A simple and efficient interference method for fabricating highly symmetric two-dimensional (2-D) quasi-periodic structures (QPSs) is theoretically and experimentally demonstrated. With a three-beam interference technique, one can fabricate a periodic 2-D structure having sixfold symmetry. When this structure is multiduplicated into other specific orientations its combination results in a QPS with multifold symmetry. By use of n exposures with a rotation angle of 60 degrees /n, one can create a 2-D QPS with six n-fold symmetry. The QPS with a super high symmetry level, as high as 60-fold, is demonstrated for the first time to the best of our knowledge. The diffraction pattern of a QPS is consistent with the Fourier transform calculation. The fabricated structures should be useful for many applications, such as isotropic bandgap materials and extraction enhancement of light-emitting diodes.
"The fabrication also employs the multiple-exposure idea but it is applied to three-beam interference technique (Lai et al., 2006b). The fabrication of quasi-periodic structures with a rotation symmetry as high as 60-fold is demonstrated and confirms the theoretical calculation (Lai et al., 2007). Moreover, we calculate the optical property of fabricated quasi-periodic structures and demonstrate that PQC possesses an isotropic PBG that could not be achieved with traditional PCs. "
[Show abstract][Hide abstract] ABSTRACT: A naturally-inspired phase-only diffractive optical element with a circular symmetry given by a quasi-periodic structure of the phyllotaxis type is presented in this paper. It is generated starting with the characteristic parametric equations which are optimal for the golden angle interval. For some ideal geometrical parameters, the diffracted intensity distribution in near-field has a central closed ring with almost zero intensity inside. Its radius and intensity values depend on the geometry or non-binary phase distribution superposed onto the phyllotaxis geometry. Along propagation axis, the transverse diffraction patterns from the binary-phase diffractive structure exhibit a self-focusing behavior and a rotational motion.
[Show abstract][Hide abstract] ABSTRACT: For the fabrication of periodic microstructures, a high-precision and highly efficient polarization-controlled three-beam interference technology (PoTBI) has been developed. With the theory of superposition of multiple laser beams, simulations on the influence of polarization upon the intensity distribution in the overlapped area have been carried out. By controlling the polarization of the interfering beams, various intensity patterns can be obtained. An optical setup for PoTBI has been realized and used to generate microstructures in polyimide foil. Micro cavities, micro bumps, eye-like cavities and rectangular columns of hexagonal symmetry and one-dimensional lines are produced. Compared with other multi-beam interference technologies, different surface textures of hexagonal symmetry with the same periodicity can be obtained only by changing the polarization status of the interfering beams without changing the geometrical interference setup. Thus, PoTBI provides a simply tunable texturing technology with a wide range of applications in surface structuring.
Journal of Micromechanics and Microengineering 08/2010; 20(9):095004. DOI:10.1088/0960-1317/20/9/095004 · 1.73 Impact Factor
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