Browsing by Author "Kurum, U."
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Item Open Access Attractive versus repulsive excitonic interactions of colloidal quantum dots control blue-to red-shifting (and non-shifting) amplified spontaneous emission(American Chemical Society, 2013-11-21) Cihan, A. F.; Kelestemur, Y.; Guzelturk, B.; Yerli, O.; Kurum, U.; Yaglioglu, H. G.; Elmali, A.; Demir, Hilmi VolkanTunable, high-performance, two-photon absorption (TPA)-based amplified spontaneous emission (ASE) from near-unity quantum efficiency colloidal quantum dots (CQDs) is reported. Besides the absolute spectral tuning of ASE, the relative spectral tuning of ASE peak with respect to spontaneous emission was shown through engineering excitonic interactions in quasi-type-II CdSe/CdS core/shell CQDs. With core shell size adjustments, it was revealed that Coulombic exciton-exciton interactions can be tuned to be attractive (type-I-like) or repulsive (type-II-like) leading to red- or blue-shifted ASE peak, respectively, and that nonshifting ASE can be achieved with the right core shell combinations. The possibility of obtaining ASE at a specific wavelength from both type-I-like and type-II-like CQDs was also demonstrated. The experimental observations were supported by parametric quantum-mechanical modeling, shedding light on the type-tunability. These excitonically engineered CQD-solids exhibited TPA-based ASE threshold as low as 6.5 mJ/cm(2) under 800 nm excitation, displaying one of the highest values of TPA cross-section of 44 660 GM.Item Open Access Blue-and red-shifting amplified spontaneous emission of CdSe/CdS core/shell colloidal quantum dots(IEEE, 2013) Kelestemur, Yusuf; Cihan, Ahmet Fatih; Güzeltürk, Burak; Yerli, Ozan; Kurum, U.; Yaglioglu H.G.; Elmali, A.; Demir, Hilmi VolkanWe report blue- and red-shifting amplified spontaneous emission of CdSe/CdS quantum dots, controlled by varying core/shell dimensions and modifying exciton-exciton interactions, with low optical gain threshold of two-photon absorption pumping. © 2013 The Optical Society.