High Purcell factor generation of indistinguishable on-chip single photons

Abstract

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.

Light Scattering from Solid-State Quantum Emitters: Beyond the Atomic Picture

“…However, unlike atoms, SSEs can experience significant dephasing from fluctuating charges [20,21] and coupling to vibrational modes of the host material [22,23]. Despite this, stateof-the-art InGaAs QD single photon sources have demonstrated essentially transform-limited photons emitted via the zero phonon line (ZPL) [24][25][26] through careful sample optimisation, exploitation of photonic structures and by using resonant π-pulse excitation at cryogenic temperatures. Although these results show ZPL broadening can be effectively suppressed, coupling to vibrational modes also leads to the emergence of a phonon sideband (PSB) in the emission spectrum [23,[27][28][29][30][31].…”

“…To study this phonon coupling experimentally, we investigate a neutral exciton state (|X ) of a self-assembled InGaAs QD with dipole moment | µ| = 27.2 D, weakly coupled ( g = 135 µeV) to a H1 photonic crystal cavity (linewidth κ = 2.51 meV) with Purcell factor F P = 43 (see Ref. [26] for full details). As well as Purcell enhancing the ZPL, the cavity also acts as a weak spectral filter; this combination can reduce the PSB component of the emission [31,33], motivating the coupling of SSEs to cavities.…”

Numerical analysis of subwavelength field effects in photonic crystal slab cavities

“…where g is the coupling constant and κ and γ are the decay rates of the cavity and the emitter, respectively [25]. This condition is stronger than others found in literature, resulting in smaller lifetimes required for achieving the strong coupling regime [4].…”

“…From the plot it can be derived that an emitter with a lifetime less than about 37.5 ns would be in the strong coupling regime. Semiconductor quantum dots, with a lifetime of about 1 ns or 1.5 ns would be in the strong coupling regime [4,25], as well as molecules, such as DBATT, with lifetimes around 10 ns [29].…”

Optimal Photonic Crystal Cavities for Coupling Nanoemitters to Photonic Integrated Circuits

“…In the last decade, integrated quantum photonics has emerged as a tool to improve the performance of SPEs by altering their emission characteristics through integration with nanophotonic devices. The use of optical resonators is especially useful for improving the photon emission rate of SPEs via the Purcell effect . This requires optical structures that support high‐quality (Q)‐factor resonator modes with small, i.e., wavelength‐scale, mode volumes ( V m ) tailored to the emission wavelength of a SPE.…”