Colour facilities in hexagonal boron nitride (hBN) are promising candidates as quantum gentle sources for future applied sciences. *
Within the article “Nanoscale resolved mapping of the dipole emission of hBN coloration facilities with a scattering-type scanning near-field optical microscope “, Iris Niehues, Daniel Wigger, Korbinian Kaltenecker, Annika Klein-Hitpass , Philippe Roell, Aleksandra Ok. Dąbrowska, Katarzyna Ludwiczak, Piotr Tatarczak, Janne O. Becker , Robert Schmidt, Martin Schnell, Johannes Binder, Andrzej Wysmołek and Rainer Hillenbrand make the most of a scattering-type near-field optical microscope (s-SNOM) to review the photoluminescence (PL) emission traits of such quantum emitters in metalorganic vapor section epitaxy grown hBN. *
On the one hand, Iris Niehues et al. reveal direct near-field optical excitation and emission by means of interplay with the nanofocus of the AFM tip leading to a subdiffraction restricted tip-enhanced PL hotspot. *
Alternatively, the authors present that oblique excitation and emission through scattering from the AFM tip considerably will increase the recorded PL depth. This demonstrates that the tip-assisted PL (TAPL) course of effectively guides the generated gentle to the detector. *
Iris Niehues et al. apply the TAPL technique to map the in-plane dipole orientations of the hBN coloration facilities on the nanoscale. This work promotes the extensively accessible s-SNOM strategy to purposes within the quantum area together with characterization and optical management. *
The investigation makes use of a scattering-type near-field optical microscope using a metallized Arrow AFM tip ( NanoWorld Arrow-NCPt AFM probe) illuminated by monochromatic laser gentle. *
The AFM tip acts as an optical antenna, remodeling the incident p-polarizedlight right into a extremely targeted close to subject on the AFM tip apex, the so-called nanofocus. *
The nanofocus interacts with the pattern resulting in modified scattering from the AFM tip and encoding native pattern properties.
In standard s-SNOM operation, the elastically scattered gentle is recorded as operate of pattern place (observe that the pattern is scanned), yielding near-field optical photographs with a spatial decision right down to 10 nm. *
To supress background scattering, the AFM is operated in tapping mode and the detector sign is demodulated at the next harmonic of the AFM tip’s oscillation frequency. *
Within the article, Iris Niehues et al. use the s-SNOM instrument to review PL from particular person hBN coloration facilities. *
To that finish, the inelastically tip-scattered gentle is recorded with a grating spectrometer coupled to a CCD digital camera. Observe that sign demodulation has not been potential with the usage of a CCD digital camera to date. It could be achieved using a photomultiplier tube or related. Importantly, the authors’ s-SNOM setup features a high-quality, silver-protected off-axis parabolic mirror with a numerical aperture (NA) of 0.72, which optimizes the focusing and assortment effectivity of the optical system and is essential for the carried out PL measurements. *
Characterization of photoluminescence mapping
Within the particular experiments carried out by “, Iris Niehues et al., the authors make use of the near-field optical microscope in tapping mode, with low oscillation amplitudes between 20 nm and 30 nm, to detect PL indicators influenced by the presence of the metallic AFM tip. *
They use customary metallic Arrow AFM suggestions (NanoWorld Arrow-NCPt) All through this examine, Iris Niehues et al., use a 532 nm (2.33 eV) laser for the optical excitation of the hBN coloration facilities. *
Photoluminescence (PL) measurement of a single coloration heart taken with an AFM tip. The pictures are proven with the identical coloration bar for higher comparability of the noticed PL intensities. (a) PL depth map with out the tip displaying a diffraction restricted emission spot. (b) PL spectrum of the studied emitter recorded with an prolonged integration time contained in the arc in (c). The zero-phonon line (ZPL) and optical phonon sidebands (PSBs) of 160 meV are marked in addition to the broad background PL (black line). (c) PL map of the identical emitter with the AFM tip displaying two subdiffraction restrict options marked as “dot” and “arc.” (d) Lineprofiles alongside the dashed traces in (a) in black and (c) in purple (darkish measurement, shiny Gaussian suits). The fitted full widths at half most (FWHM) are 110 nm (dot), 209 nm (arc), and 1,418 nm (w/o tip). (e) Schematic of the interference between direct and oblique excitation/emission of the colour heart through the AFM tip (TAPL). Inset exhibits the nanofocus interplay on the location of the colour heart explaining the dot (TEPL). (f) Analytical replica of the TAPL arc in (c) making use of the mannequin in (e).
*Iris Niehues, Daniel Wigger, Korbinian Kaltenecker, Annika Klein-Hitpass , Philippe Roell, Aleksandra Ok. Dąbrowska, Katarzyna Ludwiczak, Piotr Tatarczak, Janne O. Becker , Robert Schmidt, Martin Schnell, Johannes Binder, Andrzej Wysmołek and Rainer Hillenbrand
Nanoscale resolved mapping of the dipole emission of hBN coloration facilities with a scattering-type scanning near-field optical microscope
Nanophotonics, vol. 14, no. 3, 2025, pp. 335-342
DOI: https://doi.org/10.1515/nanoph-2024-0554
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