Simple Emitter Research Articles

Performance-improved narrowband near-ultraviolet emission from a simple butyl and cyanogen substituted indolocarbazole

High-efficiency narrowband near-ultraviolet (NUV) organic light-emitting diodes with high color purity have currently encountered great challenges. Here, using butyl (Bu) and cyanogen (CN) substituted strategy in the simplest polycyclic aromatic hydrocarbons of indolocarbazole (ICz), two simple emitters of BuICz and BuICzCN were demonstrated. This simple strategy was observed to enable both emitters to realize NUV emission at 380–381 nm with a small full width at half maximum (FWHM) of 21–23 nm and high photoluminescent quantum efficiency of 50%–59% in toluene solution. Furthermore, the BuICzCN doped devices exhibited a slightly blueshifted narrowband NUV electroluminescence at 388 nm with a small FWHM of 32.3 nm but a higher external quantum efficiency of 3.92% in comparison with the BuICz doped devices. This work provides a path to realize high-performance narrow-band NUV emission.

Multiscale design of large and irregular metamaterials

Next-generation microwave communications systems face several challenges, particularly from congested communications frequencies and complex propagation environments. We present, and experimentally test, a framework based on the coupled-dipole approximation for designing structures composed of a single simple emitter with a passive disordered scattering structure of rods that is optimized to provide a desired radiation pattern. Our numerical method provides an efficient way to model, and then design and test, otherwise inaccessibly large scattering systems. Published by the American Physical Society 2024

Algorithm Verification of Single-Shot Relativistic Emittance Proposed Measuring Method

A 6 MeV hybrid photo-cathode gun is driving a THz-FEL in Ariel University, as well as other applications. An electron bunch with small transverse emittance is extracted from a copper photo-cathode using a 1 ps UV laser pulse, and then accelerated to a kinetic energy of 6.5 MeV. The Hybrid term is due to the unique standing wave-traveling wave sections in a single RF cavity. Since low emittance is crucial for FEL operation, the characterization of the electron beam requires measuring the transverse emittance, which will be compared with the predicted design and the 3D simulation obtained values, in order to verify their correctness. In this paper, we confirm the use of the multi-slit technique to measure emittance in the Hybrid beam in a single shot and develop a simple and convenient algorithm to be used in the experimental measurements. The experimental analysis requires image processing of the measured data, combined with a custom LabVIEW and Matlab scripts to control the hardware, and analyze the obtained data. Prior to experimentally measuring emittance, we perform a simulated experiment, using a simulated beam from the General Particle Tracer (GPT) code to test these algorithms and scripts, and compare the emittance obtained using the algorithm with GPT’s estimated emittance. Once concluded, this method will allow for a simple, fast and accurate single shot emittance measurement for the Hybrid accelerator beam.

A color-tunable single molecule white light emitter with high luminescence efficiency and ultra-long room temperature phosphorescence

A simple emitter could simultaneously achieve bright white light emission with high quantum yield, ultra-long phosphorescence and excitation-dependent color-tunable emission.

High-Temperature Selective Emitter Design and Materials: Titanium Aluminum Nitride Alloys for Thermophotovoltaics.

The efficiency of a thermophotovoltaic (TPV) system depends critically upon the spectral selectivity and stability of an emitter, which may operate most effectively at temperatures in excess of 1000 °C. We computationally design and experimentally demonstrate a novel selective emitter design based on multilayer nanostructures, robust to off-normal emission angles. A computational search of the material and temperature compatibility space of simple emitter designs motivates new material classes and identifies several promising multilayer nanostructure designs for both TPV absorber and emitter applications. One such structure, comprising a thin (<100 nm) tunable TixAl1-xN (TiAlN) absorber and refractory oxide Bragg reflector is grown on W metal foil. In agreement with simulations, the emitter achieves record spectral efficiency (43.4%) and power density (3.6 W/cm2) for an emitter with at least 1 h of high temperature (>800 °C) operation.

Role of multilevel states on quantum-dot emission in photonic-crystal cavities

Semiconductor quantum dots embedded in photonic-crystal nanostructures have been the subject of intense study. In this context, quantum dots are often considered to be simple two-level emitters, i.e., the complexities arising from the internal fine structure are neglected. We show that due to the intricate spatial variations of the electric field polarization found in photonic crystal, the two orthogonal fine-structure states of quantum dots in general both couple significantly to a cavity mode, implying that the two-level description is not sufficient. As a consequence the emission dynamics and spectra, which are often recorded in experiments, are modified both in the weak- and strong-coupling regimes. The proposed effects are found to be significant for system parameters of current state-of-the-art photonic-crystal cavities.

Wearable Structured Light System in Non-Rigid Configuration

Traditionally, structured light methods have been studied in rigid configurations. In these configurations the position and orientation between the light emitter and the camera are fixed and known beforehand. In this paper we break with this rigidness and present a new structured light system in non-rigid configuration. This system is composed by a wearable standard perspective camera and a simple laser emitter. Our non-rigid configuration permits free motion of the light emitter with respect to the camera. The point-based pattern emitted by the laser permits us to easily establish correspondences between the image from the camera and a virtual one generated from the light emitter. Using these correspondences, our method computes rotation and translation up to scale of the planes of the scene where the point pattern is projected and reconstructs them. This constitutes a very useful tool for navigation applications in indoor environments, which are mainly composed of planar surfaces.

An empirical study of dynamic properties of an individual carbon nanotube electron source system

In this paper we present an empirical study of some dynamic properties of an individual carbon nanotube (CNT) field emission electron source system. We propose a circuit model that represents the CNT cathode to anode diode as a capacitor in parallel with a voltage-controlled variable resistor. The transient response of the CNT electron source system to the falling edge of a voltage step input was evaluated. For input voltages below the threshold voltage for field emission, the nanotube loop is effectively open and the circuit response is consistent with a discharging capacitor. On the other hand, for input voltages above field emission threshold, the nanotube loop conducts and now the capacitor discharges to a certain extent through the nanotube loop as well. Field emission current versus voltage data also shows that the resistance across the CNT cathode to anode diode varies as a function of applied voltage. Below turn-on voltage, the diode behaves as an open circuit (4 TΩ at the ammeter noise floor). Above turn-on voltage, resistance falls exponentially, as expected from the Fowler–Nordheim equation for cold field emission current. Experimental current–voltage data is presented for a simple emitter array consisting of two CNTs with equal lengths. Despite the similarity in their lengths the turn-on voltages of the nanotubes varied significantly, viz. 26 V versus 109 V. This large difference in the turn-on voltages can be attributed to tip imperfections. For advanced array applications such as high-throughput parallel e-beam lithography, in which precise dose control is necessary, the diode circuit model will be useful for controlling individually addressed nanotubes to account for dissimilar field emission properties. The model may also be applied to optimize the design of a SEM incorporating a single CNT electron source.

Controlled thermal emission of polarized infrared waves from arrayed plasmon nanocavities

We have demonstrated thermal emission of linearly polarized and narrow-band midinfrared waves from subwavelength gratings of narrow and deep rectangular cavities engraved on a Au surface. 100-nm-wide and 1000-nm-deep, high-aspect trenches were accurately manufactured by inversion from master molds. Organ pipe resonance of surface plasmons in the cavities exhibits a Lorentzian emission peak centered at 2.5–5.5μm. The maximum emittance reaches 0.90 and the peak width Δλ∕λ is as narrow as 0.13–0.23. This simple emitter is expected to play a key role in the infrared sensing technologies for analyzing our environment.

Deinterleaving of radar signals and PRF identification algorithms

Electronic warfare (EW) receivers are passive receivers which receive emissions from other platforms, and do certain analysis on these emissions. Some EW receivers receive radar pulses, measure the parameter of each pulse received and group the pulses that belongs to the same emitter together to determine the radar parameters for each emitter. These parameters are then compared with values stored for known radar types, to identify the emitter type. Two parts are focused, emitters deinterleaving and PRF-type identification. The deinterleaving is done through parameters clustering. Two parameters are selected for clustering direction of arrival and radio frequency. A self-organising neural network called Fuzzy ART is proposed for clustering. This algorithm has a very good clustering quality and can run in real-time applications.The PRF-type identification is done through time-of-arrival (TOA) analysis. Three previously presented algorithms are combined in new scheme to do the TOA analysis (or PRF-type identification). These algorithms are difference TOA histogram, TOA folding histogram and sequence search algorithm. The complete proposed system has been tested using three different tests. These tests are simple PRI test, jittered PRI test and staggered PRI test. The proposed system identifies up to 90 simple emitters, 20 jittered emitters and 20 staggered emitters. In all tests, the data were simulated and generated using software.

Performance of combined 〈1 0 0〉–〈1 1 0〉 ZnTe crystals in an amplified THz time-domain spectrometer

In this work we report on the performance of combined index-matched ZnTe 〈1 1 0〉–〈1 0 0〉 THz emitters and detectors for reduction of etalon effects in a nonlinear crystal-based THz time-domain spectrometer, driven by an amplified femtosecond laser. We demonstrate that the application of a combined electrooptic detector crystal reduces the strength of the first etalon and the average spectral dynamic range oscillations by a factor of two. We also show that even in a simple emitter configuration the emitter-related etalon is significantly reduced due to the transient dielectric effects of carriers created by two-photon absorption in the emitter.

Excilamps: efficient sources of spontaneous UV and VUV radiation

The results of research into high-power, high-efficiency noble-gas-halide excilamps using glow, capacitive, and barrier discharges for the excitation sources are presented. The maximum radiation powers and minimum consumption are achieved with glow discharge lamps. An excilamp with anaverage radiation power of 1.6 kW on KrCl* molecules (λ = 222 nm) and 1.1 kW on XeCl* molecules (λ = 308 nm) is developed, whose energy conversion efficiency exceeds 10%.The use of an electrodeless capacitive discharge leads to sealed off excilamps with a simple emitter design, which have a power of 1 to 10 W and a service life of about 2500 h and more. Barrier-discharge excilamps possess both high energy parameters (> 100 W m−1) and a long service life. Excilamps can find wide practical applications as new powerful sources of UV and VUV radiation.

An automatic optical fibre feedback potometer for transpiration studies

A new automatic feedback potometer for physiological studies of water uptake by root systems is described. A dual-optical-fibre amplitude-modulating displacement transducer of improved sensitivity is employed to detect the changes in liquid level. The merits of optimal double-cut fibres, which make full use of the critical angle and improve coupling between the emitter and the receiver, have resulted in a sensor that is 64 times more responsive than the simple emitter - detector probe. Positioning the optical fibre transducer in a narrow capillary and using feedback to control the liquid level allows continuous measurement of volumes in the nanolitre range. The optical sensor used does not need re-calibration for the different salt solutions used in such studies.

Simple emittance measurement of H− beams for neutral beam injectors in magnetic fusion

A novel emittance meter is developed using the pepper-pot method. Kapton foils are used to detect intensity distributions of small beamlets at the ‘‘image’’ plane of the pepperpot. Emittance of H− beams for the neutral beam injector of the large helical device has been measured. The normalized emittance (95%) of a 6 mA H− beam with an emission current density of about 10 mA/cm2 is ∼0.59 mm mrad. The present system is simple, and it eliminates many complexities of the existing schemes.

A Method for Passive Release of Solutes from an Unpumped Well

AbstractA new method was developed for releasing dissolved solutes into ground water which has application in both academic studies and practical efforts to stimulate in situ bioremediation, introduce chemical reactants, or understand flow and transport properties. The method involves the diffusion of solutes out of inexpensive, simple emitter devices which are installed in large diameter wells. Mass flux from an emitter depends on the geometry of the emitter, ground‐water flow rate, the imposed concentration gradient from the stock solution inside the emitter, and the diffusion coefficient of the solute through the emitter material. Diffusion coefficients are constants of a solute/tubing pair, and are established in simple experiments. If ground‐water flow rates and diffusion coefficients are known, emitter geometry and stock solution concentration can be tailored for a wide range of performance requirements.In laboratory experiments, benzene was released at or near 1.3 mg/1 for a total of 31 days, TCE for 17 days at approximately 4.5 mg/1, and bromide for 23 days at 667 mg/1. The emitted concentration of a wide range of solutes can be stabilized for much longer periods of time once the mass flux in the flow‐through system reaches steady‐state, provided the concentration gradient is maintained.A simple computer model was written to aid in the design of source emitters. The model was used to match diffusion coefficients to data for three solute‐tubing combinations. Once the diffusion coefficient of a given solute in a given type of tubing is determined from experimental data by curve‐matching, the model can be used in a predictive capacity. A second TCE release test showed that the diffusion coefficient calibrated from the model can be used to predict the steady‐state release concentration of TCE under different conditions.Simple two‐dimensional transport modeling suggests that a relatively uniform plume of solutes may be generated by emitters placed in wells spaced close together. The uniform introduction of nutrients and oxygen by this passive method may encourage more efficient in situ remediation, and in some situations, save time and money.

FPAD: a fuzzy nonlinear programming approach to analog circuit design

FPAD, a CAD tool for the design of analog circuits, is presented. For a set of input specifications, FPAD deduces the device sizes that optimize the performance objectives while satisfying the constraint specifications. Fuzzy set theory is used to measure the degree of fulfilment of the objectives and constraints, and hence provides a measure of the design quality. Trade-offs are handled by manipulating the shape of the membership functions that reflect the fulfilment or violation of the performance specifications. FPAD allows the optimization of several objectives simultaneously since multiple objective optimization is used. The mathematical formulation of the design problem is fuzzified to support real-world terms like high, good, small, acceptable, etc. The optimization is based on analytic models to avoid a simulator in the inner optimization loop. Using this approach, a two-stage unbuffered CMOS op amp and a simple emitter follower were designed, with promising results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

MINIMAC: A Totally Numeric 15 Channel Implanted Stimulator

After CHORIMAC-8 and CHORIMAC-12 a new multichannel cochlear implant is presented, characterized by its totally numeric sound signal processing. Owing to FFT the whole speech information is cut into 15 channels, then sequentially transmitted to an implanted receptor and electrode bearer. This digital processing provides the new system with several advantages: 1. miniaturization of outside emitter end implanted receiver; 2. compatibility of this new emitter with the 12 channel receivers implanted in the last 10 years; 3. increasing the number of stimulating electrodes from 12 to 15; 4. simple emitter programming with an IBM-PC; 5. option to postoperatively program the number (1 to 15) and the value (80 to 3,800 Hz) of the peak filters, and the amplification (6, 10, 18 dB) of each electrode. The next implanted device will have: a. constant current; b. programming of a particular current value for each electrode; and c. stimulation of the cochlear nerve through an extra cochlear electrode bearer, allowing deep implantation without deafness.

Emittance meter for time-resolved electron-beam propagation studies

A simple emittance meter is designed which is capable of measuring the temporal evolution of the emittance of a propagating electron beam. The design is based on that of a slit-pinhole emittance meter. A Cherenkov emitter is utilized as the electron detector. A streak camera is used to record the time-resolved optical Cherenkov radiation from the detector. Experimental results with a 700-keV, 4-kA, 100-ns electron beam are presented.

H− beam emittance measurements for the Penning and the asymmetric, grooved magnetron surface-plasma sources

Beam intensity and emittance measurements show that the H− beam from our Penning surface-plasma source (SPS) has twice the intensity and ten times the brightness of the H− beam from an asymmetric, grooved magnetron SPS. H− ion temperatures of 5 eV for the Penning SPS and 22 eV for the asymmetric, grooved magnetron are deduced by using a simple emittance theory and the present emittance measurements.

Output inductance of an emitter follower

A small-signal analysis of a simple emitter follower is performed to ascertain its effective output inductance as a function of circuit element values, transistor parameters and signal frequencies. It is shown that the low-frequency value of output inductance is directly proportional to the common emitter shortcircuit gain-bandwidth product. Moreover, the product of this inductance and the bandwidth over which the input port of an emitter follower behaves as a low Q reactive impedance is limited solely by transistor gainbandwidth product and collector junction capacitance