Effect of size and roughness on light transmission in a Si/SiO2 waveguide: Experiments and model

Abstract

In this letter, we experimentally evaluate the effect of miniaturization and surface roughness on transmission losses within a Si/SiO2 waveguide system, and explain the results using a theoretical model. Micrometer/nanometer-sized waveguides are imperative for its potential use in dense integrated optics and optical interconnection for silicon integrated circuits. A theoretical model was employed to predict the relationship between the transmission losses of the dielectric silicon waveguide and its width. This model accurately predicts that loss increases as waveguide width decreases. Furthermore, we show that a major source of loss comes from sidewall roughness. We have constructed a complete contour map showing the interdependence of sidewall roughness and transmission loss, to assist users in their design of an optimal waveguide fabrication process that minimizes loss. Additionally, users can find an effective path to reduce the scattering loss from sidewall roughness. Using this map, we confirm that nanometer-size silicon waveguides with 0.1 dB/cm transmission loss are possible with the currently available technology.

High-density waveguide superlattices with low crosstalk

“…3c can be attributed, in part, to the random light scattering between different waveguide modes due to sidewall roughness. Roughnessinduced scattering loss has been studied in single waveguides 37,38 . In a waveguide superlattice, scattering can cause crosstalk fluctuation or noise.…”

Silicon photonic waveguides for different wavelength regions

“…Annealing the sample in a high temperature and wet oxygen environment, oxidizes the porous silicon film and forms silicon dioxide. The oxidation process anneals lattice damage, and smoothes the sidewall at the same time [36]. The oxide can be left as a cladding or subsequently removed in buffered HF [37].…”

Development of microfabricated TiO2 channel waveguides

“…Since the coupled higher-order modes have strong distributions in intensity at the interface between a core and a cladding, the higher-order modes are sensitive to surface roughness and rapidly attenuate. However, considering the loss by surface roughness for an Si channel waveguide, 24 contribution of the surface scattering is not ignorable but small for the waveguide of 10 μm width. Therefore, the present loss would be mainly due to the imperfection of the TiO 2 film.…”