Dynamical refocusing laser guide stars with membrane mirrors

S. Rabien; J. Ziegleder

doi:10.1117/12.926537

13 September 2012 Dynamical refocusing laser guide stars with membrane mirrors

S. Rabien, J. Ziegleder

Proceedings Volume 8447, Adaptive Optics Systems III; 84474P (2012) https://doi.org/10.1117/12.926537
Event: SPIE Astronomical Telescopes + Instrumentation, 2012, Amsterdam, Netherlands

Abstract

Laser guide stars created in the earth's sodium layer are the choice for all ELTs as adaptive optics reference. With the thickness of the sodium layer spanning up to 10km, the apparent image of the guide stars on the adaptive optics wavefront sensors is elongated. The further away sub-apertures of the WFS are from the guide star launch location, the more elongated the guide star appears on the sensor. To counteract the decreased signal from the elongation, usually an increased laser power is demanded or special format radial CCDs are proposed. Another known possibility is to utilize pulsed lasers and follow dynamically the propagating pulse on its way through the sodium layer, creating a sharp spot at the wavefront sensor location. Similar processes have been used for laser guide stars created with Rayleigh scattering in the lower atmosphere, increasing greatly the number of photons that can be received from the guide star. We present here the design and first laboratory tests of such a dynamically refocus device, based on membrane mirrors. Driven acoustically at high frequencies the stroke and phase of the mirror can be controlled. With a compact appearance the system seems to be easy to use and could enable precise wavefront control with lower power pulsed lasers at ELTs and other telescopes.

Citation Download Citation

S. Rabien and J. Ziegleder "Dynamical refocusing laser guide stars with membrane mirrors", Proc. SPIE 8447, Adaptive Optics Systems III, 84474P (13 September 2012); https://doi.org/10.1117/12.926537

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