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High Power Fiber Laser Tap Couplers for Phase and Polarization Control



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: Develop innovative, bi-directional fiber laser/amplifier output tap couplers for use in high power fiber laser weapon systems, extending the efficiency, reliability and power handling beyond 1kW per channel.


DESCRIPTION: High energy lasers are required for a number of military applications including long range sensing, target designation and illumination and missile defense. Electric lasers are considered the laser of choice in the long-term since the energy supply is rechargeable and clean. The preferred type of electric laser is the semiconductor diode-pumped fiber laser or amplifier, which integrates well with other sensors and electro-optic elements in an aerospace environment. This topic seeks proposals for demonstration of concepts and hardware which would enable high-brightness, high-power scaling of fiber lasers/amplifiers. 

High power fiber optic tap couplers are needed to monitor and control optical amplifier output power, phase, pathlength and polarization of double clad gain fibers in all-fiber optical amplifier configurations. For non-polarization maintaining gain fiber operated in a linearly polarized output architecture, it is necessary to pick-off a small amount of amplified output signal for feedback to a control loop that can adjust the input polarization state to yield a linearly polarized output state. High power capable fiber optic tap couplers are required for the development and maturation of co-directional and counter-directional pumped all-fiber architectures to increase ruggedness and reliability for combined power scaling. The ideal tap coupler minimizes loss for the throughput signal for efficiency and power handling capability while picking-off a small amount of signal for closed loop control of polarization, phase and path length matching for coherent beam combining.

Spectrally combined fiber amplifier systems do not require phase and path length matching but do require linearly polarized output for efficient beam combining. High power capable fiber tap couplers compatible with large mode area double clad fibers, polarization maintaining, and non- polarization maintaining fibers are needed. Additionally, tap couplers for photonic crystal fibers and photonic band gap are needed. Fiber tap coupler designs are targeted for lasing of Ytterbium ~1064nm and Thulium ~2000nm. Optical efficiency of the tap coupler, power handling and bidirectionality will be used as metrics for all phases.


PHASE I: Deliver a design for a kilowatt capable fiber optic tap coupler and packaging for large mode area Ytterbium and Thulium doped double clad fiber. Criteria for the design includes, bi-directional power handling capability, polarization, phase and path length pick-off with robust packaging. Designs compatible with photonic crystal and photonic band gap gain fibers are also sought.


PHASE II: Based on Phase I designs and models; build, test, and demonstrate multi-kW capable bi-directional prototype fiber optic tap couplers and conduct in-depth characterization of hardware to show a maturity of technology toward potential commercial and military applications. Deliver packaged devices to solicitor designated government labs for high power evaluation.


PHASE III DUAL USE APPLICATIONS: Demonstrate multi-kW capable bi-directional prototype fiber optic tap couplers packaged for insertion into militarily relevant fiber laser weapons systems. Team with missile defense integrators to demonstrate maturity and technical readiness in military environments.


COMMERCIALIZATION: High power handling optical fiber tap couplers enable fabrication of compact and reliable fiber laser technologies for immediate insertion into military systems. Industrial commercial applications include materials marking, cutting and welding for a wide array of automated manufacturing. In a rapidly emerging medical application, tattoo removal is also an area where all-fiber optical power monitoring and control is needed.


KEYWORDS: High Power Fiber Tap Coupler, High Power All Fiber Pick-Off, Double Clad Fiber Pick-Off 

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