▎ 摘　　要

Electronics circuits keep shrinking in dimensions, as requested by Moore's law. In contrast, photonic waveguides and circuit elements still have lateral dimensions on the order of the wavelength. A key to make photonics have a microelectronics-like development is a drastic reduction of size. To achieve this, we need a low-loss nanoscale waveguide with a drastically reduced mode area and an ultra-high effective refractive index. For this purpose, we propose here several low-loss waveguide structures based on graphene nano-ribbons. An extremely small mode area (similar to 10(-7)lambda(2)(0), one order smaller than the smallest mode area of any waveguide that has ever been reported in the literature; here lambda(0) is the operating wavelength in vacuum) and an extremely large effective refractive index (several hundreds) are achieved. As a device example, a nano-ring cavity of ultrasmall size (with a diameter of similar to 10(-2)lambda(0)) is designed. Our study paves the way for future VLSI (very-large-scale integration) optoelectronics. (C)2013 Optical Society of America