In Fig. 1 we show the experimental images for hexagonal honey-comb lattice with equal and opposite TCs and two different powers at the end of the nonlinear medium (ethylene-glycol dyed with DODCI). The images show clearly the rotation of the lattice with opposite TCs and the steady propagation of the other. Due to the self-defocusing the beam spreads out at higher power.
The observed periodic structure of the intensity distribution also induces periodic modulation of the refractive index of the medium. This modulation is sufficient to cause a perpendicularly propagating He-Ne laser beam to diffract. We belive that idea gives a new way for dynamic creation of two-dimensional photonic band-gap structures.
Experimental images of the vortex lattices at 10cm
propagation in the NLM. (a) - hexagonal lattice with alternative charges
for powers 10mW and 50mW. (b) - hexagonal lattice with equal charges
for the same powers. The insets in each image represents the
size and the orientation of the elementary cell of each lattice.
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