Light induced shock wave interaction in opaque suspensions

TYPE	Solid State Institute Seminar
Speaker:	Mr. Yoav Hazan
Affiliation:	Physics Department and Solid State Institute, Technion
Date:	29.06.2016
Time:	12:30 - 13:30
Location:	Solid State Auditorium(Entrance)
Presentation:

Abstract:

To date, almost all the research in optofluidics and optical manipulation of particles in fluids is limited to
the regime of dilute suspensions, where the light field is easily manipulated deep within the fluid because
the suspension is so dilute that scattering can be neglected altogether. In fact, optical manipulation of
particles in opaque suspension was considered impossible up until 2013, when a former student in our group
has demonstrated optically-induced shock-fronts of nanoparticles propagating deep within the opaque
suspension, and light-induced phase transition in the regions where light has created very large concentration
of nanoparticles and transformed the suspensions to a gel. That work has opened the door to the investigation
of light-fluid interaction in opaque fluids.
I will present experiments studding the nonlinear interaction-collision between two light-induced shock
waves of nano-particles in highly scattering (opaque) suspensions. I will show that such collisions give rise
to the formation of gel domain walls between the shock waves. The interaction is dominated by the lateral
offset between the input beams and their optical power. The interaction of the beams with a lateral offset
creates shock-fronts, which transforms into unidirectional circulation whose direction is determined by the
lateral offset. For a centered heads-on collision interaction, the shock waves give rise to a long-lived
transverse domain wall, which is sensitive to very small asymmetry in the input beams.