The development of wave optics for light brought many new insights into our understanding of physics, driven by fundamental experiments like the ones by Young, Fizeau, Michelson-Morley and others. Quantum mechanics, and especially the de Broglie’s postulate relating the momentum p of a particle to the wave vector k of an matter wave: k = 2 λ = p/ℏ, suggested that wave optical experiments should be also possible with massive particles (see table 1), and over the last 40 years electron and neutron interferometers have demonstrated many fundamental aspects of quantum mechanics [1].

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Optics and interferometry with atoms and molecules

Journal of Scientific Instruments Editor: Dr H R Lang Vol 28 and Supplement No 1, 1951 Pp xvi + 388 + iii + 80 (London: Institute of Physics, 1951) Bound, £3 12s; unbound, £3

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A Review of Scientific Instruments

Electron beams with helical wavefronts carrying orbital angular momentum are expected to provide new capabilities for electron microscopy and other applications. We used nanofabricated diffraction holograms in an electron microscope to produce multiple electron vortex beams with well-defined topological charge. Beams carrying quantized amounts of orbital angular momentum (up to 100ħ) per electron were observed. We describe how the electrons can exhibit such orbital motion in free space in the absence of any confining potential or external field, and discuss how these beams can be applied to improved electron microscopy of magnetic and biological specimens.

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Electron Vortex Beams with High Quanta of Orbital Angular Momentum

Aspects of the present invention relate to a compact optics module for a head mounted display including a DLP image source comprising a polarized light source providing illumination light, a flat reflective polarizer to reflect the illumination light toward the DLP image source and transmit image light, wherein the illumination light is provided at an angle to the DLP, a quarter wave retarder to change the polarization state of the illumination light as it is reflected by the DLP image source thereby providing image light, at least one light trap to absorb a portion of off-state image light, a lens element to provide a viewable field of view of on-state image light in an image displayed by the DLP image source, and a combiner to reflect the on-state image light toward a user's eye and provide a see-through view of a surrounding environment.

See-through computer display systems

Control over the dispersion of the refractive index is essential to the performance of most modern optical systems. These range from laboratory microscopes to optical fibres and even consumer products, such as photography cameras. Conventional methods of engineering optical dispersion are based on altering material composition, but this process is time-consuming and difficult, and the resulting optical performance is often limited to a certain bandwidth. Recent advances in nanofabrication have led to high-quality metasurfaces with the potential to perform at a level comparable to their state-of-the-art refractive counterparts. In this Review, we introduce the underlying physical principles of metasurface optical elements (with a focus on metalenses) and, drawing on various works in the literature, discuss how their constituent nanostructures can be designed with a highly customizable effective index of refraction that incorporates both phase and dispersion engineering. These metasurfaces can serve as an essential component for achromatic optics with unprecedented levels of performance across a broad bandwidth or provide highly customized, engineered chromatic behaviour in instruments such as miniature aberration-corrected spectrometers. We identify some key areas in which these achromatic or dispersion-engineered metasurface optical elements could be useful and highlight some future challenges, as well as promising ways to overcome them. Flat metasurface optics provides an emerging platform for combining semiconductor foundry methods of manufacturing and assembling with nanophotonics to produce high-end and multifunctional optical elements. This Review highlights the design of metasurfaces, recent advances in the field and initial promising applications.

Flat optics with dispersion-engineered metasurfaces

The development of nanotechnology and atom optics relies on understanding how atoms behave and interact with their environment. Isolated atoms can exhibit wavelike (coherent) behavior with a corresponding de Broglie wavelength and phase which can be affected by nearby surfaces. Here an atom interferometer is used to measure the phase shift of Na atom waves induced by the walls of a 50 nm wide cavity. To our knowledge this is the first direct measurement of the de Broglie wave phase shift caused by atom-surface interactions. The magnitude of the phase shift is in agreement with that predicted by Lifshitz theory for a nonretarded van der Waals interaction. This experiment also demonstrates that atom waves can retain their coherence even when atom-surface distances are as small as 10 nm.

Observation of atom wave phase shifts induced by van der Waals atom-surface interactions.

An optical apparatus for a head wearable display includes a lightguide, in-coupling holograms, and an out-coupling optical element. The lightguide includes an in-coupling region for receiving display light into the lightguide, an out-coupling region for emitting the display light out of the lightguide, and a relay region for guiding a path of the display light from the in-coupling region to the out-coupling region. A first of the in-coupling holograms is disposed at the in-coupling region to redirect the path of the display light by a first angle. A second of the in-coupling holograms is disposed across from the first in-coupling hologram at the in-coupling region to redirect the path of the display light by a second angle such that the path of the display light enters a total internal reflection condition in the relay region after redirection by the first and second in-coupling holograms.

Lightguide with multiple in-coupling holograms for head wearable display

Imaging polarimetry is emerging as a powerful tool for remote sensing in space science, Earth science, biology, defense, national security, and industry. Polarimetry provides complementary information about a scene in the visible and infrared wavelengths. For example, surface texture, material composition, and molecular structure will affect the polarization state of reflected, scattered, or emitted light. We demonstrate an imaging polarimeter design that uses three Wollaston prisms, addressing several technical challenges associated with moving remote-sensing platforms. This compact design has no moving polarization elements and separates the polarization components in the pupil (or Fourier) plane, analogous to the way a grating spectrometer works. In addition, this concept enables simultaneous characterization of unpolarized, linear, and circular components of optical polarization. The results from a visible-wavelength prototype of this imaging polarimeter are presented, demonstrating remote sensitivity to material properties. This work enables new remote sensing capabilities and provides a viable design concept for extensions into infrared wavelengths.

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Triple Wollaston-prism complete-Stokes imaging polarimeter

Decoherence due to scattering from background gas particles is observed for the first time in a Mach-Zehnder atom interferometer, and compared with decoherence due to scattering photons. A single theory is shown to describe decoherence due to scattering either atoms or photons. Predictions from this theory are tested by experiments with different species of background gas, and also by experiments with different collimation restrictions on an atom beam interferometer.

Matter-wave decoherence due to a gas environment in an atom interferometer.

In atom optics a material structure is commonly regarded as an amplitude mask for atom waves. However, atomic diffraction patterns formed using material gratings indicate that material structures also operate as phase masks. In this study a well collimated beam of sodium atoms is used to illuminate a silicon nitride grating with a period of 100 nm. During passage through the grating slots atoms acquire a phase shift due to the van der Waals (vdW) interaction with the grating walls. As a result the relative intensities of the matter-wave diffraction peaks deviate from those expected for a purely absorbing grating. Thus a complex transmission function is required to explain the observed diffraction envelopes. An optics perspective to the theory of atomic diffraction from material gratings is put forth in the hopes of providing a more intuitive picture concerning the influence of the vdW potential. The van der Waals coefficient ${C}_{3}=2.7\ifmmode\pm\else\textpm\fi{}0.8\phantom{\rule{0.3em}{0ex}}\mathrm{meV}\phantom{\rule{0.3em}{0ex}}{\mathrm{nm}}^{3}$ is determined by fitting a modified Fresnel optical theory to the experimental data. This value of ${C}_{3}$ is consistent with a van der Waals interaction between atomic sodium and a silicon nitride surface.

John D. Perreault

Papers

Observation of atom wave phase shifts induced by van der Waals atom-surface interactions.

Lightguide with multiple in-coupling holograms for head wearable display

Triple Wollaston-prism complete-Stokes imaging polarimeter

Matter-wave decoherence due to a gas environment in an atom interferometer.

Using atomic diffraction of Na from material gratings to measure atom-surface interactions