PP
P. Piron
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1
Free space optical communication presents many benefits over traditional radio frequency communication such as increased bandwidth and decreased beam divergence. However, on satellite terminals, spacecraft jitter causes instantaneous pointing errors, which due to the Gaussian intensity profile of most lasers, results in lower received power and thus a decrease in communication performance metrics like bit error rate and power outage probability.
Using non-Gaussian intensity profiles theoretically alleviates this drop in performance but requires more components than a standard optical communication system. In this thesis, an experimental optical setup using a spiral phase plate was constructed to obtain a superposition of a Gaussian and an annular beam. The resulting intensity profile closely matched the theoretical while having an overall transmissive efficiency high enough to outperform a Gaussian profile in power outage probability. This experiment has shown the real potential that non-Gaussian intensity profiles have in satellite free space optical communication. ...
Using non-Gaussian intensity profiles theoretically alleviates this drop in performance but requires more components than a standard optical communication system. In this thesis, an experimental optical setup using a spiral phase plate was constructed to obtain a superposition of a Gaussian and an annular beam. The resulting intensity profile closely matched the theoretical while having an overall transmissive efficiency high enough to outperform a Gaussian profile in power outage probability. This experiment has shown the real potential that non-Gaussian intensity profiles have in satellite free space optical communication. ...
Free space optical communication presents many benefits over traditional radio frequency communication such as increased bandwidth and decreased beam divergence. However, on satellite terminals, spacecraft jitter causes instantaneous pointing errors, which due to the Gaussian intensity profile of most lasers, results in lower received power and thus a decrease in communication performance metrics like bit error rate and power outage probability.
Using non-Gaussian intensity profiles theoretically alleviates this drop in performance but requires more components than a standard optical communication system. In this thesis, an experimental optical setup using a spiral phase plate was constructed to obtain a superposition of a Gaussian and an annular beam. The resulting intensity profile closely matched the theoretical while having an overall transmissive efficiency high enough to outperform a Gaussian profile in power outage probability. This experiment has shown the real potential that non-Gaussian intensity profiles have in satellite free space optical communication.
Using non-Gaussian intensity profiles theoretically alleviates this drop in performance but requires more components than a standard optical communication system. In this thesis, an experimental optical setup using a spiral phase plate was constructed to obtain a superposition of a Gaussian and an annular beam. The resulting intensity profile closely matched the theoretical while having an overall transmissive efficiency high enough to outperform a Gaussian profile in power outage probability. This experiment has shown the real potential that non-Gaussian intensity profiles have in satellite free space optical communication.
Polarimetry in space is an increasingly prominent field in space research. Polarimetry, especially spectropolarimetry, have the potential to provide a substantial amount of information about the Earth as well as distant interstellar objects. In this field, full-Stokes spectropolarimetry is ideal for providing comprehensive polarimetric information. An instrument capable of making such measurements is often too large or complex for satellite use. A method which can theoretically perform full-Stokes spectropolarimetry while avoiding these drawbacks is currently being researched by Dr. Bogdan Vasilescu in collaboration with TU Delft. This new method makes use of a modulator formed out of 3 birefringent prisms, and a linear polariser, which together produces fluctuations in intensity. These fluctuations can be used to obtain information about any incident light.
The aim of this study was to investigate unexpected intensity fluctuations which occur even without the linear polariser, and determine the extent to which these can be explained by Fresnel behaviour at the boundaries of the prisms. To achieve this, Jones and Stokes models were produced in Python, simulations were performed in ZEMAX, and experimental measurements were taken to validate the results. For each of these methods, only the modulator first and third prisms were used as the second is designed as a structural component rather than an active element. From the models, simulations and experimental results, it was found that including Fresnel behaviour to models and simulations does result in output intensity fluctuations. Furthermore, it was determined that the periodicity of the fluctuations is very closely linked to Fresnel phenomena. The Python models and ZEMAX simulations especially returned results which appeared consistent, with easily explainable differences. On the other hand, further study is required to explain the differences in the amplitudes and average transmission of the intensity patterns between the different models, especially compared to the experimental results. The developed models and simulations can therefore demonstrate that Fresnel behaviour does explain the presence of the fluctuations but also suggests that the methods used in this thesis do not achieve a full representation of the phenomena, or that there are additional factors which must still be investigated.
...
The aim of this study was to investigate unexpected intensity fluctuations which occur even without the linear polariser, and determine the extent to which these can be explained by Fresnel behaviour at the boundaries of the prisms. To achieve this, Jones and Stokes models were produced in Python, simulations were performed in ZEMAX, and experimental measurements were taken to validate the results. For each of these methods, only the modulator first and third prisms were used as the second is designed as a structural component rather than an active element. From the models, simulations and experimental results, it was found that including Fresnel behaviour to models and simulations does result in output intensity fluctuations. Furthermore, it was determined that the periodicity of the fluctuations is very closely linked to Fresnel phenomena. The Python models and ZEMAX simulations especially returned results which appeared consistent, with easily explainable differences. On the other hand, further study is required to explain the differences in the amplitudes and average transmission of the intensity patterns between the different models, especially compared to the experimental results. The developed models and simulations can therefore demonstrate that Fresnel behaviour does explain the presence of the fluctuations but also suggests that the methods used in this thesis do not achieve a full representation of the phenomena, or that there are additional factors which must still be investigated.
...
Polarimetry in space is an increasingly prominent field in space research. Polarimetry, especially spectropolarimetry, have the potential to provide a substantial amount of information about the Earth as well as distant interstellar objects. In this field, full-Stokes spectropolarimetry is ideal for providing comprehensive polarimetric information. An instrument capable of making such measurements is often too large or complex for satellite use. A method which can theoretically perform full-Stokes spectropolarimetry while avoiding these drawbacks is currently being researched by Dr. Bogdan Vasilescu in collaboration with TU Delft. This new method makes use of a modulator formed out of 3 birefringent prisms, and a linear polariser, which together produces fluctuations in intensity. These fluctuations can be used to obtain information about any incident light.
The aim of this study was to investigate unexpected intensity fluctuations which occur even without the linear polariser, and determine the extent to which these can be explained by Fresnel behaviour at the boundaries of the prisms. To achieve this, Jones and Stokes models were produced in Python, simulations were performed in ZEMAX, and experimental measurements were taken to validate the results. For each of these methods, only the modulator first and third prisms were used as the second is designed as a structural component rather than an active element. From the models, simulations and experimental results, it was found that including Fresnel behaviour to models and simulations does result in output intensity fluctuations. Furthermore, it was determined that the periodicity of the fluctuations is very closely linked to Fresnel phenomena. The Python models and ZEMAX simulations especially returned results which appeared consistent, with easily explainable differences. On the other hand, further study is required to explain the differences in the amplitudes and average transmission of the intensity patterns between the different models, especially compared to the experimental results. The developed models and simulations can therefore demonstrate that Fresnel behaviour does explain the presence of the fluctuations but also suggests that the methods used in this thesis do not achieve a full representation of the phenomena, or that there are additional factors which must still be investigated.
The aim of this study was to investigate unexpected intensity fluctuations which occur even without the linear polariser, and determine the extent to which these can be explained by Fresnel behaviour at the boundaries of the prisms. To achieve this, Jones and Stokes models were produced in Python, simulations were performed in ZEMAX, and experimental measurements were taken to validate the results. For each of these methods, only the modulator first and third prisms were used as the second is designed as a structural component rather than an active element. From the models, simulations and experimental results, it was found that including Fresnel behaviour to models and simulations does result in output intensity fluctuations. Furthermore, it was determined that the periodicity of the fluctuations is very closely linked to Fresnel phenomena. The Python models and ZEMAX simulations especially returned results which appeared consistent, with easily explainable differences. On the other hand, further study is required to explain the differences in the amplitudes and average transmission of the intensity patterns between the different models, especially compared to the experimental results. The developed models and simulations can therefore demonstrate that Fresnel behaviour does explain the presence of the fluctuations but also suggests that the methods used in this thesis do not achieve a full representation of the phenomena, or that there are additional factors which must still be investigated.
The polarization of light has become a powerful tool for scientists in recent years. Astronomy, climatology, chemistry, and medicine are just a few sectors that are turning to this characteristic of light to produce a finer description of the environment they study.
However, the complete measurement of polarization at different wavelengths remains difficult. The difficulties are even more significant when the polarization measurement occurs in space. Current technologies are bulky, mainly featuring rotating components that can bring additional risk to the space mission. In this context, the present research discusses the development of a new method for measuring light polarization compatible with use in space.
Starting from ideas already presented in the specialized literature, we have refined here a new way to access the polarization of light that promises the construction of compact, robust, and highly accurate instruments. The present research provides a detailed theoretical description of this new method's operating principle and a practical demonstration. The results confirmed the ability to translate this method into high-performing instruments capable of accessing any polarization.
In addition, this research also highlights the versatility of the new method for measuring light polarization. It can be translated into instruments intended for use in space or for other applications; it can be adapted to determine only certain types of polarization, or it can be the basis for building imaging instruments. It opens a new horizon of development in polarimetry and spectropolarimetry. ...
However, the complete measurement of polarization at different wavelengths remains difficult. The difficulties are even more significant when the polarization measurement occurs in space. Current technologies are bulky, mainly featuring rotating components that can bring additional risk to the space mission. In this context, the present research discusses the development of a new method for measuring light polarization compatible with use in space.
Starting from ideas already presented in the specialized literature, we have refined here a new way to access the polarization of light that promises the construction of compact, robust, and highly accurate instruments. The present research provides a detailed theoretical description of this new method's operating principle and a practical demonstration. The results confirmed the ability to translate this method into high-performing instruments capable of accessing any polarization.
In addition, this research also highlights the versatility of the new method for measuring light polarization. It can be translated into instruments intended for use in space or for other applications; it can be adapted to determine only certain types of polarization, or it can be the basis for building imaging instruments. It opens a new horizon of development in polarimetry and spectropolarimetry. ...
The polarization of light has become a powerful tool for scientists in recent years. Astronomy, climatology, chemistry, and medicine are just a few sectors that are turning to this characteristic of light to produce a finer description of the environment they study.
However, the complete measurement of polarization at different wavelengths remains difficult. The difficulties are even more significant when the polarization measurement occurs in space. Current technologies are bulky, mainly featuring rotating components that can bring additional risk to the space mission. In this context, the present research discusses the development of a new method for measuring light polarization compatible with use in space.
Starting from ideas already presented in the specialized literature, we have refined here a new way to access the polarization of light that promises the construction of compact, robust, and highly accurate instruments. The present research provides a detailed theoretical description of this new method's operating principle and a practical demonstration. The results confirmed the ability to translate this method into high-performing instruments capable of accessing any polarization.
In addition, this research also highlights the versatility of the new method for measuring light polarization. It can be translated into instruments intended for use in space or for other applications; it can be adapted to determine only certain types of polarization, or it can be the basis for building imaging instruments. It opens a new horizon of development in polarimetry and spectropolarimetry.
However, the complete measurement of polarization at different wavelengths remains difficult. The difficulties are even more significant when the polarization measurement occurs in space. Current technologies are bulky, mainly featuring rotating components that can bring additional risk to the space mission. In this context, the present research discusses the development of a new method for measuring light polarization compatible with use in space.
Starting from ideas already presented in the specialized literature, we have refined here a new way to access the polarization of light that promises the construction of compact, robust, and highly accurate instruments. The present research provides a detailed theoretical description of this new method's operating principle and a practical demonstration. The results confirmed the ability to translate this method into high-performing instruments capable of accessing any polarization.
In addition, this research also highlights the versatility of the new method for measuring light polarization. It can be translated into instruments intended for use in space or for other applications; it can be adapted to determine only certain types of polarization, or it can be the basis for building imaging instruments. It opens a new horizon of development in polarimetry and spectropolarimetry.
Greenhouse gas monitoring satellites are crucial for understanding climate change and assessing the effectiveness of climate policies. This project explores a novel concept for a metasurfaced-based spectrometer in the short-wave infrared domain. Metasurfaces are artificial planar materials with subwavelength structures that can manipulate light. This project's metasurface is designed with phase change materials to function as a reconfigurable spectral filter. Filter-based spectroscopy is realized by exploiting a compressive sensing algorithm. Using the rigorous coupled wave analysis solver of Ansys Lumerical, different metasurface designs are simulated and evaluated on their transmission response and compressive sensing performance. The final metasurfaces are obtained using particle swarm optimization with a performance metric that balances computation time and accuracy. The results show great promise for accurate and precise reconstruction of the atmospheric absorption spectrum, required for greenhouse gas monitoring.
...
Greenhouse gas monitoring satellites are crucial for understanding climate change and assessing the effectiveness of climate policies. This project explores a novel concept for a metasurfaced-based spectrometer in the short-wave infrared domain. Metasurfaces are artificial planar materials with subwavelength structures that can manipulate light. This project's metasurface is designed with phase change materials to function as a reconfigurable spectral filter. Filter-based spectroscopy is realized by exploiting a compressive sensing algorithm. Using the rigorous coupled wave analysis solver of Ansys Lumerical, different metasurface designs are simulated and evaluated on their transmission response and compressive sensing performance. The final metasurfaces are obtained using particle swarm optimization with a performance metric that balances computation time and accuracy. The results show great promise for accurate and precise reconstruction of the atmospheric absorption spectrum, required for greenhouse gas monitoring.
Bachelor thesis
(2023)
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L. Alonso Antona, S. Aurori, M. Beenders, E.G. Chen, C.F.M. Kendall, D.J.D. Norbart, T. Odijk, M.H. Rusch, L.M.N. Tabaksblat, S. Yorucu, I. Akay, A.O. Başkaya, P. Piron
The goal of project Altus is to do an in-situ investigation of Polar Mesospheric Clouds (PMCs). These clouds form around an altitude of 84 km, and only for 60 to 80 days per year, during the summer. Normally, these clouds only form in the polar regions, from around 50◦ latitude north and south. Recently, however, PMCs have been observed as low as 40◦ north. There are theories linking this change in location, and other unexpected behaviours of PMCs, to climate change. However, further research is still required to confirm these theories. As these changes are happening at a slow rate, a database of PMC measurements would be extremely beneficial to track indicator values over time. Project Altus sets out to bridge this knowledge gap by taking regular measurements of PMCs over an extended period of time.
...
The goal of project Altus is to do an in-situ investigation of Polar Mesospheric Clouds (PMCs). These clouds form around an altitude of 84 km, and only for 60 to 80 days per year, during the summer. Normally, these clouds only form in the polar regions, from around 50◦ latitude north and south. Recently, however, PMCs have been observed as low as 40◦ north. There are theories linking this change in location, and other unexpected behaviours of PMCs, to climate change. However, further research is still required to confirm these theories. As these changes are happening at a slow rate, a database of PMC measurements would be extremely beneficial to track indicator values over time. Project Altus sets out to bridge this knowledge gap by taking regular measurements of PMCs over an extended period of time.