Width Dependence of Inherent TM-Mode Lateral Leakage Loss in Silicon-On-Insulator Ridge Waveguides

Abstract

We report the first experimental observation in the optical domain of a dramatic width-dependent lateral leakage loss behavior for the TM-like mode of tight vertical confinement ridge waveguides formed in silicon-on-insulator. The lateral leakage loss displays a series of sharp cyclic minima at precise waveguide widths, and appears to be inherent to waveguide geometries of central importance to a wide variety of active devices in silicon photonics requiring lateral electrical access. This behavior is not predicted by the often-used effective-index-based methods, but is understood phenomenologically and also compared to prior numerical analysis and predictions of leaky mode behavior. It is shown that TM-like mode operation, critical to the operation of some active component designs, will require precision control of waveguide dimensions to achieve high performance.

Efficient Coupling between Dielectric-Loaded Plasmonic and Silicon Photonic Waveguides

“…S2, obtained at a coupling angle of θ = -26.5°, the extinction ratio for the SOI ring-resonator whispering-gallery modes is largest near λ = 1550 nm, where the "magic-width" condition is satisfied. 4 The loaded resonator quality factor for the resonance centered near λ = 1549.5 nm is 94,000. By accounting for coupling loss, the intrinsic quality factor due to propagation loss, Q int , can be determined.…”

Experimental demonstration of TM lateral leakage in a standard SOI photonics platform

“…This depends strongly on the relative thicknesses of the waveguide core and the etched side cladding. Previous demonstrations of this phenomenon have relied on very shallow patterning (15 nm) of the rib waveguides, using a local oxidation process [1]. In this paper, we demonstrate this effect in a standard silicon photonics platform and provide a quantitative characterisation.…”

“…High-contrast rib waveguides exhibit a peculiar loss behaviour for the TM polarisation, with a strong dependence on waveguide width (w) [1]. Within the rib waveguide the TMlike mode has in-plane E-field components at the sidewalls, which gives rise to a non-zero overlap with the TE modes in the cladding.…”

“…Shallowly etched ridge silicon-on-insulator (SOI) waveguides operating in TM polarisation exhibit lateral leakage effects [1] in which the power of the guided TM mode couples laterally into cladding TE slab modes propagating at a particular angle to the waveguide axis [1], [2]. Instead of viewing this lateral leakage as loss, it can be engineered for new photonic device topologies [3].…”

“…Instead of viewing this lateral leakage as loss, it can be engineered for new photonic device topologies [3]. Previous demonstrations of lateral leakage waveguides rely on exotic and potentially non-CMOS compatible fabrication processes [1].…”