Exciton-polaritons are bosonic quasi-particles arising from strong light-matter interaction between excitons and photons. They have achieved great importance for studies - tipically made in planar microcavities (MCs) - on fascinating subjects such as Bose Einstein condensation, superfluidity and quantum vortex, but also for the realization of ultra fast and highly efficient logic devices thanks to their non linear and in-plane propagation properties. Until now room temperature propagation had never been observed due to the ionization of the exciton in inorganic systems. For this reason, organic materials, with their huge oscillator strength, are achieving a great interest for their capability to condense at room temperature. However, organic polariton lifetimes are limited by planar MCs growth difficulties when adopting these “soft” materials and it has hindered so far the possibility to observe polariton propagation in a standard planar MC system. Using a novel device structure, we couple a Bloch Surface Wave (BSW) mode with an organic exciton, observing for the first time polariton propagation at room temperature over ranges of hundreds of microns. Moreover we demonstrate the non linear interaction above a given power threshold which is the first step towards all-optical logic circuits. The BSW is a propagating mode existing at a Distributed Bragg Reflector (DBR) surface beyond the critical angle. We experimentally demonstrate the formation of a room temperature Bloch Surface Wave Polariton (BSWP) generated between this optical mode and thin organic layers.7 The group velocity of these polaritons is around 50% the speed of light, i.e. 150µm/ps, which is about two orders of magnitude higher than in planar MCs. In addition, during the propagation path, given the exciton counterpart, the polariton energy relaxation is clearly observable. Furthermore, due to the absence of the top mirror - which is necessary in standard planar MC systems -record organic polariton lifetimes (about 1ps) have been achieved.6 Moreover, resonantly pumping the BSWP, the mode dispersion blueshifts above a given threshold due to non linear polariton-polariton interactions. Regarding logic operation, this finding is an essential condition for the realization of an optical gate, i.e. the basic component of a logic device. Our results open the possibility to create room temperature BSWP polariton circuits with low dissipation and ultrafast data manipulation and transmission rates.

Room temperature organic polaritons propagation towards all-optical logic circuits

CANNAVALE, Alessandro;
2015-01-01

Abstract

Exciton-polaritons are bosonic quasi-particles arising from strong light-matter interaction between excitons and photons. They have achieved great importance for studies - tipically made in planar microcavities (MCs) - on fascinating subjects such as Bose Einstein condensation, superfluidity and quantum vortex, but also for the realization of ultra fast and highly efficient logic devices thanks to their non linear and in-plane propagation properties. Until now room temperature propagation had never been observed due to the ionization of the exciton in inorganic systems. For this reason, organic materials, with their huge oscillator strength, are achieving a great interest for their capability to condense at room temperature. However, organic polariton lifetimes are limited by planar MCs growth difficulties when adopting these “soft” materials and it has hindered so far the possibility to observe polariton propagation in a standard planar MC system. Using a novel device structure, we couple a Bloch Surface Wave (BSW) mode with an organic exciton, observing for the first time polariton propagation at room temperature over ranges of hundreds of microns. Moreover we demonstrate the non linear interaction above a given power threshold which is the first step towards all-optical logic circuits. The BSW is a propagating mode existing at a Distributed Bragg Reflector (DBR) surface beyond the critical angle. We experimentally demonstrate the formation of a room temperature Bloch Surface Wave Polariton (BSWP) generated between this optical mode and thin organic layers.7 The group velocity of these polaritons is around 50% the speed of light, i.e. 150µm/ps, which is about two orders of magnitude higher than in planar MCs. In addition, during the propagation path, given the exciton counterpart, the polariton energy relaxation is clearly observable. Furthermore, due to the absence of the top mirror - which is necessary in standard planar MC systems -record organic polariton lifetimes (about 1ps) have been achieved.6 Moreover, resonantly pumping the BSWP, the mode dispersion blueshifts above a given threshold due to non linear polariton-polariton interactions. Regarding logic operation, this finding is an essential condition for the realization of an optical gate, i.e. the basic component of a logic device. Our results open the possibility to create room temperature BSWP polariton circuits with low dissipation and ultrafast data manipulation and transmission rates.
2015
FisMat2015
978-88-907460-8-6
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11589/83737
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