Pattern Formation in Homogeneous Polymer Solutions Induced by a Continuous-Wave Visible Laser

Science  05 Jul 2002:
Vol. 297, Issue 5578, pp. 67-70
DOI: 10.1126/science.1071930

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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.

  • * Present address: Max Planck Institute of Colloids and Interfaces, Am Muehlenberg 1, 14476 Golm, Germany.

  • To whom correspondence should be addressed. E-mail: fytas{at}

  • Present address: National Hellenic Research Foundation–Theoretical and Physical Chemistry Institute, 48 Vas. Constantinou Avenue, 11635 Athens, Greece.

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