Direct fiber-coupled single photon source based on a photonic crystal waveguide

Abstract

A single photon source plays a key role in quantum applications such as quantum computers and quantum communications. Epitaxially grown quantum dots are one of the promising platforms to implement a good single photon source. However, it is challenging to realize an efficient single photon source based on semiconductor materials due to their high refractive index. Here we demonstrate a direct fiber coupled single photon source with high collection efficiency by employing a photonic crystal (PhC) waveguide and a tapered micro-fiber. To confirm the single photon nature, the second-order correlation function g(2)(τ) is measured with a Hanbury Brown-Twiss setup. The measured g(2)(0) value is 0.15, and we can estimate 24% direct collection efficiency from a quantum dot to the fiber.

Quantum photonics with layered 2D materials

“…Having a SPE inside such a cavity with a spectrally matching mode could provide an emitter-cavity system completely embedded in a single hBN flake. In addition, single photon emission from a hBN flake has been successfully coupled to a tapered optical fibre with 10 % coupling efficiency, 152 which is comparable to the other SPE platforms [153][154][155] . Finally, another approach has been the integration of SPEs in multi-layer hBN into a tunable plano-concave optical microcavity, which has shown Purcell enhanced single-photon emission by a factor of ~4 at room temperature 156 , compared to noncavity SPEs (Fig.…”

Fiber-coupled quantum light sources based on solid-state quantum emitters

“…Lithographically pre-processed 2D semiconductor slabs containing self-assembled QDs were coupled to fibers, too. This was demonstrated for tapered waveguide slabs [135], nanobeams [136], and PhC cavity slabs [137,138]. The slabs were optimized to provide for an efficient mode matching to the fibers.…”

“…A somewhat different and presumably even more fragile approach is shown in figure 20 [137]. In contrast to other schemes, the fiber is not applied parallel to the PhC waveguide, but the tapered fiber was curved to a loop with a radius of 100-150 µm, and the vertex was brought into contact with the waveguide using a piezoelectric motor stage.…”

“…A photonic crystal (PhC) waveguide is formed by a line of missing air holes in the PhC pattern.A curved microfiber is used to funnel photons from the waveguide into the tapered fiber. Reprinted from[137], with the permission of AIP Publishing.…”

Single- and Twin-Photons Emitted from Fiber-Coupled Quantum Dots in a Distributed Bragg Reflector Cavity

“…A direct near-field fiber bond realizes integrated single-QD emitters for a plug-and-play stable use for extensive study. Instead of tapered fiber evanescent lateral coupling [ 4 , 5 ] or cleaved fiber facet vertical coupling [ 6 , 7 , 8 ] with QD host precisely positioned to the fiber core, an efficient vertical coupling of a QD at wavelength (λ) ~0.9 μm is proved by random bond of V-groove fiber array with large smooth facet and no bend (i.e., angle self-aligned) to QD chip with large-area low-density InAs/GaAs QDs in a distributed Bragg reflector (DBR) cavity for vertical light extraction [ 9 ], with coupling efficiency mainly dependent on the cavity; a >3-fold enhancement of fiber-output single-photons has been achieved in an optimal pillar cavity with an intrinsic radiative lifetime < 0.2 ns (Purcell factor > 3) [ 10 ]. This work presents our resent study on fiber devices: (1) a planar DBR cavity with only fundamental cavity mode (CM) is bonded to Nurfern 780HP SM fiber (numerical aperture (NA) ~0.13, D M ~4.4 μm) for optical mode overlap ( Figure 1 a), with single QD selected by small D M and NA, enabling flexible SM-fiber selection (especially D M ~2 μm); (2) modulated Si doping as electron reservoir [ 11 ] builds electric field and level tunnel coupling [ 12 ] to reduce fine-structure splitting (FSS) and populate dominant X and XX (in pair rate ~12 Mcps) and higher excitons XX + (2e 1 2h 1 1h 2 ), XXX (2e 1 2h 1 1e 2 1h 2 ), XXX + (2e 1 2h 1 1e 2 2h 2 ) and XXXX (2e 1 2h 1 2e 2 2h 2 ); (3) epoxy thermal stress induces light hole (lh) h 1 and h 2 with various distribution in the donor field to affect exciton symmetry, FSS, Coulomb interaction and inter-level decay.…”