Abstract
The context of my thesis deals with infrared (IR) multispectral imaging and in particular with plasmonics, a field of electromagnetic optics whose the aim is to study and exploit surface waves existing at the interface between a metal and a dielectric. We seek to miniaturize optical functions thanks to nanotechnologies and more precisely to perform IR spectral filtering at the detection pixel level by integrating a nano-resonator. Usually we use dielectrics and metals, but the integration is complex. I am exploring the potential offered by heavily doped semiconductors to replace metals, which could allow better integration into technological processes for fabricate a photodetector or emitter. I use III-V semiconductors, compatible with the epitaxial growth of type 2 superlattice (T2SL) of long wave infrared photodetectors (LWIR). Furthermore, working with a heavily doped semiconductor offers the possibility of modifying the resonance frequency by adjusting the density of free carriers by the action of a potential difference.I study architectures of "GMR" components (Guided-Mode Resonance), usually formed by a waveguide in dielectric, where occurs the resonance, and a grating in dielectric or metal allowing the coupling between the incident or transmitted wave and the guided mode thanks to the ±1 orders diffracted by the grating in the thin layer. The current trend is to integrate these components directly at the level of the detection pixel but at the cost of numerous fabrication steps. I am studying the possibility of using exclusively semiconductors to simplify the fabrication process and allow monolithic integration of the filter into the detector. The waveguide consists of an intrinsic semiconductor and the grating of heavily doped semiconductor. The spectral range of interest is in the far infrared (8 μm - 14 μm).First, theoretical and experimental demonstrations of an all-semiconductor nano-structured spectral filter for infrared based on guided-mode resonance were carried out. I dimensioned and then fabricated a sample where the first step consists in depositing by epitaxy a layer of GaSb and a layer of highly doped InAsSb on a GaAs substrate before a photolithography step to define the mask of the etching reactive ionic etching in order to obtain the diffraction grating. An experimental work then made it possible to characterize the component (measurement under normal incidence, angular study, measurement at low temperature) with in particular the realization of an angular characterization setup.In parallel, I studied an appropriate stack of doped materials allowing, by applying an electrical voltage, to move the free electrons from doping in the grating and the guide, which then locally modifies the refractive index and therefore directly the conditions for guiding the light by phase variation. Different approaches have been presented in an attempt to adjust the resonance wavelength of the GMR spectral filter: accumulation and depletion of charges in the diffraction grating, insertion of a PN junction in the waveguide, ...Finally, a first brick for the integration of a T2SL in an optical nano-resonator to make an all-semiconductor nano-structured photodetector was studied. I proposed the theoretical design of several nano-resonators integrating a T2SL type photodetector (InAs/GaSb). I designed three architectures with distinct spectral properties, which differ in particular in the thickness of the T2SL layer.