168
5 Optical Measurement Techniques
Fig. 5.16 Sketch of a typical angle-resolved PL measurement of hBN-encapsulated monolayer
TMDCs with a microscope objective. In a simplified drawing, the sideways emitting light from an
out-of-plane dipole is projected angle-resolved in the backfocal (BF) plane of the objective. From
there, projection onto an imaging spectrometer’s CCD allows one to map the radiation profile with
spectral resolution, as discussed for bright and “grey” excitons in [3]. Reproduced under the terms
of the CC-BY 4.0 Licence (http://creativecommons.org/licenses/by/4.0/). [3] Copyright 2020 The
Author(s), published by Springer Nature
high aspect-ratio long-pass filter with specified edge at 700 nm (and in some scenarios a polariser) can be inserted between the sample and detector. Filtered μPL sample
signal is then detected regularly by a monochromator with research-grade imaging
camera (typically a nitrogen-cooled CCD chip). For polarisation-resolved measurements, additional quarter-wavelength or half-wavelength plates can be incorporated
into the setup, as done in [46]. At room temperature, the experimental constraints
for angle-resolved measurements are much more relaxed, as short working distances
can be used to maximise the numerical aperture for wide-angle signal collection, or
even immersion liquids can be employed between sample and objective for high-NA
measurements (see for instance [137]).
5.5.2 Dispersion Measurements
For optical dispersion measurements, time-integrated spectra were recorded in [46,
66] in Fourier-space imaging configuration, which projects the angle information
one-to-one from the microscope objective’s backfocal plane via a set of lenses onto
the entrance slit of the imaging spectrometer’s monochromator (cf. [4, 14, 66, 138]
for illustrations of this scheme, and Fig. 5.8e). In order to measure the emission
5 Optical Measurement Techniques
Fig. 5.16 Sketch of a typical angle-resolved PL measurement of hBN-encapsulated monolayer
TMDCs with a microscope objective. In a simplified drawing, the sideways emitting light from an
out-of-plane dipole is projected angle-resolved in the backfocal (BF) plane of the objective. From
there, projection onto an imaging spectrometer’s CCD allows one to map the radiation profile with
spectral resolution, as discussed for bright and “grey” excitons in [3]. Reproduced under the terms
of the CC-BY 4.0 Licence (http://creativecommons.org/licenses/by/4.0/). [3] Copyright 2020 The
Author(s), published by Springer Nature
high aspect-ratio long-pass filter with specified edge at 700 nm (and in some scenarios a polariser) can be inserted between the sample and detector. Filtered μPL sample
signal is then detected regularly by a monochromator with research-grade imaging
camera (typically a nitrogen-cooled CCD chip). For polarisation-resolved measurements, additional quarter-wavelength or half-wavelength plates can be incorporated
into the setup, as done in [46]. At room temperature, the experimental constraints
for angle-resolved measurements are much more relaxed, as short working distances
can be used to maximise the numerical aperture for wide-angle signal collection, or
even immersion liquids can be employed between sample and objective for high-NA
measurements (see for instance [137]).
5.5.2 Dispersion Measurements
For optical dispersion measurements, time-integrated spectra were recorded in [46,
66] in Fourier-space imaging configuration, which projects the angle information
one-to-one from the microscope objective’s backfocal plane via a set of lenses onto
the entrance slit of the imaging spectrometer’s monochromator (cf. [4, 14, 66, 138]
for illustrations of this scheme, and Fig. 5.8e). In order to measure the emission