Abstract
We report an unexpected nonphotothermal material organization induced by
continuous-wave visible laser light at low power levels. This effect is
observed along the laser beam propagation direction in fully transparent
entangled solutions of common homopolymers featuring sufficiently high
molecular mass and optical anisotropy along the chain backbone. The
resulting formation of long-lived stringlike or dotlike patterns on the
micrometer scale, probed by dark-field coherent imaging, depends on the
molecular mass, architecture, solvent nature, and polymer concentration.
Electrostrictive and alignment forces as well as chain cooperativity are
responsible for the osmotic compression of the polymer solute.
Subsequent waveguiding effects induce autoamplification and pattern
writing upon prolonged illumination. This wave-medium coupling could
potentially lead to photorefractive, microoptics, and nanotechnology
applications.