High Purcell factor generation of indistinguishable on-chip single photons

On-chip single-photon sources are key components for integrated photonic quantum technologies. Semiconductor quantum dots can exhibit near-ideal single-photon emission, but this can be significantly degraded in on-chip geometries owing to nearby etched surfaces. A long-proposed solution to improve the indistinguishablility is to use the Purcell effect to reduce the radiative lifetime. However, until now only modest Purcell enhancements have been observed. Here we use pulsed resonant excitation to eliminate slow relaxation paths, revealing a highly Purcell-shortened radiative lifetime (22.7 ps) in a waveguide-coupled quantum dot–photonic crystal cavity system. This leads to near-lifetime-limited single-photon emission that retains high indistinguishablility (93.9%) on a timescale in which 20 photons may be emitted. Nearly background-free pulsed resonance fluorescence is achieved under π-pulse excitation, enabling demonstration of an on-chip, on-demand single-photon source with very high potential repetition rates

Formation of allenyl ketones, 3-ethynylcoumarins, and arylfurans, furylfurans, and furylthiophenes by flash vacuum thermolysis of 3-methylidenefuran-2(3 H)-ones

Flash vacuum thermolysis (FVT) of 3-methylidenefuran-2(3H)-ones 3 causes cheletropic extrusion of CO with formation of allenyl ketones 4. o-Chloro- and o-bromophenylmethylidenefuranones also afford allenyl ketones upon flash vacuum thermolysis, but in addition, 3-ethynylcoumarins 6 are formed via E/Z isomerization of the methylidenefuranones, cyclization, halogen atom migration, and HCl (HBr) elimination. The presence of strongly electron-withdrawing groups (nitroaryl or acetyl) on the acylallene moiety causes rearrangement to give 2-arylfurans 10 and 13 as well as 2-furylfurans and 2-furylthiophenes 16 by cyclization of the allenyl ketones. The reaction mechanisms are supported by calculations at the M06-2X/6-311+G(d,p) level of theory

Direct observation of correlations between individual photon emission events of a microcavity laser

Lasers are recognized for coherent light emission, the onset of which is reflected in a change in the photon statistics(1). For many years, attempts have been made to directly measure correlations in the individual photon emission events of semiconductor lasers(2,3). Previously, the temporal decay of these correlations below or at the lasing threshold was considerably faster than could be measured with the time resolution provided by the Hanbury Brown/Twiss measurement set-up(4) used. Here we demonstrate a measurement technique using a streak camera that overcomes this limitation and provides a record of the arrival times of individual photons. This allows us to investigate the dynamical evolution of correlations between the individual photon emission events. We apply our studies to micropillar lasers(5) with semiconductor quantum dots(2,3,6-8) as the active material, operating in the regime of cavity quantum electrodynamics(9). For laser resonators with a low cavity quality factor, Q, a smooth transition from photon bunching to uncorrelated emission with increasing pumping is observed; for high-Q resonators, we see a non-monotonic dependence around the threshold where quantum light emission can occur. We identify regimes of dynamical anti-bunching of photons in agreement with the predictions of a microscopic theory that includes semiconductor-specific effects.</p