9:45 - 10:10InvitedID: 266
ORGANIC MICROLASERS SENSE THE CONTRACTION OF HEART MUSCLE CELLS AND WHOLE HEARTS
1University of St Andrews, St Andrews, United Kingdom; 2University of Edinburgh, Edinburgh, United Kingdom
We introduce a spectroscopic technique to extract transient contraction profiles of beating heart cells using organic microlasers that are implanted into the cells of interest.
Dye-doped polymer spheres represent a simple yet extremely efficient laser architecture. The whispering gallery modes supported by the refractive index contrast between the spheres and their surrounding provide impressive quality factors (Q>104). Under nanosecond optical pumping, spheres doped with a fluorescent dye or organic polymer generate bright laser emission, with nano-Joule or lower lasing thresholds for optimized systems.
We have recently shown how such lasers can be integrated into live cells and be used to label, tag and track individual cells in large cell populations over extended periods of time (up to a month). In addition, when selecting an appropriate laser size and refractive index, the whispering gallery modes have a significant evanescent component. By combining careful optical modelling with scanning confocal spectroscopy, we were now able to quantitatively monitor local changes in refractive index in beating heart muscle cells and live zebra fish hearts. We will illustrate how this represents a useful tool for local monitoring of heart contractility that outperforms currently available probes in terms of speed, sensitivity and cell specificity.
10:10 - 10:25ID: 160
PERYLENE DERIVATIVES FOR POLARITON LASING
ARC Centre of Excellence in Exciton Science, The University of Sydney, Sydney, Australia
Strong coupling in organic media holds the promise of efficient room temperature polariton lasing with solution-processed materials. Currently, however, only a handful of pure organic materials have been shown to demonstrate polariton lasing. A major challenge is to achieve high exciton-photon coupling while maintaining high photoluminescence quantum yield.
Here, we utilize a series of diimide perylene materials that possess sterically hindered substituents, dispersed within a polymer matrix. The rigid structures prevent aggregation and allow high photoluminescence quantum yields (PLQYS) at large dye loadings. We demonstrate that these systems can exhibit Rabi splittings up to 150 meV with PLQYs of > 70%, making these perylene derivatives ideal materials for polariton lasers.
1) R. P. Sabatini, B. Zhang, A. Gupta, J. Leoni, W.W. H. Wong, G. Lakhwani, J. Mater. Chem C DOI: 10.1039/C9TC00093C (2019)
10:25 - 10:40ID: 216
TOWARDS BOSE-EINSTEIN CONDENSATION OF EXCITON POLARITONS AT ROOM TEMPERATURE: TUNABLE LIQUID CRYSTAL MICROCAVITIES
1Faculty of Physics, University of Warsaw, Warsaw, Poland; 2Institute of Applied Physics, Military University of Technology, Warsaw, Poland; 3Institute of Physics, Polish Academy of Sciences, Warsaw, Poland; 4School of Physics and Astronomy, University of Southampton, Southampton, United Kingdom
The possibility to observe the exciton polaritons - quasiparticles arising from a strong coupling of cavity photons and excitons in local emitters (e.g. dye molecules, transition metal dichalcogenides (TMDs) monolayers) - relies heavily on the tuning of energy difference between excitonic and photonic mode. Exciton polaritons are bosons with a small effective mass, for which nonlinear phenomena such as superfluidity, polariton lasing or Bose-Einstein condensation can be observed at room temperature.
In this communication we present a novel kind of a tunable microcavity consisting of a nematic liquid crystalline (LC) birefringent optical medium enclosed in a typical Fabry-Perot resonator  and filled with an emitter: organic dye or TMDs. The long-range order of elongated LC molecules results in a strong anisotropy of optical properties. The liquid nature of these materials, and the large freedom of molecular reorientation, allow for convenient control of these properties by relatively weak external electric fields: significant changes can be obtained after applying merely several volts. With the ability to manipulate the permittivity tensor and, therefore, effective refractive indices for different polarizations of light, it is possible to tune the energy splitting between cavity modes which strongly influences the luminescence and lasing coming out from the microcavity (Fig.). Our novel device allows for the integration of Bose-Einstein condensates into the room-temperature operating devices.
Fig. a) Scheme of the tunable LC microcavity with MoSe2; b) the luminescence from a single MoSe2 monolayer under applied voltage; c) LC filled with a dye.
 K. Lekenta et al., Tunable optical spin Hall effect in a liquid crystal microcavity. Light Sci. Appl. 7, 74 (2018).
This work was supported by the Ministry of Higher Education, Poland under project "Diamentowy Grant": 0005/DIA/2016/45 and 0109/DIA/2015/44, the National Science Centre grant 2016/23/B/ST3/03926 and the Ministry of National Defense Republic of Poland Program ‐ Research grant MUT Project 13‐995.