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Spatial confinement effect on CN emission from nanosecond laser-induced PMMA plasma in air
摘要： In this paper, a PMMA target was ablated to study spatial confinement effect on CN emission of laser-induced PMMA plasma in air. Four cylindrical cavities with same depth and different diameters (4, 6, 8, and 10 mm) were used to confine the nanosecond laser-ablated PMMA plasma plume. Laser pulse energies were 40, 50, and 60 mJ. The influence of cavity diameter on emission band and vibration temperature of CN molecule was demonstrated, the results showed an obvious increase in the emission and vibration temperature of CN molecule by using the cylindrical cavity. When the cavity diameter was smaller at a fixed laser energy, the emission enhancement of CN molecule appeared earlier, and the CN molecule had stronger emission and vibration temperature. For a fixed diameter cavity, when the laser energy was higher, the CN molecule presented stronger emission and higher vibration temperature, and the emission enhancement also appeared earlier. The enhanced effect on the spatial confinement mainly comes from shock wave produced by the laser-induced PMMA plasma. The spatial confinement cavity can reflect the shock wave, and the shock wave compresses the plasma plume, resulting in an improvement in the temperature and density of the plasma. Therefore, the optical emission of CN molecule increases as the shock wave interacts with the PMMA plasma.
关键词： CN,PMMA,laser-induced breakdown spectroscopy,spatial confinement
更新于2025-09-23 15:19:57
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Performance enhancement of AlGaN-based deep ultraviolet light-emitting diodes by using stepped and super-lattice n-type confinement layer
摘要： In this paper, a new n-type confinement layer that uses the stepped and super-lattice structure to replace conventional n-type AlGaN layer of deep ultraviolet light-emitting diode (DUV LED) is investigated. The simulation results indicate that the new structure significantly enhances the light output power (LOP) and internal quantum efficiency (IQE) of DUV LED. This is because the capability of carrier confinement in the quantum wells (QWs) is enhanced; the carrier concentrations and the radiative recombination rate in the active region of DUV LED are improved.
关键词： n-type confinement layer,DUV LED,Performance enhancement
更新于2025-09-23 15:19:57
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Tunable Microlasers Modulated by Intracavity Spherical Confinement with Chiral Liquid Crystal
摘要： Manipulation of laser emission offers promising opportunities for the generation of new spatial dimensions and applications, particularly in nanophotonics, super-resolution imaging, and data transfer devices. However, the ability to control laser modes and wavelength in a microcavity remains challenging. Here, a novel approach is demonstrated to control laser modes by manipulating the 3D-optical confinement, chirality, and orientations in a Fabry?Pérot microcavity with cholesteric liquid crystal droplets. Different configurations of intracavity micro-/nanostructures generate versatile dimensions of laser modes, while the significantly reduced laser mode volume further leads to single-mode lasing. Theoretical analysis is carried out to support this interesting discovery. Finally, switchable lasing wavelength with various surface anchoring forces and pH interactions is demonstrated. This novel concept not only provides a simple yet highly versatile method to manipulate laser emissions, but deepens insight into how molecules interact with and modulate laser light, laying the foundation for the development of tunable photonic devices at the molecular level. Promising applications include highly selective laser devices, laser-emission imaging, and bioinspired sensing.
关键词： tunable lasing,high-order laser mode,cholesteric liquid crystals,spherical confinement,intracavity interactions
更新于2025-09-23 15:19:57
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Quantum size effect and surface defect passivation in size-controlled CsPbBr3 quantum dots
摘要： Luminescent CsPbBr3 quantum dots (QDs) with adjustable size and bandgap were grown by controlling the synthesis temperature in this paper. As the synthesis temperature increases, the QD size becomes larger and then smaller. The corresponding absorption and steady-state photoluminescence spectrum indicate that the QD band gap becomes smaller and then larger, which is a typical quantum confinement effect. Time-resolved photoluminescence spectrum and femtosecond transient absorption spectrum (fs-TAS) show that the non-radiative recombination probability of photocarriers in small QDs is small it has few defects, indicating that the ligand molecules adsorbed on the surface of QDs effectively passivate the surface defects of CsPbBr3. Finally, the hot-phonon bottleneck effect of CsPbBr3 QDs is revealed by the kinetic curves fitting of fs-TAS and the cooling kinetic process of hot carriers is also discussed in detail. This work provides new insights on size-dependent photophysical properties of CsPbBr3 QDs.
关键词： Quantum confinement effect,Metal halide perovskite QDs,Defect passivation,Hot carriers
更新于2025-09-23 15:19:57
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Nanoshell quantum dots: Quantum confinement beyond the exciton Bohr radius
摘要： Nanoshell quantum dots (QDs) represent a novel class of colloidal semiconductor nanocrystals (NCs), which supports tunable optoelectronic properties over the extended range of particle sizes. Traditionally, the ability to control the bandgap of colloidal semiconductor NCs is limited to small-size nanostructures, where photoinduced charges are confined by Coulomb interactions. A notorious drawback of such a restricted size range concerns the fact that assemblies of smaller nanoparticles tend to exhibit a greater density of interfacial and surface defects. This presents a potential problem for device applications of semiconductor NCs where the charge transport across nanoparticle films is important, as in the case of solar cells, field-effect transistors, and photoelectrochemical devices. The morphology of nanoshell QDs addresses this issue by enabling the quantum-confinement in the shell layer, where two-dimensional excitons can exist, regardless of the total particle size. Such a geometry exhibits one of the lowest surface-to-volume ratios among existing QD architectures and, therefore, could potentially lead to improved charge-transport and multi-exciton characteristics. The expected benefits of the nanoshell architecture were recently demonstrated by a number of reports on the CdSbulk/CdSe nanoshell model system, showing an improved photoconductivity of solids and increased lifetime of multi-exciton populations. Along these lines, this perspective will summarize the recent work on CdSbulk/CdSe nanoshell colloids and discuss the possibility of employing other nanoshell semiconductor combinations in light-harvesting and lasing applications.
关键词： Optoelectronic properties,Nanoshell quantum dots,CdSbulk/CdSe nanoshell,Colloidal semiconductor nanocrystals,Quantum confinement
更新于2025-09-23 15:19:57
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Low-Loss and Dispersion-Flattened Octagonal Porous Core PCF for Terahertz Transmission Applications
摘要： In order to make the direct transmission more effective, we have intended an octagonal shape cladding design in this paper. The minimum resultant effective material loss obtained from our proposed photonic crystal fiber is 0.007 cm-1 at 0.5 THz is very effective. The proposed design gives an ultra-high birefringence of 0.06 with an effective area of about 4 9 10-6 m2, a core power fraction of 70% for 290 lm core diameter with a core porosity of 80% at 1.6 THz frequency and closely zero flattened dispersion of variation of 0.3 ± 0.1 ps/THz/cm at a wide frequency range of 0.7–2.1 THz.
关键词： Terahertz,Core porosity,Effective material loss,Octagonal core,Confinement loss,Dispersion
更新于2025-09-23 15:19:57
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Blue-emitting and self-assembled thinner perovskite CsPbBr <sub/>3</sub> nanoplates: Synthesis and formation mechanism
摘要： Low dimensional semiconductor nanomaterials have a great promise for a variety of applications due to their size-dependent and excellent optoelectronic properties. In this work, we developed a strategy to synthesize uniform and very thin CsPbBr3 perovskite nanoplates (NPls) by introducing additional metal bromides. The CsPbBr3 NPls, self-assembled to a face-to-face stacked state, had a thickness of 4.4 nm (equal to only 2 monolayers, 2 MLs) and showed a maximum emission at 437 nm and a narrow FWHM of 14 nm. The formation mechanism of the CsPbBr3 NPls by adding FeBr3 was ascribed to the constrained growth of CsPbBr3 nanocubes when the surface of Cs+ ions was substituted by the protonated oleylammonium from the byproduct OLA-HBr.
关键词： blue-emitting,quantum confinement,self-assembly,CsPbBr3,perovskite nanoplates
更新于2025-09-23 15:19:57
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Methanol-Filled Hybrid Photonic Crystal Fiber with High Birefringent and Negative Dispersion
摘要： A unique hexagonal lattice structure of silica-based solid core photonic crystal fiber (PCF) surrounded by array of air holes is proposed. The cladding portion of the structure consists of five rings where core is made up of 11 small rings filled with methanol. Three different-shaped structures are used to analyze the effect on PCF parameters where the first structure uses circular air holes in cladding and core, the second structure consists of circular air holes in cladding and elliptical air holes in core, and the last structure was designed by using elliptical air holes in both cladding and core. Optical properties birefringence, confinement loss, and negative dispersion have been found theoretically and compared. A novel and relatively simple approach depicts the results that attain high birefringence, low confinement loss, and negative dispersion. It is found that the presence of elliptic air holes instead of circular air holes in the core region and the cladding brings higher birefringence, low confinement loss, and highly negative dispersion.
关键词： Photonic crystal fiber,Effective refractive index,Dispersion,Birefringence,Confinement loss
更新于2025-09-23 15:19:57
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Nanostructuring Confinement for Controllable Interfacial Charge Transfer
摘要： Carbon nanostructures supported semiconductors are common in photocatalytic and photoelectrochemical applications, as it is expected that the nanoconductors can improve the spatial separation and transport of photogenerated charge carriers. Transfer of charge carriers through the carbon-semiconductor interface is the key electronic process, which determines the role of charge separation channels, and is sensitively influenced by band structures of the semiconductor near the contacts. Usually, this electronic process suffers from excessive energy dissipation by thermionic emission, which will undesirably prevent the interfacial charge transfer and eventually aggravate the recombination of photogenerated charge carriers. Unfortunately, this critical issue has hardly been consciously considered. Here, ultrathin dopant-free tunneling interlayers coated on the surface of graphene and sandwiched between the carbon sheets and the semiconductor nanostructures are adopted as a model system to demonstrate energy saving for the interfacial charge transfer. The nanostructuring confinement of band bending within the ultrathin interlayers in contact with the graphene sheets effectively narrows the width of the potential barriers, which enables tunneling of a substantial number of photogenerated electrons to the co-catalysts without unduly consuming energy. Besides, the dopant-free tunneling interlayers simultaneously block the transferred electrons in the sandwiched graphene sheets from leakage.
关键词： nanostructuring confinement,thermionic emission,electron tunneling,charge transfer,charge transport
更新于2025-09-19 17:15:36
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Methodical engineering of defects in MnXZn1-X O(x?=?0.03, and 0.05) nanostructures by electron beam for nonlinear optical applications: A new insight
摘要： A series of MnxZn1-xO (x = 0.03, 0.05) nanostructures have been grown via the solution based chemical spray pyrolysis technique. Electron beam induced modifications on structural, linear and nonlinear optical and surface morphological properties have been studied and elaborated. GXRD (glancing angle X-ray diffraction) patterns show sharp diffraction peaks matching with the hexagonal wurtzite structure of ZnO thin films. The upsurge in e-beam dosage resulted in the shifting of XRD peaks (101) and (002) towards lower angle side, and increase in FWHM value. Gaussian deconvolution on PL spectra reveals the quenching of defect centers, implying the role of electron beam irradiation regulating luminescence and defect centers in the nanostructures. Irradiation induced spatial confinement and phonon localization effects have been observed in the films via micro Raman studies. The later are evident from spectral peak shifts and broadening. Detailed investigations on the effect of electron beam irradiation on third order nonlinear optical properties under continuous and pulsed mode of laser operation regimes are deliberated. Third order absorptive nonlinearity of the nanostructures evaluated using the open aperture Z-scan technique in both continuous and pulsed laser regimes shows strong nonlinear absorption coefficient β eff of the order 10-4 cm/W confirming their suitability for passive optical limiting applications under intense radiation environments. Laser induced third harmonic generation (LITHG) experiment results supports the significant variation in nonlinearities upon electron beam irradiation, and the effect can be utilized for frequency conversion mechanisms in high power laser sources and UV light emitters.
关键词： Mn:ZnO nanostructures,8MeV e-beam,Spatial confinement effects,Defects quenching,Third harmonic generation
更新于2025-09-19 17:15:36