TECHNOLOGY AREA(S): Materials, Materials, Weapons, Weapons, Air Platform, Air Platform, Space Platforms, Space PlatformsOBJECTIVE: Design, develop, and demonstrate high power (>1-3 W), single mode, direct diode emitters that meet the emerging government need for high-power, high-brightness laser systems with greatly reduced size, weight, and power (SWaP) consumption.DESCRIPTION: This topic seeks the development of high power, single-mode, high-brightness, narrow linewidth, near diffraction limited diode emitters that can be spectrally or coherently beam combined for further power scaling.Most current electrically-powered high energy lasers require an additional gain medium to achieve necessary beam quality (high brightness).Since an additional gain medium creates power loss, it is desirable to eliminate the additional gain medium and use high power direct diodes directly.Semiconductor laser sources offer reduced optical elements, higher efficiency, better SWaP, increased robustness, lifetime, reliability, manufacturability, and lower cost of operation and ownership when compared to other types of laser systems, such as fiber lasers.Diode lasers have proven to be very reliable, very compact, and should continue to prove to be cost effective compared to other laser sources.Maturing highly efficient laser diodes will directly benefit current research and development efforts in the field of next generation multi-kW laser sources, extending the efficiency, reliability, operating temperature, and providing multi-kW power scaling capabilities.The overall goal of this topic is to develop direct diode emitters that, when combined, produce high power direct diode laser (HPDDL) systems capable of achieving upwards of 10-100 kW (dependent on the beam combining technique) of high output power while maintaining the beam quality to a near diffraction limited spot size (M2< 1.2) in a low SWaP configuration.By combining multiple high-power, single-mode, direct diode emitters into elements, and multiple elements into a HPDDL system, the potential exists to meet these SWaP needs based on the inherently high (potentially>70%) electrical-to-optical power conversion efficiency (PCE) of direct diode systems.Solutions are highly desired to meet challenges such as short coherence length, multiple modes, and high divergence angles (which limits maintaining a tight spot while propagating over a long distance).PHASE I: Collaborate with government and industry to review and adjust, as needed, the topic objectives in order to increase commercialization prospects.Identify any significant design trades and work with the government to resolve them.Complete a preliminary direct diode emitter design and perform modeling and simulation to estimate its performance with enough fidelity to quantify major specifications.Conduct additional research, analyses, and experimentation as needed to demonstrate feasibility and/or validate models.Determine the feasibility of manufacturing the product in realistic quantities and at commercially competitive costs.Complete preliminary cost and performance estimates and compare with existing products.Complete a preliminary plan for fabricating and testing prototypes in Phase II and begin coordinating with potential service providers, suppliers, and sub-contractors.PHASE II: Complete a prototype design.Model and simulate its performance with enough fidelity to quantify almost all of its specifications.Fabricate and test HPDDL prototypes in sufficient quantities to make a preliminary assessment of yield and performance variation.Compare test results with predictions.Begin initial qualification of the new design.Finalize the cost and performance estimates based on results and compare with existing products.Begin commercialization of the new approach.Seek commitments from potential customers in order to help fund Phase III.PHASE III: Incorporate lessons-learned from the prototype into a product design.Begin producing and delivering products, at a low rate, to customers.Fully qualify the product for the intended application(s).Assist in integrating this product into a demonstrator system.KEYWORDS: High Power Direct Diode Laser, HPDDL, Direct diode emitters, Single mode, High brightness, Beam quality, Spectral and Coherent beam combining, Laser Power ScalingReferences:1. Y. Zhao and L. Zhu, “On-chip coherent combining of angled-grating diode lasers toward bar-scale single-mode lasers”, Optical Society of America, Opt. Express 6375, Vol. 20, No. 6, March 2012.2. Y. Zhao and L. Zhu, “Improved Beam Quality of Coherently Combined Angled-Grating Broad-Area Lasers,” IEEE Photonics Journal, Vol. 5, No. 2, April 2013.3. Leisher et al., “Feedback-Induced Failure of High Power Diode Lasers,” IEEE Journal of Quantum Electronics, JQE-134992-2018.R1, Oct 2018.
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