Sune Svanberg
Title:Laser spectroscopy applied in environmental, ecological, and biomedical
Abstract: Laser spectroscopy provides many powerful approaches to areas strongly influencing human daily life. Non-intrusive monitoring can be pursued locally and by remote sensing. Examples from the environmental, ecological, and biomedical fields will be given: Air pollution mapping, monitoring of flying insects and fighting antibiotic resistance.
Biography: Sune Svanberg obtained his PhD from University of Gothenburg in 1972, and is since 1980 professor of physics at Lund University, Lund, Sweden. During 30 years, he was head of the Atomic Physics Division, and during 20 years director of the Lund Laser Centre. Since 2011 he is also a distinguished professor at South China Normal University, Guangzhou. He holds 9 honorary doctor/professor appointments, is member of 6 scientific academies, a fellow of 5 learned societies, and received numerous national and international awards. He served on many boards and committees, including a 10-year membership of the Nobel Committee for Physics of the Royal Swedish Academy of Sciences. Based on a long career in basic atomic spectroscopy and high-power laser/matter interactions, his current research interests focus on laser spectroscopic applications to the environmental, ecological and biomedical fields.
Zhongtao Cheng
Title: The control and sensing of optical field in scattering media
Abstract: In contrast to clear optical media in which light travels in a deterministic way, complex media with microscopic refractive index inhomogeneity, such as biological tissues and polluted atmosphere, can scramble the information of light randomly. The scattering characteristic of light is a double-edged sword. In some applications, we need to overcome the optical scattering in order to recover the correct information carried by light while somewhere the optical scattering may be used as an important mechanism to infer the status of the scattering source. In this talk, I will introduce some cutting-edge techniques for flexible control and sensing of optical field in scattering media. I will first talk about wavefront shaping (WFS) techniques, which are used to conquer the optical scattering. WFS can help to focus light into and through scattering media, thus it has opened new avenues to breaking the optical diffusion limit in applications such as biomedical optical imaging, optical manipulation, optical stimulation, and optical therapy. Then I will talk about a technique that takes advantages of the scattered light from atmosphere to remotely sense the optical properties of the atmospheric aerosols, which is called high-spectral-resolution lidar. We will see that, in both kinds of techniques, interferometry plays very important roles in addressing these scattering problems.
Biography: Dr. Zhongtao Cheng is a postdoc in Prof. Lihong V. Wang’s group at Caltech. In 2017, he received his PhD in optical engineering at Zhejiang University, under the mentorship of Prof. Dong Liu. He is interested in developing systems and instruments for high-precision optical measurement and sensing based on fundamental properties of light such as interference, diffraction, scattering, polarization, etc. One specific interest is to developing wavefront shaping techniques to break the optical diffusion limit of the operating depth of optical techniques. He also researches on laser remote sensing techniques for detecting the optical parameters of atmospheric aerosols, which is a helpful tool for studying the environment and climate of the earth.
Yin Liu
Title: Helical van der Waals crystals with a tunable twist
Abstract: Twisted van der Waals materials with rotational stacking of two-dimensional materials have attracted tremendous attention in recent years. The twist angle strongly affects the electronic states, excitons and phonons of the twisted structures through interlayer coupling, giving rise to exotic optical, electric, excitonic and spintronic behaviors. Theoretical studies suggest that these twist-induced phenomena are common to layered materials such as transition-metal dichalcogenides, black phosphorus and germanium selenide. The ability to manipulate the twisting topology of van der Waals structures offers a new degree of freedom through which to tailor their electrical and optical properties. Twisted van der Waals materials are usually created using mechanical exfoliation and a transfer-stacking method, but limitations exist to extend this method to a variety of two-dimensional materials. In contrast, bottom-up growth methods could provide an alternative means to create twisted van der Waals structures. In this talk, I will present the bottom-up synthesis of twisted van der Waals materials with a tunable twist at both the nanoscale and the microscale. The formation of twisted van der Waals materials is driven by the Eshelby twist associated with a screw dislocation in a vdW nanowire. Key features of the twist including twisting profiles, twist angles, twist rate and period can be tuned in the growth. The twisted crystal with a single screw dislocation provides a desirable model system for understanding the interaction of phonons, electrons and ions with the screw dislocation.
Biography: Yin Liu is a postdoc researcher working for professor Jennifer Dionne in the department of materials science and engineering in Stanford University. He received his B.S. and M.S from Zhejiang University and his Ph.D from University of California Berkeley. His current research is focused on the single photon emitters in the 2D materials. His doctoral thesis work is centered on synthesis and characterization of twisted van der Waals material, which was recognized with a 2019 Materials Research Society Graduate Student Award.