arXiv subjects

Charlene J. Lobo

Publications and source records attributed to Charlene J. Lobo.

5 recordsLinked to original sources

arXiv2026

Dynamics of the spontaneous emission factor in multiple quantum well nanowire lasers

The spontaneous emission factor - often known as the \b{eta} factor - is an important quantity in the description of quantum well lasers, influencing both the threshold power as well as the general shape of the light in-light out (L-L) curve. Past work on modelling multiple quantum well (MQW) nanowire laser devices has typically assumed that the \b{eta} factor is a constant parameter that can either be estimated or fit in a post-hoc manner. However, the \b{eta} factor can be derived from the transitions between valence and conduction bands in semiconductor quantum wells, together with knowledge of the cavity modes. Here we investigate the dynamic nature of the \b{eta} factor for MQW nanowire lasers, and show how it can be computed. We also examine the dependence of the spontaneous emission rate and spontaneous emission factor \b{eta} on the charge carrier density, quantum well thickness, and composition, and discuss the impact on laser threshold and operation.

cond-mat.mes-hall↗

arXiv2023

Photophysics of blue quantum emitters in hexagonal Boron Nitride

Colour centres in hexagonal boron nitride (hBN) have emerged as intriguing contenders for integrated quantum photonics. In this work, we present detailed photophysical analysis of hBN single emitters emitting at the blue spectral range. The emitters are fabricated by different electron beam irradiation and annealing conditions and exhibit narrow-band luminescence centred at 436 nm. Photon statistics as well as rigorous photodynamics analysis unveils potential level structure of the emitters, which suggests lack of a metastable state, supported by a theoretical analysis. The potential defect can have an electronic structure with fully occupied defect state in the lower half of the hBN band gap and empty defect state in the upper half of the band gap. Overall, our results are important to understand the photophysical properties of the emerging family of blue quantum emitters in hBN as potential sources for scalable quantum photonic applications.

physics.optics↗

arXiv2022

Stark effect of quantum blue emitters in hBN

Inhomogeneous broadening is a major limitation for the application of quantum emitters in hBN to integrated quantum photonics. Here we demonstrate that blue emitters with an emission wavelength of 436 nm are less sensitive to electric fields than other quantum emitter species in hBN. Our measurements of Stark shifts indicate negligible transition dipole moments for these centers with dominant quadratic stark effect. Using these results, we employed DFT calculations to identify possible point defects with small transition dipole moments, which may be the source of blue emitters in hBN.

physics.app-ph↗

arXiv2017

Super-resolution imaging of quantum emitters in layered materials

Layered van der Waals materials are emerging as compelling two-dimensional (2D) platforms for studies of nanophotonics, polaritonics, valleytronics and spintronics, and have the potential to transform applications in sensing, imaging and quantum information processing. Amongst these, hexagonal boron nitride (hBN) is unique in that it hosts ultra-bright, room temperature single photon emitters (SPEs). However, an outstanding challenge is to locate SPEs in hBN with high precision, a task which requires breaking the optical diffraction limit. Here, we report the imaging of SPEs in layered hBN with a spatial resolution of 63 nm using ground state depletion (GSD) nanoscopy. Furthermore, we show that SPEs in hBN possess nonlinear photophysical properties which can be used to realize a new variant of GSD that employs a coincident pair of doughnut-shaped lasers to reduce the laser power that is needed to achieve a given resolution target. Our findings expand the current understanding of the photophysics of quantum emitters in layered hBN and demonstrate the potential for advanced nanophotonic and bio-imaging applications which require localization of individual emitters with super-resolution accuracy.

physics.optics↗

arXiv2016

Robust, directed assembly of fluorescent nanodiamonds

Arrays of fluorescent nanoparticles are highly sought after for applications in sensing and nanophotonics. Here we present a simple and robust method of assembling fluorescent nanodiamonds into macroscopic arrays. Remarkably, the yield of this directed assembly process is greater than 90% and the assembled patterns withstand ultra-sonication for more than three hours. The assembly process is based on covalent bonding of carboxyl to amine functional carbon seeds and is applicable to any material, and to non-planar surfaces. Our results pave the way to directed assembly of sensing and nanophotonics devices.

physics.optics↗