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Amorphous silicon PECVD photonic integrated devices are promising candidates for low cost sensing applications. This manuscript reports a simulation analysis about the impact on the overall efficiency caused by the lithography imperfections in the deposition process. The tolerance to the fabrication defects of a photonic sensor based on surface plasmonic resonance is analysed. The simulations are performed with FDTD and BPM algorithms. The device is a plasmonic interferometer composed by an a-Si:H waveguide covered by a thin gold layer. The sensing analysis is performed by equally splitting the input light into two arms, allowing the sensor to be calibrated by its reference arm. Two different 1 × 2 power splitter configurations are presented: a directional coupler and a multimode interference splitter. The waveguide sidewall roughness is considered as the major negative effect caused by deposition imperfections. The simulation results show that plasmonic effects can be excited in the interferometric waveguide structure, allowing a sensing device with enough sensitivity to support the functioning of a bio sensor for high throughput screening. In addition, the good tolerance to the waveguide wall roughness, points out the PECVD deposition technique as reliable method for the overall sensor system to be produced in a low-cost system. The large area deposition of photonics structures, allowed by the PECVD method, can be explored to design a multiplexed system for analysis of multiple biomarkers to further increase the tolerance to fabrication defects.
Alessandro Fantoni; João Costa; Paulo Lourenço; Manuela Vieira. Computer simulation study about the dependence of amorphous silicon photonic waveguides efficiency on the material quality. The European Physical Journal Applied Physics 2020, 90, 30502 .
AMA StyleAlessandro Fantoni, João Costa, Paulo Lourenço, Manuela Vieira. Computer simulation study about the dependence of amorphous silicon photonic waveguides efficiency on the material quality. The European Physical Journal Applied Physics. 2020; 90 (3):30502.
Chicago/Turabian StyleAlessandro Fantoni; João Costa; Paulo Lourenço; Manuela Vieira. 2020. "Computer simulation study about the dependence of amorphous silicon photonic waveguides efficiency on the material quality." The European Physical Journal Applied Physics 90, no. 3: 30502.
This work reports the optimisation of a plasmonic waveguide sensor based on amorphous silicon compounds (a-SiC:H, a-SiN:H or a-SiCN:H) using the FDTD method and modal decomposition. The sensor consists of an array of parallel surface plasmon interferometers with different propagation lengths, each one comprising a thin layer of metal embedded into an amorphous silicon waveguide. In order to reduce the complexity and hardware, we have proposed a structure consisting of an array of parallel surface plasmon interferometers with different propagation lengths, such that at the end of the plasmonic structure the modes can interfere constructively or destructively depending on the refractive index of the sampling medium and the propagation length. The variation of the output intensity at the end of each waveguide element provides a convenient interrogation scheme. In this work we analyse different solutions for splitting the input fundamental mode into the different parallel waveguides, including multi-mode interference structures and directional coupler splitters. 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 process that is compatible with back-end CMOS processing and wavelengths in the visible to near infrared range.
João Costa; Alessandro Fantoni; Paulo Lourenço; Manuela Vieira. Optimisation of a plasmonic parallel waveguide sensor based on amorphous silicon compounds. Optical Sensing and Detection VI 2020, 11354, 113542K .
AMA StyleJoão Costa, Alessandro Fantoni, Paulo Lourenço, Manuela Vieira. Optimisation of a plasmonic parallel waveguide sensor based on amorphous silicon compounds. Optical Sensing and Detection VI. 2020; 11354 ():113542K.
Chicago/Turabian StyleJoão Costa; Alessandro Fantoni; Paulo Lourenço; Manuela Vieira. 2020. "Optimisation of a plasmonic parallel waveguide sensor based on amorphous silicon compounds." Optical Sensing and Detection VI 11354, no. : 113542K.
Visible Light Communication (VLC) is currently a research topic under severe development due to the possibility to provide high data rates and handle the general, worldwide demanding need for climbing bandwidth. VLC uses Light Emitting Diodes (LED), operating in the visible part of the electromagnetic spectrum, as optical sources for optical wireless communication. The technology provides dual functions of lighting and communication. Its main advantages are related to high data rates, higher bandwidth, reliability and a secure data transmission compared to other wireless technologies (such as Wi-Fi). This paper explores the use of VLC to establish different optical communication links for bidirectional communication between vehicles and infrastructures, using 3 links, namely Infrastructure-To-Vehicle (I2V), Vehicle-To-Infrastructure and (V2I) communication. The proposed application uses VLC to support autonomous navigation of mobile robots inside a modern, automated warehouse, providing navigation and stock management services. Specific coding schemes are used in each optical link using On-OFF keying modulation. In the I2V link RGB white LEDs are used to allow simultaneous modulation of the emitters embedded in each LED, which enables wavelength division multiplexing of the transmitted optical signals. The detection is based on a based a-SiC:H pin-pin photodetector with tunable sensitivity in the visible range. Different indoors communication scenarios are presented and the system performance on bit error rate is discussed using a bit parity error control methodology. Requirements related to synchronous transmission and flicker mitigation were addressed to enhance the system performance.
Paula Louro; Manuela Vieira. Optical link for bidirectional communication based on visible light. Optical Sensing and Detection VI 2020, 11354, 1135402 .
AMA StylePaula Louro, Manuela Vieira. Optical link for bidirectional communication based on visible light. Optical Sensing and Detection VI. 2020; 11354 ():1135402.
Chicago/Turabian StylePaula Louro; Manuela Vieira. 2020. "Optical link for bidirectional communication based on visible light." Optical Sensing and Detection VI 11354, no. : 1135402.
Optical wireless communication has been widely studied during the last years in short-range applications. This paper investigates the applicability of an intuitive wayfinding system in complex buildings using Visible Light Communication (VLC). Typical scenarios include finding places, like a particular shop or office, guiding users across different floors, through elevators and stairs. Data from the sender is encoded, modulated and converted into light signals emitted by the transmitters. Tetra-chromatic white sources are used providing a different data channel for each chip. At the receiver side, the modulated light signal, containing the ID and the 3D geographical position of the transmitter and wayfinding information, is received by SiC photodetector with light filtering and demultiplexing properties. Since lighting and wireless data communication is combined, each luminaire for downlink transmission become a single cell, in which the optical access point (AP) is located in the ceiling and the mobile users are scattered within the overlap discs of each cells underneath. The light signals emitted by the LEDs are interpreted directly by the receivers of the users positioned underneath. The effect of the location of the Aps is evaluated and a model for the different cellular networks is analyzed. Orthogonal topologies are tested, and a 3D localization design, demonstrated by a prototype implementation, is presented. Uplink transmission is implemented and the 3D best route to navigate through venue calculated. Buddy wayfinding services are also implemented. The results showed that the system make possible to determine the position of a mobile target inside the network, to infer the travel direction along the time and to interact with information received and to optimize the route towards a static or dynamic destination.
Manuela Vieira; Paula Louro; Alessandro Fantoni; Pedro Vieira. Indoor wayfinding using visible light communication. Optical Sensing and Detection VI 2020, 11354, 1135403 .
AMA StyleManuela Vieira, Paula Louro, Alessandro Fantoni, Pedro Vieira. Indoor wayfinding using visible light communication. Optical Sensing and Detection VI. 2020; 11354 ():1135403.
Chicago/Turabian StyleManuela Vieira; Paula Louro; Alessandro Fantoni; Pedro Vieira. 2020. "Indoor wayfinding using visible light communication." Optical Sensing and Detection VI 11354, no. : 1135403.
Surface Plasmon Resonance occurs when a polarized electromagnetic field strikes a metallic surface at the separation interface between metal and an insulator. This phenomenon is characterized by the conduction electrons resonant oscillation at the interface, resulting on propagating plasmon waves on the metallic surface. Since this wave is generated at the boundary between the metallic surface and the external medium, these structures are highly sensitive to alterations on the surrounding environment, namely the refractive index, and may be used in sensing structures. The large majority of these devices use noble metals, namely gold or silver, as the active material. These metals present low resistivity, which leads to low optical losses in the visible and near infrared spectrum ranges. Gold shows high environmental stability, which is essential for long-term operation, and silver’s lower stability can be overcome through the deposition of an alumina layer. However, their high cost is a limiting factor if the intended target is large scale manufacturing. In this work, we performed Finite Differences Time Domain simulations on a Surface Plasmon Resonance based sensing structure, considering cost-effective materials such as aluminium for the active metal and hydrogenated amorphous silicon for the waveguide supporting elements, and verified that these structures are able to detect refractive index variations of the surrounding environment at the 1550 μm operating wavelength. This sensing architecture has also been modelled with dispersive materials, losses included, to reflect as much as possible physical reality, revealing good performance capabilities when compared to similar noble metals based devices.
Paulo Lourenço; Alessandro Fantoni; Paula Louro; João Costa; Manuela Vieira. Surface plasmon resonance sensing structure. Physics and Simulation of Optoelectronic Devices XXVIII 2020, 11274, 1127415 .
AMA StylePaulo Lourenço, Alessandro Fantoni, Paula Louro, João Costa, Manuela Vieira. Surface plasmon resonance sensing structure. Physics and Simulation of Optoelectronic Devices XXVIII. 2020; 11274 ():1127415.
Chicago/Turabian StylePaulo Lourenço; Alessandro Fantoni; Paula Louro; João Costa; Manuela Vieira. 2020. "Surface plasmon resonance sensing structure." Physics and Simulation of Optoelectronic Devices XXVIII 11274, no. : 1127415.
Surface plasmon resonance sensors have emerged has one of the most suitable approaches for biosensing. A common approach consists of exciting the plasmons at the interface between a functionalized metal film and a sample medium containing the analyte. The propagation of the surface plasmon is highly dependent on changes of the refractive index of the surrounding environment thus providing a mechanism for sensing. The typical interrogation schemes are based on scanning over the wavelength or the incident angle to search for the resonance condition. These solutions require additional motor-driven rotation stages, prisms or other bulky components, introducing complexity which prevents the fabrication of fully on-chip devices. This work reports a simulation study of an amorphous silicon waveguide structure consisting of an array of parallel surface plasmon interferometers with different propagation lengths, each one comprising a thin layer of gold embedded into a-Si:H waveguide. The surface plasmon modes at the end of the plasmonic structure can interfere constructively or destructively depending on the refractive index of the analyte and the interferometer’s length. The variation of the output intensity at the end of each element of the array provides a convenient interrogation scheme that is suitable for on-chip integration. In this paper we investigate this setup and analyze the output power at the end of the array as a function of the refractive index of the sampling medium. The setup is simulated and characterized by the eigenmode expansion method.
João Costa; Alessandro Fantoni; Paulo Lourenço; Manuela Vieira. Simulation of a parallel waveguide array structure suitable for interrogation scheme in a plasmonic biosensor. Physics and Simulation of Optoelectronic Devices XXVIII 2020, 11274, 112742B .
AMA StyleJoão Costa, Alessandro Fantoni, Paulo Lourenço, Manuela Vieira. Simulation of a parallel waveguide array structure suitable for interrogation scheme in a plasmonic biosensor. Physics and Simulation of Optoelectronic Devices XXVIII. 2020; 11274 ():112742B.
Chicago/Turabian StyleJoão Costa; Alessandro Fantoni; Paulo Lourenço; Manuela Vieira. 2020. "Simulation of a parallel waveguide array structure suitable for interrogation scheme in a plasmonic biosensor." Physics and Simulation of Optoelectronic Devices XXVIII 11274, no. : 112742B.
This paper investigates the applicability of an intuitive wayfinding system in complex buildings using Visible Light Communication (VLC). Typical scenarios include: finding places, like a particular shop or office, guiding users across different floors, and through elevators and stairs. Data from the sender is encoded, modulated and converted into light signals emitted by the transmitters. Tetra-chromatic white sources are used providing a different data channel for each chip. At the receiver side, the modulated light signal, containing the ID and the 3D geographical position of the transmitter and wayfinding information, is received by a SiC photodetector with light filtering and demultiplexing properties. Since lighting and wireless data communication is combined, each luminaire for downlink transmission becomes a single cell, in which the optical access point (AP) is located in the ceiling and the mobile users are scattered across the overlap discs of each cell, underneath. The light signals emitted by the LEDs are interpreted directly by the receivers of the positioned users. Bidirectional communication is tested. The effect of the location of the Aps is evaluated and a 3D model for the cellular network is analyzed. In order to convert the floorplan to a 3D geometry, a tandem of layers in a orthogonal topology is tested, and a 3D localization design, demonstrated by a prototype implementation, is presented. Uplink transmission is implemented, and the 3D best route to navigate through venue is calculated. Buddy wayfinding services are also considered. The results showed that the dynamic VLC navigation system enables to determine the position of a mobile target inside the network, to infer the travel direction along the time, to interact with received information and to optimize the route towards a static or dynamic destination.
Manuela Vieira; Paula Louro; Alessandro Fantoni; Pedro Vieira. Wayfinding in complex buildings using visible light communication. Physics and Simulation of Optoelectronic Devices XXVIII 2020, 11274, 112741V .
AMA StyleManuela Vieira, Paula Louro, Alessandro Fantoni, Pedro Vieira. Wayfinding in complex buildings using visible light communication. Physics and Simulation of Optoelectronic Devices XXVIII. 2020; 11274 ():112741V.
Chicago/Turabian StyleManuela Vieira; Paula Louro; Alessandro Fantoni; Pedro Vieira. 2020. "Wayfinding in complex buildings using visible light communication." Physics and Simulation of Optoelectronic Devices XXVIII 11274, no. : 112741V.
Paula Louro; Manuela Vieira. Bidirectional data transfer in VLC links. Light-Emitting Devices, Materials, and Applications XXIV 2020, 1 .
AMA StylePaula Louro, Manuela Vieira. Bidirectional data transfer in VLC links. Light-Emitting Devices, Materials, and Applications XXIV. 2020; ():1.
Chicago/Turabian StylePaula Louro; Manuela Vieira. 2020. "Bidirectional data transfer in VLC links." Light-Emitting Devices, Materials, and Applications XXIV , no. : 1.
In this paper we present a MUX/DEMUX device based on a multilayer a-SiC:H optical filter that requires near-ultraviolet steady state optical switches to select desired wavelengths in the visible range. The selector filter is realized by using a two terminal double pi’n/pin a-SiC:H photodetector. Five visible communication channels are transmitted together, each one with a specific bit sequence. The combined optical signal is analyzed by reading out the photocurrent, under near-UV front steady state background. Data shows that 25 current levels are detected and corresponds to the thirty-two on/off possible states. The proximity of the magnitude of consecutive levels causes occasional errors in the decoded information. To minimize the errors, four parity bit are generated and stored along with the data word. The parity of the word is checked after reading the word to detect and correct the transmitted data. Results showed that the background works as a selector in the visible range, shifting the sensor sensitivity and together with the parity check bits allows the identification and decoding of the different input channels. A transmission capability of 60 kbps using the generated codeword was achieved.
M. Vieira; P. Louro. MUX/DEMUX SiC receiver for visible light communications. Microsystem Technologies 2020, 1 -6.
AMA StyleM. Vieira, P. Louro. MUX/DEMUX SiC receiver for visible light communications. Microsystem Technologies. 2020; ():1-6.
Chicago/Turabian StyleM. Vieira; P. Louro. 2020. "MUX/DEMUX SiC receiver for visible light communications." Microsystem Technologies , no. : 1-6.
Indium sulfofluoride is an amorphous wide-gap semiconductor exhibiting high sensitivity to UV radiation. This work reports on the kinetics of photoconductivity in indium sulfofluoride thin films along with their electrical and optical properties. The films were deposited by radio-frequency plasma-enhanced reactive thermal evaporation. The film characterization includes electrical, optical, and photoconductivity measurements. The films are highly transparent in the visible-infrared range due to an indirect bandgap of 2.8 eV. The spectral response measurements have revealed existence of the band tail states. The synthesized compound is highly resistive (∼200 MΩ-cm at 300 K) and exhibits extremely slow photocurrent relaxations. Photoconductivity kinetics was studied under various excitation conditions. A dependence of the photocurrent on the incident photon flux was also determined.
Yuri Vygranenko; Miguel Fernandes; Manuela Vieira; Guilherme Lavareda; Carlos Nunes De Carvalho; Pedro Brogueira; Ana Amaral. Photoconductivity kinetics of indium sulfofluoride thin films. The European Physical Journal Applied Physics 2020, 89, 10302 .
AMA StyleYuri Vygranenko, Miguel Fernandes, Manuela Vieira, Guilherme Lavareda, Carlos Nunes De Carvalho, Pedro Brogueira, Ana Amaral. Photoconductivity kinetics of indium sulfofluoride thin films. The European Physical Journal Applied Physics. 2020; 89 (1):10302.
Chicago/Turabian StyleYuri Vygranenko; Miguel Fernandes; Manuela Vieira; Guilherme Lavareda; Carlos Nunes De Carvalho; Pedro Brogueira; Ana Amaral. 2020. "Photoconductivity kinetics of indium sulfofluoride thin films." The European Physical Journal Applied Physics 89, no. 1: 10302.
In this paper, we present a simulation study that intends to characterize the influence of defects introduced by manufacturing processes on the geometry of a semiconductor structure suitable to be used as a multimode interference (MMI) 3 dB power splitter. Consequently, these defects will represent refractive index fluctuations which, on their turn, will drastically affect the propagation conditions within the structure. Our simulations were conducted on a software platform that implements the Beam Propagation numerical method. This work supports the development of a biomedical plasmonic sensor, which is based on the coupling between propagating modes in a dielectric waveguide and the surface plasmon mode that is generated on an overlaid metallic thin film, and where the output readout is achieved through an a-Si:H photodiode. By using a multimode interference 1 × 2 power splitter, this sensor device can utilize the non-sensing arm as a reference one, greatly facilitating its calibration and enhancing its performance. As the spectral sensitivity of amorphous silicon is restricted to the visible range, this sensing device should be operating on a wavelength not higher than 700 nm; thus, a-SiNx has been the material hereby proposed for both waveguides and MMI power splitter.
Paulo Lourenço; Alessandro Fantoni; João Costa; Manuela Vieira. Lithographic Mask Defects Analysis on an MMI 3 dB Splitter. Photonics 2019, 6, 118 .
AMA StylePaulo Lourenço, Alessandro Fantoni, João Costa, Manuela Vieira. Lithographic Mask Defects Analysis on an MMI 3 dB Splitter. Photonics. 2019; 6 (4):118.
Chicago/Turabian StylePaulo Lourenço; Alessandro Fantoni; João Costa; Manuela Vieira. 2019. "Lithographic Mask Defects Analysis on an MMI 3 dB Splitter." Photonics 6, no. 4: 118.
This work reports on low temperature deposition of conducting indium oxide films by a radio-frequency plasma enhanced reactive thermal evaporation (rf-PERTE) technique. The films were deposited on polyethylene terephthalate (PET) without intentional heating of the substrate and at elevated temperatures up to 150°C. The material stoichiometry was accurately controlled by adjusting deposition conditions including the oxygen flow, process pressure, pumping speed, and RF-power. Besides, fine turning of the critical deposition parameters during the deposition was implemented by measuring the variation of film conductance in-situ. The film morphology was analyzed by scanning electron microscopy. Hall effect measurements were also performed to determine the relation between the deposition conditions and the electrical properties of the films. A resistivity of 4 × 10−4 Ω-cm was reached under optimized deposition conditions. A 250 nm-thick coating with 16 Ω/sq sheet resistance shows an 82% peak value of transmittance in the visible spectral range.
Y. Vygranenko; Miguel Fernandes; M. Vieira; Guilherme Lavareda; Carlos Alberto Nunes DE Carvalho; P. Brogueira; Ana Amaral. Conducting indium oxide films on plastic substrates by plasma enhanced reactive thermal evaporation. Thin Solid Films 2019, 691, 137604 .
AMA StyleY. Vygranenko, Miguel Fernandes, M. Vieira, Guilherme Lavareda, Carlos Alberto Nunes DE Carvalho, P. Brogueira, Ana Amaral. Conducting indium oxide films on plastic substrates by plasma enhanced reactive thermal evaporation. Thin Solid Films. 2019; 691 ():137604.
Chicago/Turabian StyleY. Vygranenko; Miguel Fernandes; M. Vieira; Guilherme Lavareda; Carlos Alberto Nunes DE Carvalho; P. Brogueira; Ana Amaral. 2019. "Conducting indium oxide films on plastic substrates by plasma enhanced reactive thermal evaporation." Thin Solid Films 691, no. : 137604.
In this paper, we will be using separate software tools (wireless network and Finite Differences Time Domain based simulators) to simulate the implementation of a wireless sensor network model based on low-rate/power transmission technology. The system operates in an unlicensed frequency range and the sensing nodes rely on surface plasmon resonance phenomenon for the detection of combustion by-products. More specifically, our simulations contemplate a system for early detection of fire in densely forested areas, which will then issue a warning in an automated way. As late detection of these events usually leads to severe flora, terrain, wild life and societal impact, an early warning system will provide better event assessment conditions, thus enabling efficient resources allocation, adequate response and would certainly be a promising improvement in minimizing such disruptive impairments.
Paulo Lourenço; Alessandro Fantoni; Manuela Vieira. Simulation of an Early Warning Fire System. Security Education and Critical Infrastructures 2019, 305 -317.
AMA StylePaulo Lourenço, Alessandro Fantoni, Manuela Vieira. Simulation of an Early Warning Fire System. Security Education and Critical Infrastructures. 2019; ():305-317.
Chicago/Turabian StylePaulo Lourenço; Alessandro Fantoni; Manuela Vieira. 2019. "Simulation of an Early Warning Fire System." Security Education and Critical Infrastructures , no. : 305-317.
This paper researches the applicability of an intuitive advertising system for large indoor environments using Visible Light Communication (VLC). This VLC based positioning system includes the use of the visible light signal to light the space and to transmit the information for travelers’ positioning and of advertising campaigns in the surroundings. White RGB-LEDs, whose original function is providing illumination, are used as transmitters due to the ability of each individual chip to switch quickly enough to transfer data. This functionality is used for communication where the multiplexed data can be encoded in the emitting light. The light signals emitted by the LEDs positioned in the area of the advertising campaign are interpreted directly by the customers’ receivers. A SiC optical sensor with light filtering and demultiplexing properties receives the modulated signals containing the ID and the geographical position of the LED and other information, demultiplexes and decodes the data and locates the mobile device in the environment. Different layouts are analysed: square and hexagonal meshes are tested, and a 2D localization design, demonstrated by a prototype implementation, is presented. The key differences between both topologies are discussed. For both, the transmitted information, indoor position and motion direction of the customer are determined. The results showed that the LED-aided VLC navigation system enables to determine the position of a mobile target inside the network, to infer the travel direction as a function of time and to interact with information received.
Manuela Vieira; Paula Louro; Alessandro Fantoni; Pedro Vieira. Indoor positioning and intuitive advertising using visible light communication. Physics and Simulation of Optoelectronic Devices XXVII 2019, 10912, 1091217 .
AMA StyleManuela Vieira, Paula Louro, Alessandro Fantoni, Pedro Vieira. Indoor positioning and intuitive advertising using visible light communication. Physics and Simulation of Optoelectronic Devices XXVII. 2019; 10912 ():1091217.
Chicago/Turabian StyleManuela Vieira; Paula Louro; Alessandro Fantoni; Pedro Vieira. 2019. "Indoor positioning and intuitive advertising using visible light communication." Physics and Simulation of Optoelectronic Devices XXVII 10912, no. : 1091217.
This paper focuses on designing and analyzing a visible light-based communication and positioning system for indoor wireless communication under light-emitting diodes (LEDs) lighting environments. The indoor positioning system uses trichromatic white LEDs, both for illumination purposes and as transmitters, and an optical processor, based on a-SiC:H technology, as a mobile receiver. An on–off keying modulation scheme is used, proving a good trade-off between system performance and implementation complexity. The relationship between the transmitted data and the received output levels is decoded. LED bulbs work as transmitters, sending information together with different identifiers, IDs, related to their physical locations. Square and diamond topologies for the unit cell are analyzed, and a two-dimensional localization design, demonstrated by a prototype implementation, is presented. Fine-grained indoor localization is tested. The received signal is used in coded multiplexing techniques for supporting communications and navigation concomitantly on the same channel. The location and motion information are found by mapping the position and estimating the location areas.
Manuela Vieira; Paula Louro; Pedro Vieira. Light-emitting diodes aided indoor localization using visible light communication technology. Optical Engineering 2018, 57, 087105 .
AMA StyleManuela Vieira, Paula Louro, Pedro Vieira. Light-emitting diodes aided indoor localization using visible light communication technology. Optical Engineering. 2018; 57 (8):087105.
Chicago/Turabian StyleManuela Vieira; Paula Louro; Pedro Vieira. 2018. "Light-emitting diodes aided indoor localization using visible light communication technology." Optical Engineering 57, no. 8: 087105.
The large majority of surface plasmon resonance (SPR)-based devices use noble metals, namely gold or silver, in their manufacturing process. These metals present low resistivity, which leads to low optical losses in the visible and near-infrared spectrum ranges. Gold shows high environmental stability, which is essential for long-term operation, and the lower stability of silver can be overcome through the deposition of an alumina layer, for instance. However, their high cost is a limiting factor if the intended target is large-scale manufacturing. This work considers a cost-effective approach through the selection of aluminum as the plasmonic material and hydrogenated amorphous silicon instead of its crystalline counterpart. This SPR structure relies on Fano resonance to improve its response to refractive index deviations of the surrounding environment. Fano resonance is highly sensitive to slight changes of the medium, hence the reason we incorporated this interference phenomenon in the proposed sensing structure. We report the results obtained when conducting finite-difference time-domain algorithm-based simulations on this metal–dielectric–metal structure when the active metal is aluminum, gold, and silver. Then, we evaluate their sensitivity, detection accuracy, and resolution. The obtained results for our proposed sensing structure show good linearity and similar parameter performance as the ones obtained when using gold or silver as plasmonic materials.
Paulo Lourenço; Alessandro Fantoni; Miguel Fernandes; Yuri Vygranenko; Manuela Vieira. Finite-difference time-domain analysis of hydrogenated amorphous silicon and aluminum surface plasmon waveguides. Optical Engineering 2018, 57, 077103 .
AMA StylePaulo Lourenço, Alessandro Fantoni, Miguel Fernandes, Yuri Vygranenko, Manuela Vieira. Finite-difference time-domain analysis of hydrogenated amorphous silicon and aluminum surface plasmon waveguides. Optical Engineering. 2018; 57 (7):077103.
Chicago/Turabian StylePaulo Lourenço; Alessandro Fantoni; Miguel Fernandes; Yuri Vygranenko; Manuela Vieira. 2018. "Finite-difference time-domain analysis of hydrogenated amorphous silicon and aluminum surface plasmon waveguides." Optical Engineering 57, no. 7: 077103.
Manuel A. Vieira; Paula Louro; Pedro Vieira; Manuela Vieira. Optical vehicular communication based on a-SiC:H technology. Science and Technology of Materials 2018, 30, 151 -156.
AMA StyleManuel A. Vieira, Paula Louro, Pedro Vieira, Manuela Vieira. Optical vehicular communication based on a-SiC:H technology. Science and Technology of Materials. 2018; 30 (3):151-156.
Chicago/Turabian StyleManuel A. Vieira; Paula Louro; Pedro Vieira; Manuela Vieira. 2018. "Optical vehicular communication based on a-SiC:H technology." Science and Technology of Materials 30, no. 3: 151-156.
The use of visible light communication (VLC) in vehicular communication systems for vehicle safety applications is proposed. The system aims to ensure the communication between a LED-based VLC emitter and an on-vehicle VLC receiver. A traffic scenario is established. Vehicle-to-vehicle (V2V) and infrastructure-to-vehicle (I2V) communications are analyzed. For the V2V communication study, the emitter was developed based on the vehicle headlights, whereas for the study of I2V communication system, the emitter was built based on streetlights. The VLC receiver is based on amorphous SiC technology and enhances the conditioning of the signal enabling to decode the transmitted information. Receivers are located at the rooftop of the vehicle, for I2V communications, and at the tails for V2V reception. Clusters of emitters, in a square topology, are used in the I2V transmission. The information and the ID code of each emitter in the network are sent simultaneously by modulating the individual chips of the trichromatic white LED. Free space is the transmission medium. An on–off code is used to transmit data. An algorithm to decode the information at the receivers is set. The proposed system was tested. The experimental results confirmed that the proposed cooperative VLC architecture is suitable for the intended applications.
Manuela Vieira; Paula Louro; Pedro Vieira. Cooperative vehicular communication systems based on visible light communication. Optical Engineering 2018, 57, 076101 .
AMA StyleManuela Vieira, Paula Louro, Pedro Vieira. Cooperative vehicular communication systems based on visible light communication. Optical Engineering. 2018; 57 (7):076101.
Chicago/Turabian StyleManuela Vieira; Paula Louro; Pedro Vieira. 2018. "Cooperative vehicular communication systems based on visible light communication." Optical Engineering 57, no. 7: 076101.
This paper reports about a study of the local plasmonic resonance (LSPR) produced by metal nanoparticles embedded in a dielectric or semiconductor matrix. It is presented an analysis of the LSPR for different nanoparticle metals, shapes, and embedding media composition. Metals of interest for nanoparticle composition are Aluminum and Gold. Shapes of interest are nanospheres and nanotriangles. We study in this work the optical properties of metal nanoparticles diluted in water or embedded in amorphous silicon, ITO and ZnO as a function of size, aspect-ratio and metal type. Following the analysis based on the exact solution of the Mie theory and DDSCAT numerical simulations, it is presented a comparison with experimental measurements realized with arrays of metal nanospheres. Simulations are also compared with the LSPR produced by gold nanotriangles (Au NTs) that were chemically produced and characterized by microscope and optical measurements.
A. Fantoni; Miguel Fernandes; Yuri Vygranenko; Paula Louro; Manuela Vieira; R. P. O. Silva; D. Texeira; A. P. C. Ribeiro; Duarte Miguel Prazeres; Elisabete Alegria. Analysis of metallic nanoparticles embedded in thin film semiconductors for optoelectronic applications. Optical and Quantum Electronics 2018, 50, 246 .
AMA StyleA. Fantoni, Miguel Fernandes, Yuri Vygranenko, Paula Louro, Manuela Vieira, R. P. O. Silva, D. Texeira, A. P. C. Ribeiro, Duarte Miguel Prazeres, Elisabete Alegria. Analysis of metallic nanoparticles embedded in thin film semiconductors for optoelectronic applications. Optical and Quantum Electronics. 2018; 50 (6):246.
Chicago/Turabian StyleA. Fantoni; Miguel Fernandes; Yuri Vygranenko; Paula Louro; Manuela Vieira; R. P. O. Silva; D. Texeira; A. P. C. Ribeiro; Duarte Miguel Prazeres; Elisabete Alegria. 2018. "Analysis of metallic nanoparticles embedded in thin film semiconductors for optoelectronic applications." Optical and Quantum Electronics 50, no. 6: 246.
Oxygen saturation levels in blood are usually measured with photoplethysmography (PPG) using two LEDs, one in the red and the other in the near infrared region of the spectrum. A number of studies have increased the number of wavelengths, not only to improve the accuracy of SpO2 measurements, but also to provide real-time measurements of other substances in blood, such as methemoglobin and carboxyhemoglobin. In addition, analysis of PPG signals at different wavelengths could provide information about skin pathologies at various tissue depths. In this work we study the advantages of using photodetection based on vertically stacked double junction photodiodes. The sensitivity of such photodetectors over a wider wavelength range is of particular interest for PPG. We have implemented a test bed, which includes the control of light sources to emulate the transmitted signals, the analog front-end to recover the time multiplexed PPG signals and post-processing to calculate the hemoglobin fractions. We use this framework to compare results of photodetection obtained using a single silicon junction and the combination of a silicon and indium gallium arsenide junction for photodetection.
João Costa; Hugo Vieira; Paula Louro; Manuela Vieira. Double junction photodiodes for multiwavelength photoplethysmography. Optical Sensing and Detection V 2018, 10680, 106802H .
AMA StyleJoão Costa, Hugo Vieira, Paula Louro, Manuela Vieira. Double junction photodiodes for multiwavelength photoplethysmography. Optical Sensing and Detection V. 2018; 10680 ():106802H.
Chicago/Turabian StyleJoão Costa; Hugo Vieira; Paula Louro; Manuela Vieira. 2018. "Double junction photodiodes for multiwavelength photoplethysmography." Optical Sensing and Detection V 10680, no. : 106802H.