Synthetic Aperture Radars (SAR) have demonstrated to be great instruments for space-based Earth observation in the microwave frequency. Metasurface antennas, on the other side, are a new type of planar antennas with a great potential for space applications, as they are compact and easy to produce. Several methods have been developed in the past years addressing one or many parts of the design and applications of these antennas, which rely in more or less measure in locally developed tools. However, some parts of these methods can take a great amount of time to implement, making this process more difficult than it should especially if the user has commercial electromagnetic simulation tools available that could accelerate this process. In this work, different procedures have been adapted to the design of a high-gain SAR anisotropic metasurface antenna for a multi-static Earth observation mission, showing that the proposed methodology produces accurate results.

This research is focused on the feasibility assessment of a novel technology of metasurfaces in order to design a spectropolarimeter with the thickness of a few micrometers integrated on the detector array. The motivation behind the research is miniaturization of state-of-the-art spectropolarimeters. The requirements for the instrument are derived from SPEXone instrument, as a reference instrument. Beside the miniaturization, two additional requirements are set as a goal: possibility to measure full-Stokes vector of polarization (including circular polarization), and to improve the spectropolarimetric resolution. The reduction in the volume of the instrument is not the main advantage, but also reduction in the number of optical components with respect to the state-of-the-art. A spectropolarimeter with fewer components allows better stability of performances over different external conditions like temperature change, and easier alignment of the whole system.
In recent years the dielectric metasurfaces attract a lot of attention. Firstly, due to its compatibility to CMOS detector technology, which allows integration of thin layers of metasurfaces directly on the detector array, and secondly due to high transmission of the dielectric materials. The metasurface is an array of scatterers with period and size of scatterers smaller than the wavelength. With proper design, the complete control of electromagnetic waves is possible, including amplitude, phase, and polarization at subwavelength resolution. This is convenient because diffraction is not present at that scale. That enables to design optical devices like lenses, waveplates, polarizing beam splitters with similar performances as current technology, but with extreme reduction in thickness. In this thesis, a systematic electromagnetic performance analysis of metasurfaces is presented. Two types of metasurfaces are designed, first acting as a waveplate, and second as a linear polarizer at different spectral wavelengths. Also, a trade-off of the most suitable spectropolarimetric techniques is done, which led to the Division of Focal Plane (DoFP) type of polarimeter. The combination of these two layers of metasurfaces can modulate the polarization state of light in form of the intensity of light, which is measured on detector pixels. It is shown that with this technique, four unique pixels, each with different polarization modulation, are required to reconstruct four unknowns, the Stokes vector, which fully describes the state of polarization of incident light. Furthermore, the spectral information is measured by designing different sets of four pixels to filter out different parts of the spectrum. The result is two-dimensional detector array which measures spectrum in the vertical axis, and spatial information in the horizontal axis. The spatial information in the vertical axis is achieved by implementing the push broom concept of a satellite. Moreover, the important spectropolarimetric parameters like spectropolarimetric accuracy, spectropolarimetric resolution, and operating spectrum range are estimated. Also, a complete overview of the instrument, which consists of a telescope unit, a bandpass spectral filter and the metasurface integrated on the detector array, is shown. In the end, the performance of the complete system is compared with the reference instrument SPEXone, in order to assess the potential of this concept.

In this thesis new dielectric metasurfaces in immersion were explored with a periodic distribution of unit cells with multiple silicon cylinder structures on a reflective gold slab with a fused quartz spacer in between. These new metasurfaces were designed with 60 nm and 130 nm gaps in order to improve manufacturability and enable larger particles to enter the hotspot region while trying to maintain high electric field enhancement and enhancement factors. This was done by simulating the plane wave excitation in a range of 750 nm to 850 nm for a large number of metasurfaces using electromagnetic modelling software Lumerical using its finite difference time domain method. After exploring multiple silicon cylinder structures the focus was put on periodic metasurfaces with unit cells containing single, dimer, and quadrumer positioning of cylinders and enhancement factors of between 500-2000 were found.
Afterwards the found fields for new promising designs were used in an optical trapping algorithm were enhancement factors for 10 nm particles were found between 10^4-10^5 and for 40 nm particles between 10^3-10^4.
The effect of exciting a metasurface with circular polarization for quadrumer structures was thoroughly investigated but yielded no better enhancement factor than previous dimer designs. A new optical trapping scheme where the laser intensity is increased near the end of optical trapping is proposed to give slight improvement of enhancement factors after trapping. Overall, the limitations of the electromagnetic simulations and optical trapping algorithm makes it difficult to assume the enhancement factors found are realizable in experiment. These limitations need to be addressed before any conclusions can be made on whether immersion SERS offers any advantages over dry SERS in the case of dielectric metasurfaces.

In this thesis a proof-of-principle demonstration is developed that uses the heat flux between a probe and a sample as a proxy for their separation. The proposed architecture uses a probe that consists of a bilayer cantilever with an attached sphere at its free end. The deflection of the cantilever that is caused by the heat input is measured using the optical beam deflection method. To eliminate temperature dependent effects the temperatures of the probe and the sample are kept constant. Moreover, a total internal reflection microscopy is included to provide an independent measurement of the separation between the probe and the sample. This architecture allows the measurement of the heat flux as a function of only the separation. An equation is derived that relates the output signal of the instrument directly to the heat flux that is absorbed by the probe. It couples the top-level design parameters to the system output and is used to study and design the separate elements. In addition to the design of the instrument, the research contributes a detailed study of the influences of the microsphere and the microcantilever on the heat flux measurement. @en

Electromagnetic metasurfaces in recent years have drawn significant attention in the Optics community due to their novel optical properties and miniaturized integration advantages. Since the optical properties of those materials are complex to model and require finer theory than what implied in geometrical optics, systematic integration study of those solutions is not reported in Literature and motivates this research. In previous work, the design of polarization-sensitive spectral filters based on metasurfaces devices and integrated into Bragg reflectors has been reported. The use of such a spectropolarimeter concept may lead to significant miniaturization improvements in Space applications, where launches of small satellites are becoming accessible to not-governmental companies and trending. Typical spectral and polarimetric functionalities are currently integrated with several additional components required for the propagation of light. The metasurface based spectropolarimeter concept operates in a division of focal plane and can be integrated on off-the-shelf CMOS sensors, when opportune factors are taken into considerations, with the use of a single lithographic step. The main difficulty in their use arises from the limited bandwidth dictated by the Bragg reflector and the polarization response of the metasurface, as well as strict requirements of telecentricity to limit angle-dependence at the focal plane. In the present work, we offer novel modeling tools to predict the electromagnetic performance of the device in terms of diffraction and spectral response. We explicit how those tools, in comparison with other approaches like Finite Element Methods, can provide an efficient and physical-based assessment for the design of the spectro-polarimetric filters. We apply then such tools to analyze the diffraction of the filters and the integration of the sensor in a Space Mission for aerosol detection in the VIS and SWIR range, by designing a set of filters able to overcome the bandwidth limitations above mentioned, finally providing simple engineering figures in terms of integration requirements to be considered. The work sets the bases for further improvements, on one side, in the modeling of those structures and on the other side in their integration in complex systems.