Physics - Mechatronics Seminar
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  • Physics - Mechatronics Seminar

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Title: Quantum dot optofluidic lasers and their prospects for biochemical sensing

Speaker: Alper Kiraz, Koç University

Date/Time: March 9, 2016 Wednesday at 13:40

Place: Sabancı University, FENS G035

Quantum dot optofluidic lasers and their prospects for biochemical sensing 

Alper Kiraz

aDepartment of Physics, Koç University, Rumelifeneri Yolu, 34450 Sariyer, Istanbul, Turkey

 We achieved three types of laser emissions with aqueous quantum dots (QDs) using the same high-Q-factor optofluidic ring resonator (OFRR) platform. In the first type, 2 μM QDs were in bulk buffer solution that filled the entire OFRR cavity volume. The lasing threshold was 0.1 μJ/mm2, over 3 orders of magnitude lower than the state-of-the-art. In the second type, the QDs were immobilized as a single layer on the interface between the OFRR inner wall and buffer solution with a surface density as low as 3 × 109–1010 cm–2. The lasing threshold of 60 μJ/mm2 was achieved. In the third type, we achieved optofluidic FRET lasing using QDs as FRET donors and Cy5 dye molecules as acceptors. We observed lasing from Cy5 emission band in QD-Cy5 pair when excited at QD absorption band, far away from Cy5 absorption maximum. The demonstrated capability of QDs as donors in FRET lasers greatly improves the versatility for optofluidic laser operation due to the broad and large absorption cross-section of QDs in the blue and UV range.

I will also discuss the comprehensive theoretical analysis of optofluidic FRET lasers that we have performed based on a Fabry-Perot microcavity using a rate equation model. By comparing FRET lasing-based sensors with conventional sensors using FRET signals obtained by spontaneous fluorescence emission, we show that for optimal pump fluence and FRET pair concentration, FRET lasing can lead to more than 100-fold enhancement in detection sensitivities of conformation changes for linker lengths in the Förster radius range.


Biography: Alper Kiraz received the B.S. degree in electrical electronics engineering from Bilkent University, Ankara, Turkey, in 1998, and the M.S. and Ph.D. degrees in electrical and computer engineering from the University of California, Santa Barbara, CA, USA, in 2000 and 2002, respectively. Between 2002 and 2004, he was a Postdoctoral Associate with the Institute for Physical Chemistry, Ludwig-Maximilians University, Munich, Germany, and received the Alexander von Humboldt Fellowship. He joined Koç University and became a Full Professor in 2014. Between 2014 and 2015, he was a Visiting Professor of biomedical engineering at the University of Michigan, Ann Arbor, MI, USA, as a Fulbright Fellow. His current research interests include optofluidics, single-molecule spectroscopy/microscopy, optical manipulation, and biomedical instrumentation. His research team worked with various research projects targeting the development of novel microoptical devices, optofluidic lab-on-a-chip devices, molecular and gas sensors, optofluidic-based renewable energy solutions, and confocal microscope device concepts.