AbstractsPhysics

This thesis addresses novel nanocomposite materials by incorporating quantum dots,and other nanoentities, into polymer and sol-gel derived matrices, aiming to produceintegrated photonic structures. Its objectives embrace the synthesis and theinvestigation of photonic materials, together with alternative fabrication methodologiesenabling the effective integration of functional nanocomposite photonic structures,such as active waveguides, micro-ring structures and diffractive optical elements forsensing applications.Design, synthesis and characterization of nanocomposite materials in thiscontext, involves QD incorporation in tailored-made polymers, synthesized usingradical polymerization as well as QD embedment in titania matrices synthesized viasol-gel methods. Low cost sol-gel derived silica incorporating NiCl2 nanoentities wasexploited in the proposed scheme of remote point sensing for ammonia detection.Commercially available hybrid organic/inorganic materials of the ORMOCER familyare also used for structure fabrication. Further to microscopy, characterization of thematerials mainly includes spectroscopic studies and refractive index measurementsusing reflectance interferometry.For the demonstration of complex photonic structures by using nanocompositeselaborated studies are presented here focusing on two fabrication methods: a) directlaser ablative microfabrication using ArF excimer radiation at λ=193 nm and, b) softlithography. To achieve this, a fully automated ArF excimer laser microfabricationstation was established comprising computer controlled nanopositioning and laserbeam control, as well as various prototype materials synthesis and fabricationdevices. QD/polymer computer generated holograms, waveguides and micro-ringstructures were simulated, designed and fabricated. Specific protocols and methodwere established. A modified solvent-assisted soft lithography method was also usedfor micropatterning and fabrication of photonic structures using QD/polymer andQD/titania films in conjunction to common UV and thermally curable materials. Asolvent vapor smoothing process was found to significantly enhance the quality of thestructures as observed with scanning electron microscopy.QD/polymer computer generated holograms, diffractive optical elements, micro-ringstructures, vertical cavity resonators and other advanced photonic structurescomprising quantum dot nanocrystals and nano-entities are investigated.A new photonic sensing scheme is proposed and demonstrated here for remote, spatially-localized sensing. It comprises a low cost diffractive thin film of a sensingmaterial remotely interrogated by use of light beams. A silica/NiCl2 system fabricatedvia the sol-gel methods and micropatterned using the direct laser ablativemicrofabrication method is demonstrated, to allow detection of as low as 1 ppm ofammonia.Finally, the merits of incorporating epitaxially grown quantum dots in highly resonantstructures for signal amplification, namely vertical cavity semiconductor opticalamplifier and micro-ring semiconductor…