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

Scholar-in-Training Award dell'AACR a Marta Cavo

Lecce, 15/01/2020
Marta Cavo, ERC-postdoctoral research fellow at the CNR Institute of Nanotechnology in Lecce (ERC-StG INTERCELLMED No., 759959, PI: Dr. Loretta L. del Mercato), have been selected to receive a Scholar-in-Training Award (USD $625). The Scholarship will support her attendance at the Conference on The Evolving Landscape of Cancer Modeling, organized by the American Association for Cancer Research (AACR), to be held on 2-5 March 2020 in San Diego (California), where she will present the work "Quantifying stroma-tumor cell interactions in three-dimensional cell culture systems". Link to the conference:

I° meeting TecnoMed Puglia

Lecce, 05 dicembre 2019 - Aula Rita Levi Montalcini - CNR NANOTEC Lecce

Si terrà domani, giovedì 05 dicembre, con inizio alle ore 14.00 presso l'aula Rita Levi Montalcini del Cnr Nanotec, il "I° meeting TecnoMed Puglia: Tecnopolo per la medicina di precisione". Il meeting mira a fare il punto sulle attività programmate, sullo stato di avanzamento e sugli highlights.

Puoi scaricare la locandina da qui

Jam session Nanotec... note di scienza su scala nanometrica

Lecce, 27 settembre 2019 - ex monastero degli Olivetani "CAR-T: l'alba di una nuova era"  con: Attilio Guarini (IRCCS Istituto Tumori “Giovanni Paolo II” di Bari)  introduce e modera: Marco Ferrazzoli (Ufficio Stampa CNR Roma) a cura di: Gabriella Zammillo 

Le CAR-T (Chimeric Antigens Receptor Cells-T) sono cellule modificate in laboratorio a partire dai linfociti T. Rappresentano una nuova strategia di cura che sfrutta il sistema immunitario per combattere alcuni tipi di tumore come linfomi aggressivi a grandi cellule e leucemie linfoblastiche acute a cellule B. Il prof Attilio Guarini, ematologo all’Istituto tumori Giovanni Paolo II di Bari, le definisce la “vis sanatrix naturae della antica medicina salernitana”, trattandosi del potenziamento dell’attività citotossica dei linfociti del paziente opportunamente ingegnerizzati per riconoscere e contrastare alcuni tipi di cellule tumorali.

 

Le CAR-T possono quindi essere definite un “farmaco vivente” proprio perché prodotto a partire dalle cellule dello stesso paziente aprendo così ad un nuovo mondo, considerato che i farmaci convenzionali sono prodotti da sostanze chimiche o, in alternativa, sono anticorpi prodotti in laboratorio dai biologi. Un trattamento estremamente complesso e costoso, non sempre applicabile, ma laddove possibile, dai risultati incoraggianti per le aspettative di vita. Lo sviluppo di nuove tecnologie per la produzione di CAR-T è parte integrante delle attività di ricerca condotte dal TecnoMed Puglia, il TecnoPolo per la Medicina di Precisione, coordinato da Giuseppe Gigli direttore del Cnr Nanotec di Lecce, e che nel suo nucleo fondatore vede anche l’IRCCS Istituto Tumori “Giovanni Paolo II” di Bari, il Centro di malattie neurodegenerative e dell’invecchiamento cerebrale dell’Università di Bari con sede presso l’Ospedale " G. Panico" di Tricase e la Regione Puglia.

 

L'evento apre la nuova stagione della rassegna divulgativa "Jam session Nanotec: note di scienza su scala nanometrica", un progetto Cnr Nanotec di Gabriella Zammillo, realizzato in collaborazione con Liberrima.

A condurre e moderare la serata, Marco Ferrazzoli, capo ufficio stampa dal CNR. Puoi scaricare la locandina da qui