R. Conselheiro Emidio Navarro

Lisbon, Portugal

R. Conselheiro Emidio Navarro

Lisbon, Portugal

Time filter

Source Type

Vieira M.,R. Conselheiro Emidio Navarro | Silva V.,R. Conselheiro Emidio Navarro | Louro P.,R. Conselheiro Emidio Navarro | Vieira M.A.,R. Conselheiro Emidio Navarro | Barata M.,CTS UNINOVA
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

In this paper we present a tandem UV/VIS/ NIR wavelength selector based on a multilayer a-SiC:H optical filter that requires appropriate ultraviolet steady states optical switches to select the desired wavelengths in the ultraviolet/visible/infrared spectral ranges. Five ultra-light communication channels are transmitted together, each one with a specific bit sequence. Results show that the background side and intensity works as a selector in the infrared, visible and ultra violet light regions, shifting the sensor sensitivity. This nonlinearity allows the identification and decoding of the different input channels. This concept is extended to implement a 1 by 5 wavelength division multiplexer with channel separation in the visible range and a transmission capability of 30 Kbps. The relationship between the optical inputs and the output signal is established and an algorithm to decode the MUX signal presented. © 2016 SPIE.


Vieira M.A.,R. Conselheiro Emidio Navarro | Vieira M.,R. Conselheiro Emidio Navarro | Silva V.,R. Conselheiro Emidio Navarro | Louro P.,R. Conselheiro Emidio Navarro | Barata M.,R. Conselheiro Emidio Navarro
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2015

In this paper we exploit the nonlinear property of the SiC multilayer devices to design an optical processor for error detection that enables reliable delivery of spectral data of four-wave mixing over unreliable communication channels. The SiC optical processor is realized by using double pin/pin a-SiC:H photodetector with front and back biased optical gating elements. Visible pulsed signals are transmitted together at different bit sequences. The combined optical signal is analyzed. Data show that the background acts as selector that picks one or more states by splitting portions of the input multi optical signals across the front and back photodiodes. Boolean operations such as EXOR and three bit addition are demonstrated optically, showing that when one or all of the inputs are present, the system will behave as an XOR gate representing the SUM. When two or three inputs are on, the system acts as AND gate indicating the present of the CARRY bit. Additional parity logic operations are performed using four incoming pulsed communication channels that are transmitted and checked for errors together. As a simple example of this approach, we describe an all-optical processor for error detection and then provide an experimental demonstration of this idea. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Louro P.,R. Conselheiro Emidio Navarro | Silva V.,R. Conselheiro Emidio Navarro | Vieira M.A.,R. Conselheiro Emidio Navarro | Vieira M.,R. Conselheiro Emidio Navarro
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2014

In this paper the viability of an integrated wavelength optical filter and photodetector for visible light communication (VLC) is discussed. The proposed application uses indoor warm light lamps lighting accomplished by ultra-bright light-emitting diodes (LEDs) pulsed at frequencies higher than the ones perceived by the human eye. The system was analyzed at two different wavelengths in the visible spectrum (430 nm and 626 nm) with variable optical intensities. The signals were transmitted into free space and measured using a multilayered photodetector based on a-SiC:H/a-Si:H. The detector works as an optical filter with controlled wavelength sensitivity through the use of optical bias. The output photocurrent was measured for different optical intensities of the transmitted optical signal and the extent of each signal was tested. The influence of environmental fluorescent lighting was also analysed in order to test the strength of the system. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Vieira M.,R. Conselheiro Emidio Navarro | Vieira M.A.,R. Conselheiro Emidio Navarro | Rodrigues I.,R. Conselheiro Emidio Navarro | Silva V.,R. Conselheiro Emidio Navarro | Louro P.,R. Conselheiro Emidio Navarro
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2014

Visible range to telecom band spectral translation is accomplished using an amorphous SiC pi'n/pin wavelength selector under appropriate front and back optical light bias. Results show that background intensity works as selectors in the infrared region, shifting the sensor sensitivity. Low intensities select the near-infrared range while high intensities select the visible part according to its wavelength. Here, the optical gain is very high in the infrared/red range, decreases in the green range, stays close to one in the blue region and strongly decreases in the near-UV range. The transfer characteristics effects due to changes in steady state light intensity and wavelength backgrounds are presented. The relationship between the optical inputs and the output signal is established. A capacitive optoelectronic model is presented and tested using the experimental results. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Louro P.,R. Conselheiro Emidio Navarro | Silva V.,R. Conselheiro Emidio Navarro | Karmali A.,CIEB ISEL | Vieira M.,R. Conselheiro Emidio Navarro
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2014

In this paper, we present a multilayer device based on a-Si:H/a-SiC:H that operates as photodetector and optical filter. The use of such device in protein detection applications is relevant in Fluorescence Resonance Energy Transfer (FRET) measurements. This method demands the detection of fluorescent signals located at specific wavelengths bands in the visible part of the electromagnetic spectrum. The device operates in the visible range with a selective sensitivity dependent on electrical and optical bias. Several nanosensors were tested with a commercial spectrophotometer to assess the performance of FRET signals using glucose solutions of different concentrations. The proposed device was used to demonstrate the possibility of FRET signals detection, using visible signals of similar wavelength and intensity. The device sensitivity was tuned to enhance the wavelength band of interest using steady state optical bias at 400 nm. Results show the ability of the device to detect signals in this range. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Vieira M.,R. Conselheiro Emidio Navarro | Vieira M.A.,R. Conselheiro Emidio Navarro | Louro P.,R. Conselheiro Emidio Navarro | Silva V.,R. Conselheiro Emidio Navarro
Plasmonics | Year: 2013

Amorphous SiC tandem heterostructures are used to filter a specific band, in the visible range. Experimental and simulated results are compared to validate the use of SiC multilayered structures in applications where gain compensation is needed or to attenuate unwanted wavelengths. Spectral response data acquired under different frequencies, optical wavelength control and side irradiations are analyzed. Transfer function characteristics are discussed. Color pulsed communication channels are transmitted together and the output signal analyzed under different background conditions. Results show that under controlled wavelength backgrounds, the device sensitivity is enhanced in a precise wavelength range and quenched in the others, tuning or suppressing a specific band. Depending on the background wavelength and irradiation side, the device acts either as a long-, a short-, or a band-rejection pass filter. An optoelectronic model supports the experimental results and gives insight on the physics of the device. © 2012 Springer Science+Business Media, LLC.


Vieira M.A.,R. Conselheiro Emidio Navarro | Vieira M.,R. Conselheiro Emidio Navarro | Louro P.,R. Conselheiro Emidio Navarro | Silva V.,R. Conselheiro Emidio Navarro
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

In this paper, we use the nonlinear property of SiC multilayer devices under UV irradiation to design an optical processor for indoor positioning. The transducer combines the simultaneous demultiplexing operation with the photodetection and self-amplification. The proposed coding is based on SiC technology. Based on that, we present a way to achieve indoor localization using the parity bits and a navigation syndrome. A representation with a 4 bit original string colour message and the transmitted 7 bit string, the encoding and decoding accurate positional information processes and the design of SiC navigation syndrome generators are discussed and tested. A visible multilateration method estimates the position of the device by using the decoded information received from several, non-collinear transmitters. The location and motion information is found by mapping position and estimates the location areas. Since the indoor position of the LED light source is known from building floor plans and lighting plans, the corresponding indoor position and travel direction of a mobile device can be determined. © 2016 SPIE.


Louro P.,R. Conselheiro Emidio Navarro | Vieira M.,R. Conselheiro Emidio Navarro | Vieira M.A.,R. Conselheiro Emidio Navarro | Costa J.,R. Conselheiro Emidio Navarro | Fernandes M.,R. Conselheiro Emidio Navarro
Sensors and Actuators, A: Physical | Year: 2011

In this paper, we present results on the use of multilayered a-SiC:H heterostructures as a device for wavelength-division demultiplexing of optical signals. These devices are useful in optical communications applications that use the wavelength division multiplexing technique to encode multiple signals into the same transmission medium. The device is composed of two stacked p-i-n photodiodes, both optimized for the selective collection of photo generated carriers. Band gap engineering was used to adjust the photogeneration and recombination rate profiles of the intrinsic absorber regions of each photodiode to short and long wavelength absorption in the visible spectrum. The photocurrent signal using different input optical channels was analyzed at reverse and forward bias and under steady state illumination. A demux algorithm based on the voltage controlled sensitivity of the device was proposed and tested. An electrical model of the WDM device is presented and supported by the solution of the respective circuit equations. © 2011 Elsevier B.V. All rights reserved.


PubMed | R. Conselheiro Emidio Navarro
Type: Journal Article | Journal: Journal of nanoscience and nanotechnology | Year: 2012

Optical colour sensors based on multilayered a-SiC:H heterostructures can act as voltage controlled optical filters in the visible range. In this article we investigate the application of these structures for Fluorescence Resonance Energy Transfer (FRET) detection, The characteristics of a-SiC:H multilayered structure are studied both theoretically and experimentally in several wavelengths corresponding to different fluorophores. The tunable optical p-i(a-SiC:H)-n/p-i(a-Si:H)-n heterostructures were produced by PECVD and tested for a proper fine tuning in the violet, cyan and yellow wavelengths. The devices were characterized through transmittance and spectral response measurements, under different electrical bias and frequencies. Violet, cyan and yellow signals were applied in simultaneous and results have shown that they can be recovered under suitable applied bias. A theoretical analysis supported by numerical simulation is presented.


PubMed | R. Conselheiro Emidio Navarro
Type: Journal Article | Journal: Journal of nanoscience and nanotechnology | Year: 2012

Toxic amides, such as acrylamide, are potentially harmful to Human health, so there is great interest in the fabrication of compact and economical devices to measure their concentration in food products and effluents. The CHEmically Modified Field Effect Transistor (CHEMFET) based on amorphous silicon technology is a candidate for this type of application due to its low fabrication cost. In this article we have used a semi-empirical model of the device to predict its performance in a solution of interfering ions. The actual semiconductor unit of the sensor was fabricated by the PECVD technique in the top gate configuration. The CHEMFET simulation was performed based on the experimental current-voltage curves of the semiconductor unit and on an empirical model of the polymeric membrane. Results presented here are useful for selection and design of CHEMFET membranes and provide an idea of the limitations of the amorphous CHEMFET device. In addition to the economical advantage, the small size of this prototype means it is appropriate for in situ operation and integration in a sensor array.

Loading R. Conselheiro Emidio Navarro collaborators
Loading R. Conselheiro Emidio Navarro collaborators