Organic random lasers

Random Lasers (RLs) are realized in disordered media with gain; the feedback for stimulated emission of light is given by the scattering and no external cavity is needed. The cavity is given by multiple scattering. Therefore, when light rays penetrate these materials they interfere with each other because of scattering and, by different material-dependent mechanisms, they establish standing modes.
In a RL the multiple scattering process defines optical modes with a certain central frequency and bandwidth, lifetime and a rich spatial profile. Recently promising methods for the fabrication of planar lasers are referred to RLs and are based on active molecular layers in which defects, aggregates or external beads behave as scattering centers. To build a RL it is important to create strong enough scattering for the material to become optically thick. However, due to the intrinsically randomness of the scattering centers, conventional methods for the fabrication of RLs do not allow for a careful control of the device geometrical parameters, and in turn of the lasing properties. We describe the use of semiconductor organic materials for RL devices in term of physical-chemical properties, characteristics and advantages. Non-conventional self-organization and lithographic processes have been used for the realization of nanoscale organic random lasers. For the first time, the glassy nature of RL spectral intensity fluctuations  was experimentally demonstrated in a solid disordered system.

Highlights:

We demonstrate the random laser emission RandomLaserfrom scattering nano-aggregates of an organic thiophene-based molecule, obtained in a controlled way by a simple soft lithography technique. The use of surface-tension driven (STD) lithographic processes allows to obtain organic RLs with desired shapes and in which the scattering centers are thiophene aggregates formed by spontaneous molecular self-assembly.

The optimization of the deposition procedure and process kinetics lead to tailor the coherent emission properties by controlling the distribution and the size of the random scatterers.

We reported on the first realization of lasing devices from flexible sheets of common and biodegradable paper, without the presence of any optical cavity and by creating on the cellulose fibres microfluidic porous channels in which a lasing dye can flow by capillarity.Fiber

Such a paper-based RL device attests a geometry induced transition in RLs: from a non-resonant RL where the feedback mechanism is solely given by the scattering effect of paper to a resonant RL where the same material, constrained in micro-channels with defined walls and acting as cavity, shows a laser-like behaviour.

We investigate pulse-to-pulse fluctuations in random lasers, we introduce and measure the intensity fluctuation overlap (IFO), the analogue of the Parisi overlap in independent experimental realizations of the same disordered sample, i.e., the experimental realization of  mathematical replicas.OrganicLaser

We find that the IFO distribution function yields evidence of a transition to a glassy light phase compatible with a replica symmetry breaking. In an amorphous crystal of thiophene-based oligomer, whose optical behavior under external pumping can be properly represented by a spin-glass theory,  we measure the IFO parameter distribution function and we find a behaviour akin to the one theoretically representing the spin-glass phase (at high pumping) and the paramagnetic/fluorescence phase (at low pumping), and we clearly identify the transition between them, i.e., the lasing threshold.

Facilities & Labs

Nanotec @ Lecce

S.Li.M. Lab @ Roma

People

Ilenia_ViolaIenia

Viola

CNR Researcher

leuzziLuca

Leuzzi

CNR Researcher

Valentina_ArimaValentina

Arima

CNR Researcher

Antonella_ZacheoAntonella

Zacheo

Associate PostDoc

Publications

  1. Ghofraniha, I. Viola, F. Di Maria, G. Barbarella, G. Gigli, L. Leuzzi, C. Conti, Experimental evidence of replica symmetry breaking in random lasers, Nat. Comm. 6, 6058 (2015), doi:10.1038/ncomms7058.
  2. Ghofraniha, I. Viola, F. Di Maria, G. Barbarella, G. Gigli, C. Conti,  Random laser from engineered nanostructures obtained by surface tension driven lithography, Laser & Photonics Rev. 7, 432-438, (2013), doi: 10.1002/lpor.201200105.
  3. Viola, N. Ghofraniha, A. Zacheo, V. Arima, C. Conti, G. Gigli, Random laser emission from paper-based device, J. Mater. Chem. C 8, 8128-8133,  (2013), doi: 10.1039/C3TC31860E.
  4. Ghofraniha, I. Viola, A. Zacheo, V. Arima, G. Gigli, C. Conti, Transition from  non-resonant to resonant random lasers by the  geometrical confinement of  disorder, Opt. Lett. 38, 5043-5046 (2013), doi: 10.1364/OL.38.005043.

Latest News

Loretta del Mercato, si aggiudica l'ERC STARTING GRANT 2017

Loretta del Mercato, si aggiudica  l'ERC STARTING GRANT 2017

uno dei bandi più competitivi a livello europeo.

Lecce, 6 settembre 2017 

Lo European Research Council, che promuove la ricerca di eccellenza in Europa, nei giorni scorsi ha reso noti i nomi dei 406 vincitori della selezione ERC STARTING GRANT 2017, il bando tra i più competitivi a livello internazionale.

Su 3085 progetti presentati, 406 i progetti selezionati a cui sono stati destinati i 605 i milioni di euro di investimento. 48 le nazioni di provenienza dei ricercatori, soltanto 17 gli Italiani che condurranno le loro ricerche nel nostro paese, tra cui Loretta del Mercato, ricercatrice dell'Istituto di Nanotecnologia del Consiglio Nazionale delle Ricerche di Lecce.

Un importante riconoscimento alla ricerca nel settore della medicina di precisione condotta presso il CNR NANOTEC, un indiscusso premio al talento della giovane ricercatrice che, a 38 anni e un contratto a tempo determinato, sarà a capo del progetto "Sensing cell-cell interaction heterogeneity in 3D tumor models: towards precision medicine – INTERCELLMED".

Il progetto, il cui obiettivo è affrontare uno dei problemi più spinosi della ricerca sul cancro, ovvero la difficoltà nel trasformare i risultati delle ricerche scientifiche in applicazioni cliniche per i pazienti e che vedrà coinvolto l'Istituto tumori "Giovanni Paolo II" di Bari, si propone di sviluppare nuovi modelli in vitro 3D di tumore del pancreas, alternativi ai modelli animali, ingegnerizzati con un set di sensori nanotecnologici che consentiranno di monitorare le interazioni delle cellule tumorali con il loro micorambiente, verificare l'appropriatezza delle terapie prima della somministrazione ai pazienti oncologici e quindi prevedere la risposta dei singoli pazienti ad una o più terapie antitumorali.

La realizzazione di queste piattaforme 3D multifunzionali consentirà di superare le evidenti differenze intercorrenti tra "modelli animali" ed esseri umani fornendo dati attendibili ed in tempi più rapidi rispetto ai dati ottenuti tramite lunghi e costosi procedimenti di sperimentazione sugli animali. Le tecnologie e i modelli sviluppati saranno estesi anche ad altre forme di tumori solidi nonché impiegati per studi nell'ambito della ingegneria tissutale e della medicina rigenerativa.

Rassegna stampa e Video

Zeiss Microscopy Technology and Complete Correlative Workflow

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Zeiss Microscopy Technology and Complete Correlative Workflow

Lecce, Italy, 2017 Wednesday July 19th 

CNR NANOTEC @ Lecce, Aula Seminari – pal. G, Piano Terra

Program - PDF

Zeiss, as microscopy technology leader, provides the unique complete imaging solution ranging from light, confocal, electron, ion and Xray modalities with a complete and straightforward correlative workflow. An overview of different technologies will be presented with a special focus on X-Rray microscopy.

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MCS 2017

International Workshop on Micropropulsion and CubeSats

Bari, Italy, 26 - 27 June 2017

Program - MSC2017

This narrow-field, invited-only meeting is the first attempt to bring together the Materials and Micropropulsion communities with a view to contribute to the development of the Global Materials and Micropropulsion Roadmap, and set such meetings to a regular basis.