Photon Emission Characteristics Research Articles

Color-Tunable Mixed-Cation Perovskite Single Photon Emitters

Quantum photonics technologies, like wavelength division multiplexing (WDM), for high-rate quantum key distribution require narrowband, spectrally tunable single photon emitters. Physical methods that rely on the application of large mechanical strain to epitaxial quantum dots or electric and magnetic fields to color centers in 2D metal dichalcogenides provide limited spectral tunability. Here we adopt a chemical approach to synthesize a family of colloidal mixed-cation perovskite quantum dots (Cs1–xFAxPbBr3) that show highly photostable, compositionally tunable single photon emission at room temperature, spanning more than 30 nm in the visible wavelength spectral range. We find that tailoring the stoichiometry of the organic formamidinium (FA) cation in all-inorganic cesium lead bromide (CsPbBr3) perovskite quantum dots detunes the electronic band structure while preserving their excellent single photon emission characteristics. We argue that the mixed-cation perovskite quantum dots studied in this work offer a new platform for the realization of color-tunable single photon emitters that could be readily integrated in a diversity of quantum photonic devices.

Dirac fermion optics and directed emission from single- and bilayer graphene cavities

High-mobility graphene hosting massless charge carriers with linear dispersion provides a promising platform for electron optics phenomena. Inspired by the physics of dielectric optical micro-cavities where the photon emission characteristics can be efficiently tuned via the cavity shape, we study corresponding mechanisms for trapped Dirac fermionic resonant states in deformed micro-disk graphene billiards and directed emission from those. In such graphene devices a back-gate voltage provides an additional tunable parameter to mimic different effective refractive indices and thereby the corresponding Fresnel laws at the boundaries. Moreover, cavities based on single-layer and double-layer graphene exhibit Klein- and anti-Klein tunneling, respectively, leading to distinct differences with respect to dwell times and resulting emission profiles of the cavity states. Moreover, we find a variety of different emission characteristics depending on the position of the source where charge carriers are fed into the cavites. Combining quantum mechanical simulations with optical ray tracing and a corresponding phase-space analysis, we demonstrate strong confinement of the emitted charge carriers in the mid field of single-layer graphene systems and can relate this to a lensing effect. For bilayer graphene, trapping of the resonant states is more efficient and the emission characteristics do less depend on the source position.

Influence of the constant electric field on the photon emission characteristics of selected utility cultivars of the Camellia plant

The article presents the research results related to the measurement of the reaction biological substance to extortion, which was a permanent field electric. To identify the degree of reaction of a biological substance, the phenomenon of generating short light pulses was used, which was registered with a photomultiplier tube turned on in appropriate measurement path. For the research, dried leaves of the Camellia plant were used, which was subjected to the influence of a constant electric field in two voltage combinations, i.e. 1kV and 3kV, and then, using the method of counting single photons, their number was summed in a 1800-second time interval. Significant differences in the number of registered photons were found between the drought subjected to the action of a constant electric field and the drought, where this interaction was not applied. It should be noted that a differentiation was also noted between the dried plants that were subjected to a constant electric field, but with different voltage. Therefore, it is possible, experimentally confirmed, to parameterize the analyzed substance by measuring the total photon emission and identifying selected properties of the substance based on the photon emission characteristics during the measurement..

Fiber-based unidirectional emission with enhanced extraction efficiency of a single quantum dot from an optimized structure

III-nitride materials play a significant role in adjusting the emission of quantum emitters. In quantum networks, photons are used as flying qubits, and Gallium nitride (GaN) semiconductor quantum dots (QDs) have shown powerful single photon emission characteristics. Due to the high refractive index contrast of the semiconductor quantum dots, the extraction efficiency is low. In this paper, we numerically simulate the unidirectional emission quantum dot of InGaN formed on the apex of a silver-coated GaN nano-pyramid structure using FDTD software, and the structure is optimized to form an enhancement of extraction efficiency at a wavelength of 520 nm, its extraction efficiency has been improved from 91.35% to 97.2%. Most of the extracted light from the quantum dots is directed to the bottom of the pyramid with high directivity and incident into the single-mode optical fiber. The new structure is expected to be applied to unidirectional, bright and high extraction efficiency quantum emitters in quantum communication systems.

Quantum acousto-optic control of light-matter interactions in nanophotonic networks

We analyze the coupling of atoms or atom-like emitters to nanophotonic waveguides in the presence of propagating acoustic waves. Specifically, we show that strong index modulations induced by such waves can drastically modify the effective photonic density of states and thereby influence the strength, the directionality, as well as the overall characteristics of photon emission and absorption processes. These effects enable a complete dynamical control of light-matter interactions in waveguide structures, which even in a two dimensional system can be used to efficiently exchange individual photons along selected directions and with a very high fidelity. Such a quantum acousto-optical control provides a versatile tool for various quantum networking applications ranging from the distribution of entanglement via directional emitter-emitter interactions to the routing of individual photonic quantum states via acoustic conveyor belts.

Single photon emissions from InAs/GaAs quantum dots embedded in GaAs/SiO2 hybrid microdisks

An approach to integrate InAs/GaAs quantum dots (QDs) active layer on SiO2/Si chip for single photon emitter is demonstrated. The QDs are embedded in GaAs/SiO2 hybrid whispering gallery mode microdisks with the diameters of 10 and 5 μm, corresponding to the quality factors (Q) of 2287 ± 167 and 4366 ± 208, respectively. Temperature tuning QD-cavity resonance is observed. The cavity-enhanced exciton spontaneous emission and single photon emission characteristics are studied.

Eigen-analysis reveals components supporting super-resolution imaging of blinking fluorophores

This paper presents eigen-analysis of image stack of blinking fluorophores to identify the components that enable super-resolved imaging of blinking fluorophores. Eigen-analysis reveals that the contributions of spatial distribution of fluorophores and their temporal photon emission characteristics can be completely separated. While cross-emitter cross-pixel information of spatial distribution that permits super-resolution is encoded in two matrices, temporal statistics weigh the contribution of these matrices to the measured data. The properties and conditions of exploitation of these matrices are investigated. Con-temporary super-resolution imaging methods that use blinking for super-resolution are studied in the context of the presented analysis. Besides providing insight into the capabilities and limitations of existing super-resolution methods, the analysis shall help in designing better super-resolution techniques that directly exploit these matrices.

Resonantly Enhanced Emission from a Luminescent Nanostructured Waveguide.

Controlling the characteristics of photon emission represents a significant challenge for both fundamental science and device technologies. Research on microcavities, photonic crystals, and plasmonic nanocavities has focused on controlling spontaneous emission by way of designing a resonant structure around the emitter to modify the local density of photonic states. In this work, we demonstrate resonantly enhanced emission using luminescent nanostructured waveguide resonance (LUNAR). Our concept is based on coupling between emitters in the luminescent waveguide and a resonant waveguide mode that interacts with a periodic nanostructure and hence outcouples via diffraction. We show that the enhancement of resonance emission can be controlled by tuning the design parameters. We also demonstrate that the enhanced emission is attributable to the accelerated spontaneous emission rate that increases the probability of photon emission in the resonant mode, accompanied by enhanced the local density of photonic states. This study demonstrates that nanostructured luminescent materials can be designed to exhibit functional and enhanced emission. We anticipate that our concept will be used to improve the performance of a variety of photonic and optical applications ranging from bio/chemical sensors to lighting, displays and projectors.

Optimal photon antibunching in a quantum-dot–bimodal-cavity system

We theoretically investigate the photon statistics in a cavity quantum electrodynamics system of a single quantum dot coupled to a bimodal nanocavity. It is shown in a recent work [A. Majumdar, M. Bajcsy, A. Rundquist, and J. Vu\ifmmode \check{c}\else \v{c}\fi{}kovi\ifmmode \acute{c}\else \'{c}\fi{}, Phys. Rev. Lett. 108, 183601 (2012)] that the system can generate strongly sub-Poissonian light when one of the cavity modes is driven coherently and resonantly. We study the two-mode coherent driving regime of the coupled system. The effect of additional cavity mode driving on statistical characteristics of photon emission is presented by evaluating the zero-delay second-order correlation function ${g}^{2}$(0). The antibunching character can be optimized by regulating the ratio between driving strengths of two cavity modes to achieve optimal combination of superbunched and coherent light. As a result ${g}^{2}$(0) can be reduced up to several orders of magnitude [${g}^{2}$(0)$\phantom{\rule{0.16em}{0ex}}\ensuremath{\sim}\phantom{\rule{0.16em}{0ex}}$10${}^{\ensuremath{-}7}$] with proper system parameters, compared with the one-mode driving system [${g}^{2}$(0)$\phantom{\rule{0.16em}{0ex}}\ensuremath{\sim}\phantom{\rule{0.16em}{0ex}}$0.1].

GaAs/AlGaAs heterostructure nanowires studied by cathodoluminescence

In this report we explore the structural and optical properties of GaAs/AlGaAs heterostructure nanowires grown by metalorganic vapour phase epitaxy using gold seed-particles. The optical studies were done by low-temperature cathodoluminescence (CL) in a scanning electron microscope (SEM). We perform a systematic investigation of how the nanowire growth-temperature affects the total photon emission, and variations in the emission energy and intensity along the length of the nanowires. The morphology and crystal structures of the nanowires were investigated using SEM and transmission electron microscopy (TEM). In order to correlate specific photon emission characteristics with variations in the nanowire crystal structure directly, TEM and spatially resolved CL measurements were performed on the same individual nanowires. We found that the main emission energy was located at around 1.48 eV, and that the emission intensity was greatly enhanced when increasing the GaAs nanowire core growth temperature. The data strongly suggests that this emission energy is related to rotational twins in the GaAs nanowire core. Our measurements also show that radial overgrowth by GaAs on the GaAs nanowire core can have a deteriorating effect on the optical quality of the nanowires. Finally, we conclude that an in situ pre-growth annealing step at a sufficiently high temperature significantly improves the optical quality of the nanowires.

A single-photon fault-detection method for nanocircuits that use GaN material

As the complexity of nanocircuits continues to increase, developing tests for them becomes more difficult. Failure analysis and the localization of internal test points within nanocircuits are already more difficult than for conventional integrated circuits. In this paper, a new method of testing for faults in nanocircuits is presented that uses single-photon detection to locate failed components (or failed signal lines) by utilizing the infrared photon emission characteristics of circuits. The emitted photons, which can carry information about circuit structure, can aid the understanding of circuit properties and locating faults. In this paper, in order to enhance the strength of emitted photons from circuit components, test vectors are designed for circuits’ components or signal lines. These test vectors can cause components to produce signal transitions or switching behaviors according to their positions, thereby increasing the strength of the emitted photons. A multiple-valued decision diagram (MDD), in the form of a directed acrylic graph, is used to produce the test vectors. After an MDD corresponding to a circuit is constructed, the test vectors are generated by searching for specific paths in the MDD of that circuit. Experimental results show that many types of faults such as stuck-at faults, bridging faults, crosstalk faults, and others, can be detected with this method.

Model of the Optical Emission of a Driven Semiconductor Quantum Dot: Phonon-Enhanced Coherent Scattering and Off-Resonant Sideband Narrowing

We study the crucial role played by the solid-state environment in determining the photon emission characteristics of a driven quantum dot. For resonant driving, we predict a phonon enhancement of the coherently emitted radiation field with increasing driving strength, in stark contrast to the conventional expectation of a rapidly decreasing fraction of coherent emission with stronger driving. This surprising behavior results from thermalization of the dot with respect to the phonon bath and leads to a nonstandard regime of resonance fluorescence in which significant coherent scattering and the Mollow triplet coexist. Off resonance, we show that despite the phonon influence, narrowing of dot spectral sideband widths can occur in certain regimes, consistent with an experimental trend.

Fluorescence photon measurements from single quantum dots on an optical nanofiber

We experimentally investigate the fluorescence photon emission characteristics for single q-dots by using optical nanofibers. We demonstrate that single q-dots can be deposited along an optical nanofiber systematically and reproducibly with a precision of 5 μm. For single q-dots on an optical nanofiber, we measure the fluorescence photon numbers coupled into the nanofiber and the normalized photon correlations, by varying the excitation laser intensity. We estimate the fluorescence photon coupling efficiency into the nanofiber guided modes.

Trade-Off between Hot Carrier Effect and Current Driving Capability Due to Drain Contact Structures in Deep Submicron MOSFETs

We, for the first time, have analyzed the contact structure dependent hot carrier effect in quarter-micron n-channel metal semiconductor field effect transistor (nMOSFETs). We measured the DC stressed current degradation characteristics, the substrate current characteristics, and the hot carrier induced photon emission characteristics of MOSFETs with W/L=20/0.25 microns having various contact structures. From experiments, we consistently observed that the degradation increases rapidly as the number of contact holes increases while current driving capability improves moderately. We also calculated the average electron temperature in devices with different contact structures from the energy distribution of emitted photons. The electron temperatures of 3- and 26-contact hole devices were about 4700 K and 6000 K, respectively. We have developed a HSPICE circuit model to simulate various contact structures. Both simulation and experimental results indicate that the current driving capability saturates at more than 5 contact holes of n-channel MOSFET with W/L=20/0.25 microns.

Photon emission from nanostructures in an STM

Using an STM we have created and investigated individual small particles with apparent lateral dimensions between 10 Å and 250 Å on metal single-crystal surfaces and metallic films. These particles are clearly observed in simultaneous measurements of STM topographs and emission of photons from the tunneling gap. The particles give rise to order-of-magnitude variations in photon intensity with subnanometer lateral resolution. We interpret the observed photon emission characteristics in terms of inelastic tunneling excitation of tip-induced, localized plasmon modes.

Coupled Monte Carlo-Energy Relaxation Analysis of Hot Carrier Light Emission in Metal Oxide Semiconductor Field Effect Transistors's

A new two-dimensional device simulator to analyze hot carrier photon emission has been developed. A new calculation algorithm of coupled Monte Carlo energy relaxation analysis is employed to obtain the carrier temperature distribution and the carrier energy distribution function at a fast computation turn around time. The relation between the hot carrier energy and the photon emission characteristics is easily obtained by using this simulator. The simulated results show excellent agreement with the experimental results. It is found from the comparison between the simulated and experimental results that the hot carrier energy distribution function is not described by the Maxwell-Boltzmann distribution.

運動負荷時のヒト呼気極微弱発光特性の測定

運動負荷時のヒト呼気極微弱発光特性の測定

Photon emission in deformation and failure of metals

The authors analyze the characteristics of the radiation (spectral composition, length, intensity) and study their relationship to the parameters of deformation and failure of metals. The nonthermal and thermal radiation accompanying plastic deformation of metals are separated. The authors study the time characteristics of photon emission and discuss its possible physical mechanisms. Various steels and iron-base alloys and other elements distinguished by different chemical activities and energies of the bond were investigated. In brittle ductile fracture of an Ni-Cr-Mo alloy (cast EP199 alloy) in the area of spectral sensitivity of the photoelectric amplifier photoelectric cathode of a light filter the intensity of the radiation pulse decreased insignificantly while the length remained equal to 1500 microsec. There are at least two possible mechanisms of radiation in the optical range, chemisorption and resonant.

The measurement of energy parameters for atoms sputtered in excited states

Ti I lines from excited Ti atoms sputtered from Ti and a variety of Ti compounds by 55 keV Ar + bombardment have been studied and the intensity decay, as a function of distance, has been measured in front of the target surface for normal incidence bombardment. These decay curves have been analyzed using the model of Dzioba et al. The model has been examined with respect to its internal consistency in the predictions for integral and differential yield measurements using several Ti I and an Al I line. Although care must be taken in defining an adequate slit size for each particular decay curve, the integral and differential measurements infer consistent E∗ values. These values have been generally found to increase with the excitation energy of the Ti I level studied, and to decrease with surface (or bulk) contamination of O, N, C and B. Selected characteristics of photon emission are discussed in relation to the E∗ values obtained.