Shamsul Abedin (Potma Group) and Yunpeng Xia (Ho Group) - CaSTL Seminar/Talks

Thursday, May 2, 2019 - 13:00
2201 Natural Sciences II | Live Zoom Meeting IBroadcast - MTG D#: 127 130 761
Shamsul Abedin UC Irvine (Potma Group) and Yunpeng Xia (Ho Group)
Event Title: 
1:00pm: Confined Optical Field Enhanced Fluorescence Emission | 1:30pm: Superradiance in Molecular Oligomers
CaSTL Center - V. Ara Apkarian, Director | Eric Potma and Wilson Ho (Group Member Resereach presentations)

Time: 1:00 PM

Shamsul Abedin (Potma Group)

Title: Confined Optical Field Enhanced Fluorescence Emission

Abstract: In this talk, Shamsul is going to discuss the development and application of a surface plasmon enhanced optical sensor that uses the two-photon excited luminescence of the gold film as the optical reporter signal. Light is coupled to the gold/sample interface, in a manner similar to surface plasmon resonance (SPR) sensors. The light emitted from the sensor surface is detected in the epi-direction by a far-field photodetector, which can be related to binding/unbinding of molecular targets. The novelty of the optical sensor is that the traditional CW laser used in SPR devices is replaced by a femtosecond source, allowing for the generation and detection of optical nonlinearities at the sensor surface. The binding events show up in the detector as diffraction limited spots. I will also discuss the performance of this sensor for real time measurement of DNA hybridization adsorption on planar gold surfaces.

Bio: Shamsul Abedin is a second year Chemical Engineering PhD student in Prof. Eric Potma’s research group at UC Irvine where he works on the development of surface plasmon enhanced optical sensors for label free detection of nanoscale particles facilitated by two-photon excited luminescence of gold films. He has received his B.S. in Chemical Engineering degree from Bangladesh University of Engineering and Technology in 2017.



Time: 1:30pm - Yunpeng Xia (Ho Group)

Title: Superradiance in Molecular Oligomers

Abstract: In this talk, Yunpeng is going to discuss some experimental and theoretical progresses on the optical properties of chains of chromophores. With STM manipulation, ZnPc oligomers of up to 12 sub-units is constructed one by one. The sub-nanometer-resolved photon maps of the superradiance modes suggest that coherence is well maintained in these multi-molecule systems and the exciton is delocalized on each sub-unit molecule. The time correlation measurement was carried out with a home-built Hanbury Brown and Twiss (HBT) set. The antibunching dips was observed in the second-order correlation functions, which reveal the single-photon behavior of the superradiance emission. This is the first observation of single-photon superradiance from a single molecular chain. Further analyses of the linewidth and the peak position with increasing number of sub-units shows expected results considering the exciton delocalization and the specificity of STML. Then, we study the emission behavior of the other collective modes of the oligomers apart from the superradiance mode. The luminescence patterns of these collective modes show the spatial distribution of the coupling of the dynamic transition dipoles. Yunpeng will also discuss about the vibrionic features of the STML spectra from an oligomer. Our results offer feasibility to design the molecular quantum systems.

Bio: TBA