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Highly Nonlinear, Dispersion Flattened Equiangular Spiral Photonic Crystal Fiber in Telecommunications Window
摘要： This paper presents an equiangular spiral (ES) cladding photonic crystal fiber (PCF) made of lead silicate glass SF57. The proposed ES-PCF exhibits a flat dispersion at the telecommunications window with high nonlinearity and low confinement loss, showing an ultra-flattened dispersion at wavelengths ranging from 1.51 to 1.81 μm (300 nm band), with confinement losses of less than 0.0031 dB/km within this wavelength range, and two zero-dispersion wavelengths at 1.55 and 1.76 μm. Moreover, this fiber also has a high nonlinear coefficient of 1285 W-1km-1 at 1.55 μm.
关键词： Photonic crystal fiber,Ultra-flattened dispersion,Confinement loss,High nonlinearity
更新于2025-09-09 09:28:46
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Entanglement Reduction Induced by Geometrical Confinement in Polymer Thin Films
摘要： We report simulation results on melts of entangled linear polymers confined in a free-standing thin film. We study how the geometric constraints imposed by the confinement alter the entanglement state of the system compared to the equivalent bulk system using various observables. We find that the confinement compresses the chain conformation uniaxially, decreasing the volume pervaded by the chain, which in turn reduces the number of the accessible interchain contact that could lead to entanglements. This local and nonuniform effect depends on the position of the chain within the film. We also test a recently presented theory that predicts how the number of entanglements decreases with geometrical confinement.
关键词： simulation,polymer thin films,primitive path,geometrical confinement,entanglement
更新于2025-09-09 09:28:46
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Tailoring the confined states for exciton-polaritons in a one-dimensional ZnO microrod
摘要： The application of confinement potential is an efficient way to improve the optical properties of exciton polaritons. In this work, we report experimental studies on the effects of potential landscapes on confined polariton states. The spatial confinement of polaritons was realized by imposing two optically-controlled barriers on a one-dimensional ZnO microrod. Two types of quantized polariton states were observed, where energies of the levels depend either linearly or quadratically on their quantum number. The formation of optical traps with parabolic or square-well profiles was confirmed to be responsible for the observed different states. These results demonstrate the importance of the potential landscapes in tailoring the optical properties of exciton polaritons, which would be helpful in the design of polariton-based optoelectronic devices.
关键词： optoelectronic devices,exciton-polaritons,optical traps,ZnO microrod,confinement potential
更新于2025-09-09 09:28:46
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Nanowires for energy: A review
摘要： Semiconductor nanowires (NWs) represent a new class of materials and a shift from conventional two-dimensional bulk thin films to three-dimensional devices. Unlike thin film technology, lattice mismatch strain in NWs can be relaxed elastically at the NW free surface without dislocations. This capability can be used to grow unique heterostructures and to grow III-V NWs directly on inexpensive substrates, such as Si, rather than lattice-matched but more expensive III-V substrates. This capability, along with other unique properties (quantum confinement and light trapping), makes NWs of great interest for next generation optoelectronic devices with improved performance, new functionalities, and reduced cost. One of the many applications of NWs includes energy conversion. This review will outline applications of NWs in photovoltaics, thermoelectrics, and betavoltaics (direct conversion of solar, thermal, and nuclear energy, respectively, into electrical energy) with an emphasis on III-V materials. By transitioning away from bulk semiconductor thin films or wafers, high efficiency photovoltaic cells comprised of III-V NWs grown on Si would improve performance and take advantage of cheaper materials, larger wafer sizes, and improved economies of scale associated with the mature Si industry. The thermoelectric effect enables a conversion of heat into electrical power via the Seebeck effect. NWs present an opportunity to increase the figure of merit (ZT) of thermoelectric devices by decreasing the thermal conductivity (j) due to surface phonon backscattering from the NW surface boundaries. Quantum confinement in sufficiently thin NWs can also increase the Seebeck coefficient by modification of the electronic density of states. Prospects for III-V NWs in thermoelectric devices, including solar thermoelectric generators, are discussed. Finally, betavoltaics refers to the direct generation of electrical power in a semiconductor from a radioactive source. This betavoltaic process is similar to photovoltaics in which photon energy is converted to electrical energy. In betavoltaics, however, energetic electrons (beta particles) are used instead of photons to create electron-hole pairs in the semiconductor by impact ionization. NWs offer the opportunity for improved beta capture efficiency by almost completely surrounding the radioisotope with semiconductor material. Improving the efficiency is important in betavoltaic design because of the high cost of materials and manufacturing, regulatory restrictions on the amount of radioactive material used, and the enabling of new applications with higher power requirements.
关键词： photovoltaics,light trapping,nanowires,quantum confinement,thermoelectrics,lattice mismatch,betavoltaics,III-V materials,semiconductor,energy conversion
更新于2025-09-09 09:28:46
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Fabrication of GaOx Confinement Structure for InGaN Light Emitter Applications
摘要： An indium gallium nitride (InGaN) light-emitting diode (LED) with an embedded porous GaN reflector and a current confined aperture is presented in this study. Eight pairs of n+-GaN:Si/GaN in stacked structure are transformed into a conductive, porous GaN/GaN reflector through an electrochemical wet-etching process. Porous GaN layers surrounding the mesa region were transformed into insulating GaOx layers in a reflector structure through a lateral photoelectrochemical (PEC) oxidation process. The electroluminescence emission intensity was localized at the central mesa region by forming the insulating GaOx layers in a reflector structure as a current confinement aperture structure. The PEC-LED structure with a porous GaN reflector and a current-confined aperture surrounded by insulating GaOx layers has the potential for nitride-based resonance cavity light source applications.
关键词： insulating GaOx,current confinement aperture structure,porous GaN,InGaN
更新于2025-09-04 15:30:14
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Enhanced Luminescence from InGaN/GaN Nano-disk in a wire Array Caused by Surface Potential Modulation during Wet Treatment
摘要： Here we have demonstrated the profound impact of surface potential on the luminescence of an array of InGaN/GaN nano-disk in a wire heterostructure. The change in surface potential is brought about by a combination of dry and successive wet-processing treatments. The photoluminescence (PL) properties are determined as a function of size and varying surface potential. The change in hole bound state energy due to parabolic potential well near the side-wall is found to be the dominating factor. The PL peak position, full width at half-maximum (FWHM), strain relaxation and integrated PL intensity are studied as a function of incident power and temperature. The devices demonstrate higher integrated PL intensity and slope efficiency.
关键词： exciton binding energy,photoluminescence,QCSE,nano-disk,surface potential,strain relaxation,InGaN/GaN,quantum confinement
更新于2025-09-04 15:30:14
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Photoluminescence from GaAs nanostructures
摘要： The confinement properties of semiconductor nanostructures have promising potential in technological application. The main objective of this study is to describe the dependence of Photoluminescence (PL) intensity on different parameters like temperature, excitation wavelength, time and photon energy of GaAs quantum dots (QDs). The model equations are numerically analyzed and simulated with matlab and FORTRAN codes. The experimental fitted values and physical properties of materials are used as data source for our simulation. The result shows that at low temperature the peak is quite sharp, as temperature increases the PL intensity decreases and get quenched at particular thermal energy.
关键词： quantum confinement,Photoluminescence (PL) intensity,GaAs quantum dots,nanostructures,thermal quenching energy
更新于2025-09-04 15:30:14
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Effect of the anchoring strength on the phase behaviour of discotic liquid crystals under face-on confinement
摘要： In this study we have performed molecular dynamics simulations to study a Gay-Berne discotic fluid confined in a slab geometry for a fixed confinement length. Four different anchoring strengths with a homeotropic (face-on) configuration were studied. We found that changing the anchoring strength changes the normal component of the stress tensor, which in turn changes the density of the system’s bulk. This phenomenon leads to a shift in the isotropic-nematic transition temperature. We observe that the temperature regions where the nematic phase is present diminishes as the anchoring strength increases. The anchoring strength also affects the nematic-columnar coexistence temperature-region: it spans over more temperatures at higher anchoring strengths.
关键词： molecular dynamics simulations,discotic liquid crystals,anchoring strength,phase behaviour,face-on confinement
更新于2025-09-04 15:30:14
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[Ceramic Transactions Series] Proceedings of the 12th Pacific Rim Conference on Ceramic and Glass Technology (Ceramic Transactions) || Dielectric Properties of Confined Ionic Liquids
摘要： Ionic liquids, as solvent free electrolytes, are promising materials improving the energy density of future storage devices. Two key requirements for such an application are a broad electrochemical window and a high ionic mobility of ionic liquids. A thorough measurement of the dielectric properties in a broad temperature and frequency regime allows analyzing the latter one in detail. Ionic mobility is influenced by intrinsic relaxations. These relaxations are influenced by correlation between the molecules. Confining the molecules allows to access this correlation length and to address the fundamental questions regarding supercooled liquids. We demonstrate this by confining the ionic liquid 1-butyl-3-methyl-imidazolium chloride in a metal-organic-framework, namely MFU-4. The preliminary results of an enhanced rotational motion compared to the bulk ionic liquid point towards a temperature, where the correlation length corresponds to the pore diameter of the confining host.
关键词： Ionic liquids,confinement,metal-organic-framework,BMIM-Cl,MFU-4,dielectric properties
更新于2025-09-04 15:30:14
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Note: Radiochemical measurement of fuel and ablator areal densities in cryogenic implosions at the National Ignition Facility
摘要： A new radiochemical method for determining deuterium-tritium (DT) fuel and plastic ablator (CH) areal densities (ρR) in high-convergence, cryogenic inertial confinement fusion implosions at the National Ignition Facility is described. It is based on measuring the 198Au/196Au activation ratio using the collected post-shot debris of the Au hohlraum. The Au ratio combined with the independently measured neutron down scatter ratio uniquely determines the areal densities ρR(DT) and ρR(CH) during burn in the context of a simple 1-dimensional capsule model. The results show larger than expected ρR(CH) values, hinting at the presence of cold fuel-ablator mix.
关键词： cryogenic inertial confinement fusion,neutron down scatter ratio,National Ignition Facility,areal densities,fuel-ablator mix,plastic ablator,deuterium-tritium fuel,radiochemical method,Au hohlraum
更新于2025-09-04 15:30:14