Keigo Masuda

Azo-polymer film twisted to form a helical surface relief by illumination with a circularly polarized Gaussian beam

A helical surface relief can be created in an azo-polymer film simply by illuminating circularly polarized light with spin angular momentum and without any orbital angular momentum. The helicity of the surface relief is determined by the sign of the spin angular momentum. The illumination of circularly polarized light induces orbital motion of the azo-polymer to shape the helical surface relief as an intermediate form; a subsequent transformation to a non-helical bump-shaped relief with a central peak creates a final form with additional exposure time. The mechanism for the formation of such a helical surface relief was also theoretically analyzed using the formula for the optical radiation force in a homogeneous and isotropic material.

Optical vortex induced chiral mass-transport of azo-polymer through two photon absorption

We discover that 1.06 μm picosecond vortex pulses induce chiral mass-transport to form a single-armed chiral surface relief in azo-polymer through two photon absorption process. The surface relief exhibits a diameter of a 2.5μm, i.e. 0.7 times of diffraction limit.

Shrinking optical vortex to the nanoscale

Optical beams with Orbital Angular Momentum (OAM) can potentially be used to probe forbidden transitions. However, the size of the vortex beam has to be comparable to that of an atom, molecule or an artificial atom. We propose and demonstrate a de-magnifying hyperlens allowing reducing the size of the vortex beam to the nanometer scale.

Circularly polarized lights twist azo-polymer to form helical surface relief

We discovered that a helical surface relief can be created in azo-polymer film merely by the irradiation of circularly-polarized light without any orbital angular momentum. The chirality of the surface relief was also determined by the handedness of the circular polarized light.