TECHNOLOGY AREAS: Sensors, Electronics, Battlespace, Weapons

ACQUISITION PROGRAM: PMA-272, Tactical Aircraft Protection Systems

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 3.5.b.(7) of the solicitation.

OBJECTIVE: Develop innovative, packaged fiber laser pump coupler for use in military systems, such as high energy laser weapon systems, extending the efficiency, reliability and power handling beyond current state of the art.

DESCRIPTION: Fiber lasers offer unprecedented size, weight and efficiency compared to other laser sources and have the potential to revolutionize a number of military systems, most notably high energy laser weapon systems. Cladding pumped (double clad) fiber lasers can utilize a range of laser diode pump sources which are themselves rapidly advancing to higher levels of power and brightness. Pump couplers are used to transport the pump light between the high brightness laser diode pump sources and the double clad fiber amplifiers. These are essential for development of an all-fiber laser to maximize ruggedness and reliability. The ideal pump coupler minimizes the loss in brightness between the pump diode and the fiber. It also has minimal loss, both for efficiency and power handling capability. Since many fiber laser systems possess a narrow line width, polarized output master oscillator power amplifier (MOPA) configuration, couplers are needed that are compatible with polarization-maintaining (PM) large mode area (LMA) fibers. These fibers are typically low numerical aperture and are not strictly single mode, making them particularly sensitive to external stresses and deformations. In addition, couplers for air- or glass-clad fibers, which may be desirable for power handling and/or reliability issues, present additional fabrication difficulties.

PHASE I: Develop a design and perform initial proof-of-principle tests and analysis on a pump coupler compatible with current PM-LMA fibers and high brightness laser diode pump sources in the 900-980 nm range. Designs for pumping Yb (1 micron wavelength) and Er (1.5 micron wavelength) are sought, with emphasis on the Yb. Criteria for the design include brightness preservation, power handling capability, and packaging free of organics or other power limiting materials. Designs compatible with air-clad, high NA fibers or glass-clad gain fibers are also of interest.

PHASE II: Build, test and demonstrate packaged prototype coupler for PM LMA MOPA systems capable of inserting greater than 2kW of pump power into a double clad fiber, based on the Phase I design and tests. Perform complete testing, including loss characterization (goal of <0.2 dB per splice), optical performance and assessment of power handling capability. Perform reliability testing to assess component lifetime and serviceability in a military environment with severe temperature and humidity requirements.

PHASE III: Transition to multiple programs including ONR-funded FY11 FNC and JTO-funded eye-safer high energy laser weapon systems

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Components for high power fiber lasers have significant potential markets in both commercial and military systems. High efficiency diode pump couplers will find applications for anything and every place a fiber laser has applications. This includes ladar/lidar systems, medical lasers, cutting and welding lasers.

REFERENCES:
1. F. Gonthier, "All-fiber pump coupling techniques for double-clad fiber amplifiers", Lasers and Electro-Optics Europe, 2005. CLEO/Europe. 2005 Conference, pp. 716-716. F. Gonthier et al, "High-power All-Fiber components: the missing link for high-power fiber lasers", Proc. SPIE 5335 (2004).

2. C. Headley et al, "Tapered fiber bundles for combining laser pumps", Proc. SPIE 5709, pp. 263-272, (2005).

3. A. Wetter et al, "Tapered fused-bundle splitter capable of 1 kW CW operation", Proc. SPIE 6453, 64530I (2007).

4. M. Nielsen et al, "High power PCF-based pump combiners", Proc. SPIE 6453, 64532C (2007).

KEYWORDS: High Energy Laser; Laser Weapons; fiber lasers; laser pump couplers; high brightness couplers; high efficiency couplers

** TOPIC AUTHOR (TPOC) **

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