In this paper, active planar waveguides based on the incorporation of CdSe and CdTe nanocrystal quantum dots in a polymer matrix are demonstrated. In the case of doping the polymer with both types of quantum dots, the nanocomposite film guides both emitted colors, green (550 nm, CdTe) and orange (600 nm, CdSe). The optical pumping laser can be coupled not only with a standard end-fire coupling system, but also directing the beam to the surface of the sample, indicating a good absorption cross-section and waveguide properties. To achieve these results, a study of the nanocomposite optical properties as a function of the nanocrystal concentration is presented and the optimum conditions are found for waveguiding.
In this paper we review our recent progress in a still young type of active waveguides based on hybrid organic (polymer)—inorganic (semiconductor quantum dots) materials. They can be useful for the implementation of new photonic devices, because combining the properties of the semiconductor nanostructures (quantum size carrier confinement and temperature independent emission) with the technological capabilities of polymers. These optical waveguides can be easily fabricated by spin-coating and UV photolithography on many substrates (SiO2/Si, in the present work). We demonstrate that it is possible to control the active wavelength in a broad range (400–1100 nm), just by changing the base quantum dot material (CdS, CdSe, CdTe and PbS, but other are possible), without the necessity of changing fabrication conditions. Particularly, we have determined the optimum conditions to produce multi-color photoluminescence waveguiding by embedding CdS, CdSe and CdTe quantum dots into Poly(methyl methacrylate). Finally, we show new results regarding the incorporation of CdSe nanocrystals into a SU-8 resist, in order to extrapolate the study to a photolithographic and technologically more important polymer. In this case ridge waveguides are able to confine in 2D the light emitted by the quantum dots.
In this paper, active nanocomposite waveguides based on the dispersion of CdS, CdTe, and CdSe colloidal quantum dots (QDs) in PMMA are proposed. Their propagation properties are studied as a function of the concentration of nanoparticles in the polymer using the variable length stripe method. When the three nanostructures are dispersed in the same film, the structure is able to waveguide the three basic colors: red (CdSe), green (CdTe), and blue (CdS), it being possible to engineer any waveguided color by an appropriate choice of the filling factor of each QD in the PMMA matrix. For this purpose, it is important to take into account reabsorption effects and the Fo ¨rster energy transfer between the different QDs families. As a final application, white waveguided light at the output of the structure is demonstrated. This energy transfer can be also the origin of the surprising observation that initial gain (losses) are much higher (smaller) in these active multinanopaticle waveguides than in single-loaded ones.
We have developed a patternable nanocomposite sensor based on luminescent CdSe QDs and a polyisoprene-based photoresist (PIP) as host matrix that showed chemosensing response against MET and EDA in vapour with a LOD around 0.1 pg and 15 ng, respectively.
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