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Photonic Crystal Surface Emitting Semiconductor Laser

Description:

TECHNOLOGY AREA(S): Weapons

OBJECTIVE: : Develop the design space for high-power, high-beam quality photonic-crystal surface emitting lasers (PCSELs) and demonstrate a set of PCSEL prototypes.

DESCRIPTION: High power diode lasers have been almost exclusively reserved to edge emitting diodes. However, edge emitting diodes bring about challenges with respect to mode quality, beam symmetry, and the combination of many diodes into high power diode arrays and modules. Surface emitting diodes such as the vertical-cavity surface-emitting lasers (VCSEL) have many beneficial properties to include advantageous mode quality, beam shape, absence of catastrophic optical damage COD. However, the output power of element emitters is on the order or milliwatts, hence, thousands or diodes need to be efficiently combined to generate high power laser beams. This leads to a complicated and challenging beam combination process.Recently, photonic-crystal surface-emitting lasers (PCSEL) have emerged as potential solution that rivals edge emitting diode lasers in output power while maintaining radially high symmetric beam quality of approximately M2 = 1.1 [1-3]. A properly designed and implemented square-lattice photonic crystal will produce a singularity point, which allows for single-mode two-dimensional wave coupling and hence, two-dimensional broad-area cavity modes for high power lasing. By coupling this two dimensional architecture to radiation modes outside the photonic crystal via diffraction, vertical emission, i.e. a surface-emitted output beam can be realized [4].The design considerations for a PCSEL need to be explored and understood clearly to inform the trade and implementation space in the context of high energy laser weapons. These design considerations include selections in the photonic crystal structure and fabrication techniques, semiconductor layer design, materials and fabrication, beam mode quality and coherence properties as well as beam shape and divergence angle. Previous academic work promises PCSEL output power on the order of 1 Watt per emitter, and beam quality of M2 < 1.1, which as a combination may outperform current state of the art edge emitting as well as surface emitting diode solutions considered for HEL weapons. Furthermore, forecasting technology advancements suggest that output powers of greater than 10W may be achievable without loss in M2 performance. Additionally, the design freedoms associated with the crystal structure and electrode placement may allow for active beam steering [5].

PHASE I: Formulate the trade-space towards the design and development of high-power, high-beam quality PCSELs through a modelling and simulation (M&S) approach. The M&S approach will address photonic crystal structures, layer placement and respective thicknesses, geometries to couple from the two-dimensional cavity into free space for high-quality surface emission, choice of materials, and fabrication techniques and challenges. The deliverable will be a modelling and simulation tool to investigate PCSEL performance and characteristics as a function of the aforementioned trade space, and two PCSEL solutions will be proposed for development and fabrication in Phase 2.

PHASE II: Design and fabricate two separate PCSEL emitters that vary in their respective approach in terms of photonic crystal structure, layer structure and material choices, and fabrication technique. The PCSEL prototypes will be fabricated and delivered in a package similar to a development board to report on and allow for independent test and evaluation of various laser parameters to include mode quality, coherence, conversion efficiencies, thermal stability, etc.

PHASE III: Develop beam steering solutions to transition high power PSCEL technology into sensor applications such as automated driving, and free space high bandwidth telecommunication. Develop a high power PCSEL array towards the next generation high energy laser weapons.

KEYWORDS: Direct Diode HEL, high-brightness diode laser, surface emitting lasers

References:

K. Hirose et al., “Watt-class high-power, high-beam-quality photonic crystal lasers,” Nature Photon., vol. 8, pp. 406–411, 2014; E. Miyai et al., “Lasers producing tailored beams,” Nature, vol. 441, p. 946, 2003; S. Noda, T. Okino, K. Kitamura, Y. Tanaka, and Y. Liang, “Two dimensional Photonic Crystal Surface-Emitting Lasers,” Japanese Patent 6080941, Jan. 27, 2017; S. Noda, et al., “Photonic-Crystal Surface-Emitting Lasers: Review and Introduction of Modulated-Photonic Crystals,” IEEE Journal of Sel. Top. In Quant. Elec., vol. 23, 4900107, 2017; D. Yasuda, A. Nishigo, K. Kitamura, and S. Noda, “Investigation of photonic-crystal lasers with two-dimensional beam scanning capability (III),” presented at 63rd Japanese Society of Applied Physics, Spring Meeting, Tokyo, Japan, Mar. 19–22, 2016, Paper 21a-S621-10

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