Quantum Optoelectronics

Abstract:

Exciton-polaritons are quasiparticles consisting of a linear superposition of photonic and excitonic states, offering potential for nonlinear optical devices. The excitonic component of the polariton provides a finite Coulomb scattering cross section, such that the different types of exciton found in organic materials (Frenkel) and inorganic materials (Wannier-Mott) produce polaritons with different interparticle interaction strength. A hybrid polariton state with distinct excitons provides a potential technological route towards in situ control of nonlinear behaviour. Here we demonstrate a device in which hybrid polaritons are displayed at ambient temperatures, the excitonic component of which is part Frenkel and part Wannier-Mott, and in which the dominant exciton type can be switched with an applied voltage. The device consists of an open microcavity containing both organic dye and a monolayer of the transition metal dichalcogenide WS2. Our findings offer a perspective for electrically controlled nonlinear polariton devices at room temperature.

Abstract:

Generally confinement size is considered to determine the dimensionality of nanostructures. While the exciton Bohr radius is used as a criterion to define either weak or strong confinement in optical experiments, the binding energy of confined excitons is difficult to measure experimentally. One alternative is to use the temperature dependence of the radiative recombination time, which has been employed previously in quantum wells and quantum wires. A one-dimensional loop structure is often assumed to model quantum rings, but this approximation ceases to be valid when the rim width becomes comparable to the ring radius. We have evaluated the density of states in a single quantum ring by measuring the temperature dependence of the radiative recombination of excitons, where the photoluminescence decay time as a function of temperature was calibrated by using the low temperature integrated intensity and linewidth. We conclude that the quasi-continuous finely-spaced levels arising from the rotation energy give rise to a quasi-one-dimensional density of states, as long as the confined exciton is allowed to rotate around the opening of the anisotropic ring structure, which has a finite rim width.

Abstract:

These data were created in order to assess the high temperature polarisation properties of a-plane InGaN quantum dots, in micro-photoluminescence experiments and kp band simulations, from 2015 to 2017. OriginPro has been used to analyse the data.

Abstract:

These data all relate to GaAs photonic crystal waveguides with SU-8 photoresist disks patterened on top them to create cavities. The waveguides contain high-density embedded InGaAs quantum dots which couple to the cavity modes.

The folder fig2 contains data from an FDTD simulation measuring cavity Q factor and mode volume against disk diameter.

The folder fig3 contains micro-photoluminescence (uPL) spectra of the waveguides taken before and after cavity fabrication. See fig3/readme.txt for more information.

The folder fig4 contains the Q factor, disk thickness, and disk diameter data for all the devices studied.

The folder fig5 contains a scanning electron microscope image and associated 2D uPL map of one of the cavities.

More information and details of file formats is contained in the following files:
readme.txt
asc_file_format.txt
fig2/readme.txt
fig3/readme.txt

Note that those .txt files use unix-style line endings (LF), not Windows-style ones (CRLF). They may not display correctly in Notepad. The difficulty of achieving reliable spectral and spatial overlap is a serious problem when fabricating photonic crystal (PhC) cavities around self-assembled quantum dots. We present a method for using photoresist to optically fabricate heterostructure cavities in a PhC waveguide with a combined photolithography and micro-photoluminescence spectroscopy system. We confirm the creation of cavity modes with high quality factors (mean = 3.8*10^3, maximum = 7.4(2)*10^3). This method offers a promising route towards bright, on-chip single photon sources for quantum information applications.

Abstract:

The data were created from k.p simulation, polarization-resolved microphotoluminescence, and Hanbury Brown and Twiss experiments, from 2015 to 2016. The data were created to demonstrate the rigorous generation of polarised single photons with a deterministic axis, and to explain the origin of high polarisation degree and fixed axis, in a-plane InGaN quantum dots. All data were hence used in Figures 2-5 in the publication “Direct generation of linearly polarized single photons with a deterministic axis in quantum dots”