Project Description

 

 

The Exploratory Research Projects have as main goal the development of the knowledge/ knowledge broadening in all the research domains, including the socio-human sciences, both by fundamental research and by advanced research in order to solve complex issues, of frontier, by obtaining new knowledge regarding processes and phenomena, by formulating and validating original suppositions, concept models and theories.

The goal of the research project is to developfundamentally new generations of soft material classes and eventually metamaterials, created for visible, infrared and other optical frequencies, based on the use of photonics, nano-physics and self-assembly of soft matter systems and as an alternative the use of lithography or multi-beam holography. This manufacturing and assembling path will result greatly innovative being tightly focused on the design of new categories of active reconfigurable photonic systems for moulding the flow of light. The implementation of the project relies on the strategic conjunction of the following complementary disciplines:

  1. Self-assembly methods (either spontaneous or directed) and nano scale lithographical techniques, capable of organizing matter into vastly varied structures at scales ranging from nanometers to hundreds of microns. Grouping with the aforementioned synthetic nano-objects opens the road to a quasi unlimited set of attainable nanostructured artificial materials, far beyond the limited number of existing models.
  2. Theory and EM analysis routines are proposed to occupy a decisive role, by providing chemists and physicists with achievable models of soft matter systems and metamaterials having designed EM physical properties.
  3. Characterization of the EM properties via advanced optical techniques and the non-trivial expansion of connected models for data analysis.

Finally, one must also consider as stimulus the feasibility of the original nano-physics toolbox exploited in the project, that will be adopted towards further scientific developments, i.e. taking into account issues such as reconfigurable photonic systems based on the mutual presence of active media and metamaterials (MTMs) etc.

Various types of photonic crystals and quasicrystal matrices

Various types of photonic crystals and quasicrystal matrices (Property of John D. Joannopoulos, Steven G. Johnson, Joshua N. Winn, and Robert D. Meade - 'Photonic Crystals: Moulding the Flow of Light' Princeton University Press, 2008)

Some of the main objectives:

  • Analysis of the effects of a lossy medium in the propagation of eigenmodes of 1D, 2D and 3D gain soft materials and/or metamaterials, based on integral-equation approaches;
  • Determination of a linearized model for the preamble of the gain medium;
  • Approximation of the gain needed to recover material properties equivalent to the loss-less designed structures; -Assessment of effects of coupling between active EM model at signal frequency and pumping mechanism;
  • Assessment of saturation non-linear effects;
  • Study of loss compensation feasibility in the framework of the active media engineered as function of organic dye or nanocrystals concentrations;
  • Definition of the main geometrical parameters and physical properties from single element to the amassed structures; - Development of nanosized building blocks (nanoparticles, nanocrystals) with superior control of size, shape and composition for fabrication of novel metamaterials by using colloidal material tools or gels;
  • Assembly the suitably engineered nanomaterials and substrates by using spontaneous or directed assembly (liquid crystal formation, solvent evaporation technique);
  • Chemical and physical characterization of the fabricated structures;
  • Enhanced Scattering Raleigh of dye doped nanoparticle/active media dispersions;
  • Experiments of polarized fluorescence, gain amplification, transmittance and reflectance as function of the gain;
  • Experiments of overall transmission and polaritonic propagation length estimation;
  • Ellipsometric characterization of complex refractive index as function of the gain; - Pump-probe experiments to evaluate the total internal reflection attenuation;
  • Experiments for evaluating the far-field emission profile and gain efficiency. 

All these research activities will be oriented towards the possibility to organize the proper complexes configuring them as guest-host structures. Soft materials like polymers, liquid crystals and composites will be used to tailor responsive systems possessing very attractive optical, mechanical, chemical, and thermal properties, as well as flexible manufacturing processes for fabricating optical gain systems and linked devices. These properties will be precisely directed towards the creation of new reconfigurable photonic systems, as quasi-periodic lasing sources, open cavities, high efficiency diffraction gratings, hyper-lenses.   

Nano-Structuration and Fabrication of Soft Gain Media and Metamaterials.

The general objective will be to organize and assemble gain media and nanoparticles integrating them into specific matrices by using different approaches, all oriented towards the possibility to create nano- and micro-structures with novel reconfigurable optical properties. One possible approach we will be based on the fabrication and use of templating organic matrices which are constructed mainly on two phenomena: the self-assembly properties of block copolymers in the solid state or in solvent dispersions and the polymerization method of composite mixtures in quasi-periodic configurations.

Nanoparticles can be introduced at the stage of ordering the copolymer system or by selectively swelling of the nanodomains by a solvent containing nanoparticles. The focus will be on incorporating a large enough quantity of particles, to produce gain-like nanodomains. In order to create polymer-based quasi-periodic structures, a CGH-SLM single-beam and single step process technique could be adopted to photo polymerize suitable pre-polymer mixtures including the needed resonant entities. This technique is favored because it facilitates high precision engineering of various structures at different resolutions, spanning the range from the micrometer to the nanometer length scale.

The resulting configurations, including Cantor and Fibonacci types, will be used for enhancing the optical emission properties of a series of gain materials, such as highly luminescent core-shell colloidal nano-crystals, dye doped organic mixtures, fluorescent liquid crystals and other soft materials doped with gain media that exhibit high emission efficiency.  

Computer-generated holography (CGH) is a very attractive technique that permits to create almost any two-dimensional, and even three-dimensional, spatial distribution of the intensity of the optical beam, by controlling the phase profile of the laser beam impinging on a Diffractive Optical Element (DOE), which is designed as a CGH.

Another possible approach will concern the exploration of gain soft materials and/or MTMs based on the controlled stacking and assembly of nanoparticles into well-defined spatial structures. The main concept here is to have the nano-objects of interest self-assembled directly, driven by inter-particle forces. The end result is the assembly of dense 2D or 3D structures (colloidal crystals and “superlattices”) presenting a degree of order which can extend over tens or hundreds of particle radii depending on conditions, and within which nanoparticles are in near close contact. These dense materials will then be shaped into real, sizeable samples.

An important part of the project will be dedicated to address and solve the fundamental problem of the optical losses. In fact, most gain materials suffer from a rather strong damping of the plasmon fields which can become disruptive for most optical and photonic applications. The influence of a gain medium on surface plasmon-polariton propagation has been receiving more and more attention over the past years, especially with the rise of nano-photonics.

Several researchers have demonstrated, either theoretically and experimentally, in various situations and set-ups, that the losses associated with plasmon resonances could efficiently be reduced by the nearby presence of a gain medium via non-radiative transfers. This transfer of energy from a gain component to plasmonic elements is a key concept that will be studied and highly considered when acting to reduce losses in gain material designs.

The novelty of the concepts developed in this project is that, thanks to the sophisticated techniques available, there is a tremendous flexibility at all levels for the design and organization of loss-compensated structures / materials (Polymers, Monomers, Colloids, LCs, various Si nanoparticles, porous membranes, Surfactants, gels etc) that can be employed in combination with the gain matrices. This makes it possible to introduce a variety of gain elements (fluorescent dyes, quantum dots, semiconductors, nanoparticles) right at the heart of the designed structures, by studying  optimized geometries and ensuring enhanced amplification effects.


Property of Center for Soft Condensed Matter Physics & Interdisciplinary Research Soochow University, China.

Pagină actualizată la 15 Decembrie 2016.