Journal: Nature Communications

Article Title: Coherent momentum control of forbidden excitons

doi: 10.1038/s41467-022-34740-5

Figure Lengend Snippet: a PL emission momentum distribution mapping with \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{{{{{\bf{k}}}}}}}_{{{{{{\bf{x}}}}}}}$$\end{document} k x and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{{{{{\bf{k}}}}}}}_{{{{{{\bf{y}}}}}}}$$\end{document} k y axis. Four shining emission spots, located at the Γ-X line and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{{{{{\bf{k}}}}}}}_{{{{{{\bf{x}}}}}}}$$\end{document} k x or \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{{{{{\bf{k}}}}}}}_{{{{{{\bf{y}}}}}}}$$\end{document} k y = 0.74 with C 4 symmetry, are clearly visible. b Polarization analysis of the PL emission momentum distribution in a . The four shining emission spots show radial polarization indicating they are from dark excitons. c Angle-resolved PL emission spectra mapping extracted from y-polarized PL emission momentum distribution mapping in b . It is clear to see the dark exciton directional emissions have small divergence angles at wavelengths of around 772 nm and towards oblique emission angles of around 48°. d The measured (red solid line) and FDTD simulated (dark green dashed line) PL intensity as a function of the in-plane momentum ( \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{{{{{\bf{k}}}}}}}_{{{{{{\bf{y}}}}}}}/{{{{{\bf{k}}}}}}$$\end{document} k y / k ) along the y-direction. The full-width-half-maximum (FWHM) of the measured X D emission lobes is 7° indicating the ultra-low divergence angle of the directional emission. e Spectra extracted from oblique angles of 48° and 23° for the dark exciton emission and the bright exciton emission, respectively. f The simulated PL emission momentum distribution by the Lumerical FDTD. Four shining emission spots show high correspondence to the measured PL emission pattern in a .

Article Snippet: To further understand the coupling mechanism between the out-of-plane dipole and the Friedrich-Wintgen BIC supported by the PhC slab, a Finite-difference time-domain (FDTD) simulation was performed using commercial software (Lumerical FDTD Solutions, ANSYS Inc.) to show how the PhC slab selectively couples with the out-of-plane dipole and enhances their emission.

Techniques: