Ultrafast Optical Imaging and the Development of Micro/Nano-Lasers by Prof Liu Xinfeng and Assoc Prof Zhang Qing

The IAS and the Graduate Students’ Clubs of EEE, MSE and SPMS jointly organised the STEM Graduate Colloquium featuring two outstanding alumni of NTU, Prof Liu Xinfeng and Assoc Prof Zhang Qing, on 29 November 2023 at SPMS LT3. The colloquium with the broad theme of the fundamentals and applications of light-matter interaction at the micro/nano level offered a comprehensive view of ultrafast optical imaging and micro/nano lasing.

Prof Sum Tze-Chien (Director, IAS) welcoming and introducing the two outstanding NTU alumni speakers to the audience.

Prof Liu Xinfeng is the Deputy Director of the Chinese Academy of Sciences Key Laboratory for Standardisation and Measurement for Nanotechnology, National Center for Nanoscience and Technology, China. He started with an overview of how understanding carrier dynamics is vital to the development of devices with higher efficiencies. He delineated his approach of linking micro/nano structures with macro physical properties via studying the micro area steady/transient or angle-resolved spectra. After laying this foundational understanding, he explained how ultrafast spectroscopy helps in the study of Boron Arsenide, a material featuring better transport properties than Silicon with the potential to further augment electronic device speeds. The talk next covered his work on light emission from Cadmium Selenide (CdSe) and details of how ultrafast spectroscopy-aided study of electron-phonon coupling helped unveil the mechanism of efficient upconversion in two-dimensional perovskites.  

Following Prof Liu Xinfeng’s interesting seminar, Assoc Prof Zhang Qing (Peking University, School of Materials Science and Engineering) detailed her work on developing low-threshold micro/nano lasers. Low-power on-chip micro/nano lasers are key in realising integrated photonic components. However, losses increase disproportionately upon scaling to lower dimensions. Assoc Prof Zhang then explained how her work on understanding light-matter interactions has helped achieve energy-efficient polaritonic devices based on halide-perovskites. She then unveiled her work on developing continuous wave (CW) optically pumped perovskite lasers with record low areas. Building on this, her group’s work on developing room temperature CW optically pumped polariton condensation featuring lead halide perovskite-based semiconductors was presented.

A captivated audience listening with keen interest to the insightful presentations by Prof Liu (left) and Assoc Prof Zhang (right).

In the final segment, an engaging question-and-answer session ensued where students probed the two speakers with various enquiries of their intriguing endeavours in developing efficient devices. Both professors readily addressed all these questions which ranged from interpreting ultrafast spectroscopy results to queries on achieving on-chip lasing. Given how both the speakers were accomplished alumni of NTU, the Director of IAS, Prof Sum Tze-Chien asked them to advise the attendees on achieving similar success in research. Both speakers stressed upon the importance of hard-work, dedication, and mindfulness. They emphasised how understanding what doesn’t work helps attain a clearer picture of the underlying science.

The lively colloquium helped the audience gain profound insights into the intricate world of light-matter interaction. Through the engaging discussions with Prof Liu and Assoc Prof Zhang, the colloquium kindled the audience's enthusiasm for both light-matter interaction and focused research. 

Memorable snapshot of the audience alongside the speakers.

"Learning about advancements in a different field of study is captivating." - Lock Wen Hao Daniel (PhD Student, MSE)

"The research subjects are interesting." - Alhassan Moses Onu-Ogwu (PhD Student, IGP-Collaborative Initiative)

"The discussion on future work directions is intriguing." - Goh Si Heng (PhD Student, MAE)

Watch the Video recording.

Written by Navaratna Nikhil (SPMS Graduate Students' Club)