Antenna-coupled detectors provide uncooled, cost-effective solutions for infrared and millimeter-wave imaging. This work describes the design, fabrication, measurement, and optimization of several types of antenna-coupled detectors for LWIR (8 - 12 µm) and 94 GHz radiation. Two types of millimeter-wave antenna-coupled detectors were fabricated and tested: a slot antenna coupled to a bolometer, and a patch antenna coupled to a SiC Schottky diode. Electromagnetic modeling of the antennas helped guide the design of antennas with better impedance matching to the detectors. Schottky diodes are discussed as detectors for millimeter-wave and infrared radiation, with the goal of increasing the cutoff frequency to allow infrared detection. The magnitude of response of antenna-coupled bolometric detectors to infrared radiation is affected by the thermal-conduction properties of the sensor structure. Two fabrication processes were developed to improve the thermal isolation of the antenna-coupled bolometer from its substrate. The first process creates a membrane beneath the device. Measured results show a factor of 100 increase in responsivity over an identical device without a membrane. The second process thermally isolates the device from its substrate by suspending the metallic structure in air. Several factors for optimization of infrared antenna-coupled detectors are investigated. The complex dielectric function of the metal from which the antenna is constructed can affect the performance of the device. The use of a ground plane and dielectric standoff layer beneath the antenna can increase the sensor responsivity. Dielectric material properties and thicknesses are considered, and incorporated in device simulations. Finally, a potential fabrication process is presented for via connections from the antenna-coupled detector through a ground plane to bond pads to mitigate the effect of bias lines on antenna behavior.

Infrared antennas are employed in sensing applications requiring specific spectral, polarization, and directional properties. Because of their inherently small dimensions, there is significant interaction, both thermal and electromagnetic, between the antenna, the antenna-coupled sensor, and the low-frequency readout structures necessary for signal extraction at the baseband modulation frequency. Validation of design models against measurements requires separation of these effects so that the response of the antenna-coupled sensor alone can be measured in a calibrated manner. Such validations will allow confident extension of design techniques to more complex infrared-antenna configurations. Two general techniques are explored to accomplish this goal. The extraneous signal contributions can be measured separately with calibration structures closely co-located near the devices to be characterized. This approach is demonstrated in two specific embodiments, for removal of cross-polarization effects arising from lead lines in an antenna-coupled infrared dipole, and for removal of distributed thermal effects in an infrared phased-array antenna. The second calibration technique uses scanning near-field microscopy to experimentally determine the spatial dependence of the electric-field distributions on the signal-extraction structures, and to include these measured fields in the computational electromagnetic model of the overall device. This approach is demonstrated for infrared dipole antennas which are connected to coplanar strip lines. Specific situations with open-circuit and short-circuit impedances at the termination of the lines are investigated.

Le but de cette thèse est d’établir une modélisation électromagnétique du détecteurbolométrique térahertz (THz). Ce travail aide à faciliter la conception de bolomètre THz dontla structure est basée sur celle de bolomètre infrarouge à température ambiante. Le contextede la thèse est l’imagerie THz active. Nous avons étudié le comportement électromagnétiqued’un bolomètre à antenne de bande spectrale 1 – 5 THz. Deux modes de simulation ont étéréalisées : l’une est en mode de réception et l’autre est d’émission. La combinaison de cesmodes de simulation constitue un outil important pour concevoir le bolomètre THz. Latechnique de spectroscopie par transformée de Fourier a été utilisée pour caractériserexpérimentalement le comportement électromagnétique du détecteur. Nous avons mesuré laréflectivité de la surface du plan focal de détecteur ainsi que la réponse spectrale du détecteur.Les deux sont confrontées avec la simulation et elles se trouvent en bon accord. Avec lesconnaissances obtenues des résultats théorique et mesuré, la recherche aide à améliorer desperformances du détecteur actuel. Nous avons aussi proposé un design pour le bolomètre defaible fréquence (850 GHz). Ce dernier ouvre la perspective d’emmener la technologie debolomètre d’infrarouge vers la bande sous-térahertz où l’imagerie est beaucoup plusfavorable. / This PhD thesis aims to establish an electromagnetic modeling of the bolometer atterahertz (THz) range that can facilitate the design of the detector from the uncooled infraredbolometer technology. The envisaged application for the detectors lies in active THz imagingat room temperature. We have studied the optical coupling of a THz antenna-coupledbolometer operating in the range 1 – 5 THz. Simulations in receiving and transmitting modeshave been performed to study the optical characteristics of the bolometer. The combination ofthese two simulation types leads to a powerful toolset to design terahertz bolometers. For theexperimental aspect, measurements have been performed by using Fourier-transformtechnique to study experimentally the electromagnetic behavior of the bolometer. They aremeasurement of reflectivity of the focal plane array’s surface and spectral responsemeasurement. The results of measurement were found to be in good agreement with thesimulation. The understanding from the study in this PhD helps us make improvement to theactual detector. Also the design of bolometer for low frequency (850 GHz) has beenproposed. This leads to a perspective of using bolometer for terahertz imaging at thefrequency where many characteristic of the terahertz radiation are favorable for imagingapplication.

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