N211-005 TITLE: Packaged Mid-Infrared Non-Mechanical Beam Steerer

RT&L FOCUS AREA(S): General Warfighting Requirements

TECHNOLOGY AREA(S): Air Platforms; Battlespace Environments; Weapons

OBJECTIVE: Design and develop a packaged, high-throughput, non-mechanical beam steering device that is able to maintain stable operation with multiple-wavelength laser sources in the midwave infrared (MWIR) band with high beam quality, efficiency, and power on target.

DESCRIPTION: Non-mechanical beam steering (NMBS) has numerous advantages over conventional mechanical gimbals, including high point-to-point steering speeds, low size, weight, and power consumption, and low operating costs. To date, NMBS devices have primarily been developed and matured in the short-wave and near-infrared bands. Recent advances in refractive NMBS technology have resulted in MWIR-compatible liquid crystal-based refractive devices [Refs 1, 2], but they have primarily been demonstrated at the laboratory scale and require additional development for Department of Defense (DoD) applications. Of particular interest is development of robust packaging for refractive NMBS devices that combines the steering head, associated optical components, and thermal management in a compact package that is able to operate from room temperature to beyond 55 degrees C, using the latest MIL-STD 810 for thermal testing. Additional considerations include optical optimization of refractive NMBS devices to improve throughput performance and steering magnitude.

Driven by DoD application requirements, the Navy seeks development of technologies capable of continuously steering a beam across the field of regard (FOR) without blind spots. Steerers should satisfy specifications including, but not limited to:

• point-to-point steering speed: Threshold of 1 kHz (1 ms point-to-point transition time) across >75% of the FOR, Objective of 10 kHz (100 �s point-to-point transition time) for >75% of the FOR;
• angular steering range: Threshold of 15� horizontally by 2� vertically, Objective of 30� horizontally by 5� vertically;
• throughput: Threshold of 30%, Objective of 50%; and
• power-on-target: Threshold of >1 W, Objective of >10 W;
• beam quality: Threshold of M2 <5, Objective of M2<1.5;
• aperture: Threshold of 2 mm, Objective of 1 cm;
• total packaged beam steerer volume (including associated coupling optics and thermal management): Threshold of <50 cm3, Objective of <10cm3; and
• electrical power consumption of the steerer head and associated thermal management while under active illumination: Threshold <10 W, Objective <1 W.

While it is desired that the full angular steering range be accessible without any wavelength-based steering effects, solutions that incorporate wavelength-tuning methods may be considered. The steerer must be capable of transitioning between any arbitrary points within the FOR and holding position at any arbitrary point; the primary operation mode necessary to achieve threshold and objective specifications should not be a continuous raster scan. The designed device must be able to accommodate coupling and steering of multiple laser lines, individually, but in a single device, between 2-5�m with high efficiency.

The design should reasonably expect to achieve a manufacturing readiness level (MRL) of 5 within 3 years and MRL 7 within 5 years of beginning work on this NMBS device.

PHASE I: Design, develop, and demonstrate feasibility of refractive NMBS waveguides for improved optical performance, to include designs for improved steering while minimizing total optical path length. Designs for packaging of such a device should also be considered, taking into account thermal management and optical coupling of remoted lasers. An assessment of whether the proposed technology functions in reverse, as a scannable receiving optic, should be included. The Phase I effort will include prototype plans to be developed under Phase II. A schedule and explanation of the manufacturing readiness level shall be included in the Phase I final report.

PHASE II: Develop a packaged NMBS prototype device from the proposed design. Demonstrate that it is capable of maintaining stable operating temperature while meeting radiant power and M2 requirements. Include, in this demonstration, provisions to steer, either simultaneously or in rapid sequence, multiple wavelengths in the MWIR band. Ensure that volume and electrical power requirements apply to the prototype device.

PHASE III DUAL USE APPLICATIONS: Perform final testing the packaged NMBS device in a relevant environment, to include appropriate integration as applicable to the specific Navy platform. Transition and integrate to an airborne platform of interest chosen in consultation with PMA-272.

This technology is beneficial for medical diagnostics, chemical sensing, and other applications that utilize mid-infrared spectroscopy. Additionally, non-traditional beam steering may have lidar applications if the technology transitions the wavelength used in the lidar system.

REFERENCES:

1. Frantz, J.A.; Myers, J.D.; Bekele, R.Y.; Spillmann, C.M.; Naciri, J.; Kolacz, J.; Gotjen, H.G.; Nguyen, V.Q.; McClain, C.C.; Shaw, L.B. and Sanghera, J.S. "A chip-based non-mechanical beam steerer in the midwave infrared." Journal of the Optical Society of America B, 35(12), 2018, pp. C29-C37. https://doi.org/10.1364/JOSAB.35.000C29
2. Myers, J.D.; Frantz, J.A.; Spillmann, C.M.; Bekele, R.Y.; Kolacz, J.; Gotjen, H.; Naciri, J.; Shaw, B. and Sanghera, J.S. "Refractive waveguide non-mechanical beam steering (NMBS) in the MWIR [Paper presentation]." Proceedings of SPIE OPTO 10539, Photonic Instrumentation Engineering V, San Francisco, CA, United States, January 27-February 1 2018. https://doi.org/10.1117/12.2290379

KEYWORDS: non-mechanical; directed energy; lidar; mid-infrared; quantum cascade laser; beam steering; NMBS