Presenter: Prof. Ni Zhao (Chinese University of Hong Kong)
Topic: Device Technologies for Functional Near-infrared Spectroscopy
Time: 10:00 am, July 17th (Monday)
Location: 909-B,C
Abstract:
Brain monitoring in situ and with long duration is essential for cognitive psychology and brain diseases research. A promising technology to realize such monitoring capability is fNIRS, which exploits near-infrared wavelengths to noninvasively probe the hemodynamic responses associated with neural activities. Current fNIRS systems rely on either avalanche photodiodes that require large-sized high-voltage suppliers or silicon photodiodes that exhibit low light responsivity. A wearable (thus enabling brain monitoring during daily activities) and high sensitivity fNIRS system is yet to be developed. In this talk, I will introduce our recent efforts in developing high brightness near-infrared LEDs and new photodetector structures with self-amplification mechanisms to enhance the sensitivity of the fNIRS detection unit. First, I will discuss how the notorious instability problems of OIHP LEDs may be addressed through surface engineering methods and highlight the underlying mechanisms revealed by experimental characterization and theoretical modelling. Secondly, I will talk about the commonly seen gain – bandwidth trade-off problem of photodetectors and introduce a monolithically integrated photovoltaic transistor (PVT) design to solve this dilemma. The PVT exploiting a lead halide perovskite as the photoactive layer achieved a record high gain – bandwidth product. Finally, I will talk about our recent exploration of using quasi-two-dimensional Dion-Jacobson (DJ) phase perovskites for laser application. With properly selected organic spacers, DJ phase OIHPs offer excellent chemical resistance and thermal processability. These properties allow us to achieve optically pumped perovskite lasers with record-high quality factor, record-low lasing threshold and excellent operational stability.
Short biography
Prof. Ni Zhao received her Ph.D. degree in Physics from University of Cambridge (UK) in 2008. From 2008-2010 she worked as a postdoctoral research associate at the Research Laboratory of Electronics at Massachusetts Institute of Technology (USA). She joined the Department of Electronic Engineering at The Chinese University of Hong Kong in 2010 and is now a Full Professor. Her recent work focuses on development of low-cost energy harvesting devices, nanostructured optoelectronic devices and sensors for biomedical applications. Her research to date has generated over 180 journal publications, with an h-index of 67. Prof. Zhao was listed as Highly Cited Researchers 2018 by Clarivate Analytics and is a Fellow of Royal Society of Chemistry. She currently serves as the Associate Editor of Science Advances and Journal of Materials Chemistry C.
Contact: Sun Baoquan