Abstract
We present the design, fabrication, and characterization of an infrared (IR) polarization sensing detector with a wide dynamic range and sub-wavelength dimensions. The detector consists of two orthogonal slot antennas, each loaded with two microbolometers at its edges. The polarization of the incoming IR radiation is detected by comparing the received power levels in the bolometer pairs corresponding to each slot antenna. The IR radiation is sensed by applying a dc bias voltage to each antenna and measuring the changes in the dc current caused by the change of the bolometer resistance as they absorb the incoming IR radiation. In this design, the ratio of the absorbed power in the bolometers is a one to one function of the polarization of the incident wave. A prototype of this detector, designed to have maximum sensitivity at λ = 10.6 μm, was designed, fabricated, and characterized. The fabricated detector has an area of 0.7λ × 0.7λ, where λ is the free-space wavelength. The polarization sensing response is characterized under different angles of incidence. The measurement results show that the device has a dynamic range of 24 dB between two orthogonal orientations of EM wave polarization for incidence angles in the range of ±20° from boresight.
Highlights
Polarization sensing systems are used for many applications such as facial recognition[10], target tracking[11], remote sensing[8], and astronomy[12]
Since slot antennas absorb the EM radiation best if the electric field of the incident wave is perpendicular to the slot, they provide excellent polarization sensitivity[32]
The bottom side of the SiO2, layer is completely covered with a 200 nm-thick layer of aluminium, which serves as a floating ground plane for the slot antenna
Summary
Polarization sensing systems are used for many applications such as facial recognition[10], target tracking[11], remote sensing[8], and astronomy[12]. Slot antennas offer desirable traits such as fabrication ease, higher gains, and wider bandwidths[28] Most of these previously presented designs[27,28] do not sense the polarization of the incident wave and were proposed as simple antenna-coupled IR detectors. Two arrays of orthogonal slot antennas coupled to microbolometers were used to design a dual polarized detector for submilimeter imaging[30] Their detector was designed for lower frequencies than IR, which resulted in larger feature sizes and easier fabrication procedure. By using the slot antennas and the ratio of the variations in temperature, we have managed to drastically reduce the effects of the external measurement setups, bias lines, and the irradiance of the EM wave on the final response function of the detector.
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