Birefringence and optical power confinement in horizontal multi-slot waveguides made of Si and SiO2

Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA.
Optics Express (Impact Factor: 3.49). 07/2008; 16(12):8623-8. DOI: 10.1364/OE.16.008623
Source: PubMed


Through simulations and measurements, we show that in multi-slot thin film waveguides, the TM polarized modes can be confined mostly in the low refractive index layers of the waveguide. The structure consisted of alternating layers of a-Si and SiO(2), in the thickness range between 3 and 40 nm, for which the slots were the SiO(2) layers. Simulations were performed using the transfer matrix method and experiments using the m-line technique at 1.55 mum. The dependence of the birefringence and of the power confinement in the slots was studied as a function of the waveguide thickness, the Si and SiO(2) layer thicknesses, and the SiO(2) / Si layer thickness ratio. We find a large birefringence-a refractive index difference between TE and TM modes-as large as 0.8. For TM polarized modes, up to ~ 85% of the total power in the fundamental mode can be confined in the slots.

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