Beam shape of coherently-combined optical arrays

Irl W. Smith

doi:10.1117/12.883402

13 May 2011 Beam shape of coherently-combined optical arrays

Irl W. Smith

Proceedings Volume 8052, Acquisition, Tracking, Pointing, and Laser Systems Technologies XXV; 80520P (2011) https://doi.org/10.1117/12.883402
Event: SPIE Defense, Security, and Sensing, 2011, Orlando, Florida, United States

Abstract

In many applications, the utility of coherently-driven arrays of spatially distributed optical apertures is highly dependent on the "power in the bucket", i.e., power in the main lobe of the beam. This depends on the illumination pattern of the individual apertures (e.g., truncated-Gaussian) via a geometric efficiency η of order unity. It depends more strongly on the areal fill factor FA, i.e., the degree to which the emitting apertures (exclusive of the support structure between the apertures) cover the entire array face. Starting from first principles, we derive rigorous formulations of certain measures of array beam shape and extract a small set of heuristically-motivated but robust performance measures. At a range R, the peak irradiance I_p is P_totA_arrayF_Aη/λ²R². In terms of the effective diameter D_eff, which depends on the second moment <x²> of the emitted amplitude and is equal to the actual diameter for a uniformly illuminated ("top-hat") circular emitter, we find for a wide range of near-field irradiance distributions that the power in the bucket P_B is given by (1.05±0.05)×(λR/D_eff)²I_p.

Citation Download Citation

Irl W. Smith "Beam shape of coherently-combined optical arrays", Proc. SPIE 8052, Acquisition, Tracking, Pointing, and Laser Systems Technologies XXV, 80520P (13 May 2011); https://doi.org/10.1117/12.883402

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