121 research outputs found
Dot projector based on phase diffuser
This disclosure describes low-weight, low-cost, high-efficiency techniques to project coherent infrared dots onto a subject to sense the depth contour of the subject while capturing a photograph. The techniques generate dot patterns of high number and density. A phase diffuser placed in the path of an infrared laser beam causes the wavefront of the laser beam to develop random undulations. The speckle pattern formed at the plane of the subject due to the randomized wavefront serves as a matrix of infrared dots
Observation of atom wave phase shifts induced by van der Waals atom-surface interactions
The development of nanotechnology and atom optics relies on understanding how
atoms behave and interact with their environment. Isolated atoms can exhibit
wave-like (coherent) behaviour 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 quantum electrodynamics
for a non-retarded 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.Comment: 4 pages, 4 figures, submitted to PR
Measurement of atomic diffraction phases induced by material gratings
Atom-surface interactions can significantly modify the intensity and phase of
atom de Broglie waves diffracted by a silicon nitride grating. This affects the
operation of a material grating as a coherent beam splitter. The phase shift
induced by diffraction is measured by comparing the relative phases of serveral
interfering paths in a Mach-Zehnder Na atom interferometer formed by three
material gratings. The values of the diffraction phases are consistent with a
simple model which includes a van der Waals atom-surface interaction between
the Na atoms and the silicon nitride grating bars.Comment: 4 pages, 5 figures, submitted to PR
Phasor analysis of atom diffraction from a rotated material grating
The strength of an atom-surface interaction is determined by studying atom
diffraction from a rotated material grating. A phasor diagram is developed to
interpret why diffraction orders are never completely suppressed when a complex
transmission function due to the van der Waals interaction is present. We also
show that atom-surface interactions can produce asymmetric diffraction
patterns. Our conceptual discussion is supported by experimental observations
with a sodium atom beam.Comment: 5 pages, 6 figures, submitted to PR
Matter-Wave Decoherence due to a Gas Environment in an Atom Interferometer
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.Comment: 4 pages, 3 figures, accepted to PR
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