Advanced Photonics, Vol. 2, Issue 3, 036001 (2020)
Subwavelength self-imaging in cascaded waveguide arrays
Wange Song1,2, Hanmeng Li1,2, Shenglun Gao1,2, Chen Chen1,2, Shining Zhu1,2, and Tao Li1,2,*
- 1Nanjing University, College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Integration, Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing, China
- 2Collaborative Innovation Center of Advanced Microstructures, Nanjing, China
Self-imaging is an important function for signal transport, distribution, and processing in integrated optics, which is usually implemented by multimode interference or diffractive imaging process. However, these processes suffer from the resolution limit due to classical wave propagation dynamics. We propose and demonstrate subwavelength optical imaging in one-dimensional silicon waveguide arrays, which is implemented by cascading straight and curved waveguides in sequence. The coupling coefficient between the curved waveguides is tuned to be negative to reach a negative dispersion, which is an analog to a hyperbolic metamaterial with a negative refractive index. Therefore, it endows the waveguide array with a superlens function as it is connected with a traditional straight waveguide array with positive dispersion. With a judiciously engineered cascading silicon waveguide array, we successfully show the subwavelength self-imaging process of each input port of the waveguide array as the single point source. Our approach provides a strategy for dealing with optical signals at the subwavelength scale and indicates functional designs in high-density waveguide integrations.
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