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99% beta factor and directional coupling of quantum dots to fast light in photonic crystal waveguides determined by spectral imaging

Scarpelli, L, Lang, B., Masia, F, Beggs, D, Muljarov, E. A., Young, A. B., Oulton, R., Kamp, M., Hoffling, S., Schneider, C. and Langbein, W 2019. 99% beta factor and directional coupling of quantum dots to fast light in photonic crystal waveguides determined by spectral imaging. Physical Review B 100 (3) , 035311. 10.1103/PhysRevB.100.035311

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Abstract

Spontaneous emission from excitonic transitions in InAs/GaAs quantum dots embedded in photonic crystal waveguides at 5 K into nonguided and guided modes is determined by direct spectral imaging. This enables measurement of the absolute coupling efficiency into the guided modes, the beta factor, directly, without assumptions on decay rates used previously. Notably, we found beta factors above 90% over a wide spectral range of 40 meV in the fast light regime, reaching a maximum of (99±1)%. We measure the directional emission of the circularly polarized transitions in a magnetic field into counterpropagating guided modes, to deduce the mode circularity at the quantum dot sites. We find that points of high directionality, up to 97%, correlate with a reduced beta factor, consistent with their positions away from the mode field antinode. By comparison with calibrated finite-difference time-domain simulations, we use the emission energy, mode circularity, and beta factor to estimate the quantum dot position inside the photonic crystal waveguide unit cell.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Biosciences
Physics and Astronomy
Publisher: American Physical Society
ISSN: 2469-9950
Date of First Compliant Deposit: 20 July 2019
Date of Acceptance: 10 July 2019
Last Modified: 30 Nov 2019 06:21
URI: http://orca.cf.ac.uk/id/eprint/124364

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