Surface Plasmon Enhancement on Infrared Photodetection

AbstractInAsSb based infrared photodetector is an alternative to the existing HgCdTe, PbSnTe, and InSb counterparts, but its room temperature performance is still relatively poor. One of the ways to improve its performance is through surface plasmon, which provides near field confinement that leads to enhancement in light matter interaction. In this work, the role of each parameter of two dimensional metallic hole arrays in plasmonic enhancement is studied in details, such as the periodicity of hole array, hole diameter and metal film thickness. The plasmonic resonances and their corresponding electric field distributions are comprehensively studied in finite difference time domain simulation, which also would serve as a guide for designing surface plasmon enhanced InAsSb infrared detector with high quantum efficiency and signal-to-noise ratio

High quality InAsSb-based heterostructure n-i-p mid-wavelength infrared photodiode

We present the effect of interface quality on the performance of InAsSb based hetero n-i-p middle wavelength infrared (MWIR) photodiodes. By adopting heavily doping wide bandgap p- and n-type layers and inserting a thin layer between the two doped layers and the absorbing InAsSb region, the interface quality can be improved. We also employed proper fabrication processes in device fabrication to improve surface quality. It is found that the improved interface and surface quality can reduce the noise current and enhance detection performance. A detectivity of ~1.5×109 cmHz1/2W-1 can be achieved at room temperature, and it can be increased to ~4.0×109 cmHz1/2W-1 at 250 K.ASTAR (Agency for Sci., Tech. and Research, S’pore)MOE (Min. of Education, S’pore)EDB (Economic Devt. Board, S’pore)Accepted versio

Optimal design of all-dielectric 3D gradient metasurfaces

International audienceMetasurfaces are flat surfaces consisting of sub-wavelength nanoresonators, made of plasmonic or high dielectric refractive index materials patterned in a specific way. These flat surfaces provide nearly full control of the light properties in a very short propagation distance with high resolution [1]. By changing the dimensions, shapes, and orientation of these nanoresonators, different functionalities can be obtained [2, 3]. The complexity of the problem and the wide parameter space, make the direct modelling problem insufficient. Recently, several optimization techniques have been applied to the field of nanopho-tonics (including metasurfaces) [4] by solving an inverse design problem. Generally speaking, there are two classes of optimization techniques that have been used in the metasurface designs; local and global techniques. The local methods depend on the initial guess and most of them require the computation of the gradient, which might be challenging. On the other hand, global optimization techniques are easier to use because the solver is considered as a black box moreover, they do not stuck in a local minima/maxima like the local methods [4]. However, most of the global techniques used in the metasurface designs require costly simulations (for large parameter space), which make them inapplicable for modelling 3D real-life designs that require 3D solvers. In our work, we use two efficient global optimization techniques based receptively on advanced evolution strategies and statistical learning. The first one is the covariance matrix adaptation evolution strategy (CMA-ES) [5]. The CMA-ES has been gaining a lot of attention since it requires fewer cost function evaluations compared to the other evolutionary algorithms like genetic algorithms (GA) [6] especially for 3D real designs that require expensive simulations even with the high-performance computational resources. The second method is the Efficient Global Optimization (EGO) algorithm [7]. The EGO algorithm is based on the surrogate modelling, that is to say, replacing the complex or costly evaluation process by a simpler and cheaper model [7] to reduce dramatically the computational cost (number of calls for the electromagnetic simulations). We use our rigorous Discontinuous Galerkin Time Domain (DGTD) solver from the Diogenes-suite [8] together with the optimization algorithms, in order to optimize 3D meta-gratings (periodic in two directions) in the visible regime. The proposed metasurfaces are based on GaN due to its negligible losses and due to its high refractive index in the visible regime, which make it ideal nanoresonator (phase-shifters) for metasurface designs [1]. As a first design, we aim to maximize the total transmission at a desired wavelength λ = 600 nm using CMA-ES and EGO methods by optimizing 6 parameters. A comparison between the results obtained from the two methods will be presented. Our results reveal that CMA-ES and EGO seem to be more efficient than GA [6]. Based on the above methods together with our 3D solver, different metasurface designs will be presented with different functionalities including theoretical and experimental study of enhancing the diffraction efficiency of 3D real-life gradient metasurface designs. REFERENCES 1. P. Genevet, F. Capasso, F. Aieta, M. Khorasaninejad, and R. Devlin, "Recent advances in planar optics: from plasmonic to dielectric metasurfaces,", "Outlook for inverse design in nanophotonics," arXiv preprint arXiv:1801.06715, 2018. 5. N. Hansen, S. Muller, and P. Koumoutsakos, "Reducing the time complexity of the derandomized evolution strategy with covariance matrix adaptation (CM

Study of dual color infrared photodetection from n-GaSb/n-InAsSb heterostructures

We report detailed investigation of n-GaSb/n-InAsSb heterostructure photodetectors for infrared photodetection at different temperatures and biases. Our results show that the heterostructure photodetectors are capable of dual color photodetections at a fixed forward bias with its highest responsivity occurred at room temperature; With the decrease of the forward bias, a turning point, at which the photocurrent changes its direction, exist and the corresponding voltage values increases with the decrease of temperature; At all reverse biases, the photocurrents flow in the same direction but the maximum current occurs at about 205 K. A new model is proposed, which can well explain all the observations.ASTAR (Agency for Sci., Tech. and Research, S’pore)MOE (Min. of Education, S’pore)Published versio

Directional emissions from perovskite nanocrystals thin film enabled by metasurface integration through one step spin-coating process

Advances in thin film light-emitting devices have fueled the rapid growth of a new class of solid-state lighting devices, featuring low fabrication cost, high quantum efficiency, and broadband spectrum coverage, etc. In contrast to the conventional inorganic semiconductors that rely on lattice matched high crystalline quality substrate, solution processable thin films eliminate the dependence on the substrate, which is highly desired for the ease and versatility of integrations with foreign medium. By taking this advantage, this work develops an ultracompact solution to control the directionality of thin film emitters using integrated dielectric metasurface through one step spin-coating process. As a proof of concept, directional emissions from perovskite nanocrystal thin film, including collimated light emissions, two-dimensional beam steering, are experimentally demonstrated. Notably, our approach, where light emitters were integrated on the back side of substrate after the fabrication of metasurface, judiciously avoids any potential degradation of material optical quality caused by the multi-step nanofabrication. Therefore, it can serve as a generalized scheme to engage the advantageous properties of dielectric metasurface, including the compactness, high efficiency, and beam controllability with the emerging thin film LEDs, which is applicable to a wide range of solution processable materials, including organic light-emitting diodes, quantum-dot light emitting diodes, polymer LEDs, and perovskite LEDs, opening up new pathways to develop low-cost, ultra-compact solid state light sources with versatile beams characteristics

Directional emissions from perovskite nanocrystals thin film enabled by metasurface integration through one step spin-coating process

Advances in thin film light-emitting devices have fueled the rapid growth of a new class of solid-state lighting devices, featuring low fabrication cost, high quantum efficiency, and broadband spectrum coverage, etc. In contrast to the conventional inorganic semiconductors that rely on lattice matched high crystalline quality substrate, solution processable thin films eliminate the dependence on the substrate, which is highly desired for the ease and versatility of integrations with foreign medium. By taking this advantage, this work developed an ultracompact solution to control the directionality of thin film emitters using integrated dielectric metasurface through one step spin-coating process. As a proof of concept, directional emissions from perovskite nanocrystal thin film, including collimated light emissions and two-dimensional beam steering, are experimentally demonstrated. Notably, our approach, where light emitters were integrated on the back side of substrate after the fabrication of metasurface, judiciously avoids any potential degradation of material optical quality caused by the multi-step nanofabrication. Therefore, it can serve as a generalized scheme to engage the advantageous properties of dielectric metasurface, including the compactness, high efficiency, and beam controllability with the emerging thin film light-emitting diodes (LEDs), which is applicable to a wide range of solution processable materials, including organic light-emitting diodes, quantum-dot light emitting diodes, polymer LEDs, and perovskite LEDs, opening up new pathways to develop low-cost and ultra-compact solid state light sources with versatile beams characteristics. [Figure not available: see fulltext.]

Leitfaden zur qualitätssicheren Aktenführung nach DIN ISO-15489-1 erschienen

Der Arbeitskreis Schriftgutverwaltung im DIN NABD 15 als verantwortliches Normungsgremium zur Schriftgutverwaltung/ Records Management in Deutschland hat einen Leitfaden zur qualitätssicheren Aktenführung nach DIN ISO-15489-1 veröffentlicht. Dies zeigt prägnant die rechtlichen und fachlichen Rahmenbedingungen, Verantwortlichkeiten und Prozesse sowie notwendigen Schritte zur geeigneten IT-Unterstützung auf. Ergänzt um eine umfangreiche Literaturliste kann der Leitfaden als guter Einstieg in di..

An Etching‐Free Approach Toward Large‐Scale Light‐Emitting Metasurfaces

International audienceA new class of quasi 2D optical components, known as metasurfaces and exhibiting exceptional optical properties have emerged in recent years. The scattering properties of their subwavelength patterns allow molding the wavefront of light in almost any desired manner. While the proof of principle is demonstrated by various approaches, only a handful of low cost and fabrication friendly materials are suitable for practical implementations. To further develop this technology toward broadband application and industrial production, new materials and new fabrication methods are required. In addition, moving from passive to active devices with, for instance, dynamic tuning requires to move from dielectrics to semiconductors. Here, an etching-free process is presented that combines nanoimprint and selective area sublimation of a semiconductor material to realize centimeter-scale metalenses of high optical quality. Use of gallium nitride is chosen for this demonstration, as it is a widespread semiconductor which can be transparent and active in the visible. The sublimation leads to reduced surface roughness and defects compared to reactive ion etching. As a result, the devices show enhanced photoluminescence efficiency with respect to etched devices. Amplification due to gain in the semiconductor based metaoptics could lead to a new type of optoelectronic devices

Hybrid MoS 2 -gap-mode metasurface photodetectors

International audienc