OMITEC: Photopolymerization - Long and narrow polymer fibers or hollow cylinders

Photopolymerization of long and narrow fibers or hollow cylinders

We used zero-order Bessel beam to fabricate a homogeneous polymer fiber as narrow as 2 μm and as long as centimeters. The constant diameter of the fiber along all its length is done by the propagation invariant properties of the Bessel beam. The length of the fiber is determined by the maximum propagation distance of the Bessel beam which is much longer than the classical Gaussian beam of comparable width.

Experimental set-up

The incident Gaussian beam of half-width w passes through an axicon with apex angle α and is transformed to the Bessel beam existing over a distance z_max. Telescope made of lenses L1 and L2 scales down the original Bessel beam radius and the maximal BB propagation distance z_maxto new values z'_maxin the air and z'_maxpinside the cuvette filled with liquid optical glue.

Examples of the fabricated fibres for different Bessel beam diameters 2rB are shown in the following figure.

Surprisingly, the length of the polymer fiber Lfiber is longer than the region zmax where the Bessel beam exists. Therefore we prepared short Bessel beam so that all the axial region of its existence could be seen by CCD. We observed self-writing effect when the polymerized part of the fiber serves as a waveguide and enables grow of the fiber on its end. (see also MOVIE)

If the laser power was higher than certain limit, chaotic fiber growth occured even in backward direction

Photopolymerization of hollow cylinders

We created hollow fibers by revolving the single Bessel beam around an axis parallel to the Bessel beam propagation. In this case the Bessel beam passed through rotating slightly tilted plan-parallel plate. The width of the polymer fiber wall was determined by the diameter of the Bessel beam core (2 micrm) and the inner diameter of the hollow fiber was defined by the tilt of the plan-parallel plate.