Research

For most up-to-date details check our annual reports and publications page


1.  Neutral Atoms for Quantum Technologies Group

Group members: Tridib Ray, Kristoffer Karlsson, Thomas Nieddu, Krishnapriya Subramonian Rajasree,  Ratnesh Kumar Gupta

Ultrathin (or nano) optical fibres (Fig. 1) provide a unique and non-destructive technique to probe and manipulate laser-cooled atoms and have exciting prospects in the development of hybrid quantum systems.   In this subgroup we have several projects:  (i) multiphoton processes with laser-cooled Rb atoms mediated via the nanofibre.  The ultrahigh intensities achievable in the evanescent field allow us to explore regimes that would be very difficult to access in free space experiments, (ii) interactions between the atoms and higher order optical fibre modes for studies in quadrupole transitions and orbital angular momentum transfer, (iii) formation and manipulation of Rydberg atoms at sub-wavelength distances from the dielectric surface of an optical nanofibre for the study of atom-surface and atom-atom van der Waal's interactions, (iv) enhancement of light-matter interactions by using a nanofibre-based cavity,  and (v)  Purcell-enhanced single photon emission from single quantum dots (artificial atoms) coupled to a structured optical nanofibre.  We predict enhancement of the coupling from the quantum dots into tailored optical nanofibres.  

Fig. 1: Schematic of an ultrathin optical fibre. 


2. NanoBioOptics Group

Group Members:  Viet Giang Truong, Xue Han, Georgiy Tkachenko,  Peter Mekhail, Cindy Esporlas 
 
We are following a stream of research whereby small systems are forced to interact with light in order to study a variety of phenomena such as (i) trapping of nanoscaled particles using plasmonics, (ii) manipulation of microparticles using higher order modes of ultathin optical fibres,  (iii) detection of low light level emissions from neurone cells and (iv) light influence on fluorescence emissions from marine species such as Symbiodinium cells.  We also study the effect of using complex light beams (e.g. vector beams) for studying the behaviour in ultrathin fibres with the aim of demonstrating negative force effects.  Facilities for these studies include an optical tweezers setup at 1064 nm, a tunable picosecond laser from 488-640 nm, a Ti:Saph laser, a fs laser,  Leica and Zeiss microscopes and access to OIST's biology and physics shared facilities such as the clean room fabrication and characterisation systems, confocal microscopes, and OIST's neuroscience and marine resources.   Facilities for these studies include an optical tweezers setup at 1064 nm, a tunable picosecond laser from 488-640 nm, a tuning CW and a 140 fs Ti: Sapphire lasers from 690 nm - 1035 nm, Leica and Zeiss microscopes and access to OIST's biology and physics shared facilities such as the clean room fabrication and characterisation systems, confocal microscopes, and OIST's neuroscience and marine resources.   
 
Examples of projects in this group include a study on the effect of using complex light beams (e.g. vector beams) for probing the spin structured components of the ‘usual’ longitudinal, ‘unusual’ transverse and vertical ‘electric’ spin momenta in the evanescent field of guided modes in ultrathin fibres. We aim to demonstrate that the longitudinal, transverse and vertical spin components can push (positive repulsive forces), pull (negative attractive torques), twist, and spin a Mie regime, anisotropic particle in the evanescent field of ultrathin fibres.
 

3.  Optical Cavities and Sensing Group

Group Members:  Jonathan Ward, Fuchuan Lei, Priscila Romagnoli, Sho Kasumie, Maki Maeda

This subgroup is interested in spherical resonators, i.e. whispering gallery resonators, for applications into sensing, cavity QED, optomechanics and photonics, and other novel cavities.   Recent work has focussed on (i) developing a resonator-based optical frequency comb in the visble spectral region using a microbuble resonator, (ii) nanoparticle trapping inside hollow resonators to understand the particle dynamics, (iii) laser suppresion in microcavity resonators.  In the future, we plan to expand our knowledge of visible frequency combs to push the boundaries of this nonlinear effect in microresonators. We are also continuously working towards developing novel techniques and cavity geometries to try to resolve the many technical issues that inhibit the real world applications using Whispering Gallery Resonators.