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- 2018
- Signal-to-Noise Ratio (SNR)
- Infinite Gain Multiple Feedback (IGMF)
- Visible Light Communications (VLC)
- LED
- Trans-Impedance Amplifier (TIA)
- Optoelectronic Information Science and Engineering
- University of Northumbria
- University of Huddersfield
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Photonic Topological Insulating Phase Induced Solely by Gain and Loss
摘要： We reveal a one-dimensional topological insulating phase induced solely by gain and loss control in non-Hermitian optical lattices. The system comprises units of four uniformly coupled cavities, where the successive two have loss; the others experience gain, and they are balanced under two magnitudes. The gain and loss parts are effectively dimerized, and a bulk band gap, topological transition, midgap topological edge, and interface states in finite systems can all be achieved by controlled pumping. We also clarify non-Hermitian topological invariants and edge states in gapless conditions.
关键词： Topological Transition,Photonic Topological Insulating Phase,Non-Hermitian Optical Lattices,Midgap Topological Edge States,Gain and Loss Control
更新于2025-09-23 15:21:01
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Ti/Au/Al/Ni/Au low contact resistance and sharp edge acuity for highly scalable AlGaN/GaN HEMTs
摘要： In this letter, we have reported a novel metal scheme Ti/Au/Al/Ni/Au for ohmic contact on AlGaN/GaN high electron mobility transistors (HEMTs). The reported metal scheme is observed to show minimum metal out-diffusion and sharp edge acuity at high temperature annealing, which facilitates aggressive scaling of source drain separation (LSD). We have demonstrated LSD as low as 300 nm with gate length (Lg) of 100 nm for this metal stack. We observed improvement in ON-Resistance (RON) from 3 ?.mm to 1.25 ?.mm, transconductance (gm) from 276 mS/mm to 365 mS/mm, saturation drain current (IDS,sat) from 906 mA/mm to 1230 mA/mm and unity current gain frequency (fT) from 70 GHz to 93 GHz by scaling LSD from 3 μm to 300 nm. The gate length for all devices were 100 nm.
关键词： Edge acuity,HEMT,smooth surface,current gain cut-off frequency,ohmic contact resistance,GaN
更新于2025-09-23 15:21:01
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[Lecture Notes in Electrical Engineering] Microelectronics, Electromagnetics and Telecommunications Volume 521 (Proceedings of the Fourth ICMEET 2018) || Performance Analysis of a PV System Using HGB Converter
摘要： A photovoltaic array based system using a transformer-less high gain interleaved dc–dc boost converter is proposed in this paper. The renewable energy sources such as photovoltaic array and fuel cells provide only a time-varying and low dc voltage which cannot be directly used as the front-end for the loads or dc grid. Hence, there is a need for power electronic interfaces for matching the environmental-friendly sources of energy to the load. The interleaved converter used in the proposed system has the capability of canceling the input current ripple without increasing the component counts in the converter using a preselected duty cycle. Also, the large voltage gain and high ef?ciency of the converter are the added advantages to the proposed system. Analysis, simulation, and experimental investigation of the system proposed were carried out and the results are compared to validate the proposed system effectiveness.
关键词： Photovoltaic array,Interleaving technique,A high gain boost converter,Transformer-less dc–dc converter
更新于2025-09-23 15:21:01
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Effects of Parasitic Region in SiC Bipolar Junction Transistors on Forced Current Gain
摘要： Effects of a parasitic region in SiC BJTs on conductivity modulation and a forced current gain (????) were investigated by using TCAD simulation with various device structures. By introducing an Al+-implanted region below the base parasitic region, ???? can be improved because the implanted region can reduce the base spreading resistance, leading to alleviation of debiasing effect. ???? in devices with various parasitic areas, whose base spreading resistances were reduced by the Al+-implantation, were compared. We found that ???? can be enhanced by expanding the parasitic area if the base spreading resistance is sufficiently reduced. The higher ???? is attributed to an expanded conductivity-modulated region. The collector current spreading in the collector layer and hole injection from the parasitic region as well as from the intrinsic region can play a role to evoke conductivity modulation. Thus, the larger parasitic region can expand the conductivity-modulated region, which results in expansion of an active area and the enhancement of ????, though a higher base voltage is required.
关键词： forced current gain,conductivity modulation,parasitic region,hole injection,SiC BJT,base spreading resistance
更新于2025-09-23 15:21:01
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Overall Noise Analysis for Transisition Edge Sensor at Optical and Infra-Red Wavelengths
摘要： Transition-Edge Sensors (TESs) are the most promising devices as single photon detectors in the visible and infrared range. In particular ultra-fast TESs with few hundred ns response time and high quantum efficiency find application in different fields like quantum optics, quantum metrology and quantum information. In this work, the main objective is to measure the noise effect on the performance of the TESs when operated at visible and infrared wavelengths as the TESs performance depends on the sensor parameters and also on the noise level. The noise analysis is done by experimentally calculating the noise generated by the different block of the Single quantum interface device and to the TES. We have also . The above estimate is valid for seen from our numerical analysis that the overall noise of the system is the low-temperature steady –state biasing conditions of our TES device.
关键词： Photo Detectors,Single Quantum Interference Device,Gain of Op-Amp,Tank Circuit
更新于2025-09-23 15:21:01
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Dynamics of pulse amplification in tapered-waveguide quantum-dot semiconductor optical amplifiers
摘要： Tapered-waveguide quantum dot semiconductor optical amplifiers (TW-QDSOAs) have been modeled using numerical calculation of the rate and propagation equations in this article and the amplification characteristics and dynamics of pulse propagation in non-tapered QDSOA, linear, and exponential TW-QDSOA structures have been studied and compared in detail. It has been found that TW-QDSOAs apply less distortion to the amplified pulse and have greater optical gain than non-tapered QDSOA. In TW-QDSOAs, the amplified pulse becomes much less broadening and this amount is negligible, therefore the pulse bit rate can be increased. While the amplified pulse in a non-tapered QDSOA is much broadening than the TW-QDSOAs. The carrier density distribution and dependency of the amplifier gain to the output energy for both non-tapered and tapered structures have been studied. The carrier density and gain in non-tapered QDSOA decreases more than TW-QDSOAs, indicating that the tapered amplifiers are saturated at higher input energies. Our obtained results agree well with those previously obtained for conventional tapered amplifiers.
关键词： Quantum dot semiconductor optical amplifier,tapered QDSOA,gain saturation
更新于2025-09-23 15:19:57
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Carrier transport and recombination dynamics of InAs/GaAs sub-monolayer quantum dot near infrared photodetector
摘要： Here, we present a relative study of tunnel-induced photocarrier escape processes in a laterally coupled InAs sub-monolayer quantum dot-based photodetector (SML QD-PD) as a function of fractional coverage from 0.4 ML to 0.8 ML. Both by simulation and experiment, we have quantitatively described the temperature dependent interband photoresponse spectrally tuned in the near infrared region (835 nm–890 nm) on the basis of mutual competition between the interband carrier recombination and interdot tunneling lifetime with varying SML coverage. The progressively increasing recombination lifetime and decreasing interdot tunneling lifetime with increasing SML coverage has attributed to a faster photoresponse and greater responsivity. At higher coverage fraction, tunnel induced fast speed photocarrier transit through lateral array of SML QDs has been found to be capable of offering a faster temporal response (100 μs) with faithful reproducibility up to higher frequencies (1.3 KHz). Here, we report a powerful strategy to simultaneously tune responsivity, speed of time response and detectivity by externally controlling the SML coverage. This time response is measured to be nine times faster than a conventional SK QD photodetector. With increased coverage, inhibition of dark current due to trapping of injected charge carriers up to higher temperatures have resulted in high sustainable photodetectivity of 8 × 1011 cm Hz1/2 w?1 at ~250 K that offers near room temperature photodetection.
关键词： photoconductive gain,quantum dot photodetector,inter-dot tunneling,submonolayer coverage,near-infrared photoresponse,recombination dynamics,temporal photoresponse
更新于2025-09-23 15:19:57
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A Graphene based bimetallic plasmonic waveguide to increase photorefractive effect
摘要： In this paper, for enhancement of the nonlinear optical properties of photorefractive gain, a novel plasmonic waveguide is proposed. The geometry of the proposed structure is optimized to reach the highest photorefractive gain. The proposed structure is based on bimetallic structure and it includes a graphene layer. It is shown that a strong mode can be coupled to a weak mode by means of photorefractive effect. It is found that comparing with the conventional symmetric and asymmetric metal-insulator-metal plasmonic waveguides, the proposed structure with different metals and a graphene layer with an optimized notch has higher photorefractive gain and longer propagation distance, the distance for which a net photorefractive gain exists. The effect of the crystal thickness and amplitude inputs are also analyzed. It is found that there is an optimum crystal thickness that yields the maximum photorefractive gain.
关键词： asymmetric structure,Photorefractive e?ect,graphene,plasmonic waveguide,photorefractive gain
更新于2025-09-23 15:19:57
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Loss compensated extraordinary transmission in hybridized plasmonic nanocavities
摘要： Extraordinary optical transmission has been utilized in many optical applications, but the plasmonic losses hinder their full potential. To obtain enhanced transmission, one of the loss compensation methods is to introduce gain. However, an enhanced transmission or even eliminated absorption does not guarantee plasmonic loss compensation. Here, we reveal the distinction between the transmission enhancement mechanisms in gain-assisted plasmonic arrays. To uncover the underlying mechanisms of the modi?ed transmissions, we calculate the e?ective electric permittivity by employing a self-consistent gain model. We demonstrate that a large transmission enhancement in a plasmonic system composed of periodic nanocavities and coaxially placed nanoislands, is led by the loss compensation, which manifests itself as narrowing in e?ective permittivity. In contrast, a slight transmission enhancement in a plasmonic array without the nanoislands arises from the background ampli?cation.
关键词： gain,loss,extraordinary optical transmission,plasmon hybridization,compensation
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE International Symposium on Phased Array System & Technology (PAST) - Waltham, MA, USA (2019.10.15-2019.10.18)] 2019 IEEE International Symposium on Phased Array System & Technology (PAST) - Periodic Substrate Integrated Waveguide Based Leaky Wave Antenna for Backward Endfire Radiation
摘要： A new substrate integrated waveguide (SIW) based leaky wave antenna (LWA) is presented in this paper for backward endfire (-900) radiation. Measured gain at backward endfire is 12.1 dBi. To verify the simulated results, a prototype is fabricated. The proposed antenna is well suited for applications including unmanned aerial vehicles (UAVs), modern RADAR systems, directional communication systems, modern missiles and self-driving cars etc.
关键词： Endfire,Leaky Wave Antenna,Backfire,Broadside,Substrate Integrated Waveguide,Gain
更新于2025-09-23 15:19:57