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GHz, Octavespanning Photodetectors for MWIR/LWIR


TECHNOLOGY AREA(S): Chemical/Biological Defense, Electronics

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 5.4.c.(8) of the solicitation.


OBJECTIVE: Design, build, and demonstrate a high-speed (5 GHz), high-sensitivity (NEP < 1pW/Hz^1/2) photodetector with octave spanning responsivity in the mid-wave infrared (MWIR) and/or long-wave infrared (LWIR) spectral regions.


DESCRIPTION: There is a critical need for DoD capabilities that would provide improved detection sensitivity of threat explosives and chemical warfare species. The MWIR and LWIR spectral regions are technologically important for numerous applications including communications, environmental and industrial monitoring, thermal imaging, and chemical sensing for defense and homeland security [1]. Despite the pressing physical motivations for extending such applications to the MWIR and LWIR, the lack of suitable radiation sources and detectors in these spectral regions has resulted in applications being developed in the less favorable, near-infrared (NIR) spectral region where the telecom industry has driven the development of laser and detector technologies. The maturation of quantum cascade laser technology and the recent development of microresonator-based optical frequency comb technology [2] have changed the current and future MWIR/LWIR landscape. To fully exploit the application potential [3] of chip-scale optical frequency comb sources now under development, new high-speed, broad spectral coverage, and highly sensitive detectors are needed to replace the often bulky, cryo-cooled systems that are currently in use.


PHASE I: Design a photodetector with <1 pW/Hz^1/2 noise equivalent power (NEP) for operation in the MWIR (3- 6 microns) and/or LWIR (6-15 microns) spectral regions. The photodetector should exhibit the specified NEP without cryo-cooling and with 5 GHz electronic bandwidth when illuminated by femtosecond to picosecond pulse trains. Room temperature operation is desirable; however, cooling and/or temperature stabilization consistent with thermoelectric cooling is acceptable. Phase I deliverables include a design review detailing expected device performance and a report presenting Phase II plans for device fabrication and characterization. The design review should specify device responsivity versus wavelength in the targeted spectral region, spanning at least one spectral octave. In addition to the NEP and electronic bandwidth, the detector active area should be defined to establish the device D*. Detector output power and saturation properties should be addressed. The final report should describe device operational principles and limits, materials platforms and fabrication techniques, and any required supporting electronics. Experimental data demonstrating feasibility of the proposed design is favorable.


PHASE II: Fabricate and test a prototype device demonstrating the performance outlined in Phase I. Multiple devices demonstrating detector uniformity (including the potential for arrayed operation) are desirable. If not demonstrated in the prototype fabrication, a clear path toward scalable fabrication should be identified. The Technology Readiness Level to be reached is 5: Component and/or bread-board validation in relevant environment.  

At the completion of Phase II, the prototype device(s) will be delivered to a laboratory of DARPA’s specification for characterization and integration with optical frequency comb sources. The final device should be adequately packaged and integrated with all relevant supporting electronics for delivery to and operation by the test verification facility. Guidance for device operation should be provided for test facility personnel. 


PHASE III DUAL USE APPLICATIONS: The same physical motivations underlying defense and security application of spectroscopic detection in the MWIR and LWIR spectral regions are true for numerous commercial applications of the same technology including environmental monitoring, toxic industrial chemical detection, and first responder safety and assessment. A key specification for many commercial applications is the device SWaP enabled by the elimination of cryo-cooling.

Spectroscopic detection in the MWIR and LWIR spectral regions, where fundamental molecular vibration transitions occur, combined with key atmospheric transmission windows, is critical for improved detection sensitivity of threat explosives and chemical warfare species. Active standoff detection schemes based on optical frequency comb technology, when paired with the detectors developed in this SBIR, hold great potential to exploit these fundamental physical aspects of molecular and atmospheric chemistry for improved detection limits while simultaneously achieving improved chemical selectivity.


KEYWORDS: Photodetector, MWIR, LWIR, Optical Frequency Comb 

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