Orta kızılötesi kuantum çağlayan lazer

Cataloged from PDF version of article.Thesis (M.S.): Bilkent University, Department of Electrical and Electronics Engineering, İhsan Doğramacı Bilkent University, 2017.Includes bibliographical references (leaves 105-111).Mid-infrared quantum cascade laser technology has been developed rapidly since it was demonstrated in 1994. Since quantum cascade laser technology is small, robust and efficient, they have become commonly used mid-infrared laser source for various applications. The particular application fields of quantum cascade lasers are free space communication, chemical spectroscopy, environmental monitoring and infrared countermeasure. This work presents a comprehensive study over mid-infrared quantum cascade laser including review of theoretical background, theoretical analyses, active layer design, quantum mechanical, thermal and optical simulations, device fabrication, optimization and experimental characterization. As a result of this work mid-infrared quantum cascade laser have been successfully demonstrated.by Berkay Bozok.M.S

Nanocrystal skins with exciton funneling for photosensing

Highly photosensitive nanocrystal (NC) skins based on exciton funneling are proposed and demonstrated using a graded bandgap profile across which no external bias is applied in operation for light-sensing. Four types of gradient NC skin devices (GNS) made of NC monolayers of distinct sizes with photovoltage readout are fabricated and comparatively studied. In all structures, polyelectrolyte polymers separating CdTe NC monolayers set the interparticle distances between the monolayers of ligand-free NCs to <1 nm. In this photosensitive GNS platform, excitons funnel along the gradually decreasing bandgap gradient of cascaded NC monolayers, and are finally captured by the NC monolayer with the smallest bandgap interfacing the metal electrode. Time-resolved measurements of the cascaded NC skins are conducted at the donor and acceptor wavelengths, and the exciton transfer process is confirmed in these active structures. These findings are expected to enable large-area GNS-based photosensing with highly efficient full-spectrum conversion

Mn²⁺-Doped CdSe/CdS Core/Multishell Colloidal Quantum Wells Enabling Tunable Carrier–Dopant Exchange Interactions

In this work, we report the manifestations of carrier–dopant exchange interactions in colloidal Mn²⁺-doped CdSe/CdS core/multishell quantum wells. The carrier–magnetic ion exchange interaction effects are tunable through wave function engineering. In our quantum well heterostructures, manganese was incorporated by growing a Cd_0.985Mn_0.015S monolayer shell on undoped CdSe nanoplatelets using the colloidal atomic layer deposition technique. Unlike previously synthesized Mn²⁺-doped colloidal nanostructures, the location of the Mn ions was controlled with atomic layer precision in our heterostructures. This is realized by controlling the spatial overlap between the carrier wave functions with the manganese ions by adjusting the location, composition, and number of the CdSe, Cd_1–<i>x</i>Mn_<i>x</i>S, and CdS layers. The photoluminescence quantum yield of our magnetic heterostructures was found to be as high as 20% at room temperature with a narrow photoluminescence bandwidth of ∼22 nm. Our colloidal quantum wells, which exhibit magneto-optical properties analogous to those of epitaxially grown quantum wells, offer new opportunities for solution-processed spin-based semiconductor devices