Photonics and Nanostructures-Fundamentals and Applications最新文献

Miniaturized spectrometers are attracting widespread interest due to the rising demand for portable spectroscopic applications. While the chip-scale spectrometers are widely investigated using silicon photonics technology, few research have addressed the need for a mid-infrared (MIR) integrated chip-scale spectrometer due to the lack of an effective reconfigurable photonics approach. In this paper, we present a novel solution using silicon photonics MEMS technology in the MIR region (3.6–5 µm wavelength range). We adopt a computational spectrometry scheme using the digitalized control of cascaded MEMS-tunable waveguide couplers. The MEMS waveguide couplers are operated in digital on/off mode, thus making the device immune to driving voltage fluctuations and robust for on-chip field sensing applications. Moreover, a comprehensive numerical analysis method is discussed to systematically evaluate the performance of the computational spectrometer, including its resolution and operational bandwidth. As a proof-of-concept, a chip-scale spectrometer realized by seven cascaded MEMS-actuated waveguide coupler is demonstrated. The sparse spectral reconstruction is demonstrated in the wavelength range from 3.65 to 4.1 µm and the dual-peaks reconstruction results indicate a resolution of 8 nm. Besides, response time and power consumption of the proposed device are experimentally characterized. Benefitting from good scalability, the spectral resolution can be further improved by increasing the number of waveguide coupler stages. The proposed work has the potential to realize lab-on-a-chip applications with advances in MIR silicon photonics. © 2001 Elsevier Science. All rights reserved.

Integrated sensors based on guided optical devices can efficiently and selectively detect molecules in the mid-infrared (mid-IR) spectral range, exploiting the vibrational and rotational modes of these molecules at these wavelengths. In this work, a ridge waveguide based on porous silicon (PSi) layers was developed by electrochemical etching followed by a photolithographic process. The ridge waveguide is capable of propagating light in the mid-IR range (3.90–4.35 µm) with optical losses of approximately 10 dB/cm. An oxidation study was performed to stabilize the porous structure and identify the optimal oxidation degree, that allow mid-IR light to propagate in a ridge waveguide based on PSi material for sensing application. The results showed that the ridge waveguide remains capable of propagating light after undergoing partial oxidation at 300 °C and 600 °C (15% and 36% of the oxidation degree respectively) with optical losses of around 30 dB/cm and 60 dB/cm at the wavelength of 4.1 µm, respectively.

A novel direct binary search algorithm based on rotation (RDBS) is proposed in this paper. A 1*2 ultra-compact 2.4*3.6µm² multimode wavelength demultiplexer (DEMUX) is designed in reverse, which is roughly two orders of magnitude smaller than the size of a conventional waveguide device. It can simultaneously perform wavelength demultiplexing and mode conversion. This DEMUX separates the 1310 and 1550 nm wavelengths while converting the input light from the fundamental transverse electric mode (TE0) to the first-order transverse electric mode (TE1). The simulation results using RDBS show that the insertion loss($IL$) of the upper channel (wavelength 1310 nm) is −0.9644 dB, the $IL$ of the lower channel (wavelength 1550 nm) is −0.9752 dB, and the crosstalk values(CT) are −10.079 dB and −9.261 dB, respectively.

The present study employs a cost-effective laser ablation technique in combination with the RF sputtering method to successfully synthesize silver nanoparticles encapsulated by zinc oxide on a silicon (Si) substrate. This synthesis approach aims to enhance the efficiency of photodetector devices while concurrently reducing material expenses, thereby promoting advancements in photodetector applications. The incorporation of various plasmonic nanoparticles (NPs) into the photodetector's architecture is demonstrated as a means to substantially improve the photoresponse of UV photodetectors. Three distinct samples, denoted as AgNPs/Si, AgNPs/ZnO/Si, and ZnO/AgNPs/Si, underwent comprehensive analysis and characterization of their morphological attributes, crystal structures, elemental composition, and optical properties. The UV photodetection efficacy of these samples was evaluated by subjecting them to 385 nm UV light at different bias voltages. The current-voltage (I-V) characteristics of the ZnO/AgNPs/Si photodetector revealed significantly enhanced conductivity in comparison to the AgNPs/Si and AgNPs/ZnO/Si counterparts. Remarkably, the ZnO/AgNPs/Si photodetector exhibited the highest responsivity value of 132 A/W, accompanied by quantum efficiency of 429.88, sensitivity of 31,400%, gain of 315, detectivity of 18 × 10¹⁰ Jones, and a noise equivalent power (NEP) of 0.556 × 10^–13 W. These findings underscore the efficacy of our innovative broadband photodetector, highlighting its potential for practical implementation. This research offers valuable insights into the enhancement of photodetector performance and its applicability in real-world scenarios.

In this work, a novel solar absorber with wide angle tolerance and insensitivity to polarization is proposed. The upper layer of the absorber comprises two polygonal structures, which can achieve an absorption rate of 94.2% across a broad wavelength range of 2218 nm (584 nm - 2802 nm). The performance of the absorber is simulated and verified using the finite difference time domain (FDTD) method combined with impedance matching theory. Through examining the electromagnetic field distribution at absorption peaks, the physical mechanism is elucidated. Moreover, incorporating refractory metals and nonmetallic materials in its design enhances the stability of the absorber, making it suitable for various extreme environments. This indicates its potential applications in solar energy storage and solar thermal photovoltaic systems.

We report mid-infrared photoconductive atomic-force microscopy (AFM) of a graphene sheet with doped-diamond AFM probes illuminated with a quantum cascade laser. The diamond probe ensures high mechanical and electrical stability. We observe a prominent photoconduction at finite biases that we interpret as the overcoming of a potential barrier formed at the graphene-diamond junction by free carriers excited by mid-infrared photons (220 meV photon energy). Moreover, we observe a small photo-thermoelectric effect of graphene under zero applied bias. We demonstrate that the use of diamond AFM probes for mid-infrared photoconductive AFM has great potential to investigate the nanometric inhomogeneities of the Fermi level and of the work function across integrated semiconductor devices.

The rapid development of thin-film light emitting devices (LED) technologies has recently been associated with the superior optoelectronic properties of luminescent materials based on lead halide perovskite nanocrystals (NCs) due to their narrow emission line with high color purity. However, the large surface area of NCs leads to the need to use solvating ligands to prevent their agglomeration, which limits their use in optoelectronics. Here we develop a class of modular polyfluorene (PF) copolymer with 4-hydroxyphenyl-, diethylamino- and diethoxyphosphoryl- groups designed to stabilize perovskite NCs. We show that as-synthesized CsPbBr₃ NCs can easily be mixed with custom-designed PFs resulting in polymer/NCs composite that shows efficient Förster energy transfer (FRET) from PF to NC with green photoluminescence (PL). We also found that the NCs composite studied here can be used as an effective emissive layer in LED due to the strong interaction between polymer host and perovskite NCs providing an efficient charge transfer from the PF matrice to the NC emitter. The fabricated LED show excellent performance with a highest current efficiency of ∼25.2 cd A^–1. Our approach provides a low-cost and efficient way for light-emitting optoelectronic applications based on perovskite NCs.

In this paper, the colorimetric and fluorescent biosensors prepared from polyethylene glycol diacrylate (PEGDA)-based inverse opal photonic crystal (IOPC) decorated with graphene oxide (GO) (termed as GO-modified PEGDA-based IOPC) have been explored for simple and rapid semi-quantitative and quantitative detections of biomarker lipocaline-1 (LCN1) in tear at low level, respectively. We found that only after the concentration of GO (C_GO) was sufficiently high to create a thin GO layer due to intermolecular interactions between neighboring GO molecules on the PEGDA surface, the red-shift of the reflection peak position (λ_stb) became effective. This widening of the shift in λ_stb became significant when GO-modified PEGDA-based IOPC was selectively attached with LCN1 via the immunoassay, because the attachment with LCN1 caused a reverse shift in λ_stb. Correspondingly, the visualizable photonic color could vary in wider range depending on the concentration of LCN1 (C_LCN1), from orange color of blank solution to light blue color of solution containing LCN1 at C_LCN1 of 0.06 mg/mL using C_GO = 2.5 mg/mL. For quantification, C_GO and enrichment time of LCN1 were optimized for getting the maximum fluorescence microscopy intensity. The diagram for the relationship between fluorescence intensity and C_LCN1 showed various advantages of GO-modified PEGDA-based IOPC over non-GO-modified PEGDA-based IOPC. Those were higher fluorescence intensity, wider linear range and higher detection sensitivity. Thus, our results revealed potential applications of GO-modified PEGDA-based IOPC in screening patients with diabetic retinopathy (DR) in early stage.

This paper presents systematic design and analysis of a dual-purpose integrated processor based on graphene hybrid plasmonic concentric add-drop microring resonators for fast differentiation and integration. The footprint of this processor is equal to 4 × 4.358 μm², containing two concentric rings with small radii of 1679 and 1204 nm. Performance of the designed dual-purpose processor for the first and fractional-orders differentiation and integration has been analyzed by the three-dimensional finite-difference time-domain method in the frequency and time domains and the accuracy of the results has been confirmed using the formulas of the ideal math differentiator and integrator. From the point of view of the performance specifications, the designed dual-purpose temporal processor has excellent 3 dB bandwidth, insertion loss, energy efficiency, and accuracy in the first and fractional-orders differentiation and integration.

We have developed a theory of the Bragg scattering for metallic nanohybrid made of an ensemble of metallic nanorods doped in a substrate. The substrate can gas, liquid or solid. An external laser field is applied to study the Bragg scattered light. The photons from the incident laser interact with the surface plasmons od nanorods and produce surface plasmon polaritons (SPPs). The incident laser field also induced dipoles in the ensemble of nanorods and they interact with each other via the dipole-dipole interaction (DDI). We have developed a theory for Bragg scattering for metallic nanohybrids using the coupled-mode formulism based on Maxwell’s equation in the presence of SPP and DDI fields. It is found that the theory of Bragg scattered depends on the susceptibility induced by the SPP and DDI fields. We used the quantum mechanical density matrix method to calculate the susceptibility. An analytical expression of the Bragg scattered light intensity is obtained. These expressions can be useful for experimental scientists and engineers who can used them to compare their experiments and make new types of plasmonic devices. Next, we have compared our theory with the experiment data for a nanohybrid made of ensemble of Au-nanoris doped in water. We found a good agreement between theory and experiments. We have also performed the numerical simulations to study the effect of SPP and DDI fields on the Bragg intensity. We have predicted an enhancement the Brag intensity due to the SPP and DDI couplings. The enhancement is due to the two extra scattering mechanisms of the SPP and DDI polaritons with acoustic phonons. We have also found that the one peak in the Bragg intensity can be split int many peaks due the SPP coupling, DDI coupling and phase factor. The splitting is due the Bragg factor appearing in the theory, and it includes the coupling of the incident laser, SPP and DDI electric fields with of acoustic phonons. The enhancement effect can be used to fabricate new types of nanosensors. Similarity, splitting phenomenon can be used to fabricate new types nanoswitches where one peak can be considered as the OFF position and many peaks can be considered as the ON position.