TECHNOLOGY AREA(S): Air Platform, Electronics

ACQUISITION PROGRAM: JSF Joint Strike Fighter

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with section 3.5 of the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

OBJECTIVE: Develop and package fiber pigtailed high-power diode-pumped solid state lasers, operating at 1.55, 1.06, and 1.32 micron wavelengths, for wideband Radio Frequency (RF) photonics applications.

DESCRIPTION: Current airborne military communications and electronic warfare systems require ever-increasing bandwidths while simultaneously requiring reductions in space, weight, and power (SWaP). The replacement of the coaxial cable used in various onboard RF/analog applications with RF/analog fiber optic links will provide increased immunity to electromagnetic interference, reduction in size and weight, and an increase in bandwidth. However, for some airborne platform applications, RF/analog fiber optic links require the development of shot noise limited lasers that can operate over extended temperature ranges (-40 to 100�C).

Diode-pumped solid state lasers built to operate at 1.55, 1.06, and 1.32 micron wavelengths, such as those utilizing Gallium Arsenide (GaAs) pump lasers, have been known to operate over an extended temperature range without the need for thermo-electric cooling. These devices are also known to have shot-noise-limited noise properties throughout the Gigahertz regime inherent in their design due to the slow gain dynamics of rare-earth doped crystals and glasses.

The developed linear-polarization laser packaging must include a single-spatial-mode polarization-maintaining fiber pigtail with the polarization aligned to one axis of the fiber having a polarization extinction ratio of better than -18dB. Single-longitudinal mode operation at 1.55-micron wavelength is the most desirable; however, it would be advantageous if multi-longitudinal-mode designs (i.e., laser mode spacing greater than 50 GHz) as well as wavelengths of 1.06 or 1.32 microns were also available in the same form factor package as the wide variety of applications may dictate the use of one of these alternative designs. The minimum target threshold for laser output power is 50 mW and stretch goals of 200 to 500 mW, all with shot-noise-limited intensity noise levels at RFs above 1 GHz. This target threshold eliminates designs based on lower power seed lasers combined with optical power amplifiers designed to boost output power. The packaged laser is required to have a height less than or equal to 14 mm, and an overall package volume of less than 50 cubic centimeters, not including the fiber optic pigtail, but including all power electronics for controlling pump laser current and/or temperature control. The packaged laser must operate over a minimum temperature range of 0�C to 70�C with a stretch goal of -40�C to 100�C, and maintain hermeticity and optical alignment upon exposure to air platform vibration, thermal shock, mechanical shock, and temperature cycling environments [Refs 3 � 5]. Only fiber pigtailed lasers will be considered for this topic. Uncooled designs are preferred; however, thermoelectric cooled designs are acceptable especially given the operating temperature stretch goals.

PHASE I: Design and analyze the proposed approach for 1.55 micron lasers. Demonstrate feasibility of 1.55-micron laser power with a supporting proof of principle bench top experiment showing path to meeting Phase II goals. Design and analyze a laser package prototype. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Optimize the 1.55-micron single-longitudinal-mode laser and packaged laser designs from Phase I. Build and test the laser to meet design specifications. Test the prototype in an RF photonic link with the minimum performance levels reached. Characterize the packaged laser transmitter over temperature and air platform thermal shock, temperature cycling, vibration, and mechanical shock spectrum. If necessary, perform root-cause analysis and remediate laser package failures. Deliver 1.55-micron laser packaged prototype. Design and analyze the applicability of the proposed approach to the other desired wavelengths and longitudinal mode options.

PHASE III DUAL USE APPLICATIONS: Finalize and transition the packaged laser prototype into manufacturing, potentially with a U.S.-based photonic component supplier, making the component available to the public and defense industry. Commercial applications include wireless networks based on remoted antennas used in commercial telecommunication systems.

REFERENCES:

1. Beranek, M. and Copeland, E. �Accelerating Fiber Optic and Photonic Device Technology Transition via Pre-qualification Reliability and Packaging Durability Testing.� IEEE Avionics and Vehicle Fiber-Optics and Photonics Conference: Santa Barbara, 2015. https://ieeexplore.ieee.org/document/7356630/

2. Urick, V., Mckinney, J. and Williams, J. �Fundamentals in Microwave Photonics� John Wiley & Sons, Inc.: Hoboken, 2015, pp. 469-472.

3. MIL-STD-38534J, General Specification for Hybrid Microcircuits. http://www.landandmaritime.dla.mil/programs/milspec/ListDocs.aspx?BasicDoc=MIL-PRF-38534

4. MIL-STD-810G, Environmental Engineering Considerations and Laboratory Tests. http://everyspec.com/MIL-STD/MIL-STD-0800-0899/MIL-STD-810G_12306/

5. MIL-STD-883K, DoD Test Method Standard Microcircuits. http://www.dscc.dla.mil/downloads/milspec/docs/mil-std-883/std883.pdf

KEYWORDS: Laser; Diode-Pumped; Solid State; RF-Over-Fiber; Fiber Optics; Packaging; Radio Frequency