Experimental Soft Condensed Matter Group Professor David A. Weitz Division of Engineering and Applied Sciences Department of Physics Harvard University
Transverse patterns in class-B broad area lasers 


  • Time-resolved dynamics of two-dimensional patterns 
  • Evolution of the correlation between orthogonal polarization patterns
  • Dynamis transition form modelike patterns to turbulent like patterns

Transverse patterns in a CO2 class-B broad area laser
We are interested on studying the mechanism which gives rise to the spatial distribution of the electromagnetic field in the plane orthogonal to the direction of propagation of the light. In large aperture lasers pattern formation becomes almost boundary-free, and it is dominated by bulk parameters and nonlinearities of the active medium.

In particular, we have reported the first experimental observation of the fast dynamics of 2D transverse patterns. We have used a TEA pulsed CO2  broad area laser with Fresnel number ~ 10. The transverse pattern is formed by laser emission bright peaks (optical filaments) which are aperiodically flashing in time with different growing rates. The lifetime of these optical filaments is around 2 ns.

Pairs of consecutive instantaneous patterns separated by different time delays
The transmitted pattern (left) is recorded a time td before than the reflected pattern (right).

For small time delays, there are many common filaments (high spatio-temporal correlation)
small delay

When increasing time between consecutive patterns they become more dissimilar without any common filaments (loss of spatio-temporal correlation)
large delay


setup

Collaborators within the Optics Department  UCM Laser Physics Group

Oscar G. Calderón, Departamento Optica, UCM
Eduardo Cabrera,
Departamento Optica, UCM
Fernando Encinas-Sanz, Departamento Optica, UCM
Jose Manuel Guerra,
Departamento Optica, UCM


Publications 
Proceedings: International Meetings

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