In recent years, plasmonic resonant antennas have seen widespread consideration in many detection and chemistry applications due to their potential for enhancing and confining the emission and polarization of electromagnetic fields. Examples include optical couplers to ultra-compact photodetectors, high-resolution optical microscopy, enablers of single molecule Raman signal detection and heating elements that facilitate nanostructure growth. An asymmetric cross-bowtie antenna is investigated for providing a broad circular polarized frequency response in the long wave infrared (LWIR). The asymmetric cross-bowtie antenna is constructed with two perpendicular bowtie antennas with differing arm lengths. The asymmetric cross-bowtie antenna is numerically analyzed using a finite element method (FEM) solver; Ansys High Frequency Structural Simulator (HFSS). The two perpendicular bowtie antennas, under illumination, provide a wide-band localized circularly-polarized field within a shared antenna feed-gap. At the center frequency of 28.3 THz (10.6μm), a circularly-polarized state over 30% bandwidth is achieved. The antenna is then loaded with a metal-oxide-metal diode in order to design a circularly polarized antenna-coupled detector.
Planar leaky-wave antennas (LWA) that are capable of full-space scanning have long since been the pursuit for applications
including, but not limited to, integration onto vehicles and into cameras for wide-angle of view beam-steering. Such a
leaky-wave surface (LWS) was designed for long-wave infrared frequencies with frequency scanning capability. The LWS
is based on a microstrip patch array design of a leaky-wave impedance surface and is made up of gold microstrip patches
on a grounded zinc sulphide substrate. A 1D composite right/left-handed (CRLH) metamaterial made by periodically
stacking a unit cell of the LWS in the longitudinal direction to form a LWA was designed. This paper deals with loading
the LWA with a nickel bolometer to collect leaky-wave signals. The LWA radiates a backward leaking wave at 30 degrees
at 28.3THz and scans through broadside for frequencies 20THz through 40THz. The paper deals with effectively placing
the bolometer in order for the collected signal to exhibit the designed frequency regime. An effective way to maximize the
power coupling into the load from the antenna is also explored. The benefit of such a metamaterial/holographic antennacoupled
detector is its ability to provide appreciable capture cross-sections while delivering smart signals to subwavelength
sized detectors. Due to their high-gain, low-profile, fast response time of the detector and ease of fabrication,
this IR LWA-coupled bolometer harbors great potential in the areas of high resolution, uncooled, infrared imaging.
The goal in the design of an efficient and low-noise antenna coupled receiver is to achieve a maximal capture cross section for the incident electromagnetic radiation compared to the dimensions of the sub-wavelength sized sensor loading the antenna. Collection efficiency captures this concept of power output/input and is made up of several subefficiencies. In the ideal case all of the available, incident power is collected and transferred to the load. However, many of the fundamental limits of antennas are based on theory describing the transmitting mode, whereas certain questions remain open for receiving antennas. Textbook antenna theory predicts that only 50% of available incident power can be absorbed by an antenna, yet under specific conditions this limitation can be surpassed. Two considerations are presented; (1) fundamental limits on antenna absorption, and (2) practical participation of dissipative media in achieving impedance matching between antenna and load, and the associated performance compromise. Specifically we seek to determine whether antenna-coupled detectors can approach unity absorption efficiency under matched conditions. Further, we identify practical conditions that must be met in order to overcome fundamental limitations that inhibit total absorption. Then antenna loss is split into radiative and dissipative terms in order to identify trade-offs between impedance matching and radiation efficiency.