Imaging and spectroscopy of solid-state quantum emitters

Abstract

Efficient generation of single photons can revolutionize the field of quantum communication and linear optical quantum computing. Solid-state semiconductor quantum dots present a promising platform to realize this long term vision. In particular, self-assembled InAs quantum dots exhibit near unity radiative efficiency. Enhancement of collection efficiency of photon from self-assembled InAs quantum dots is a key necessity to realize quantum technologies. In this respect, GaAs nanowire single photon source and planar membrane devices have shown considerable promise. Photoluminescence spectroscopy has been undertaken to study the photon collection from these devices and the behaviour such as lifetime of quantum dots when embedded in these nanophotonic structures. The ease of implementing electrical contacts onto the planar membrane devices is another significant feature which allows complete control over the number of electrons in the quantum dot. The key concept behind the enhancement of photon emission from planar membrane devices is the radiation from an electric dipole emitter whose angular radiation pattern is modified by choice of materials and design of sample. Using Fourier microscopy also known as back focal plane imaging, a match between the design of the angular radiation profile and the obtained experimental data is made. This is an excellent way to figure out if the light being emitted by the quantum emitter is being collected into the optical system. In addition, the transfer-matrix model used for design of angular radiation profile also yields different efficiency depending upon the orientation of the emission dipole in the quantum emitter. Thus, in order to design samples for higher photon collection efficiency, the knowledge of the orientation of the emission dipole is important. In order to extract the full three-dimensional orientation of the quantum emitter, defocused imaging of the dipole radiation is performed. A relatively new material system for quantum photonics is based on novel two-dimensional semiconductors such as WSe2. To understand the nature of emission from these solid-state emitters, Fourier microscopy and defocused imaging have been used to obtain the angular distribution of radiation and orientation of emission dipoles in these emitters, respectively.