Overview
In the angle-resolved cathodoluminescence (ARCL) mode, the direction in which a photon is emitted is determined. An objective lens or, more commonly, a collection mirror projects an image of the emitted light onto a pixelated detector, e.g., a camera. When an appropriate optical system is used, each pixel in the captured image corresponds to a unique emission direction from the specimen. Typically, the raw image is transformed into polar coordinates for display and interpretation.
The result of an angle-resolved measurement contains no wavelength or polarization information unless additional filtering of dispersion is used (e.g., wavelength- and angle-resolved mode).
Angle-filtered information may be captured by using an iris or a pinhole to select a certain (range of) angle(s). However, the low resolution and highly serial nature of this particular acquisition mode have limited its usefulness.
Sometimes referred to as Fourier imaging or momentum spectroscopy.
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Data collection
Emission pattern or angle-resolved emission pattern: The emission pattern is a plot of the direction in which photons are emitted from a specimen, typically presented in polar coordinates where the emission direction is described by the azimuthal and zenith angles. A single emission pattern may be captured from a point or region of the sample exposed to the electron beam of the electron microscope.
Emission pattern image or angle-resolved spectrum image: The electron beam is scanned across the specimen surface, and an emission pattern is recorded at each location, creating a hyperspectral (4D) data construct.
Uses
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Investigating the optical properties of nanophotonic materials far below the diffraction limit |