title: Spatially graded TiO₂-SiO₂ Bragg reflector with rainbow-colored photonic band gap.
abstract: A simple single-step method to fabricate spatially graded TiO2-SiO2 Bragg stack with rainbow colored photonic band gap is presented. The gradation in thickness of the Bragg stack was accomplished with a modified glancing angle deposition (GLAD) technique with dynamic shadow enabled by a block attached to one edge of the rotating substrate. A linear gradation in thickness over a distance of about 17 mm resulted in a brilliant colorful rainbow pattern. Interestingly, the photonic band gap position can be changed across the whole visible wavelength range by linearly translating the graded Bragg stack over a large area substrate. The spatially graded Bragg stack may find potential applications in the tunable optical devices, such as optical filters, reflection gratings, and lasers.
authors.forename: Dhruv Pratap
authors.initials: DP
authors.lastname: Singh
authors.forename: Seung Hee
authors.initials: SH
authors.lastname: Lee
authors.forename: Il Yong
authors.initials: IY
authors.lastname: Choi
authors.forename: Jong Kyu
authors.initials: JK
authors.lastname: Kim