I develop research within the field of semiconductor laser structures (DFB; VCSEL) Phone: +351-21-8417977 Address: Lab Medidas Eléctricas- Instituto Superior Técnico
Av. Rovisco Pais 1049-001 Lisboa
COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, 2008
PurposeThe aim of this paper is to develop simulation tools for the analysis of modified structur... more PurposeThe aim of this paper is to develop simulation tools for the analysis of modified structures of distributed feedback (DFB) laser diodes adequate for single longitudinal mode (SLM) operation.Design/methodology/approachThe paper uses matricial techniques: the transfer matrix method (TMM). When compared to the eigenvalue approach, the matricial techniques are more general and flexible and hence are especially adequate to deal with the analysis and structural design of DFB laser diodes. In this work, the author makes a general description of the TMM, enhancing its importance with some applications by considering the threshold and above‐threshold analysis of a modified DFB laser structure.FindingsThe increasing demands on laser performance, mainly in the area of optical communication systems, have lead to the fabrication of more‐and‐more complex structures. In viewing the development of the associated technology, the importance of the simulation tools revealed of crucial importanc...
The climate changes observed over the last decades have been promoting a massive transformation o... more The climate changes observed over the last decades have been promoting a massive transformation on the energy sector, that is still, in truth highly dependent on fossil fuels. Renewable energies are a plausible alternative, because they have lower emissions of toxic gases in comparison with non-renewable ones. In the group of renewable energies, solar technology has the biggest overall potential, mainly because it is cheap and easy to set. Several solar technologies allow to equip their photovoltaic panels with concentrators, mostly to increase the output power and possibly their efficiency. However, some problems related to the use of concentrators have to be dealt in order to improve the entire photovoltaic system performance. One of these issues is the corrosion of the concentrators, leading to a premature ageing and, consequently an increase in maintenance costs. This problem is going to be analysed in this paper, presenting some simulation from a ray traicing software and also ...
In this work, the study of different remuneration schemes for the implementation of a solar energ... more In this work, the study of different remuneration schemes for the implementation of a solar energy system on a building was performed. The photovoltaic system was implemented on a public educational building, and four different schemes are compared to understand the economic feasibility of self-consuming solar energy with and without a battery system, versus selling to the electricity grid. The system performance is compared to the building’s needs, and the different consumption and grid-injection shares are analyzed. Three of the schemes are applied according to the conditions and requirements of the Portuguese Law, while the remaining one is not yet allowed, and so the legislation from another chosen country is considered. Lastly, a financial analysis was performed to evaluate and compare the feasibility of each project implementation. The results of this analysis show that both the non-legislated and legislated self-consumption schemes make for an attractive investment, and that ...
A stable and sustainable energy industry contributes indubitably to the business development, as ... more A stable and sustainable energy industry contributes indubitably to the business development, as well as to guarantee the quality of life of a population. However, the economic and social development of insular regions is very vulnerable, due to the high external energetic dependency. Therefore, it is necessary to change the current paradigm of those regions, to take advantage of their endogenous resources to generate electrical energy. The developed work analyses the potential renewable energies (wind and solar) present on the island of Brava, Cape Verde, and assesses its capacity to combine them with an energy storage system that can meet the energetic requirements of the island. The first step consists in the analysis and profiling of the data (energy consumption, solar radiation, wind speed) observed in the island for one year. Simultaneously, several types of storing technologies are analyzed to find the best fitting solution, given the characteristics of the electrical system ...
Currently, the nine islands of the Autonomous Region of the Azores have fossil fuel-fired power s... more Currently, the nine islands of the Autonomous Region of the Azores have fossil fuel-fired power stations as the main source of electric power. Each island has an independent electrical system classified as an isolated micro-system, given its size and location. The aim of this paper is to analyse the best set of technologies to have nine sustainable hybrid systems. For this purpose, some factors will be considered, such as actual data production of the island, economic scenarios, growth perspectives of consumption and reliability of supply. The results of these studies will allow us to conclude on the applicability of these systems and to quantify the consequent socio-economic, environmental and fossil energy-saving benefits. A system is projected to the archipelago, in order to reduce the energy production due to non-renewable energies, budgeted on 783.28 million euros, which intend to instal wind farms and photovoltaic parks (using polycrystalline and cadmium telluride technologies).
The stochastic resonance (SR) in direct-modulated laser diodes is investigated using an analytica... more The stochastic resonance (SR) in direct-modulated laser diodes is investigated using an analytical approach based on the laser rate equations for the carrier and photon densities, that include the cross correlation between the photon and carrier noises. This subject may be particularly important in the domain of Optical Communication Systems, where increasing demands on laser performance have led to the fabrication of more and more complex structures. In viewing the development of the associated technology, the importance of the simulation tools revealed of crucial importance.
The world is witnessing a tide of change in the photovoltaic industry like never before; we are f... more The world is witnessing a tide of change in the photovoltaic industry like never before; we are far from the solar cells of ten years ago that only had 15–18% efficiency. More and more, multi-junction technologies seem to be the future for photovoltaics, with these technologies already hitting the mark of 30% under 1-sun. This work focuses especially on a state-of-the-art triple-junction solar cell, the GaInP/GaInAs/Ge lattice-matched, that is currently being used in most satellites and concentrator photovoltaic systems. The three subcells are first analyzed individually and then the whole cell is put together and simulated. The typical figures-of-merit are extracted; all the I−V curves obtained are presented, along with the external quantum efficiencies. A study on how temperature affects the cell was done, given its relevance when talking about space applications. An overall optimization of the cell is also elaborated; the cell’s thickness and doping are changed so that maximum ef...
Due to the excessive dependence of the energy sector on fossil fuels, whose prices are in constan... more Due to the excessive dependence of the energy sector on fossil fuels, whose prices are in constant growth and its use is inconvenient due to the emission of greenhouse gases, the energy sector is currently being reconsidered in order to meet the global energy demand resorting to renewable energy sources. Solar collectors have more and more competitive prices on the market due to the reduction of the production costs, achieved by reducing the area occupied by photovoltaic cells in the collector (using concentrators to direct solar radiation to the desired location) and through continuous cooling of the photovoltaic cells, leading to the increase of their efficiency. The CPVT collector produced by Solarus AB has been designed taking into account these two principles. However, there are shading effects inherent to the use of concentrators, which may result in a sudden increase in the temperature of the photovoltaic cells. Therefore, it was developed a simulation model in MATLAB based o...
This paper presents a numerical procedure for the accurate optimization of a three phase-shift (3... more This paper presents a numerical procedure for the accurate optimization of a three phase-shift (3PS) distributed feedback (DFB) laser structure. The optimization regards the main figures of merit concerning the laser single longitudinal mode operation: the normalized mode selectivity (S) and the flatness (F). The normalized threshold gain (αth L) is also assessed. A step-by-step description of the numerical method, based in matrix techniques, is performed. S = 0.78 and F = 0.010, with αth L = 1.18 are achieved for the optimized 3PS-DFB laser structure, which strongly improves the performances reported elsewhere relative to optima designs for similar structures. Besides, those results are highly competitive in comparison with the ones achieved with the popular quarterly wavelength-shifted DFB laser structure.
COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, 2008
PurposeThe aim of this paper is to develop simulation tools for the analysis of modified structur... more PurposeThe aim of this paper is to develop simulation tools for the analysis of modified structures of distributed feedback (DFB) laser diodes adequate for single longitudinal mode (SLM) operation.Design/methodology/approachThe paper uses matricial techniques: the transfer matrix method (TMM). When compared to the eigenvalue approach, the matricial techniques are more general and flexible and hence are especially adequate to deal with the analysis and structural design of DFB laser diodes. In this work, the author makes a general description of the TMM, enhancing its importance with some applications by considering the threshold and above‐threshold analysis of a modified DFB laser structure.FindingsThe increasing demands on laser performance, mainly in the area of optical communication systems, have lead to the fabrication of more‐and‐more complex structures. In viewing the development of the associated technology, the importance of the simulation tools revealed of crucial importanc...
The climate changes observed over the last decades have been promoting a massive transformation o... more The climate changes observed over the last decades have been promoting a massive transformation on the energy sector, that is still, in truth highly dependent on fossil fuels. Renewable energies are a plausible alternative, because they have lower emissions of toxic gases in comparison with non-renewable ones. In the group of renewable energies, solar technology has the biggest overall potential, mainly because it is cheap and easy to set. Several solar technologies allow to equip their photovoltaic panels with concentrators, mostly to increase the output power and possibly their efficiency. However, some problems related to the use of concentrators have to be dealt in order to improve the entire photovoltaic system performance. One of these issues is the corrosion of the concentrators, leading to a premature ageing and, consequently an increase in maintenance costs. This problem is going to be analysed in this paper, presenting some simulation from a ray traicing software and also ...
In this work, the study of different remuneration schemes for the implementation of a solar energ... more In this work, the study of different remuneration schemes for the implementation of a solar energy system on a building was performed. The photovoltaic system was implemented on a public educational building, and four different schemes are compared to understand the economic feasibility of self-consuming solar energy with and without a battery system, versus selling to the electricity grid. The system performance is compared to the building’s needs, and the different consumption and grid-injection shares are analyzed. Three of the schemes are applied according to the conditions and requirements of the Portuguese Law, while the remaining one is not yet allowed, and so the legislation from another chosen country is considered. Lastly, a financial analysis was performed to evaluate and compare the feasibility of each project implementation. The results of this analysis show that both the non-legislated and legislated self-consumption schemes make for an attractive investment, and that ...
A stable and sustainable energy industry contributes indubitably to the business development, as ... more A stable and sustainable energy industry contributes indubitably to the business development, as well as to guarantee the quality of life of a population. However, the economic and social development of insular regions is very vulnerable, due to the high external energetic dependency. Therefore, it is necessary to change the current paradigm of those regions, to take advantage of their endogenous resources to generate electrical energy. The developed work analyses the potential renewable energies (wind and solar) present on the island of Brava, Cape Verde, and assesses its capacity to combine them with an energy storage system that can meet the energetic requirements of the island. The first step consists in the analysis and profiling of the data (energy consumption, solar radiation, wind speed) observed in the island for one year. Simultaneously, several types of storing technologies are analyzed to find the best fitting solution, given the characteristics of the electrical system ...
Currently, the nine islands of the Autonomous Region of the Azores have fossil fuel-fired power s... more Currently, the nine islands of the Autonomous Region of the Azores have fossil fuel-fired power stations as the main source of electric power. Each island has an independent electrical system classified as an isolated micro-system, given its size and location. The aim of this paper is to analyse the best set of technologies to have nine sustainable hybrid systems. For this purpose, some factors will be considered, such as actual data production of the island, economic scenarios, growth perspectives of consumption and reliability of supply. The results of these studies will allow us to conclude on the applicability of these systems and to quantify the consequent socio-economic, environmental and fossil energy-saving benefits. A system is projected to the archipelago, in order to reduce the energy production due to non-renewable energies, budgeted on 783.28 million euros, which intend to instal wind farms and photovoltaic parks (using polycrystalline and cadmium telluride technologies).
The stochastic resonance (SR) in direct-modulated laser diodes is investigated using an analytica... more The stochastic resonance (SR) in direct-modulated laser diodes is investigated using an analytical approach based on the laser rate equations for the carrier and photon densities, that include the cross correlation between the photon and carrier noises. This subject may be particularly important in the domain of Optical Communication Systems, where increasing demands on laser performance have led to the fabrication of more and more complex structures. In viewing the development of the associated technology, the importance of the simulation tools revealed of crucial importance.
The world is witnessing a tide of change in the photovoltaic industry like never before; we are f... more The world is witnessing a tide of change in the photovoltaic industry like never before; we are far from the solar cells of ten years ago that only had 15–18% efficiency. More and more, multi-junction technologies seem to be the future for photovoltaics, with these technologies already hitting the mark of 30% under 1-sun. This work focuses especially on a state-of-the-art triple-junction solar cell, the GaInP/GaInAs/Ge lattice-matched, that is currently being used in most satellites and concentrator photovoltaic systems. The three subcells are first analyzed individually and then the whole cell is put together and simulated. The typical figures-of-merit are extracted; all the I−V curves obtained are presented, along with the external quantum efficiencies. A study on how temperature affects the cell was done, given its relevance when talking about space applications. An overall optimization of the cell is also elaborated; the cell’s thickness and doping are changed so that maximum ef...
Due to the excessive dependence of the energy sector on fossil fuels, whose prices are in constan... more Due to the excessive dependence of the energy sector on fossil fuels, whose prices are in constant growth and its use is inconvenient due to the emission of greenhouse gases, the energy sector is currently being reconsidered in order to meet the global energy demand resorting to renewable energy sources. Solar collectors have more and more competitive prices on the market due to the reduction of the production costs, achieved by reducing the area occupied by photovoltaic cells in the collector (using concentrators to direct solar radiation to the desired location) and through continuous cooling of the photovoltaic cells, leading to the increase of their efficiency. The CPVT collector produced by Solarus AB has been designed taking into account these two principles. However, there are shading effects inherent to the use of concentrators, which may result in a sudden increase in the temperature of the photovoltaic cells. Therefore, it was developed a simulation model in MATLAB based o...
This paper presents a numerical procedure for the accurate optimization of a three phase-shift (3... more This paper presents a numerical procedure for the accurate optimization of a three phase-shift (3PS) distributed feedback (DFB) laser structure. The optimization regards the main figures of merit concerning the laser single longitudinal mode operation: the normalized mode selectivity (S) and the flatness (F). The normalized threshold gain (αth L) is also assessed. A step-by-step description of the numerical method, based in matrix techniques, is performed. S = 0.78 and F = 0.010, with αth L = 1.18 are achieved for the optimized 3PS-DFB laser structure, which strongly improves the performances reported elsewhere relative to optima designs for similar structures. Besides, those results are highly competitive in comparison with the ones achieved with the popular quarterly wavelength-shifted DFB laser structure.
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Papers by Carlos Fernandes