OAM-induced chiral surface relief in azo-polymer via two-photon absorption

Azo-polymer exhibits mass-transport through cis-trans photo-isomerization by irradiation of visible light, so as to establish a surface relief [1]. To date, we have discovered that azo-polymer film is deformed to shape a spiral surface relief (‘OAM-induced chiral surface relief’) on micro-scale by illumination of a cw green optical vortex beam, in which orbital angular momentum (OAM) of the vortex beam twists the azo-polymer [2-3]. In recent years, surface relief formation in the azo-polymer film via two-photon absorption process by illumination of tightly focused femto-/pico- second pulses has been reported to create structures on a na-noscale beyond the diffraction limit [4].