathin, lightweight, and ultracompact meta -optics. In addition to controlling classical light, meta -optics demonstrate the potential to efficiently manipulate nonclassical light and start to enter the realm of quantum photonics. Here, we briefly overview recent advances in quantum meta -optics for generation and manipulation of nonclassical light, highlighting innovative approaches, and discuss future opportunities in this burgeoning area, ranging from fundamental research to practical applications. [ABSTRACT FROM AUTHOR]

Nanoantennas and nanocavities are widely used for at‐source manipulation of quantum emission based on the well‐known Purcell effect. Here, the configuration is explored consisting of silver (Ag) nanocube dimers positioned on Ag substrates to realize large Purcell enhancement of molecular spontaneous emission. The relationship is investigated between the cube sizes and separation gap of a nanocube dimer and the resulting Purcell enhancement, and shows the possibility of achieving the enhancement of up to 6.4 × 106. Furthermore, to experimentally demonstrate large Purcell enhancements, atomic force microscopy is used to assemble Ag nanocube dimers in the corner‐to‐corner configuration with the help of prefabricated corner‐to‐corner dielectric bricks. The decrease of the lifetime of Ru dye molecules from 91.7 ns (on a glass substrate) to the instrument response function limit (1.5 ns) after coupling with nanocube dimers is observed. This work provides a promising design and realization method for advanced photon sources, e.g., atom‐like single‐photon emitters with extremely large decay rates. [ABSTRACT FROM AUTHOR]

We theoretically study the impact of bismuth-chalcogenide microparticles on the linear absorption and dispersion properties of a four-level double-V-type quantum system. The quantum system interacts with two circularly polarized laser fields of the same frequency but with different phases and electric field amplitudes. Our study indicates that the inclusion of bismuth-chalcogenide microparticles leads to notable alterations in the absorption and dispersion spectra corresponding to one of the probe laser fields (while both fields are present). These alterations are much more dramatic compared to those induced by common plasmonic materials. By manipulating the field amplitudes as well as the phase difference between the two incident waves, the optical properties of the system can be efficiently controlled. Our study also highlights several effects, including complete optical transparency, zero absorption with nonzero dispersion, and gain without inversion. [ABSTRACT FROM AUTHOR]

We study the spontaneous emission dynamics of a quantum emitter near a topological insulator Bi 2 Se 3 spherical nanoparticle. Using the electromagnetic Green's tensor method, we find exceptional Purcell factors of the quantum emitter up to 10 10 at distances between the emitter and the nanoparticle as large as half the nanoparticle's radius in the terahertz regime. We study the spontaneous emission evolution of a quantum emitter for various transition frequencies in the terahertz and various vacuum decay rates. For short vacuum decay times, we observe non-Markovian spontaneous emission dynamics, which correspond perfectly to values of well-established measures of non-Markovianity and possibly indicate considerable dynamical quantum speedup. The dynamics turn progressively Markovian as the vacuum decay times increase, while in this regime, the non-Markovianity measures are nullified, and the quantum speedup vanishes. For the shortest vacuum decay times, we find that the population remains trapped in the emitter, which indicates that a hybrid bound state between the quantum emitter and the continuum of electromagnetic modes as affected by the nanoparticle has been formed. This work demonstrates that a Bi 2 Se 3 spherical nanoparticle can be a nanoscale platform for strong light–matter coupling. [ABSTRACT FROM AUTHOR]

This work investigates the UV and visible chemiluminescence signatures of laminar ammonia-hydrogen-air flames. A counterflow burner was used to stabilize flat and steady premixed ammonia-hydrogen-air twin-flames for wide ranges of ammonia fuel fractions (0.55 ≤ X NH 3 ≤ 0.90), equivalence ratios (0.35 ≤ ϕ ≤ 1.70), and strain rates (50 ≤ a ≤ 300 / s). The chemiluminescence spectra in the UV and visible regions were measured. The important contributors to the chemiluminescence of ammonia-hydrogen-air flames were first identified and their sensitivities to equivalence ratio and ammonia fuel fraction were then quantified. Promising ratios of chemiluminescence intensities for the non-intrusive optical sensing of equivalence ratio and ammonia fuel fraction in premixed ammonia-hydrogen-air flames were also identified. Among the 36 ratios that could be formed with the 9 contributors to chemiluminescence that were defined, 3 are particularly promising, namely, OH*/NO*, OH*/ violet (violet refers to the 350 to 400 nm range), and red/blue (blue and red refer to the 450 to 500 nm and 650 to 750 nm ranges, respectively). Ratios OH*/NO* and OH*/ violet were found to provide suitable measures of equivalence ratio for lean and rich ammonia-hydrogen-air flames, respectively, because these ratios are very sensitive to equivalence ratio, are insensitive to ammonia fuel fraction, and are marginally sensitive to strain rate. Once equivalence ratio is known, the ammonia fuel fraction can then be measured with ratio red/blue because it is sensitive to the ammonia fuel fraction and it is globally insensitive to strain rate. [ABSTRACT FROM AUTHOR]

We demonstrate heterogeneous integration of active semiconductor materials into the conventional passive metal-insulator-metal (MIM) waveguides to provide compact on-chip light generation and detection capabilities for chip-scale active nanophotonic platforms. Depending on its bias conditions, a metal-semiconductor-metal section can function as either a light emitting diode or a photodetector directly connected to the MIM waveguides. We experimentally verify the independent and combined operations of electrically-driven on-chip light sources and photodetectors.

It is important to elaborate on versatile strategies for achieving the perfect nonreciprocal reflection amplification, which is the key technology of high-quality nonreciprocal photonic devices. In this work, we ingeniously design a coherent four-level N-type atomic system to harness the nonreciprocal light amplification, in which the uniform distribution of atoms is driven by two strong coupling fields and a weak probe field. In our regime, the strength of the two control fields is designed with linear variation along the x direction to destroy the spatial symmetry of the probe susceptibility, leading to the nonreciprocity of the reflection. In particular, the closed-loop transitions to amplify the probe field are due to the combined effect of the control fields and spontaneous emissions. The numerical simulation indicates that the perfect nonreciprocal reflection amplification can be realized and modulated by the appropriate settings of the control fields and the detuning, Δc. Our results will open a new route toward harnessing nonreciprocity, which can provide more convenience and possibilities in experimental realization.

We study theoretically the emergence of an anisotropic Purcell factor in random two-dimensional fractal aggregates of nanoparticles. These nanoparticles can either be metallic nanoparticles made of silver, which exhibit surface plasmon resonances, or high-index dielectric nanoparticles like silicon, which possess optical Mie resonances. To calculate the spontaneous emission rates of a quantum emitter, we utilize the electromagnetic Green's tensor within the framework of the coupled-dipole method. Our findings reveal that the Purcell factor exhibits spatial variations, with certain regions, referred to as hot spots, displaying high values for dipoles oriented within the plane of the fractal aggregate, while dipoles oriented vertically to the aggregate have values close to unity. This anisotropy in the Purcell factor leads to significant quantum interference effects in the spontaneous emission paths of multi-level quantum emitters. As a consequence of this quantum interference, we demonstrate the occurrence of population trapping in a V-type quantum emitter embedded within a fractal aggregate of nanoparticles which cannot otherwise take place if the emitter is placed in vacuum. [ABSTRACT FROM AUTHOR]

An improved technique for thermal resistance measurement of edge-emitting diode lasers using spontaneous emission spectra, collected through the opening in the n-contact within the range of operating currents, has been proposed. The advantage of the proposed technique is that systematic errors typical for measurements based on lasing spectra are excluded. The accuracy of the method was verified by measuring the dependence of the thermal resistance on the cavity length for diode lasers with 100 μm strip width. Obtained results are in good agreement with the model, and the minimum measurement error was ±0.1 K/W. The proposed technique can be used in metrological support of fabrication process of semiconductor lasers. [ABSTRACT FROM AUTHOR]

We examine theoretically the effect of bismuth chalcogenide microparticles on the spontaneous emission of a double-V-type quantum emitter in free space. We have found, in particular, that the presence of a single microparticle causes a high degree of quantum interference in the way the quantum emitter releases energy in the process of spontaneous emission. This, in turn, leads to significant changes in the spectrum of the emitted energy. The quantum emitter's initial state is crucial to how the energy is released in the presence of the microparticle. This observation has potential implications for quantum computing, particularly for reading the state of atomic qubits. When two microparticles are present, the effect is more pronounced, particularly when the quantum emitter is located in the gap between the particles. [ABSTRACT FROM AUTHOR]

We propose a method of analysis of spontaneous emission of a quantum emitter (an atom, a luminescence center, a quantum dot) inside or in vicinity of a cylinder. At the focus of our method are analytical expressions for the scattering matrix of the cylindrical nanoobject. We propose the approach to electromagnetic field quantization based of eigenvalues and eigenvectors of the scattering matrix. The method is applicable for calculation and analysis of spontaneous emission rates and angular dependences of radiation for a set of different systems: semiconductor nanowires with quantum dots, plasmonic nanowires, cylindrical hollows in dielectrics and metals. Relative simplicity of the method allows obtaining analytical and semi-analytical expressions for both cases of radiation into external medium and into guided modes.

Spontaneous photon emission can be drastically modified by placing quantum emitters (QEs) in nanostructured environment, resulting in dramatically enhanced emission rates due to the Purcell effect along with generation of collimated single‐photon beams propagating in design directions and featuring well‐defined polarization states. Recent advances in single‐photon generation engineering demonstrate fascinating possibilities for the directional emission of photons with designed spin and orbital angular momenta, a development that is crucial for exploiting the full potential of QEs within quantum information technologies. Although many different nanostructured configurations are considered for hosting QEs to mold single‐photon beams, collimating of the latter requires relatively large interaction areas to be involved, thus making the use of metasurfaces preferential. Furthermore, optical metasurfaces consisting of planar arrays of resonant nanoscale elements offer complete control over optical fields and thereby design freedom in shaping single‐photon emission. Here, recent advances in exploiting quantum optical metasurfaces for achieving enhanced and directional emission of single photons with specified polarization properties are overviewed. Special attention is paid to hybrid plasmon–QE coupled metasurfaces based on efficient QE coupling to surface plasmon modes that are subsequently outcoupled by designed dielectric nanoarrays into free propagating photon emission. Perspectives for future developments of metasurface empowered QEs are also discussed. [ABSTRACT FROM AUTHOR]

Converting ionizing radiation into visible light is essential in a wide range of fundamental and industrial applications, such as electromagnetic calorimeters in high‐energy particle detectors, electron detectors, image intensifiers, and X‐ray imaging. These different areas of technology all rely on scintillators or phosphors, i.e., materials that emit light upon bombardment by high‐energy particles. In all cases, the emission is through spontaneous emission. The fundamental nature of spontaneous emission poses limitations on all these technologies, imposing an intrinsic trade‐off between efficiency and resolution in all imaging applications: thicker phosphors are more efficient due to their greater stopping power, which however comes at the expense of image blurring due to light spread inside the thicker phosphors. Here, the concept of inverse‐designed nanophotonic scintillators is proposed, which can overcome the trade‐off between resolution and efficiency by reshaping the intrinsic spontaneous emission. To exemplify the concept, multilayer phosphor nanostructures are designed and these nanostructures are compared to state‐of‐the‐art phosphor screens in image intensifiers, showing a threefold resolution enhancement simultaneous with a threefold efficiency enhancement. The enabling concept is applying the ubiquitous Purcell effect for the first time in a new context—for improving image resolution. Looking forward, this approach directly applies to a wide range of technologies, including X‐ray imaging applications. [ABSTRACT FROM AUTHOR]

In this paper, we have studied the squeezing and entanglement properties of the light generated by three-level atoms available in an open cavity and pumped to the top level by electron bombardment at a constant rate. We have conducted our analysis by putting the noise operators associated with the vacuum reservoir in normal order by considering the interaction of the three-level atoms with the vacuum reservoir outside the cavity. Applying the large-time approximation scheme, we have obtained the steady-state solutions of the evolution equations for the expectation values of the atomic operators and the quantum Langevin equations for the cavity mode operators. Applying the solutions of the equations of evolution for the expectation values of the atomic operators and the quantum Langevin equations for the cavity mode operators, the squeezing properties, entanglement amplification, and the normalized second-order correlation function of the cavity radiation are described. The three-level laser generates squeezed light under certain conditions, with maximum intracavity squeezing being 50 % below the vacuum-state level. Moreover, it is found that the presence of spontaneous emission increases the quadrature squeezing and entanglement. It is found that the squeezing and entanglement in the two-mode light are directly related. As a result, an increase in the degree of squeezing directly leads to an increase in the degree of entanglement and vice versa. This shows that whenever there is squeezing in the two-mode light, there exists an entanglement in the system. In addition, it is shown that the photons in the laser cavity are highly correlated, and the degree of photon number correlation increases with the spontaneous emission decay constant, γ . [ABSTRACT FROM AUTHOR]

The emission features of Cdse/ZnS quantum dots doped step-index polymer optical fibers are computationally analyzed in this paper. Spontaneous emission and amplified spontaneous emission were calculated by a theoretical model based on the rate equations in terms of time, fiber length, and wavelength. All the calculated parameters are derived from experiments. Through the comparative analysis of the calculated and experimental results of spontaneous emission, we found that the pump power and overlap between the emission and absorption cross-sections may be the two main reasons for the red shift of the output spectra. When the pump power exceeds the threshold of amplified spontaneous emission, the width of the output spectra will rapidly decrease, the output wavelength will fall back toward the maximum emission cross-section, and the final output wavelength will still be affected by the doping concentration and pump power, while amplified spontaneous emission will not be generated when the total number of doped quantum dots is less than 1.27 × 1012. [ABSTRACT FROM AUTHOR]

This work reports on the chemiluminescence signature of premixed ammonia-methane-air swirling flames. Wide ranges of equivalence ratios (0.6 ≤ Φ ≤ 1.3), ammonia fractions in the fuel blend (0 ≤ X NH3 ≤ 0.70), and Reynolds numbers (10,000 ≤ Re ≤ 40,000) were investigated to understand effects of these parameters on the light emitted by these flames. Excited radicals contributing to chemiluminescence in the UV and visible ranges were confirmed, namely NO*, OH*, NH*, CN*, CO 2 *, CH*, and NH 2 *. With non-intrusive flame monitoring in mind, various ratios of chemiluminescence intensities were carefully studied because these allow removing effects of time-varying flame surface area that is inherent in turbulent flames. Consistent with previous findings in laminar flames, ratios CN*/OH*, CN*/NO*, and NH*/CH* were found to be promising candidates. Ratios CN*/OH* and CN*/NO* were identified as potential surrogates for equivalence ratio if X NH3 ≥ 0.20 and 0.05 ≤ X NH3 ≤ 0.50, respectively. Ratio NH*/CH* was identified as a potential surrogate for the ammonia fraction in the fuel blend provided that equivalence ratio is roughly known. Ratio Blue /NH 2 *, obtained exclusively from measurements in the visible range, is another interesting surrogate for the ammonia fraction but its sensitivity to Reynolds number may limits its range of applications. Trends of measured exhaust NO concentration with equivalence ratio and ammonia fraction were found to qualitatively match that of NO*, NH*, and CN*, implying that emissions from these excited radicals could be used to monitor the NO performance of practical ammonia-methane-air flames. [ABSTRACT FROM AUTHOR]

We suggest a method for spontaneous emission in a four-level atomic system driven by vortex light beams that generates structured light. The atom in consideration has two excited states that are closely spaced and linked to the ground state by two control fields. The excited states have the ability to spontaneously decay into a fourth level, known as a metastable state. We demonstrate that in such configuration the orbital angular momentum (OAM) of the vortex pumping light beams can be transferred from both control fields to the spontaneously emitted photons by analyzing the spontaneously generated output spectrum. Furthermore, we discover that by spontaneous emission, the azimuthal phase dependency may be used to develop different kinds of structured light, the spatial intensity distribution of which can be significantly modified by varying the OAM of the control fields. The concept we propose could indeed have significant implications in fields such as optical communication and optical storage, where structured light plays a crucial role. • The atomic system generates structured light through interference between two decay channels via superposition of initial atomic states. • This emitted photon holds information about the new structured light's azimuthal quantum (winding) number. • We employ semi-classical techniques in a steady-state regime, guided by the Weigner-Weisskopf theory, to derive an analytical formula for the generated spontaneous spectrum. • This method offers a novel and straightforward solution that holds great promise for applications in quantum information technology. [ABSTRACT FROM AUTHOR]

We theoretically study the impact of bismuth-chalcogenide microparticles on the linear absorption and dispersion properties of a four-level double-V-type quantum system. The quantum system interacts with two circularly polarized laser fields of the same frequency but with different phases and electric field amplitudes. Our study indicates that the inclusion of bismuth-chalcogenide microparticles leads to notable alterations in the absorption and dispersion spectra corresponding to one of the probe laser fields (while both fields are present). These alterations are much more dramatic compared to those induced by common plasmonic materials. By manipulating the field amplitudes as well as the phase difference between the two incident waves, the optical properties of the system can be efficiently controlled. Our study also highlights several effects, including complete optical transparency, zero absorption with nonzero dispersion, and gain without inversion.

We study the spontaneous emission dynamics of a quantum emitter near a topological insulator Bi2Se3 spherical nanoparticle. Using the electromagnetic Green’s tensor method, we find exceptional Purcell factors of the quantum emitter up to 1010 at distances between the emitter and the nanoparticle as large as half the nanoparticle’s radius in the terahertz regime. We study the spontaneous emission evolution of a quantum emitter for various transition frequencies in the terahertz and various vacuum decay rates. For short vacuum decay times, we observe non-Markovian spontaneous emission dynamics, which correspond perfectly to values of well-established measures of non-Markovianity and possibly indicate considerable dynamical quantum speedup. The dynamics turn progressively Markovian as the vacuum decay times increase, while in this regime, the non-Markovianity measures are nullified, and the quantum speedup vanishes. For the shortest vacuum decay times, we find that the population remains trapped in the emitter, which indicates that a hybrid bound state between the quantum emitter and the continuum of electromagnetic modes as affected by the nanoparticle has been formed. This work demonstrates that a Bi2Se3 spherical nanoparticle can be a nanoscale platform for strong light–matter coupling.

The Purcell effect is commonly used to increase the spontaneous emission rate by modifying the local environment of a light emitter. Here, we propose a silicon dielectric cuboid nanoantenna for simultaneously enhancing electric dipole (ED), magnetic dipole (MD) and electric quadrupole (EQ) emission. We study the scattering cross section, polarization charge distribution, and electromagnetic field distribution for electromagnetic plane wave illuminating the silicon dielectric cuboid nanoantenna, from which we have identified simultaneous existence of ED, MD and EQ resonance modes in this nanoantenna. We have calculated the Purcell factor of ED, MD and EQ emitters with different moment orientations as a function of radiation wavelength by placing these point radiation source within the nanoantenna, respectively. We find that the resonances wavelengths of the Purcell factor spectrum are matching with the resonance modes in the nanoantenna. Moreover, the maximum Purcell factor of these ED, MD and EQ emitters is 18, 150 and 118 respectively, occurring at the resonance wavelength of 475, 750, and 562 nm, respectively, all within the visible range. The polarization charge distribution features allow us to clarify the excitation and radiation of these resonance modes as the physical origin of large Purcell factor simultaneously occurring in this silicon cuboid nanoantenna. Our theoretical results might help to deeply explore and design the dielectric nanoantenna as an ideal candidate to enhance ED, MD and EQ emission simultaneously with very small loss in the visible range, which is superior than the more popular scheme of plasmonic nanoantenna.

Hollow waveguide (HWG) as an absorption cell for gas spectral sensing has the advantages of low transmission loss, fast response speed, and high path length to volume ratio. However, due to the tubular structure of the HWG, the spontaneous emission generated in the HWG will be transmitted together with the incident laser, which reduces the measured absorbance. We measured and verified the spontaneous emission at the outlet of the HWG by basing on the laser gas absorption spectroscopy and combining with the distinguished polarization characteristics of laser and spontaneous emission. Then, we quantitatively determined the intensity distribution of the spontaneous emission output from the HWG based on the infrared (IR) imaging using an IR camera. We also investigated the effect of the spontaneous emission on the measured absorbance as a function of the HWG length by comparative experiments. The effect exponentially decreases as the HWG length increases since the increased loss. The method could be used for designing or optimizing of HWG-based sensors.

In this paper, a hybrid photonic-plasmonic resonator is proposed. The device consists of a partially encapsulated 1D photonic crystal waveguide and a plasmonic nanoparticle to yield high radiation efficiency for integrated photonic platforms, owing to a high Q-factor and a small mode volume. The design of the resonator is accomplished in two consecutive steps: first of all, a partially encapsulated photonic crystal nanobeam with a robust mechanical stability and a high-Q factor is prepared; secondly, a plasmonic nanoparticle is placed on the surface of the nanobeam to interact the optical mode with the localized surface plasmons of the gold nanoparticle which is being present in the vicinity of the radiating dipole. Strongly enhanced electromagnetic field, regenerated through the optical mode field inside the hybrid resonator, enables to reduce the optical mode volume of the device and significantly enhance the Purcell factor.

The impact of ring-shaped collector contact (RCC) on total ionizing dose (TID) susceptibility of 40-V vertical n-p-n bipolar transistors is investigated. The 60Co $\gamma $ -ray irradiation experiment shows that the devices with RCC suffer less current gain degradation than their counterparts with conventional collector contact structure, which is independent of the emitter area and bias condition during irradiation. Technology computer-aided design (TCAD) simulation results indicate that the enhancement in radiation tolerance of the RCC devices should be attributed to the mitigation of trap-assisted carrier recombination at the Si/SiO2 interfaces near emitter–base (EB) junction rather than the concentration or distribution variations of radiation-induced traps. Moreover, the mitigation of carrier recombination in RCC devices could result from the creation of new current flow paths that suppress the diffusion of injected electrons toward the trap-enriched Si/SiO2 interfaces. [ABSTRACT FROM AUTHOR]

Metasurfaces have the ability to control classical and non‐classical states of light to achieve controlled emission even at the level of a single emitter. Here, the Kerker condition induced emission rate enhancement with strong directivity is unveiled from a single emitter integrated within a dielectric metasurface consisting of silicon nano‐disks. The simulation and analytical calculations attest the Kerker condition with unidirectional light scattering evolved by the constructive interference between electric dipole, toroidal dipole, and the magnetic quadrupole. The results evince spatially‐dependent enhanced local density of optical states, which reciprocates localized field intensity. The emission rate enhancement of 400 times is achieved close to the zero phonon line of the nitrogen‐vacancy center with superior emission directivity and collection efficiency. The results have implications in on‐demand single photon generation, spin‐photon interface, many‐body interactions, and strong coupling. [ABSTRACT FROM AUTHOR]

In this work, we have investigated perovskite-based solar cells (PSCs) with seven different organic hole transport layers (HTLs), which include spiro-2,2’,7,7’-Tetr- akis-(N, N-di-4-methoxyphenylamino) −9,9’-spirobifluorene (OMeTAD), poly(triaryl amine) (PTAA), poly (3,3”’-dialkyl- quaterthiophene) (PQT), poly (3, 4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), poly (3-hexylthioph- ene-2,5-diyl) (P3HT), Poly [2-methoxy-5-(2’-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV), and n-Propyl Bromide (nPB). This article reports the impact of several device parameters, such as perovskite layer defect density, and thickness, on the solar cell performance. We examined the device performance for the PSC device architecture, i.e., fluorine-doped tin oxide (FTO)/TiO2/CH3NH3PbI3/HTLs/Au. For this study, numerical simulation has been performed and optimized for optimum absorber layer thickness and defect density. In this study, we report the power conversion efficiency (PCE) with various HTLs, such as 10.01% for MEH-PPV, 13.94% for PEDOT:PSS, 14.75% for P3HT, 15.42% for PQT, 15.74% for NPB, 17.08% for PTAA, and 17.11% for spiro-OMeTAD at an optimized thickness of 300 nm. It is asserted that there is an enhancement in the photovoltaic performance observed while using spiro-OMeTAD and PTAA as HTL. PSC using spiro-OMeTAD as HTL shows exceptional performance compared to other HTLs. Other parameters obtained for PSC using spiro-OMeTAD are ${V}_{OC}$ of 1.10 V, ${J}_{SC}$ of 20.772 mA/cm2, FF of 0.74%, and PCE of 17.11%. The elicited simulation results suggest that spiro-OMeTAD is the most promising candidate for HTL to fabricate low-cost, highly efficient, and low-temperature processed hybrid PSC. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have garnered considerable attention due to their advantageous properties, including tunable bandgap, prominent carrier mobility, tunable response and absorption spectral band, and so forth. The above-mentioned properties ensure that 2D materials hold great promise for various high-performance infrared (IR) applications, such as night vision, remote sensing, surveillance, target acquisition, optical communication, etc. Thus, it is of great significance to acquire better insight into IR applications based on 2D materials. In this review, we summarize the recent progress of 2D materials in IR light emission device applications. First, we introduce the background and motivation of the review, then the 2D materials suitable for IR light emission are presented, followed by a comprehensive review of 2D-material-based spontaneous emission and laser applications. Finally, further development directions and challenges are summarized. We believe that milestone investigations of 2D-material-based IR light emission applications will emerge soon, which are beneficial for 2D-material-based nano-device commercialization. [ABSTRACT FROM AUTHOR]

We investigate the phenomenon of quantum interference in spontaneous emission for a three-level V-type quantum emitter placed between two bismuth-chalcogenide (Bi 2 Te 3 , Bi 2 Se 3 ) microspheres. In particular, we find that the degree of quantum interference can become as high as 0.994, a value which is attributed to the strong dependence of the spontaneous emission rate on the orientation of an atomic dipole relative to the surfaces of the microspheres, at the excitation frequencies of phonon-polariton states of the bismuth-chalcogenide microspheres (anisotropic Purcell effect). As a consequence of the high degree of quantum interference, we observe the occurrence of strong population trapping in the quantum emitter. To the best of our knowledge, the reported values of the degree of quantum interference are record values and are obtained for a relatively simple geometrical setup such as that of a microparticle dimer. [ABSTRACT FROM AUTHOR]

It has been shown that the spontaneous emission rate of photons by free electrons, unlike stimulated emission, is independent of the shape or modulation of the quantum electron wavefunction (QEW). Nevertheless, here we show that the quantum state of the emitted photons is non-classical and does depend on the QEW shape. This non-classicality originates from the shape dependent off-diagonal terms of the photon density matrix. This is manifested in the Wigner distribution function and would be observable experimentally through homodyne detection techniques as a squeezing effect. Considering a scheme of electrons interaction with a single microcavity mode, we present a QED formulation of spontaneous emission by multiple modulated QEWs through a build-up process. Our findings indicate that in the case of a density modulated QEWs beam, the phase of the off-diagonal terms of the photon state emitted by the modulated QEWs is the harbinger of bunched beam superradiance, where the spontaneous emission is proportional to N_e^2 . This observation offers a potential for enhancement of other quantum electron interactions with quantum systems by a modulated QEWs beam carrying coherence and quantum properties of the modulation., (Creative Commons Attribution license.)

Abstract Single-photon source in micro- or nanoscale is the basic building block of on-chip quantum information and scalable quantum network. Enhanced spontaneous emission based on cavity quantum electrodynamics (CQED) is one of the key principles of realizing single-photon sources fabricated by micro- or nanophotonic cavities. Here we mainly review the spontaneous emission of single emitters in micro- or nanostructures, such as whispering gallery microcavities, photonic crystals, plasmon nanostructures, metamaterials, and their hybrids. The researches have enriched light-matter interaction as well as made great influence in single-photon source, photonic circuit, and on-chip quantum information.

The defect centers in solid-state materials especially the nitrogen-vacancy (NV) centers in diamond have shown a tremendous potential for their utilization in quantum technology applications. However, they exhibit certain drawbacks such as the feeble zero phonon line with huge phonon contribution and the higher lifetime values. Here, we present a novel approach to control the spontaneous emission from NV centers in nanodiamond using engineered self-assembled photonic crystals. Using two complimentary emission measuring geometries at room temperature, we show a 63% suppression and 17% enhancement of NV center emission intensity using photonic stopgap, supported with simulations. The emission rates are modified in a broad spectral range of NV center emission and are consistent with the Barnett–Loudon sum rule. The results are crucial for emerging quantum technologies using NV centers in diamond.