Theory and design of quantum light sources from quantum dots embedded in semiconductor-nanowire photonic-crystal systems

Abstract

We introduce a new platform for realizing on-chip quantum electrodynamics using photoniccrystal waveguide structures comprised of periodic nanowire arrays with embedded semiconductor quantum dots to act as a quantum light sources. These nanowire-based structures, which can now be fabricated with excellent precision, are found to produce waveguide Purcell factors exceeding 100 and on-chip β factors up to 99%. We investigate the fundamental optical properties of photonic crystal waveguides and finite-size structures, using both photonic band structure calculations and rigorous Green function computations which allow us to obtain the modal properties and the local density of photon states. A comparison with slab-based photonic crystals is also made and we highlight a number of key advantages in the nanowire system, including the potential to reduce extrinsic scattering losses and produce high theoretical Purcell factors and β factors on-chip. We also demonstrate that these structures exhibit rich photonic Lamb shifts over broadband frequencies.

Entanglement dynamics and Mollow nonuplets between two coupled quantum dots in a nanowire photonic-crystal system

“…All G components are thus given in units of Im{G h (r, r; ω)} to highlight the rate enhancements present in this system relative to a pair of QDs in free space. We note that the largest LDOS peak corresponds to the quasimode formed at the mode edge of a slow-light waveguide mode [22], whereas the lower frequency peaks are Fabry-Pérot ripples due to facet reflections [22]. Optimal coupling is achieved by choosing the mode which maximizes the symmetric photon exchange terms, |Im{G(r 1/2 , r 2/1 ; ω)}|.…”

“…In our specific design, the waveguide has a length and width of 41a and 7a, with lattice constant a = 0.5526 µm to produce a single vertically-polarized waveguide band with a mode edge near the telecom wavelength of 1.550 µm. As described previously [22], a waveguide is formed by reducing the radius of a single row of NWs, from r b = 0.180a to r d = 0.140a. Light remains confined to the higher index (GaAs, ǫ = 13) upper portion (height 2.27a) of the NWs, and the lower index portion (AlO, ǫ = 3.1, height 2a) separates the NWs from the substrate.…”

“…Figure 1 shows a schematic of our proposal, which can be fabricated using current growth techniques, as well as an energy level diagram for a pair of embedded QDs. The geometry exploits the large spontaneous emission (SE) enhancements and a near lossless waveguide mode of the NW PCs [22] to mediate inter-QD interactions. Using a quantum master equation formalism centered on the photonic Green function, we demonstrate that this system can strongly couple a pair of qubits.…”

Polariton waveguides from a quantum dot chain in a photonic crystal waveguide: an architecture for waveguide quantum electrodynamics

“…Photonic crystals (PCs) with embedded quantum dots (QDs) have had much success in this regard by modifying the LDOS [4][5][6][7], although they have been hindered by fabrication issues including surface roughness [8][9][10] and limited control of the QD properties [11]. Arrays of nanowires (NWs) grown through a molecular beam epitaxy (MBE) technique [12,13] have been proposed as an alternative PC platform to help mitigate these issues [14,15], with the potential to contain identical or very similar QDs inside each NW of a given radius [16,17]. This opens the idea of NW PC waveguides where each waveguide channel NW contains an identical QD embedded in its center.…”

“…Our proposed structure exploits the elevated NW PC waveguide design of Ref. 14, where a PC waveguide is formed from an organized array of GaAs NWs extended from an AlO substrate [24], with the waveguide channel introduced by reducing the radius of a row of NWs from r b = 0.180 a to r d = 0.140 a along e x . Importantly, this structure is based on current fabrication techniques and properties are determined through full 3D calculations including radiative coupling effects.…”