Carrier Reservoir Research Articles

Topologically Protected Single Edge Mode Lasing in Photonic Crystal Su–Schrieffer–Heeger Lattice with Directional Loss Control

AbstractTopological photonics is considered to be a robust and flexible platform for the design of nanophotonic devices against structural imperfections and performance degradation. Combining with parity‐time (PT) symmetry systems based on spatially distributed gain and loss, photonic crystal (PhC) lasers with micron‐size carrier reservoirs offer an ideal test bed for lasing mode competition and topological protection in nanophotonic structures. In this study, single topological edge mode (TEM) lasing is demonstrated in PhC lasers with a Su–Schrieffer–Heeger lattice comprised of coupled nanoresonators. By inducing directional loss control, a mode selection strategy is implemented, that achieves single TEM lasing with a side‐mode‐suppression ratio exceeding 30 dB. One of the TEMs exhibits remarkable robustness against local potential variation introduced by additional loss channels. This strategy integrating both topological protection and PT symmetry in nanophotonics would open up new prospects for the development of on‐chip single‐mode topological lasers unperturbed by output channels in nanophotonic integrated circuits.

All-Optical 4-Bit Parity Generator and Checker Utilizing Carrier Reservoir Semiconductor Optical Amplifiers

All-Optical 4-Bit Parity Generator and Checker Utilizing Carrier Reservoir Semiconductor Optical Amplifiers

Enhanced Light Absorption and Photo-Generated Charge Separation Efficiency for Boosting Photocatalytic H2 Evolution through TiO2 Quantum Dots with N-Doping and Concomitant Oxygen Vacancy.

Low-range light absorption and rapid recombination of photo-generated charge carriers have prevented the occurrence of effective and applicable photocatalysis for decades. Quantum dots (QDs) offer a solution due to their size-controlled photon properties and charge separation capabilities. Herein, well-dispersed interstitial nitrogen-doped TiO2 QDs with stable oxygen vacancies (N-TiO2-x-VO) are fabricated by using a low-temperature, annealing-assisted hydrothermal method. Remarkably, electrostatic repulsion prevented aggregation arising from negative charges accumulated in situ on the surface of N-TiO2-x-VO, enabling complete solar spectrum utilization (200-800 nm) with a 2.5 eV bandgap. Enhanced UV-vis photocatalytic H2 evolution rate (HER) reached2757µmol g-1 h-1, 41.6 times higher than commercial TiO2 (66µmol g-1 h-1). Strikingly, under visible light, HER rate was 189µmol g-1 h-1. Experimental and simulated studies of mechanisms reveal that VO can serve as an electron reservoir of photo-generated charge carriers on N-doped active sites, and consequently, enhance the separation rate of exciton pairs. Moreover, the negative free energy (-0.35 V) indicates more favorable thermodynamics for HER as compared with bulk TiO2 (0.66 V). This research work paves a new way of developing efficient photocatalytic strategies of HER that are applicable in the sustainable carbon-zero energy supply.

Low parasitic carrier reservoir of AlGaN-based DUV-LED via controlled-polarization step-graded superlattice electron blocking layer for high luminescence lighting

Achieving high luminescence intensity of deep-ultraviolet light-emitting diode (DUV-LED) is generally performed through the implementation of electron blocking layer (EBL) on the chip’s epilayers. However, the issue of parasitic carrier reservoir that originated from the uncontrolled piezoelectric field polarization has restricted the performance of DUV-LED by reducing the radiative recombination in the active region. This work reports on the numerical computation analysis of the DUV-LED with different types of EBL designs which are reference EBL, conventional superlattice EBL and step-graded superlattice EBL. The analysis of the DUV-LED focuses on the band diagram, carrier concentration at the EBL interfaces, current density of the carrier in the active region, radiative recombination rates, and luminescence spectrum. Remarkably, it is found that the DUV-LED step-graded superlattice EBL provides the polarization-controlled band diagram and emits 272 nm UVC-wavelength in which it is superior in performance compared to the other structures, specifically in terms of its radiated intensity. The parasitic electron and hole reservoir have been reduced by 30% and 60%, respectively. The luminescence intensity was also enhanced by 11% compared with the reference EBL and the IQE obtained by the DUV-LED with step-graded superlattice EBL is 50.12%.

Identification of blaSHV and blaTEM extended spectrum beta-lactamase genes in Klebsiella pneumoniae in the dairy wastewater, East Java Province, Indonesia

Abstract. Dameanti FNAEP, Yanestria SM, Effendi MH, Plumeriastuti H, Tyasningsih W, Ugbo EN, Sutrisno R, Safri MAAS. 2023. Identification of blaSHV and blaTEM extended spectrum beta-lactamase genes in Klebsiella pneumoniae in the dairy wastewater, East Java Province, Indonesia. Biodiversitas 24: 6092-6099. Klebsiella pneumoniae infection in dairy cows causes various livestock production hazards and threatens public health because it acts as a Multi-Drug Resistance Bacteria (MDRB), especially Extended-Spectrum Beta-Lactamase (ESBL) strains. Livestock wastewater is a repository for commensal isolates including K. pneumoniae and potentially can be a reservoir for ESBL spreaders for the environment. The aim of this study was to identify the blaSHV and blaTEM ESBL genes in K. pneumoniae from wastewater of dairy cattle farms in East Java Province. This study used a sample of 342 dairy farm wastewater isolated on 2% BPW media from 6 cities/regencies with the highest population of dairy cows in East Java, Indonesia, namely Pasuruan District, Malang District, Tulungagung District, Blitar District, Batu City and Kediri District. Samples were identified on MCA media, Gram staining, EMBA, and biochemical tests. Confirmation of ESBL phenotypically used the Double Disc Synergy Test (DDST) method and the Polymerase Chain Reaction (PCR) test to detect the ESBL gene. The result showed that bacterial isolation and identification were 14.32% (49/342), confirmed K. pneumoniae. DDST confirmation results of ESBL-producing K. pneumoniae isolates from the wastewater of dairy farms in East Java obtained were 5.55% (19/342). The sample was continued with the PCR test showing positive for the blaSHV gene 63.1% (12/19) and blaTEM 31.57% (6/19). In conclusion, the ESBL gene blaSHV and blaTEM identification in K. pneumoniae isolates, indicate that wastewater from dairy farms has the potential to be a reservoir of ESBL carriers in the environment and pose a threat to public health in East Java Province, Indonesia.

Design and analysis of all optical header recognition system employing combination of carrier reservoir SOA and conventional SOA

Design and analysis of all optical header recognition system employing combination of carrier reservoir SOA and conventional SOA

Facile and efficient chitosan-based hygroscopic aerogel for air dehumidification

Sorption dehumidification, as an energy-saving and eco-friendly approach, has been emerging in application for air dehumidification. Here, a prospective method is proposed to prepare biomass-based hygroscopic aerogels that are easily applicable, sustainable, high-efficient, and recyclable. The chitosan-based aerogel with a porous and hydrophilic network acts as the carrier and water reservoir for the uniformly distributed lithium chloride hygroscopic salt, and provides the hygroscopic salt with more liberal water channels to facilitate moisture capture and transfer. As a consequence, the prepared chitosan/polyvinyl alcohol@lithium chloride (chitosan/PVA@LiCl) hygroscopic aerogel exhibits an excellent moisture absorption capacity of up to 2.77 g g−1 at a relative humidity of 90 %. Meanwhile, as the chitosan/PVA@LiCl aerogel is set in a closed space about 2200 times larger than its own volume, the relative humidity can be reduced from 90 % to 32 % within 2 h, and further lower to 25 % after 4 h. Furthermore, combined with multi-walled carbon nanotubes, the photothermal hygroscopic aerogel is obtained that can rapidly desorb water under sunlight, thus to realize energy-free cycle. Overall, the renewable biomass-based aerogel materials with the advantages of simple preparation and excellent hygroscopic performance provides a new path for the development of sorption dehumidification technology.

All optical 4 bit digital to analog converter based on carrier reservoir SOA-Mach Zehnder Interferometer (MZI) configuration

All optical 4 bit digital to analog converter based on carrier reservoir SOA-Mach Zehnder Interferometer (MZI) configuration

Design and analysis of cross phase modulation based all optical half subtractor using carrier reservoir semiconductor optical amplifier

Design and analysis of cross phase modulation based all optical half subtractor using carrier reservoir semiconductor optical amplifier

Improving thermoelectric performance of CuCrSe2 by manipulating the precipitated ferromagnetic spinel phase

As a superionic conductor, CuCrSe2 has recently attracted renewed attention in thermoelectric community for its phonon-liquid electron-crystal transport behaviours. Here, we demonstrate that the usually undesired second phase of ferromagnetic spinel CuCr2Se4 can play a significantly positive role in synergistically optimizing the thermoelectric properties of the CuCrSe2 compound. After systematically investigating the substitution behaviour of Ni for Cr, it is found that the contents of the ferromagnetic spinel phase can be controlled by virtue of the unique occupation preference of Ni in the tetrahedral and octahedral sites of CuCrSe2. A small amount of ferromagnetic CuCr2Se4 spinel phase essentially does not affect the weighted mobility but can act as carrier reservoirs in its ferromagnetic state, releasing additional holes into the matrix in the paramagnetic state. Furthermore, the presence of CuCr2Se4 precipitations in the CuCrSe2 matrix can drastically reduce the lattice thermal conductivity by generating extra phonon scattering mechanisms. Consequently, a zT value around 0.95, which is 33.8% higher than the absolutely pure sample, is achieved in the CuCr0·99Ni0·01Se2 sample with 3.64 wt% ferromagnetic spinel impurity.

Computational investigation of all-optical NOR logic operation using carrier reservoir semiconductor optical amplifiers at 120 Gb/s

Computational investigation of all-optical NOR logic operation using carrier reservoir semiconductor optical amplifiers at 120 Gb/s

All-optical latches using carrier reservoir semiconductor optical amplifiers

Lightwave communication systems, optical random memories, and photonic encryption/decryption are important applications that rely on all-optical latches. For the first time, the carrier reservoir semiconductor optical amplifiers (CR-SOAs) are employed to simulate two basic optical latches, Set-Reset (SR) latch, and D Flip-Flop, at a data rate of 120 Gb/s. All-optical NAND and NOT logic operations are used to build these latches, which are implemented using Mach-Zehnder interferometers (MZIs) with CR-SOAs. In the presence of the amplified spontaneous emission noise, the variation of the output quality factor (Q-factor) against the CR-SOA key operating parameters is studied. This is achieved by exploiting and numerically solving a set of coupled partial differential equations that describe the CR-SOAs gain and phase dynamics when operated as nonlinear elements and embedded in MZIs. The results demonstrate that CR-SOAs-based MZIs can achieve a high Q-factor while implementing the logical SR latch and D Flip-Flop at a high speed of 120 Gb/s.

MXene as charge reservoir promotes the thermoelectric performance of layered metal selenide SnSe2

Layered metal selenides have attracted widespread attention in thermoelectrics. However, the thermoelectric performance of these compounds holding n-type conduction suffers from low electrical conductivity especially along out-of-plane direction mainly due to the carrier deficiency. Herein, two-dimensional MXene with metallic conductivity is introduced into SnSe2 matrix as a carrier reservoir to alleviate the electron shortage. Br-doped SnSe2/Ti3C2Tx composites are successfully fabricated by a hydrothermal method combined with solid-state synthesis. Compared with that of pristine SnSe2, the carrier concentration of SnSe1.97Br0.03/0.4 wt% Ti3C2Tx is enlarged by three orders of magnitude from 1017 cm–3 to 1020 cm–3. Meanwhile, it is revealed that the electrons transfer from the MXene layers into the SnSe2 matrix facilitated by elevated temperature based on the first-principles calculations. Combining with the intrinsically low lattice thermal conductivity, a peak zT close to unity is achieved along out-of-plane direction at 818 K in SnSe1.97Br0.03/0.4 wt% Ti3C2Tx sample. These findings offer an available strategy to efficiently increase the carrier concentration of wide-gap layered compounds.

Carrier dynamics in quantum-dot tunnel-injection structures: Microscopic theory and experiment

Tunneling-injection structures are incorporated in semiconductor lasers in order to overcome the fundamental dynamical limitation due to hot carrier injection by providing a carrier transport path from a cold carrier reservoir. The tunneling process itself depends on band alignment between quantum-dot levels and the injector quantum well, especially as in these devices LO-phonon scattering is dominant. Quantum dots with their first excited state near the quantum well bottom profit the most from tunnel coupling. As inhomogeneous broadening is omnipresent in quantum dot structures, this implies that individual members of the ensemble couple differently to the injector quantum well. Quantum dots with higher energy profit less, as the phonon couples to higher, less occupied states. Likewise, if the energy difference between ground state and quantum well exceeds the LO-phonon energy, scattering becomes increasingly inefficient. Therefore, within 20–30 meV, we find quantum dots that benefit substantially different from the tunnel coupling. Furthermore, in quantum dots with increasing confinement depth, excited states become successively confined. Here, scattering gets more efficient again, as subsequent excited states reach the phonon resonance with the quantum well bottom. Our results provide guidelines for the optimization of tunnel-injection lasers. Theoretical results for electronic state calculations in connection with carrier–phonon and carrier–carrier scattering are compared to the experimental results of the temporal gain recovery after a short pulse perturbation.

Single- Versus Multi-Step Trap Assisted Tunneling Currents—Part I: Theory

Leakage currents through dielectrics in modern logic, memory, and power devices, and back-end interlevel layers can severely increase the time-zero power dissipation and shorten the lifetime of the material structure. Depending on thickness, material properties, and fabrication quality, different conduction mechanisms through the insulating layer, such as band-to-band and trap-assisted tunneling (TAT) are observed. These leakage currents can be distinguished by their dependence on electric field strength, temperature, and their transient characteristics. The identification of the underlying mechanisms is of utmost importance for the selection of suitable dielectrics and optimization of device processing. In this work, we present a nonradiative multiphonon model which extends our compact physics (Comphy) reliability framework to also account for TAT. The model is based on a single physical defect parameter set from which charge transfer kinetics between charge carrier reservoirs and oxide defects (single-TAT) as well as between the defects (multi-TAT) can be derived. We thereby demonstrate that the thermal barrier for inelastic defect–defect carrier tunneling is approximately twice as large in comparison to reservoir-defect interaction and further show in which parameter regime multi-TAT plays a role. Our results show that multi-TAT currents are a less important contribution to the overall tunnel current than previously assumed.

Anomalous photoluminescence of InAs surface quantum dots: intensity enhancement and strain control by underlying quantum dots

Strain control and photoluminescence (PL) enhancement of InAs surface quantum dots (SQDs), exposed to ambient conditions, have been achieved by introducing underlying buried quantum dots (BQDs). The PL wavelength has been tuned from 1270 to as long as 1780 nm, redshifted as the size of the SQDs is reduced. This is in strong contrast to standard QDs, in which blueshift is observed from smaller QDs following basic quantum mechanics. Here, smaller SQDs, both in height and base area, as observed by atomic force microscopy, were obtained with wider GaAs spacer thickness between the SQDs and BQDs. The result strongly suggests that strain and related effects dominate the electronic properties of the SQDs rather than their size, and that a change in the complex strain field occurs through the spacer. The underlying BQDs also serve as effective carrier reservoirs. A PL intensity enhancement of 17 fold was observed as the GaAs spacer thickness was reduced from 150 to 10 nm. A large portion of the photoexcited carriers is initially captured and stored in the BQDs. When sufficient carriers are transferred to fill non-radiative surface states, the excess may be transferred to the SQDs enhancing the luminescence.

320 Gb/s all-optical logic operations based on two-photon absorption in carrier reservoir semiconductor optical amplifiers

When a train of optical pulses is injected, two-photon absorption (TPA)-induced pumping results in significant and fast gain and phase shifts in the carrier reservoir semiconductor optical amplifier (CR-SOA). Therefore, in this work, the effect of TPA on all-optical (AO) exclusive-OR (XOR), AND, NOT-OR (NOR), OR, NOT-AND (NAND), and exclusive-NOR (XNOR) logic operations using CR-SOAs is theoretically implemented for the first time at 320 Gb/s. The XOR, AND, NOR, NAND, and XNOR logic gates are implemented using the Mach-Zehnder interferometer, which has two symmetrical CR-SOAs in each of its two arms, whereas the OR logic gate is produced by combining a CR-SOA with a delayed interferometer. The quality factor (QF) and the associated bit error rate (BER) metrics are employed to evaluate the operations’ performance. The obtained simulation results indicate that when exploiting TPA in CR-SOAs the target Boolean functions can be executed with QF and BER that are more than acceptable than without TPA at a high speed up to 320 Gb/s. Various circuits of enhanced logic functionality, such as AO half-adder, latches, comparator, half-subtractor, and encoder can be implemented by combing the presented AO gates and hence exploiting the ultrafast TPA-induced gain and phase changes in CR-SOAs. Furthermore, the potential of CR-SOAs as nonlinear elements is systematically and thoroughly established for a wide suite of AO logic operations.

Temperature response of all-optical XOR logic function based on different semiconductor optical amplifiers

A critical area of research is studying the performance of semiconductor optical amplifiers (SOAs) at high temperatures. In this paper, the performance of all-optical exclusive-OR (XOR) logic gate is investigated at high operating temperatures (TOP) using different SOAs technologies such as conventional SOAs, carrier reservoir (CR)-SOAs, reflective SOAs (RSOAs), and photonic crystal (PC)-SOAs, for the first time to our knowledge. The time-dependent differential equations of SOAs, CR-SOA, RSOAs, and PC-SOAs at different operating data rates have been solved. The performance of the XOR logic gate is evaluated by calculating the quality factors and plotting the eye diagrams for each amplifier. Besides, the dependence of the key operating parameters on the TOP is examined and assessed for each scheme. The results showed that the RSOAs perform better at high temperatures than other proposed SOA technologies.

Local Destruction of Tumors for Systemic Immunoresponse: Engineering Antigen-Capturing Nanoparticles as Stimulus-Responsive Immunoadjuvants.

Immunotherapy has established a new paradigm for cancer treatment and made many breakthroughs in clinical practice. However, the rarity of immune response suggests that additional intervention is necessary. In recent years, it has been reported that local tumor destruction (LTD) can cause cancer cell death and induce an immunologic response. Thus, the combination of immunotherapy and LTD methods will be a promising approach to improve immune efficiency for cancer treatment. Herein, a nanobiotechnology platform to achieve high-precision LTD for systemic cancer immunotherapy has been successfully constructed. Possessing radio-sensitizing and photothermal properties, the engineered immunoadjuvant-loaded nanoplatform, which could precisely induce radiotherapy (RT)/photothermal therapy (PTT) to eliminate local tumor and meanwhile lead to the release of tumor-derived protein antigens (TDPAs), has been facilely fabricated by commercialized SPG membrane emulsification technology. Further on, the TDPAs could be captured and form personal nanovaccines in situ to serve as both reservoirs of antigen and carriers of immunoadjuvant, which can effectively improve the immune response. The investigations suggest that the combination of RT/PTT and improved immunotherapy using adjuvant-encapsulated antigen-capturing nanoparticles holds tremendous promise in cancer treatments.

Tailoring Dirac Plasmons via Anisotropic Dielectric Environment by Design

Dirac plasmons in a two-dimensional (2D) crystal are strongly affected by the dielectric properties of the environment, due to interaction of their electric field lines with the surrounding medium. Using graphene as a 2D reservoir of free carriers, one can engineer a material configuration that provides an anisotropic environment to the plasmons. In this work, we discuss the physical properties of Dirac plasmons in graphene surrounded by an arbitrary anisotropic dielectric and exemplify how $h$-$\mathrm{BN}$--based heterostructures can be designed to bear the required anisotropic characteristics. We calculate how dielectric anisotropy impacts the spatial propagation of the plasmons and find that an anisotropy-induced plasmon mode emerges, together with a damping pathway, that stem from the out-of-plane off-diagonal elements in the dielectric tensor. Furthermore, we find that one can create hyperbolic plasmons by inheriting the dielectric hyperbolicity of the designed material environment. Strong control over plasmon propagation patterns can be realized in a similar manner. Finally, we show that in this way one can also control the polarization of the light-matter excitations that constitute the plasmon. Taken together, our results promote the design of the dielectric environment as an effective path to tailor the plasmonic response of graphene on the nanoscopic level.