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LIGO Seminar

Tuesday, July 16, 2019
1:00pm to 2:00pm
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West Bridge 351 (LIGO Science Conference Room)
Characterization of LIGO optics point defects using the lens-free imaging method ptychography
Tega Edo, Dr, Physics, Sheffield University,

The occurrence of point defects on Advanced LIGO test masses contribute to scattering losses in the LIGO detectors and degrades squeezed coherent states through parasitic interference induced by scattered light. However, the precise mechanism for their formation is not well understood. The scattering losses from these defects is currently being measured at millimeter-scale resolutions using the total integrated scattering method, whose output intensity image measures the coherent scattering strength of collections of point defects over the surface. A promising new high-resolution method for investigating the detailed microscopic structure of these defects is the diffractive imaging method, ptychography. A major benefit of ptychography is that its output image, the complex reflection profile of the surface under investigation, will permit high fidelity numerical simulation of surface scattering and losses from Advanced LIGO test masses. In this talk, we will discuss the solution to the phase problem as it relates to ptychography, the standard iterative phase-retrieval algorithm for computing its output image, techniques for superseding its diffraction-limited resolution and the implications of its fundamental sampling requirement.

For more information, please contact Syd Meshkov by phone at 626-840-3707 or by email at syd@ligo.caltech.edu.