Planarized spatially-regular arrays of spectrally uniform single quantum dots as on-chip single photon sources for quantum optical circuits

Abstract

A long standing obstacle to realizing highly sought on-chip monolithic solid state quantum optical circuits has been the lack of a starting platform comprising buried (protected) scalable spatially ordered and spectrally uniform arrays of on-demand single photon sources (SPSs). In this paper we report the first realization of such SPS arrays based upon a class of single quantum dots (SQDs) with single photon emission purity > 99.5% and uniformity < 2nm. Such SQD synthesis approach offers rich flexibility in material combinations and thus can cover the emission wavelength regime from long-to mid-to near-infrared to the visible and ultraviolet. The buried array of SQDs naturally lend themselves to the fabrication of quantum optical circuits employing either the well-developed photonic 2D crystal platform or the use of Mie-like collective resonance of all-dielectric building block based metastructures designed for directed emission and manipulation of the emitted photons in the horizontal planar architecture inherent to on-chip optical circuits. Finite element method-based simulations of the Mie-resonance based manipulation of the emitted light are presented showing achievement of simultaneous multifunctional manipulation of photons with large spectral bandwidth of ~ 20nm that eases spectral and mode matching. Our combined experimental and simulation findings presented here open the pathway for fabrication and study of on-chip quantum optical circuits.

On-chip scalable highly pure and indistinguishable single-photon sources in ordered arrays: Path to quantum optical circuits

“…The observed spectral nonuniformity can be further reduced by reducing the alloy composition fluctuation among MTSQDs (fig. S2) (27) to reach potentially subnanometer-scale spectral nonuniformity. The uniformity of MTSQDs, to our knowledge, is one of the best among reported site-controlled QDs [~15 to 50 nm for SAQDs in holes (21)(22)(23), ~9 nm for nanowire QDs (19), and ~3 nm for QDs in V-grooves (24)].…”

Integrated Quantum Nanophotonics with Solution‐Processed Materials

“…Such scalability, however, remains an important unsolved problem for many of these inorganic QDs due to random spatial positioning and inhomogeneous broadening. Despite several promising results on deterministic growth of these semiconductor QDs, [71][72][73] there is still no large-scale demonstrations of many indistinguishable QD single photon sources. There are also very few reports on cavity integration with such deterministically positioned semiconductor QD, [74][75][76][77][78] including nanohole arrays and the buried stressor growth technique, [76][77][78] let alone cavity integrated array of QDs.…”

Chip-Scale Quantum Emitters

“…The quantum nature of emission in terms of high single-photon purity and photon indistinguishability was measured and values of g (2) (0) = 0.026 ± 0.026 and a post-selected two-photon interference visibility V= (87.1 ± 9.7)% with an associated coherence time of τ c = (194 ± 7) ps were obtained [34]. Recently, planarized SPS arrays based on a unique class of shape-controlled single quantum dots (SQDs) synthesized on a mesa top (dubbed MTSQDs) were reported by Zhang et al [35]. To enable the spatially selective growth, they used substrate-encoded size-reducing epitaxy (SESRE) on spatially regular arrays of patterned GaAs (001) while square nanomesas with edges along <100> were chosen [35].…”

“…Recently, planarized SPS arrays based on a unique class of shape-controlled single quantum dots (SQDs) synthesized on a mesa top (dubbed MTSQDs) were reported by Zhang et al [35]. To enable the spatially selective growth, they used substrate-encoded size-reducing epitaxy (SESRE) on spatially regular arrays of patterned GaAs (001) while square nanomesas with edges along <100> were chosen [35]. In this study, the planarizing overgrowth process over arrays of InGaAs SQDs largely maintains the SQDs' high single-photon emission purity (>98%) and spectral uniformities (~5 nm) are demonstrated [35].…”

“…To enable the spatially selective growth, they used substrate-encoded size-reducing epitaxy (SESRE) on spatially regular arrays of patterned GaAs (001) while square nanomesas with edges along <100> were chosen [35]. In this study, the planarizing overgrowth process over arrays of InGaAs SQDs largely maintains the SQDs' high single-photon emission purity (>98%) and spectral uniformities (~5 nm) are demonstrated [35]. To demonstrate highly efficient quantum light sources in visible frequencies for photonic quantum technologies, an embedded droplet-epitaxial QD in an L3 type photonic crystal nanocavity was developed to introduce a bright single-photon source [36].…”