Publications by authors named "Shawn Divitt"

We experimentally apply incoherent Fourier ptychography to enhance the resolution of recorded images by projecting known, uncorrelated, random patterns at high speed onto 3D moving and distant objects. We find that the resolution enhancement factor can be greater than 2, depending on the projection and camera optics.

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We consider the application of a modified optical vortex coronagraph as a transmissometer. We find, through theory and simulation, that the rejection of scattered light benefits from increasing the charge number of the vortex masks in the image plane, and that a combination of a vortex mask and binary pinhole can outperform the pinhole alone.

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Coherence has been used as a resource for optical communications since its earliest days. It is widely used for the multiplexing of data, but not for the encoding of data. Here we introduce a coding scheme, which we call mutual coherence coding, to encode information in the mutual coherence of spatially separated light beams.

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Correlations of broadband speckle have important implications for passive, non-line-of-sight imaging. We examine the spectral and spatial correlations of broadband, around-the-corner speckle and reveal a set of equations that locate the spatial maximum of the paraxial spatial-spectral correlation function. We confirm the validity of the spatial-spectral correlation framework through experiment, theory and simulation.

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Speckle correlation imaging offers the ability to see objects through diffusive materials and around corners. Imaging self-illuminating thermal objects in non-line-of-sight scenarios is of particular interest. Here, using bispectrum and phase retrieval methods, we demonstrate speckle correlation imaging of mid-infrared objects through diffusers and around corners at resolutions near the diffraction limit.

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Article Synopsis
  • Shrinking traditional optical systems to chip-scale sizes can greatly enhance applications in imaging, sensing, and metrology, among others.
  • This study showcases advanced metasurface optical components that operate at ultraviolet wavelengths, including deep ultraviolet, and enables functions like high-numerical-aperture lensing and hologram projection.
  • The nanostructures in these metasurfaces are made from hafnium oxide and represent a step towards versatile, compact ultraviolet technologies for fields such as lithography and quantum information processing.*
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Advances in ultrafast lasers, chirped pulse amplifiers, and frequency comb technology require fundamentally new pulse-modulation strategies capable of supporting unprecedentedly large bandwidth and high peak power while maintaining high spectral resolution. We demonstrate how dielectric metasurfaces can be leveraged to shape the temporal profile of a near-infrared femtosecond pulse. Finely tailored pulse-shaping operations, including splitting, compression, chirping, and higher-order distortion, are achieved using a Fourier-transform setup embedding metasurfaces able to manipulate, simultaneously and independently, the amplitude and phase of the constituent frequency components of the pulse.

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A scattering layer is usually considered an obstacle to imaging. However, using speckle correlation imaging techniques, the scattering layer effectively acts as a lens. To date, the speckle correlation imaging method has been limited to imaging sparse samples.

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The interference pattern observed in Young's double-slit experiment is intimately related to the statistical correlations of the waves emitted by the slits. As the waves in the slits become more correlated, the visibility of the interference pattern increases. Here, we experimentally modulate the statistical correlations between the optical fields emitted by a pair of slits in a metal film.

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Non-conservative forces in optical tweezers generate undesirable behavior, such as particle loss due to radiation pressure and the preclusion of the thermodynamic equilibrium. Here, we rigorously derive criteria for the elimination of non-conservative forces, and describe how these criteria can be met by a large class of counter-propagating, focused optical beams.

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We present an experimental method for the fast measurement of both the spectral (spatial) and complex degrees of coherence of an optical field using only a binary amplitude mask and a detector array. We test the method by measuring a two-dimensional spectral degree of coherence function created by a broadband thermal source. The results are compared to those expected by the van Cittert-Zernike theorem and found to agree well in both amplitude and phase.

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Light emission from the junction of a scanning tunneling microscope (STM) is examined in the presence of 20 nm topographical features in thin gold films. These features significantly modify the emission rates of the junction. Contributions to this modification are discriminated by examining emission rates on samples where the material is varied spatially.

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