Sagnac interferometry can provide a substantial improvement in signal-to-noise ratio compared to conventional magnetic imaging based on the magneto-optical Kerr effect. We show that this improvement is sufficient to allow quantitative measurements of current-induced magnetic deflections due to spin-orbit torque even in thin-film magnetic samples with perpendicular magnetic anisotropy, for which the Kerr rotation is second order in the magnetic deflection. Sagnac interferometry can also be applied beneficially for samples with in-plane anisotropy, for which the Kerr rotation is first order in the deflection angle. Optical measurements based on Sagnac interferometry can therefore provide a cross-check on electrical techniques for measuring spin-orbit torque. Different electrical techniques commonly give quantitatively inconsistent results so that Sagnac interferometry can help to identify which techniques are affected by unidentified artifacts.
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Shower curtain effect and source imaging
The shower curtain effect is commonly described as being able to see a person behind a shower curtain better than that person can see us. This asymmetric phenomenon has been observed in numerical simulations in various propagation models and in optics experiments. Here we present an analysis in the paraxial regime to give a novel characterization of the mechanism behind this effect and we discuss applications to imaging. The paraxial regime is for instance appropriate to model the propagation of a laser beam in a turbulent atmosphere. The theory that we present has also applications to tissue imaging. We consider two different measurement and imaging setups (matched field imaging and optical imaging) to clarify the shower curtain mechanism. We give a quantitative description of how the placement of the shower curtain, modeled as a randomly heterogeneous section, affects the optical imaging resolution. We moreover analyze the signal-to-noise ratio of the image. The analysis involves the study of multifrequency fourth-order moments associated with the Itˆo-Schr¨odinger equation and reveals that broadband sources are necessary to ensure statistical stability and high signal-to-noise ratio.
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- Award ID(s):
- 2308389
- PAR ID:
- 10518791
- Publisher / Repository:
- AIMS
- Date Published:
- Journal Name:
- Inverse Problems and Imaging
- Volume:
- 18
- Issue:
- 4
- ISSN:
- 1930-8337
- Page Range / eLocation ID:
- 993 to 1023
- Subject(s) / Keyword(s):
- Optics, waves in random media, shower curtain effect, imaging, multiple scattering, paraxial approximation
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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