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Broadband Photoconductive Terahertz Focal Plane Arrays


TECHNOLOGY AREA(S): Chem Bio Defense, Electronics, Sensors

OBJECTIVE: Develop photoconductive terahertz focal plane arrays that offer large pixel count, high dynamic range, and high speed over a broad terahertz (THz) frequency range.

DESCRIPTION: Electromagnetic waves in the THz spectral band (roughly covering the 0.1 - 3 THz frequency range) offer unique properties for chemical identification, non-destructive imaging, and remote sensing. However, existing THz devices, such as THz sources and detectors, have not yet provided all of the functionalities required to fulfill many of these applications. Although Complementary metal–oxide–semiconductor (CMOS) technologies have been offering robust solutions below 1 THz, the high-frequency portion of the THz band still lacks mature devices. For example, most of the THz imaging and spectroscopy systems utilize single-pixel detectors, which results in a severe trade-off between the measurement time and field-of-view.To address this problem, a large pixel count, high dynamic range, high speed, and broadband THz focal plane array (THz-FPA) needs to be developed. The proposed THz-FPA can operate either as a frequency-tunable continuous-wave detector or a broadband-pulsed detector. It should be able to operate over a 1 - 3 THz frequency range, while offering above 30 dB dynamic range per pixel. It should have more than 1 kilo pixels and a frame rate of at least 1 Hz. Smart readout integrated circuits to increase the data collection efficiency and frame-rate can be investigated.

PHASE I: Demonstrate a proof-of-concept THz-FPA with at least 16 pixels. Show that each pixel of the THz-FPA meets the dynamic range and bandwidth requirements. Introduce a data readout method that can maintain the large dynamic range and broad bandwidth requirements for more than 1 kilo pixels and a frame rate of at least 1 Hz. Develop a Phase II plan that includes technology integration, test and validation with representative structures.

PHASE II: Realize the THz-FPA consisting of at least 1 kilo pixels integrated with the read-out circuits. Demonstrate the functionality of the final prototype to take THz images with more than a 30 dB dynamic range over a 1-3 THz bandwidth in less than 1 second. The prototype system will vary based on the proposed approach, but it may include hardware and software. Develop technology transition plan and business case assessment.

PHASE III: Broadband THz Imaging focal plane arrays enable sensors for detailed feature and frequency spectrum capture that support several DoD missions, among these are battlespace target assessment, surveillance in low-visibility conditions, and nondestructive material quality control (e.g., defects/corrosion in ship, aircraft, vehicle components), and law enforcement agencies for detection of illicit drugs and narcotics, and regulatory agencies (e.g., FDA, NIFA) for detection of toxins in drug, food, and agricultural products.

KEYWORDS: Broadband Terahertz, Imaging, Focal Plane Array


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