From Event: SPIE Optical Engineering + Applications, 2017
Quantum Cascade Lasers represent one of the most significant recent advances in solid state lasers. Their ability to generate mid-IR through THz wavelengths have found numerous application in IR Countermeasures and Remote Sensing for defence, security, and commercial application. In many practical defence and security applications, to achieve the required power levels, it may become desired to combine several beams to form a single focused beam. This paper examines both coherent and incoherent beam combining, and the effects imposed by atmospheric turbulence on the propagation of these combined beams. Here, beam centroid wander and beam spread are analyzed along with their eventual contribution to laser spot size to obtain energy/power on target at range for varying turbulence levels. Interestingly, it is found that there is little difference between the energy/power delivered to a target whether beams are coherently or incoherently combined. Additionally, it is found that there is a maximum intensity that can be propagated to a target that is independent of initial beam quality and size for km-type ranges and at moderate turbulence levels.
Robert J. Grasso, "Atmospheric propagation of coherently and incoherently combined quantum cascade lasers," Proc. SPIE 10408, Laser Communication and Propagation through the Atmosphere and Oceans VI, 104080A (Presented at SPIE Optical Engineering + Applications: August 08, 2017; Published: 31 August 2017); https://doi.org/10.1117/12.2275867.
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