Advanced Photonics Research最新文献

Colloidal quantum dots (CQDs) are nanocrystals synthesized in solution, boasting remarkable optical properties and notable electronic characteristics, such as size-tunable bandgaps and high photoluminescence quantum yield. These features, coupled with solution processability, position CQDs as potential candidates for cost-effective and high-performance optoelectronic devices. However, several technological challenges hinder the full exploitation of CQDs in optoelectronics. Among these is the need for long insulating organic ligands in liquid-phase synthesis, which restrict efficient charge injection and transport in quantum dot (QD) films. Furthermore, the high surface-to-volume ratios and core–shell structures prompt complexities in terms of doping and modifying electronic properties. The colloidal nature of quantum dots (QDs) also raises challenges regarding controlled deposition and patterning, which are critical for device fabrication. In this review, the imperative is outlined to tailor CQDs for optoelectronic applications, the limitations that obstruct the implementation of desired modifications are elaborated on, and the specific hurdles confronting electronic coupling, targeted doping, and precision patterning of CQDs are focused on. Additionally, herein, a summary of the solutions proposed to date is offered, insights are shared on the discussed topics, and areas warranting future investigation are highlighted.

High-dimensional multiplexing technology is of importance in the on-chip photonic interconnections and challenging to design within ultracompact footprint. Herein, high-dimensional demultiplexers are proposed and demonstrated to enable wavelength-division and mode-division simultaneously. The functional regions of digital metamaterials are obtained by inverse design individually and are cascaded to work as high-dimensional demultiplexers. The gradient-based inverse design is carried out with an efficient method combining finite-element method, density method, and method of moving asymptotes. The performances are simulated by 3D finite difference time domain with silicon-on-insulator configuration. The proposed demultiplexer with four-channel has ultracompact footprint of 4.1 × 3.65 μm². Its average transmission efficiency is 38.7% and contrast ratios are higher than 13.0 dB. Besides, the proposed demultiplexer with six-channel has a footprint of 4.55 × 5.55 μm². Its average transmission efficiency is 24.3% and contrast ratios are higher than 11.8 dB.

Strain engineering is one of the leading mechanical ways to tune the optical properties of monolayer transition metal dichalcogenides among different techniques. Here, uniaxial strain is applied on exfoliated 1L-WSe₂ flakes transferred on flexible polycarbonate substrates to study the strain tuning of upconversion photoluminescence. It is demonstrated that the peak position of upconversion photoluminescence is redshifted by around 20 nm as the applied uniaxial strain increases from 0% to 1.17%, while the intensity of upconversion photoluminescence increases exponentially for the upconversion energy difference ranging from −155 to −32 meV. The linear and sublinear power dependence of upconversion photoluminescence is observed for different excitation wavelengths with and without uniaxial strain, suggesting the multiphonon-assisted mechanism in one-photon regime for the upconversion process. These results offer the potential to advance 2D material-based optical upconversion applications in night vision, strain-tunable infrared detection, and flexible optoelectronics.

Herein, the optical properties of the azimuthally radially polarized beam (ARPB), a superposition of an azimuthally polarized beam and a radially polarized beam, which can be tuned to exhibit maximum chirality at a given energy density, are investigated. This condition is called “optimal chiral light” since it represents the maximum possible local chirality at a given energy density. The transverse fields of an ARPB dominate in the transverse plane but vanish on the beam axis, where the magnetic and electric fields are purely longitudinal, leading to an optical chirality density and an energy density that stem solely from the longitudinal field components on the beam axis, where the linear and angular momentum densities vanish. The ARPB does not have a phase variation around the beam axis and nonetheless exhibits a power flow around the beam axis that causes a longitudinal orbital angular momentum density. Herein, a concise notation for the ARPB is introduced and field quantities are provided, especially for the optimally chiral configuration. The ARPB shows promise for precise 1D chirality probing and enantioseparation of chiral particles along the beam axis, relying solely on its longitudinal electric and magnetic fields. Herein, a setup is provided to generate ARPBs with controlled chirality and orbital angular momentum.

Field manipulations of bands in the infrared spectra of thin films are studied by Karsten Hinrichs and co-workers (see article number 2300212). This work demonstrates the necessity of optical analyses for gaining a detailed understanding of band properties and their relation to the materials dielectric functions, the measurement geometry, the thickness, structure and morphology of the film as well as the polarization of the probing electromagnetic fields.

The cover picture referring to article number 2300241 by Myungkoo Kang, Tian Gu, and co-workers showcases photochemically induced micro-gratings for a hybrid diffractive–refractive lens. These lenses, composed of diffractive and refractive elements, aim to achieve achromatic optics with significantly reduced size, weight, and power consumption. Here, metastable As₂S₃ chalcogenide glasses underwent direct laser writing and subsequent selective etching to create diffractive micro-gratings. The grid on the lens’ surface represents photochemically induced micro-gratings, while the surrounding residue indicates ongoing selective etching. Incident parallel beams converge into a single focal point upon passing through the lens. (Cover illustration: courtesy of Ella Maru Studio.)

Topological defects (TDs) manifest in many condensed matter systems. In liquid crystals (LCs), they occur as point or line singularities in the otherwise smooth director profile. Engineered and controllable TDs are of great interest for functional optoelectronic devices; however, the formation mechanism in patterned devices is not fully understood. In this work, electrically addressable TDs in doped mixtures of prototypical n-alkyl-cyanobiphenyl LCs 4-cyano-4′-pentylbiphenyl (5CB) and 4-cyano-4′-octylbiphenyl (8CB) are focused on. Doping concentrations of hexadecyltrimethylammonium bromide (CTAB) are varied and the effect of varying the host LC properties (through binary 5CB:8CB mixtures) on defect formation is studied. In the results, a strong correlation between LC “fluidity” and the ease of defect array formation is presented, with 0.5 wt% CTAB-doped 5CB giving the best controllability/uniformity of TDs at low-threshold voltages. Furthermore, it is demonstrated that the devices can be utilized as electrically switchable optical diffractive elements. In these findings, directions are mapped out that future studies can take in designing deterministic, electrically or magnetically tunable TD-based photonic devices using LC systems.

The potential of geometrically induced terahertz surface wave technology for communications can only be realized if communication links based on them are studied and benchmarked. The frequency-dependent transmission characteristics of interconnects based on three different archetypal textured surfaces (namely, gratings, dominos, nails) are analyzed numerically and the impact of the geometry and realistic surface roughness on the maximum capacity and energy efficiency is quantified. Unlike conventional hollow waveguides, the analysis shows that the capacity of uncoated corrugated surfaces is limited by loss and not dispersion. This work provides the guidelines for the design of terahertz surface wave interconnects.

Optical antennas are nanostructures that introduce unprecedented possibilities for light–matter interaction at the nanoscale. An appropriately tailored plasmonic antenna can enhance the total radiative decay rate and modify the angular radiation pattern of a single-quantum emitter through controlled near-field coupling. Despite their ability to surpass the fundamental diffraction limit and confine the electromagnetic field to a tiny mode volume, fabricating 3D sharp scanning nanoscale plasmonic structures with desired aspect ratio is yet an ambitious goal. The fabrication of nanocones by gold evaporation on commercial atomic force microscopy probes followed by a focused ion beam milling technique is presented. The method is versatile and allows the fabrication of nanocones with desired dimensions around 100 nm along with an aspect ratio of ≈1. Their optical properties are studied and it is shown how the variation in the refractive index of the dielectric substrate affects the localized surface plasmon resonance of the nanocones, the decay rate enhancement, and the quantum yield of an emitter relevant for fluorescence/Raman scanning experiments. Theoretical studies using finite-difference time-domain calculations have guided the fabrication process and are consistent with experimental results.

Total internal reflection prevents photons from escaping deep-ultraviolet (DUV) LED, resulting in serious energy waste and reduced service life. To lift the limitation of extraction ability of AlGaN-based DUV LEDs, an inspiration was drawn from biological visual systems with wide field, which have obtained highly optimized features through evolution. By reconfiguring planar compound eye lens (PCEL) on the n-AlGaN surface utilizing bio-inspired features acquired from praying mantis, light extraction efficiency (LEE) enhancement over 180% is demonstrated both for transverse electric (TE) and magnetic fields by finite difference-time domain (FDTD) simulation. Owing to its ultrathin planar structure and compatibility of material, PCEL provides a pathway to improve energy utilization efficiency of DUV-LED utilizing one-step nanoimprint.