Tuning the spectral distribution of p-i-n a-SiC : H devices for colour detection

ZnO:Al/p (SiC:H)/i (Si:H)/n (SiC:H) large area image and colour sensor are analysed. Carrier transport and collection efficiency are investigated from dark and illuminated current-voltage (I-V) dependence and spectral response measurements under different optical and electrical bias conditions. Results show that the carrier collection depends on the optical bias and on the applied voltage. By changing the electrical bias around the open circuit voltage it is possible to filter the absorption at a given wavelength and so to tune the spectral sensitivity of the device. Transport and optical modelling give insight into the internal physical process and explain the bias control of the spectral response and the image and colour sensing properties of the devices

Stacked pin devices for imaging applications

In this paper we present results on the optimization of device architectures for colour and imaging applications, using a device with a TCO/pinpi'n/TCO configuration. The effect of the applied voltage on the color selectivity is discussed. Results show that the spectral response curves demonstrate rather good separation between the red, green and blue basic colors. Combining the information obtained under positive and negative applied bias a colour image is acquired without colour filters or pixel architecture. A low level image processing algorithm is used for the colour image reconstruction

A non-pixel image reader for continuous image detection based on tandem heterostructures

An optically addressed read-write sensor based on two stacked p-i-n heterojunctions is analyzed. The device is a two terminal image sensing structure. The charge packets are injected optically into the p-i-n writer and confined at the illuminated regions changing locally the electrical field profile across the p-i-n reader. An optical scanner is used for charge readout. The design allows a continuous readout without the need for pixel-level patterning. The role of light pattern and scanner wavelengths on the readout parameters is analyzed. The optical-to-electrical transfer characteristics show high quantum efficiency, broad spectral response, and reciprocity between light and image signal. A numerical simulation supports the imaging process. A black and white image is acquired with a resolution around 20 mum showing the potentiality of these devices for imaging applications

metamaterials to the rescue

This research was supported by EU funds through the FEDER European Regional Development Fund (project LISBOA-02–0145-FEDER-031311 )and by Instituto Politécnico de Lisboa with projects IPL/2021/wavesensor_ISEL and IPL/2021/MuMIA2D . Publisher Copyright: © 2022 The AuthorsCoupling light into and/or out of a photonic integrated circuit is often accomplished by establishing a vertical link between a single-mode optical fiber and a resonant waveguide grating, which is then followed by a tapered and a single-mode waveguides. The tapered waveguide operates as a spot-size converter, laterally expanding or contracting the light beam between the single-mode waveguide and the resonant waveguide grating. In this work, we propose using subwavelength structures to achieve tapering functionalities. To this end, we designed a metamaterial structure that enables the modulation of the refractive index necessary to either expand or focus a beam of light. Furthermore, we simulated the metamaterial structure through adequate numerical methods and the expanding, and focusing performances were analyzed in terms of efficiency and mode profile matching. We achieved over 43 % and 48 % for the integral overlap with the transverse magnetic fundamental mode for the focusing and expanding configurations, respectively, out of 49 % and 51 % of power transferred.publishersversionpublishe

Silicon nitride based devices: lithographic mask roughness mitigation

Lithographic technology has been one of the main upholders to Moore's law in the semiconductor industry for the last decades. The underlying reason that enabled the evolution in semiconductor industry has been a steady silicon wafer printing cost, while being able to dramatically increase the number of nodes that can be printed per chip. Key developments in lithography such as wavelength decreasing, together with performance increase in lens and imaging technology, should be accounted for almost all the reduction of cost per function in integrated circuits technology. In this work, we will be presenting the simulation of two mitigation techniques for the impact of defects introduced by manufacturing processes. Namely, the lithographic mask limited resolution on the geometry of the representative device. These perturbations are a consequence of the lithographic mask limited resolution on the geometry of the representative device. For this purpose, the Beam Propagation and Finite Differences Time Domain methods will be used to simulate a multimode interference structure based on silicon nitride. The structure will be affected by previously mentioned perturbations and we expect results revealing a strong dependence between mask resolution, and imbalance and power loss. Two strategies will be followed concerning the mitigation of power loss and imbalance introduced by the limited resolution of lithographic mask: - Access waveguides tapering; - Adjustable power splitting ratios through the electro-optic effect. Through both strategies we aim to achieve an improvement on device’s performance but, in the latter are expected finer tuning capabilities, being enabled by dynamic compensation of power loss and imbalance when in a closed loop control architecture.info:eu-repo/semantics/publishedVersio

Optimisation of a plasmonic parallel waveguide sensor based on amorphous silicon compounds

This work reports the simulation of a plasmonic waveguide sensor working in the visible range based on amorphous silicon compounds. Typical plasmonic sensor interrogation schemes are based on scanning over the wavelength or the incident angle to search for the resonance condition. These solutions usually require expensive or bulky components, such as prisms, motor-driven rotation stages or tunable lasers. In this work we propose an amorphous silicon nitride waveguide structure consisting of an array of parallel surface plasmon interferometers of different lengths, each one comprising a thin layer of aluminium embedded into the waveguide. Using modal decomposition simulations, we show that the variation of the output power at the end of each waveguide array element provides a convenient interrogation scheme. By exploring amorphous silicon compounds that can be deposited by Pressure Enhanced Chemical Vapor Deposition (PECVD) at low temperatures, we aim to achieve a low-cost fabrication process that is compatible with backend CMOS processing and wavelengths in the visible range.info:eu-repo/semantics/publishedVersio

Cross-section mismatch: metamaterials to the rescue

Coupling light into and/or out of a photonic integrated circuit is often accomplished by establishing a vertical link between a single-mode optical fiber and a resonant waveguide grating, which is then followed by a tapered and a single-mode waveguides. The tapered waveguide operates as a spot-size converter, laterally expanding or contracting the light beam between the single-mode waveguide and the resonant waveguide grating. In this work, we propose using subwavelength structures to achieve tapering functionalities. To this end, we designed a metamaterial structure that enables the modulation of the refractive index necessary to either expand or focus a beam of light. Furthermore, we simulated the metamaterial structure through adequate numerical methods and the expanding, and focusing performances were analyzed in terms of efficiency and mode profile matching. We achieved over 43 % and 48 % for the integral overlap with the transverse magnetic fundamental mode for the focusing and expanding configurations, respectively, out of 49 % and 51 % of power transferred.info:eu-repo/semantics/publishedVersio

Comparative study of three-nucleon potentials in nuclear matter

A new generation of local three-body potentials providing an excellent description of the properties of light nuclei, as well as of the neutron-deuteron doublet scattering length, has been recently derived. We have performed a comparative analysis of the equations of state of both pure neutron matter and symmetric nuclear matter obtained using these models of three-nucleon forces. None of the considered potentials simultaneously explains the empirical equilibrium density and binding energy of symmetric nuclear matter. However, two of them provide reasonable values of the saturation density. The ambiguity concerning the treatment of the contact term of the chiral inspired potentials is discussed.Comment: 14 pages, 8 figure

a-SiH p-i-n structures with extreme i-layer thickness

We present measurements and numerical simulation of a-Si:H p-i-n detectors with a wide range of intrinsic layer thickness between 2 and 10 pm. Such a large active layer thickness is required in applications like elementary particle detectors or X-ray detectors. For large thickness and depending on the applied bias, we observe a sharp peak in the spectral response in the red region near 700 nm. Simulation results obtained with the program ASCA are in agreement with the measurement and permit the explanation of the experimental data. In thick samples holes recombine or are trapped before reaching the contacts, and the conduction mechanism is fully electron dominated. As a consequence, the peak position in the spectral response is located near the optical band gap of the a-Si:H i-layer. (C) 2009 Elsevier B.V. All rights reserved.http://ac.els-cdn.com/S0040609009003393/1-s2.0-S0040609009003393-main.pdf?_tid=1048124c-577b-11e3-bf9f-00000aab0f27&acdnat=1385567361_28bd7b0c0165dd29d894b963fd4cbd1