22 May 2013 Colloidal PbS nanocrystals integrated to Si-based photonics for applications at telecom wavelengths
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In the last decade, Si based photonics has made major advances in terms of design, fabrication, and device implementation. But due to Silicon’s indirect bandgap, it still remains a challenge to create efficient Si-based light emitting devices. In order to overcome this problem, an approach is to develop hybrid systems integrating light-emitting materials into Si. A promising class of materials for this purpose is the class of semiconducting nanocrystal quantum dots (NCs) that are synthesized by colloidal chemistry. As their absorption and emission wavelength depends on the dot size, which can easily be controlled during synthesis, they are extremely attractive as building blocks for nanophotonic applications. For applications in telecom wavelength, Lead chalcogenide colloidal NCs are optimum materials due to their unique optical, electronic and nonlinear properties. In this work, we experimentally demonstrate the integration of PbS nanocrystals into Si-based photonic structures like slot waveguides and ring resonators as optically pumped emitters for room temperature applications. In order to create such hybrid structures, the NCs were dissolved into polymer resists and drop cast on top of the device. Upon optical pumping, intense photoluminescence emission from the resonating modes is recorded at the output of the waveguide with transmission quality factors up to 14000. The polymer host material was investigated with respect to its ability to stabilize the NC’s photoluminescence emission against degradation under ambient conditions. The waveguide–ring coupling efficiency was also investigated as function of the NCs concentrations blended into the polymer matrix. The integration of colloidal quantum dots into Silicon photonic structures as demonstrated in this work is a very versatile technique and thus opens a large range of applications utilizing the linear and nonlinear optical properties of PbS NCs at telecom wavelengths.
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M. Humer, M. Humer, R. Guider, R. Guider, W. Jantsch, W. Jantsch, T. Fromherz, T. Fromherz, "Colloidal PbS nanocrystals integrated to Si-based photonics for applications at telecom wavelengths", Proc. SPIE 8767, Integrated Photonics: Materials, Devices, and Applications II, 87670V (22 May 2013); doi: 10.1117/12.2016763; https://doi.org/10.1117/12.2016763

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