An Angle-Sensing Infrared Detector Using a Two-Element Biomimetic Antenna Array

We present a technique for designing the angle-sensing infrared detectors with subwavelength dimensions. The proposed detector is composed of a two-element long-wave infrared (LWIR) biomimetic antenna array. The detector consists of two closely spaced and strongly coupled IR antennas whose natural mutual coupling is augmented by using an external coupling network. Each antenna is connected to a microbolometer to detect the incoming IR radiation. By controlling the mutual coupling between the antennas and designing an optimum coupling network, the ratio of the power absorbed in the two bolometers is made to a one-to-one function of the incidence angle. This allows for determining the angle of incidence of the incoming IR light by measuring the changes of the dc currents passing through the bolometers when the antennas are biased with a dc voltage source. A prototype of the proposed angle-sensing detector is designed to operate at 10.6 μm in the LWIR band. The prototype is fabricated and characterized. Measurement results show that the device has a one-to-one response function for transverse electric waves within a field of view of ±60°. The response of the device for incident waves having the transverse magnetic or random polarizations was also simulated and measured. In all cases, the measurement results are found to be in good agreement with the theoretical predictions.