Nematicon-driven injection of amplified spontaneous emission into an optical fiber

We investigate experimentally the interaction between amplified spontaneous emission (ASE) and a soliton, which are both generated in a dye-doped nematic liquid crystal (LC) cell. A light beam is injected through an optical fiber slid into the cell to form a soliton beam. ASE is then automatically collected by this self-induced waveguide and efficiently coupled into the same optical fiber, in the backward direction. We demonstrate that the presence of the soliton improves the ASE collection by one order of magnitude. We also show that the ASE is highly polarized in the plane of the LC cell and that the ASE spectrum depends on the pump stripe orientation with respect to the LC director. The origin of the spectral anisotropy of the gain curves is determined with the help of femtosecond pump-probe spectroscopy.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Local tuning of Rydberg exciton energies in nanofabricated Cu2O pillars

Funding: This work was supported by the EPSRC through grant No. EP/S014403/1, by The Royal Society through RGS\R2\192174, and by the Leverhulme Trust through grant No. RPG-2022-188. A.S.P. acknowledges the PhD scholarship from University of St Andrews and Macquarie University and the support of Sydney Quantum Academy, Sydney, NSW, Australia for The SQA Supplementary Scholarship. S.K.R. acknowledges the Carnegie Trust for the Universities of Scotland Research Incentive Grant RIG009823. T.V. acknowledges support through the ARC Centre of Excellence for Engineered Quantum Systems (CE170100009). The authors acknowledge the support of EPSRC Capital for Great Technologies Grant EP/L017008/1 and the EPSRC Strategic Equipment Resource Grant EP/R023751/1 for the use of the FIB equipment for the fabrication of the pillars.Rydberg excitons in Cu2O feature giant optical nonlinearities. To exploit these nonlinearities for quantum applications, the confinement must match the Rydberg blockade size, which in Cu2O could be as large as a few microns. Here, in a top-down approach, we show how exciton confinement can be realised by focused-ion-beam etching of a polished bulk Cu2O crystal without noticeable degradation of the excitonic properties. The etching of the crystal to micron sizes allows for tuning the energies of Rydberg excitons locally, and precisely, by optically induced temperature change. These results pave the way for exploiting the large nonlinearities of Rydberg excitons in micropillars for making non-classical light sources, while the precise tuning of their emission energy opens up a viable pathway for realizing a scalable photonic quantum simulation platform.Peer reviewe

Quantum confined Rydberg excitons in Cu2O nanoparticles

Funding: UK EPSRC Grant No. EP/S014403/1 and The Royal Society RGS\R2\192174. K.O. acknowledges EPSRC for PhD studentship support through grant no. EP/L015110/1. S.K.R. acknowledges the Carnegie Trust for the Research Incentive Grant RIG009823.The quantum confinement of Rydberg excitons is an important step towards exploiting their large nonlinearities for quantum applications. We observe Rydberg excitons in natural nanoparticles of Cu2O. We resolve up to the principal quantum number n=12 in a bulk Cu2O crystal and up to n=6 in nanoparticles extracted from the same crystal. The exciton transitions in nanoparticles are broadened and their oscillator strengths decrease as ∝n−4 compared to those in the bulk (decreasing as ∝n−3). We explain our results by including the effect of quantum confinement of exciton states in the nanoparticles. Our results provide an understanding of the physics of Cu2O Rydberg excitons in confined dimensions.Publisher PDFPeer reviewe

PRILOG POZNAVANJU ŽIVOTA SPLIĆANA U DOBA TEŠKE EPIDEMIJE KUGE 1783/1784.

Funding: UK EPSRC hybrid polaritonics program grant (EP/M025330/1)Organic semiconductor materials have been widely studied for light emission and lasing due to their ability to tune the emission wavelength through chemical structural modification and their relative ease of fabrication. Strong light-matter coupling is a promising route towards a coherent light source because it has the potential for thresholdless polariton lasing. However, the materials studied so far have relatively high thresholds for polariton lasing. Here we report the suitability of pentafluorene for strong coupling and low threshold polariton lasing. We use a protective buffer layer to reduce degradation during fabrication and lower the lasing threshold using negative detuning to maximize radiative decay. We obtain a low threshold of 17 µJ cm-2, corresponding to an absorbed energy density of 11.7 µJ cm-2. This study shows that pentafluorene is an attractive material for polariton lasing and will assist in the development of low threshold electrically pumped lasing from polariton devices.PostprintPeer reviewe

Lévy defects in matrix-immobilized J aggregates : tracing intra-and intersegmental exciton relaxation

L.L. thanks the EC for financial support by the cofunded Amarout program and the Spanish Ministry for economy and competitiveness (plan nacional, Project MultiCrom (CTQ2014-58801)). G.C. acknowledges financial support by the European Research Council (ERC-2011-AdG No. 291198). D.G.L. and D.C. thank the UK EPSRC for funding via research grant EP/M025330/1 “Hybrid Polaritonics”One-dimensional J aggregates present narrow and intense absorption and emission spectra that are interesting for photonics applications. Matrix immobilization of the aggregates, as required for most device architectures, has recently been shown to induce a non-Gaussian (Lévy type) defect distribution with heavy tails, expected to influence exciton relaxation. Here we perform two-dimensional electronic spectroscopy (2DES) in one-dimensional J aggregates of the cyanine dye TDBC, immobilized in a gel matrix, and we quantitatively model 2DES maps by nonlinear optimization coupled to quantum mechanical calculations of the transient excitonic response. We find that immobilization causes strong non-Gaussian off-diagonal disorder, leading to a segmentation of the chains. Intersegmental exciton transfer is found to proceed on the picosecond time scale, causing a long-lasting excitation memory. These findings can be used to inform the design of optoelectronic devices based on J aggregates as they allow for control of exciton properties by disorder management.PostprintPostprintPeer reviewe

Low-threshold polariton lasing in a highly disordered conjugated polymer

Funding. China Scholarship Council; Engineering and Physical Sciences Research Council (EP/L015110/1, EP/M025330/1).Low-threshold, room-temperature polariton lasing is crucial for future application of polaritonic devices. Conjugated polymers are attractive candidates for room-temperature polariton lasers, due to their high exciton binding energy, very high oscillator strength, easy fabrication, and tunability. However, to date, polariton lasing has only been reported in one conjugated polymer, ladder-type MeLPPP, whose very rigid structure gives an atypically narrow excitonic linewidth. Here, we observe polariton lasing in a highly disordered prototypical conjugated polymer, poly(9,9-dioctylfluorene), thereby opening up the field of polymer materials for polaritonics. The long-range spatial coherence of the emission shows a maximum fringe visibility contrast of 72%. The observed polariton lasing threshold (27.7  μJ/cm2, corresponding to an absorbed pump fluence of 19.1  μJ/cm2) is an order of magnitude smaller than for the previous polymer polariton laser, potentially bringing electrical pumping of such devices a step closer.Publisher PDFPeer reviewe

Nonlinear Rydberg exciton-polaritons in Cu2O microcavities

Funding; We acknowledge UK EPSRC grants EP/V026496/1, EP/S014403/1 and EP/S030751/1. OK and KWS acknowledge UK EPSRC grants EP/V00171X/1 and EP/X017222/1, and NATO SPS project MYP.G5860. HO acknowledges The Leverhulme Trust (Agreement No. RPG-2022-188).Rydberg excitons (analogues of Rydberg atoms in condensed matter systems) are highly excited bound electron-hole states with large Bohr radii. The interaction between them as well as exciton coupling to light may lead to strong optical nonlinearity, with applications in sensing and quantum information processing. Here, we achieve strong effective photon-photon interactions (Kerr-like optical nonlinearity) via the Rydberg blockade phenomenon and the hybridisation of excitons and photons forming polaritons in a Cu2O-filled microresonators. Under pulsed resonant excitation polariton resonance frequencies are renormalised due to the reduction of the photon-exciton coupling with increasing exciton density. Theoretical analysis shows that the Rydberg blockade plays a major role in the experimentally observed scaling of the polariton nonlinearity coefficient as ∝ n4.4 ± 1.8 for principal quantum numbers up to n = 7. Such high principal quantum numbers studied in a polariton system for the first time are essential for realisation of high Rydberg optical nonlinearities, which paves the way towards quantum optical applications and fundamental studies of strongly-correlated photonic (polaritonic) states in a solid state system.Peer reviewe

The reduction of oscillator strength in nanoscale reveals the fragility of high-<i>n</i> Rydberg excitons in Cu2O

Quantum confinement of Rydberg excitons is an important step towards exploiting their large nonlinearities for quantum applications. We observe Rydberg excitons in synthetic as well as natural nanoparticles of Cu2O. While we can resolve up to n = 12 in bulk Cu2O, only resonances up to n = 5 are distinguished in nanoparticles. Due to confinement the exciton transitions in nanoparticles broaden by nearly two folds and the oscillator strength decreases as n-4 compared to those in the bulk (decreasing as ∝ n-3). Our results demonstrate the fragile nature of Rydberg excitons in confined dimensions