title: Dispersionless Manipulation of Reflected Acoustic Wavefront by Subwavelength Corrugated Surface.
abstract: Free controls of optic/acoustic waves for bending, focusing or steering the energy of wavefronts are highly desirable in many practical scenarios. However, the dispersive nature of the existing metamaterials/metasurfaces for wavefront manipulation necessarily results in limited bandwidth. Here, we propose the concept of dispersionless wavefront manipulation and report a theoretical, numerical and experimental work on the design of a reflective surface capable of controlling the acoustic wavefront arbitrarily without bandwidth limitation. Analytical analysis predicts the possibility to completely eliminate the frequency dependence with a specific gradient surface which can be implemented by designing a subwavelength corrugated surface. Experimental and numerical results, well consistent with the theoretical predictions, have validated the proposed scheme by demonstrating a distinct phenomenon of extraordinary acoustic reflection within an ultra-broad band. For acquiring a deeper insight into the underlying physics, a simple physical model is developed which helps to interpret this extraordinary phenomenon and predict the upper cutoff frequency precisely. Generations of planar focusing and non-diffractive beam have also been exemplified. With the dispersionless wave-steering capability and deep discrete resolution, our designed structure may open new avenue to fully steer classical waves and offer design possibilities for broadband optical/acoustical devices.
authors.affiliation: 1] Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics, Department of Physics, Nanjing University, Nanjing 210093, P. R. China [2] Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093, P. R. China.
authors.forename: Yi-Fan
authors.initials: YF
authors.lastname: Zhu
authors.affiliation: 1] Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics, Department of Physics, Nanjing University, Nanjing 210093, P. R. China [2] Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093, P. R. China.
authors.forename: Xin-Ye
authors.initials: XY
authors.lastname: Zou
authors.affiliation: Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics, Department of Physics, Nanjing University, Nanjing 210093, P. R. China.
authors.forename: Rui-Qi
authors.initials: RQ
authors.lastname: Li
authors.affiliation: Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics, Department of Physics, Nanjing University, Nanjing 210093, P. R. China.
authors.forename: Xue
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics, Department of Physics, Nanjing University, Nanjing 210093, P. R. China.
authors.forename: Juan
authors.initials: J
authors.lastname: Tu
authors.affiliation: 1] Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics, Department of Physics, Nanjing University, Nanjing 210093, P. R. China [2] Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093, P. R. China.
authors.forename: Bin
authors.initials: B
authors.lastname: Liang
authors.affiliation: 1] Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics, Department of Physics, Nanjing University, Nanjing 210093, P. R. China [2] Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093, P. R. China [3] State Key Laboratory of Acoustics, Chinese Academy of Sciences, Beijing 100190, P. R. China.
authors.forename: Jian-Chun
authors.initials: JC
authors.lastname: Cheng