Ultrasmall all-optical switch in a single silicon nanostructure

Yu-Lung Tang^1*, Yi-Shiou Duh¹, Yusuke Nagasaki², Pan-Han Wu¹, Hao-Yu Cheng³, Te-Hsin Yen¹, Kentaro Nishida^2,4, Ikuto Hotta², Katsumasa Fujita^2,4, Chih-Wei Chang⁷, Kung-Hsuan Lin³, Junichi Takahara^2,8, Shi-Wei Chu^1,9

¹Physics, National Taiwan University, Taipei, Taiwan
²Graduate School of Engineering, Osaka University, Suita, Japan
³Institute of Physics, Academia Sinica, Taipei, Taiwan
⁴AIST-Osaka University Advanced Photonics and Biosensing Open Innovation Laboratory, Osaka University, Suita, Japan
⁵Institute of Photonic System, National Chiao Tung University, Tainan, Taiwan
⁶Institute of Imaging and Biomedical Photonics, National Chiao Tung University, Tainan, Taiwan
⁷Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
⁸Photonics Centerr, Graduate School of Engineering, Osaka University, Suita, Japan
⁹Molecular Imaging Center, National Taiwan University, Taipei, Taiwan

* Presenter:Yu-Lung Tang, email:r08222024@ntu.edu.tw

Integrated optical modulator with large modulation depth, high modulation speed, small footprint and low energy consumption is the key missing element for all-silicon-based photonics circuits1. However, it is challenging to create silicon-based all-optical switch owing to its relatively weak nonlinear optical properties. All-optical switch in silicon have been achieved by using watt-level high power in non-planar structures2 or using cavity effects on micrometers sized structures3. Nonetheless, none of them can compete with the current electronic transistor. In this work, we discover, by shrinking down the volume of Si resonator to ~10-3 μm3, a giant photothermal nonlinearity that yields 400% reversible and repeatable deviation from linear scattering response at milliwatt low excitation power. The underlying mechanism is Mie resonance of the high-index material combine with high-efficiency heating in the thermally isolated nanostructure. Due to its ultrasmall size, the thermal relaxation time reaches nanosecond, implying modulator speed at GHz. This silicon-based optical modulator, with advantages of large modulation depth, high modulation speed, ultrasmall footprint and low operation power, can enable all-silicon-based photonics circuit on one chip.

Keywords: Silicon photonics, All-optical switch, Photonics circuits, Ultrafast Photothermal nonlinearity, Ultrasmall modulator