Photonics and Nanostructures-Fundamentals and Applications最新文献

Using the previously introduced modified discrete dipole approximation (DDA) method by applying the full details of the nanoparticle and its surrounding environment, the detection sensitivity of molecules by plasmonic Rod-based nanosensors, including U-shaped and Rod-shaped structures, was investigated. In the calculations, the two factors of the magnitude of the wavelength shift and the ability to distinguish molecules with similar properties were of significant interest. The results indicated that the sensitivity of Rod-based nanostructures is significantly higher than that of spherical nanoparticles. Among the plasmonic Rod-based nanosensors, the silver U-shaped structure performs better than others. The wavelength shift of the absorption spectrum of different nanosensors for a given molecule was very different, making it possible to detect very similar molecules from each other by testing different sensors.

Mid-infrared spectroscopy enabled by silicon photonics has received great interest in recent years as a pathway for a scalable sensing technology. The development of such devices would realise inexpensive and accessible instrumentation for a wide variety of uses over numerous fields. However, not every sensing application is the same; to produce sensors for real-world scenarios, engineers need flexibility in device design but also need to maintain compatibility with scalable fabrication processes. Sub-wavelength gratings can offer a solution to this problem, as they enable the engineering of optical properties using standard fabrication techniques and without requiring new materials. By using sub-wavelength gratings, specific design approaches can be tailored to different applications, such as increasing the interaction of a sensor with an analyte or broadening the bandwidth of an integrated photonic device. Here, we review the development of sub-wavelength grating-based devices for mid-infrared silicon photonics and discuss how they can be exploited for spectroscopic and sensing devices.

Metal–organic frameworks (MOFs) have recently emerged as a new class of functional materials for opto- and micro-electronic applications. Herein, the transition from laboratory samples of devices to their prototypes remains a challenge. Here we report a prototype of memristive device based on MOF (HKUST-1). The MOF thin film with a thickness of 130 nm and a size of 1 × 1 in. has been fabricated Layer-by-layer technique on a conductive substrate followed by the deposition of top Ag contacts. A fully automated process of applying voltage to write the binary data (at 0.8 ± 0.1 V), read it (by 0.4 V) and then erase (by inverted polarity with 0.4 ± 0.1 V) made it potentially possible to process arbitrary words for at least 10 cycles. The provided prototype, consisting of 10 × 10 memory cells, opens up prospects for real-life application of MOF-based logic elements, as well as reveals the challenges for their fabrication and exploitation.

The selection of a suitable plasmonic material is crucial for achieving high-performance photonic crystal fiber-based surface plasmon resonance (PCF-SPR) sensors. However, most numerical investigations have been limited to PCF-SPR sensors with conventional circularly coated plasmonic metals due to their availability and rigid properties. In this work, a single-core arc-shaped PCF is designed and studied with sensing ingredients coated outside the fiber. The simulation and numerical analyses are performed using the full-vector finite element method to examine the effects of using gold as an active metal and also the deposition of Ta₂O₅ on gold. The results show that the arc-shaped sensor with gold film can obtain the maximum wavelength interrogation sensitivity (WIS) of 9500 nm/RIU within the refractive index (RI) range of 1.25–1.39 while the maximum amplitude interrogation sensitivity (AIS) reaches 579.26 RIU⁻¹ at 1.39 and resolution is 1.05 × 10⁻⁵. However, depositing Ta₂O₅ on the gold gives an improved maximum WIS and AIS of 22,000 nm/RIU and 1209.21 RIU⁻¹, respectively. With the coating of Ta₂O₅, the resolution improves to 4.55 × 10⁻⁶, making the proposed sensor design undoubtedly effective in detecting food chemicals such as butyl acetate and hydrocarbons along with different bio-analyte samples with a wide range of RI.

Luminescent organic thin films are widely used in optoelectronic devices for sensing, imaging and data processing. Herein, the transition to a flexible form is accompanied by a number of challenges associated with a limited endurance and bending-dependent properties. Here we report a study on the growth of thin films based on thiophene-based luminescent molecular crystals (MC) on a flexible polypropylene (PP) substrate of a various thicknesses (400 μm to 50 μm). The resulting flexible thin films demonstrate the stability of their luminescent properties under mechanical bending (up to 100 times) at ambient conditions, which pave the way for large scale production of planar optoelectronic components.

A new design of polarization-maintaining and spectral filtering negative curvature hollow-core fiber tailored for the telecommunication bands in the near-infrared region is presented. The optical fiber, consisting of a six-tube silica structure, incorporates vertically nested tubes anchored radially by a pole structure. By contrast, standard nested tubes in the horizontal direction form the asymmetric fiber structure, which encounters birefringence. This unique fiber design not only preserves the polarization states of light but also exhibits frequency selective transmission exclusively in the vertical direction due to the pole structure. Through fiber design optimization, a transmission loss below 0.1 dB/km for spectrally filtered wavelengths is achieved, with birefringence on the order of 10⁻⁵ within the wavelength range of 1.45 µm to 1.60 µm. These results demonstrate significant improvements in terms of birefringence, distinct loss separation between horizontally and vertically polarized states, and a reduced number of spectrally filtered wavelengths compared to previously reported findings. The proposed fiber design holds untapped potential for applications requiring selective transmissions with specific polarization.

Quadrupole topological insulators have recently attracted great attention in the field of topological physics, while they are limited to square and hexagonal lattices. In this work, we theoretically show that nontrivial quadrupole topology can be obtained in generalized non-square lattice photonic crystals with translation symmetry, which are composed of parallelogram-shaped unit cells. The translation symmetry is described by the fractional linear combination of primary lattice vectors, leading to the quantization of fractional quadrupole moment in conjunction with an additional symmorphic symmetry. For parallelogramatic lattice with inversion symmetry, in particular, the quantization of the quadrupole moment is independent of the choice of primary lattice vectors, enabling cavity structures with arbitrary angles. For the change of structural parameters, quadrupole bandgaps undergo second-order topological phase transitions, accompanying with double band inversions. Nontrivial quadrupole phases are manifested by the appearance of disorder-immune in-gap corner states localized at the topological interfaces. Furthermore, the proposed parallelogramatic lattice photonic crystal has multiple quadrupole bandgaps for proper structural parameters, exhibiting multiband second-order topological corner states. The presented results will further extend the class of quadrupole topological photonic crystals and pave a broad way towards their practical applications due to improved design flexibility.

Modern metal-semiconductor-metal nano- and micro-structures exhibit unique properties related to both light emission and detection. Here we develop a novel optimized numerical model to calculate charge carrier density inside a n-type semiconductor micro-crystal that is sandwiched between two Schottky contacts. We use drift-diffusion equations and finite difference methods and utilize the Scharfetter-Gummel discretization technique. We demonstrate that the concentration of majority charge carriers in the semiconductor can be reduced below the level observed at zero applied bias by surpassing the current density of minority charge carriers beyond that of the majority charge carriers. Subsequently, minority charge carrier concentration increases and becomes the dominant charge carrier inside the semiconductor at high applied bias. In addition, we provide evidence that the open circuit voltage of a semiconductor under illumination occurs at the point where the minority-majority current densities intersect. By adjusting the Schottky contact barrier, the crossing potential between minority and majority carriers can be controlled, thereby allowing for manipulation of the open circuit voltage. This is an important factor in determining the density of trap states in the semiconductor and designing an open circuit voltage photodetector. We verify our results using COMSOL Multiphysics software and show that our numerical approach is found to be more time-efficient than the methods employed by COMSOL Multiphysics.

In this work we investigate a structure based on p-doped Ge/SiGe asymmetric-coupled quantum wells (ACQW) that enables the second harmonic generation in SiGe waveguide by double-resonant intersubband transitions (ISBTs). These transitions lead to χ⁽²⁾ coefficients in the range 10⁴-10⁵ pm/V, significantly higher compared to the one of conventional nonlinear materials. We developed a model for the integration of Quantum Wells (QWs) into the active region of the waveguide through an adiabatic taper. Furthermore, we modelled the second harmonic (SH) conversion efficiency as a function of the propagation length, under both non-phase matching and phase-matching conditions. Our work demonstrates that the SiGe ACQWs can be used in spectral ranges not covered by the majority of conventional non-linear crystals, while allowing for the ready-integration with the CMOS technologies.

Silicon photonics, in conjunction with complementary metal-oxide-semiconductor (CMOS) fabrication, has greatly enhanced the development of integrated optical phased arrays. This facilitates a dynamic control of light in a compact form factor that enables the synthesis of arbitrary complex wavefronts in the infrared spectrum. We numerically demonstrate a large-scale two-dimensional silicon-based optical phased array (OPA) composed of nanoantennas with circular gratings that are balanced in power and aligned in phase, required for producing elegant radiation patterns in the far-field. For a wavelength of 1.55 μm, we optimize two antennas for the OPA exhibiting an upward radiation efficiency as high as 90%, with almost 6.8% of optical power concentrated in the field of view. Additionally, we believe that the proposed OPAs can be easily fabricated and would have the ability to generate complex holographic images, rendering them an attractive candidate for a wide range of applications like LiDAR sensors, optical trapping, optogenetic stimulation, and augmented-reality displays.