FRET-assisted laser emission from dye-doped nanoparticles.
The use of commercial long-wavelength (>650 nm) laser dyes in many biophotonic applications has several important limitations, including low absorption at the standard pump wavelength (532 nm) and poor photostability. Here, we demonstrate that the use of Fo¨rster type (FRET) energy transfer can overcome these problems to enable efficient, stable near-infrared lasing in a colloidal suspension of latex nanoparticles containing a mixture of Rhodamine 6G and Nile Blue dyes. Experimental and theoretical analyses of the photophysics suggest that the dominant energy transfer mechanism is Fo¨rster type via dipole–dipole coupling, and also reveal an unexpected core/shell morphology in the dye-doped nanoparticles. FRET-assisted incoherent random lasing is also demonstrated in solid samples obtained by evaporation of colloidal suspensions.
“FRET-assisted Laser Emission in Colloidal Suspensions of Dye-Doped Latex Nanoparticles
L. Cerdan, E. Enciso, V. Martin, J. Bañuelos, I. Lopez Arbeloa, A. Costela and I. Garcia-Moreno,
Nat. Photonics, 2012, 6, 621-626


The development of new O-BODIPYs,
synthesized via the replacement of fluorine atoms by carboxylate groups in the commercial F-BODIPYs, is a successful strategy to obtain optimized laser dyes. Poly(methyl methacrylate) (PMMA) doped with these new derivatives leads to laser materials economically affordable with optimized emission properties in the visible spectral region (540-650 nm).
“Carboxylates versus fluorines: Boosting the Emission Properties of Commercial BODIPYs in Liquid and Solid Media”,
G. Duran-Sampedro, A.R. Agarrabeitia, L. Cerdan, M.E. Perez-Ojeda, A. Costela, I. García-Moreno, I. Esnal, J. Bañuelos, I. Lopez Arbeloa and M.J. Ortiz, 
Advanced Functional Materials 2013




Efficient random lasing (RL) from self-assembled dye-doped latex nanoparticles presenting size polydispersity.
Both the nanoparticle size and size polydispersity influences the RL emission properties. The use of binary mixtures of nanoparticles with different sizes improves the RL emission properties with respect to the mixture constituents separately, due to an increase in the filling fraction.
“Random Lassing in Self-Assambled Dye-Doped Latex Nanoparticles: Packing Density Effects”
L. Cerdan, A. Costela, E. Enciso, I. Garcia-Moreno,
Advanced Functional Materials, 2013





Research lines

The present research of our group is centered in the design and development of new materials nanostructured, both organic and organic-inorganic hybrids, with specific properties and applications in the fields of biomedicine and optoelectronics, as well as the knowledge of the processes that control their synthesis, performance and properties in relation to their structure and nanostructure.

In the field of optoelectronics, the new materials are studied and developed as laser systems, microlasers, photonic coatings and colloidal suspensions. In the field of biomedicine, it is studied the utilization of the new nanostructured materials in applications such as photodynamic therapy or systems for the controlled release of medical drugs.

Our research also involves a high technological interest, which will lead to the industrial validation of the new materials as gain media in solid-state dye lasers by incorporating them into a commercial device being developed with our collaboration by a Spanish company

Solid-state dye lasers
This research program is aimed to the systematic study of the properties of the laser emission in organic dyes incorporated into solid matrices. Both commercial dyes and dyes newlysynthesized in our laboratories will be used. As host matrices both organic polymers and organic-inorganic hybrid materials are utilized.





 Research stages:
  • Development of new functionalized organic dyes with efficient and stable emission in the blue, red and near IR spectral regions.
  • Desing, synthesis and analysis of new photosensitized materials, nanostructured by the incorporation to linear and crosslinked polymers of nanometric silica (polyhedric oligomeric silsesquioxanes, POSS), oxide nanoparticles (TiO2, ZnO) or metal nanoparticles (gold and silver), both bare and coated with dye-doped polymers or oxide layer (SiO2,TiO2, ZnO).
  • Structural, morphological, optical, photophysical and photochemical characterization of the synthesized dyes, both if liquid phase, confined in or covalently bonded to nanoparticles (polymeric, POSS, metal) incorporated into polymeric matrix (bulk, thin films), and into nanochannels.
  • Characterization of the new materials as laser systems, microlasers and photonic coatings.
  • Development of commercial laser systems based on our materials.

Waveguides

There has been significant work over the last few years exploring the development of organic thin film lasers based on dye doped polymers because of their potential applications as coherent light sources suitable for integration in optoelectronic and disposable spectroscopic and sensing devices. In our group we explore the suitability of both commercial and newly synthesized laser dyes doped into adequate polymers as amplified spontaneous emission sources, waveguide random lasers and distributed feedback (DFB) lasers.










a) AFM topography of the 1D corrugated substrate with period 386 nm used to obtain DFB lasing in Perylene Orange doped PMMA.
b) Characteristic laser spot of a 2nd order 1D DFB laser.
c) Evolution of the DFB laser emission spectrum as the pump intensity is increased (spectra I to IV correspond to points I-IV in d)).
d) Dependence of the DFB laser output intensity on pump intensity (light-light curve).


Dye lasers with scattering feedback

Scattering has always been considered detrimental to conventional lasers, being a source of losses which scramble the directionality and intensity of the output emission. Hence, conventional wisdom requires scattering in laser materials being always kept at the lowest possible level. Nevertheless, we have demonstrated that the presence of nanoscatterers up to a certain density, homogeneously distributed in gain media, instead of being detrimental may result in an increase of the output energy due to an enlargement in the effective optical path, in what is called non-resonant feedback or incoherent feedback. We undergo studies on dye doped systems based on solid or liquid solutions incorporating silica nanoparticles (silsesquixanes) as scatterers, colloidal solutions of dye doped latex nanoparticles with sizes below 40 nm or in thin film, and we have obtained random lasing based on coherent feedback.







Random laser emission spectra for different dyes doped into adequate polymer blends











Sketch of a waveguide random laser





Laser emission assisted by energy transfer processes in coloidal suspensions of dye-doped nanoparticles
It is studied the influence of resonant energy transfer processes (FRET) in the fluorescence and laser emission of mixtures of dyes confined into latex nanoparticles in colloidal suspension. The experimental studies are complemented with a thorough theoretical study with allows to gain insight on the processes taking place and provides guidance about the morphology of the nanoparticles










FRET based laser emission
Interaction of laser emission with biological tissues
  • It is investigated the interaction processes of laser radiation with different wavelengths with dental tissue and skin.
  • It is studied the effectiveness of the laser radiation in the removal of dental calculus, disinfection of periodontal lesions and bactericidal effect on dental biofilms. The effect of the laser radiation, UV, visible end IR on the structure of enamel and dentin is evaluated, as well as the application of laser radiation for the detection ann removal of caries, and its use in sealing cracks.

  • Study of laser ablation processes of skin and soft tissues as mechanism for the controlled and localized release of pharmacological agents through the skin. Removal of tattoos by means of selective photothermolysis process.
  • Development of organic dyes in the red and near infrared for applications in photodynamic therapy.
  • Study of the use of gold nanostructures as nanocarriers in photothermal therapeutic schemes for the controlled release of medial drugs or delivery of photosensitizing agent in photodynamic therapy.