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Xiao Wu, Thi Thanh Ngan Nguyen, Isabelle Ledoux-Rak, Chi Thanh Nguyen, Ngoc Diep Lai, Appl. Phys. B - Laser and Optics 107, 819-822 (2012)
An efficient method is demonstrated to improve the formation of a surface relief grating (SRG) with a high amplitude. The SRG is realized by a two-beam interference technique (532 nm) in an azobenzene side-chain copolymer. An UV laser beam (355 nm), called assisting beam, was used to accelerate the photoisomerization process from cis-form to trans-form, resulting in a rapid cis-form - trans-form cycle. This UV beam-assisted method allowed to increase the diffraction efficiency of the formed SRG as well as its depth. Stable gratings with modulation depth as high as 410 nm were obtained at room temperature with moderate laser power