Light possesses orbital angular momentum (OAM) and spin angular momentum (SAM) arising from its helical wavefront and helical electric field . The OAM of light enables us to twist a variety of irradiated materials with the aid of the spin angular momentum of light, so as to create various helical structures . To date, we and our co-workers have demonstrated the formation of helical surface relief in azo-polymers, exhibiting trans-cis isomerization , by illumination of a visible optical field with OAM, so-called optical vortex . Nonlinear optical phenomenon, such as two-photon-absorption (TPA) process, has always been offering us new fundamental and advanced sciences, for instance, 3-dimentional micro/nanofabrication, however, most studies of surface relief formation in azo-polymers are still based on single-photon-absorption (SPA). In this presentation, we report on the TPA induced chiral surface relief formed in an azo-polymer film by the illumination of picosecond near-infrared optical vortex pulses.
© 2019 Japan Society of Applied Physics, The Optical Society (OSA)PDF Article