Adaptive laser beam steering with micro-optical arrays

Matthias Rungenhagen; Hans Dieter Tholl

doi:10.1117/12.737290

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10 October 2007 Adaptive laser beam steering with micro-optical arrays

Matthias Rungenhagen, Hans Dieter Tholl

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Proceedings Volume 6738, Technologies for Optical Countermeasures IV; 67380G (2007) https://doi.org/10.1117/12.737290
Event: Optics/Photonics in Security and Defence, 2007, Florence, Italy

Abstract

Micro-lens arrays of large formats are well suited for agile laser beam steering. State-of-the-art beam steering devices comprise three microlens arrays which are distributed among two cascaded substrates. The substrates are decentered laterally by piezoelectric transducers. This arrangement acts like a blazed grating structure with variable blaze angle. Beam steering with blazed grating micro-lens arrays suffers from non-uniformity of the optical parameters across the aperture which leads to a reduction of the spatial coherence between the interfering beamlets and an increase in the beam divergence. This disadvantage can be resolved by combining the blazed grating beam steerer with an array of phase shifting elements. If the number of phase shifting elements (pixels) is sufficiently large, several pixels cover one subaperture of the blazed grating and phase piston as well as higher wavefront errors (tip/tilt, defocus) may be corrected. In the VIS and NIR spectral range large format liquid crystal spatial light modulators (SLM) are available for adaptive correction of the wavefront of each subaperture of the blazed grating beam steerer. Spatial light modulators based on micro-mirrors or electro-optical ceramics which cover a broader spectral range up to the MWIR are under development. This paper outlines the concept of adaptive compensation of the wavefront error of each subaperture in a blazed grating beam steerer. The combination of micro-lens arrays with large format spatial light modulators for the NIR and the MWIR spectral ranges will be described. Investigations and measurements at component level (micro-lens arrays and a commercially available liquid-crystal-on-silicon spatial light modulator) at 1.5 μm will be presented in order to support the theory.

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Matthias Rungenhagen and Hans Dieter Tholl "Adaptive laser beam steering with micro-optical arrays", Proc. SPIE 6738, Technologies for Optical Countermeasures IV, 67380G (10 October 2007); https://doi.org/10.1117/12.737290

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