Microphotonics devices based on silicon microfabrication technology

This work presents our recent progress in the development of an Si wire waveguiding system for microphotonics devices. The Si wire waveguide promises size reduction and high-density integration of optical circuits due to its strong light confinement. However, large connection and propagation losses had been serious problems. We solved these problems by using a spot-size converter and improving the microfabrication technology. As a result, propagation losses as low as 2.8 dB/cm for a 400/spl times/200 nm waveguide and a coupling loss of 0.5 dB per connection were obtained. As we have the technologies for the fabrication of complex, practical optical devices using Si wire waveguides, we used them to make microphotonics devices, such as a ring resonator and lattice filter. The devices we made exhibit excellent characteristics because of the microfabrication with the precision of a few nanometers. We have also demonstrated that Si wire waveguides have great potential for use in nonlinear optical devices.

I. Introduction

An Si wire waveguide based on the silicon-on-insulator (SOI) structure is a promising platform for highly integrated, ultrasmall optical circuits or microphotonics devices, which are required for future optical network systems [1] [2]–[5]. Si/ waveguides achieve strong light confinement because of the large refractive-index difference between Si and (). The large makes possible core sizes of less than a micrometer, which can provide single-mode propagation at a wavelength of 1.5 . Moreover, the strong confinement allows sharp bends with radii of just a couple of micrometers. Therefore, Si wire waveguides should enable us to make optical circuits that are significantly smaller and have a higher integration density than would be otherwise possible. And it may also be possible to integrate Si wire waveguides with Si electronic circuits because both can be made on an SOI substrate. This could lead to new functional optical devices that are controlled electronically. Another feature of Si wire waveguides is their high power density due to the strong confinement. Even a 50-mW laser diode can yield a power density of 100 . Si wires might become a platform for nonlinear optical devices. In addition, the matured fabrication technologies and high-quality substrates for Si microelectronic devices can be used to make Si wire systems. This is a great advantage in the development of the Si wire waveguide system.