Reports: UR652644-UR6: Experimentally Study Nonlinear Optics and Wave Dynamics in Colloidal Suspensions Study

Weining Man, PhD, San Francisco State University

The scientific objective of this project is to experimentally study nonlinear optics and wave dynamics in colloidal suspensions study. Since we received the funding in 2012, a series of experiments have been performed to explore the different nonlinear optical responses in various colloidal suspensions and other soft condensed matter systems. We focused on the demonstration of non-diffracting beams and self-induced transparency in colloidal systems.

In particular, the P.I. and her research group have created colloidal suspensions with tunable nonlinear optical responses by engineering the polarizabilities of the colloidal suspensions and varying the mixing ratio of different types of colloids. Together with their collaborators, the PI’s team designed and performed successful experiments in the following aspects. 1) The demonstration of optically induced self-focusing and enhanced transparency in colloidal suspensions with negative polarizabilities. 2) The demonstration of saturatable and stable nonlinear responses in colloidal suspensions with negative polarizabilities and unstable and non-saturatable responses in colloidal suspensions with positive polarizabilities. 3) The demonstration of phase-controlled attractive or repulsive actions between two non-diffracting beams in colloidal suspensions with negative polarizabilities. 4) The demonstration of enormous and tunable self-defocusing nonlinearity in nylon/M-cresol dispersions due to thermal effects. 5) The demonstration of stable non-diffracting dark soliton in nylon/M-cresol dispersions.

Another objective is to promote education and research of students at San Francisco State University, one of the nationally recognized minority institutions, in the fields of physical sciences and engineering. These objectives have also been fulfilled very well. Many undergraduate and graduate students received training in this project and two students are finishing their master’s degree thesis on this proposed project in fall 2013.

We are happy to report that, during the first project year, we have made significant progress in this funded project. Three conferences papers have been presented on leading peer-reviewed conference in the field, Conference on Lasers and Electro-Optics. One paper has been published in a top-rated refereed journal, Optics Letters, and another one is under review with Physical Review Letters. One more manuscript is to be submitted soon to Optics Material Express. Equally important is that several students supported by this grant have made remarkable contribution to the project. Overall, we have made significant progress in this project, with active participation of undergraduate and graduate students.

In the coming year, we will continue in these successful studies and focus on the following aspects:

1)                  Observing and explaining the phase transition between saturatable and non-saturatable nonlinearity in colloidal systems with mixed polarizabilities.

2)                  Observing and understanding the behaviors of various non-conventional beams (i. e. Vortex beams, Airy beams) in these new nonlinear soft-matter systems in order to control their propagations and interactions.

3)                  Studying dark soliton interactions in strongly self-defocusing non-linear media and exploring their applications.