%A Peng WANG, Aron MICHAEL, Chee Yee KWOK %T Silicon waveguide cantilever displacement sensor for potential application for on-chip high speed AFM %0 Journal Article %D 2018 %J Front. Optoelectron. %J Frontiers of Optoelectronics %@ 2095-2759 %R 10.1007/s12200-018-0774-4 %P 53-59 %V 11 %N 1 %U {https://journal.hep.com.cn/foe/EN/10.1007/s12200-018-0774-4 %8 2018-04-02 %X

This paper reviews an initial achievement of our group toward the development of on-chip parallel high-speed atomic force microscopy (HS-AFM). A novel AFM approach based on silicon waveguide cantilever displacement sensor is proposed. The displacement sensing approach uniquely allows the use of nano-scale wide cantilever that has a high resonance frequency and low spring constant desired for on-chip parallel HS-AFM. The approach consists of low loss silicon waveguide with nano-gap, highly efficient misalignment tolerant coupler, novel high aspect ratio (HAR) sharp nano-tips that can be integrated with nano-scale wide cantilevers and electrostatically driven nano-cantilever actuators. The simulation results show that the displacement sensor with optical power responsivity of 0.31%/nm and AFM cantilever with resonance frequency of 5.4 MHz and spring constant of 0.21 N/m are achievable with the proposed approach. The developed silicon waveguide fabrication method enables silicon waveguide with 6 and 7.5 dB/cm transmission loss for TE and TM modes, respectively, and formation of 13 nm wide nano-gaps between silicon waveguides. The coupler demonstrates misalignment tolerance of ±1.8 µm for 5 µm spot size lensed fiber and coupling loss of 2.12 dB/facet for standard cleaved single mode fiber without compromising other performance. The nano-tips with apex radius as small as 2.5 nm and aspect ratio of more than 50 has been enabled by the development of novel HAR nano-tip fabrication technique. Integration of the HAR tips onto an array of 460 nm wide cantilever beam has also been demonstrated.