Coupling between quantum dots and photonic nanostructures

Semiconductor quantum dots (QDs) are usually recognized as "artificial atoms" that have discrete states due to the quantum confinement of electrons and holes in three dimensions. Several methods have been developed for growing QDs, in which the self-assembled QDs grew by StranskiKrastanov method possess superior optical properties, including high radiative efficiency and high purity of single photon。

Transport of a topologically protected photonic waveguide on-chip

We propose a design on integrated optical devices on-chip with an extra width degree of freedom by using a photonic crystal waveguide with Dirac points between two photonic crystals with opposite valley Chern numbers.With such an extra waveguide,we demonstrate numerically that the topologically protected photonic waveguide retains properties of valley-locking and immunity to defects.Due to the design flexibility of the width-tunable topologically protected photonic waveguide,many unique on-chip integrated devices have been proposed,such as energy concentrators with a concentration efficiency improvement of more than one order of magnitude,and a topological photonic power splitter with an arbitrary power splitting ratio.The topologically protected photonic waveguide with the width degree of freedom could be beneficial for scaling up photonic devices,and provides a flexible platform to implement integrated photonic networks on-chip.

Low-threshold topological nanolasers based on the second-order corner state

Topological lasers are immune to imperfections and disorder.They have been recently demonstrated based on many kinds of robust edge states,which are mostly at the microscale.The realization of 2D on-chip topological nanolasers with a small footprint,a low threshold and high energy efficiency has yet to be explored.Here,we report the first experimental demonstration of a topological nanolaser with high performance in a 2D photonic crystal slab.A topological nanocavity is formed utilizing the Wannier-type 0D corner state.Lasing behaviour with a low threshold of approximately 1μW and a high spontaneous emission coupling factor of 0.25 is observed with quantum dots as the active material.Such performance is much better than that of topological edge lasers and comparable to that of conventional photonic crystal nanolasers.Our experimental demonstration of a low-threshold topological nanolaser will be of great significance to the development of topological nanophotonic circuitry for the manipulation of photons in classical and quantum regimes.

Diabolical points in coupled active cavities with quantum emitters

In single microdisks,embedded active emitters intrinsically affect the cavity modes of the microdisks,resulting in trivial symmetric backscattering and low controllability.Here we demonstrate macroscopic control of the backscattering direction by optimizing the cavity size.The signature of the positive and negative backscattering directions in each single microdisk is confirmed with two strongly coupled microdisks.Furthermore,diabolical points are achieved at the resonance of the two microdisks,which agrees well with theoretical calculations considering the backscattering directions.Diabolical points in active optical structures pave the way for an implementation of quantum information processing with geometric phase in quantum photonic networks.