Seminar: Disordered Structures and Their Applications

Dr. Zhiwen Liu, professor of electrical engineering at Penn State, will be the speaker.

Abstract:

Applications of passive and active disordered optical structures realized in particle assembly platform will be discussed. A layer of random particles can behave as an imaging encoder, transforming a point source into a scattering pattern. The scattering pattern of an object, being a linear superposition of patterns created by all its constituent point sources, can be inverted to reconstruct its image. Our recent work by using random assembly of nanowires to achieve lensless imaging will be presented, which can achieve a large angular field of view of about ±45°.

We also show that a multi-shot approach implemented by using dynamic particle assembly can significantly improve the reconstruction quality. Disordered structures with gain can result in random lasing, which exploits multiple scattering to trap and amplify light without the use of an ordinary laser cavity.

Recently we have demonstrated the ability to control disorder in a nanoparticle platform for controlling random lasing and tuning the emission characteristics. We control anisotropic nanowire orientation by alternating current electric field to dynamically engineer the collective scattering within gain media. Random lasing intensity improvement of nearly 20X is observed with aligned particle orientation. Both experimental results and simulations will be discussed.

Biography:

Dr. Zhiwen Liu is a professor of electrical engineering at Penn State. He received his Ph. D. degree in electrical engineering from the California Institute of Technology in 2002. After staying at Caltech for a year as a postdoctoral researcher, he joined Penn State in 2003. His current research at Penn State is focused on optical imaging and spectroscopy, ultrafast nonlinear optics, and nano-photonics.

Dr. Liu chairs the SPIE conference on Ultrafast Nonlinear Imaging and Spectroscopy as part of the SPIE Optics and Photonics, annually held in San Diego. He is an associate editor for the Photonics Research journal.