Demonstration of submicron square-like silicon waveguide using optimized LOCOS process

Abstract

We demonstrate the design, fabrication and experimental characterization of a submicron-scale silicon waveguide that is fabricated by local oxidation of silicon. The use of local oxidation process allows defining the waveguide geometry and obtaining smooth sidewalls. The process can be tuned to precisely control the shape and the dimensions of the waveguide. The fabricated waveguides are measured using near field scanning optical microscope at 1550 nm wavelength. These measurements show mode width of 0.4 µm and effective refractive index of 2.54. Finally, we demonstrate the low loss characteristics of our waveguide by imaging the light scattering using an infrared camera.

Low-loss photonic wires defined by local oxidation of silicon (LOCOS)

“…The LOCOS method utilizes a protective stack, consisting of a thin thermal pad oxide layer overlaid by a thicker LPCVD silicon nitride, to mask the waveguides during the growth process of the field oxide. Similar processes have been reported to make rib [8][9][10][11] and square-like [12] silicon waveguides. The estimated propagation loss ranges from 0.35 dB/cm to 2 dB/cm, with a minimum dimension of 300 nm (FWHM) × 85 nm (height).…”

Ultrahigh-Q silicon resonators in a planarized local oxidation of silicon platform

“…Furthermore, CMP makes use of a mechanical force to remove the material, and thus may result in strain and cracks in the polished layer. As an alternative, we propose and demonstrate the use of local oxidation of silicon (LOCOS) [4][5][6] combined with a preliminary short etching step in order to achieve planar silicon structures. As a by-product, the scattering loss of the fabricated devices is drastically reduced, allowing for optical resonators with ultrahigh quality factors (Q factors) to be achieved.…”

Experimental demonstration of locally oxidized hybrid silicon-plasmonic waveguide

“…Implementation of the LOCOS technique is compatible with standard CMOS technology and enables integration of optical components onto silicon-on-insulator ͑SOI͒ substrate with thin buried oxide layer ͑BOX= 70 nm͒ currently used in modern electronics. 21 The LOCOS process can be tuned to precisely control the shape and the dimensions of the waveguide 22 and it allows avoiding lateral misalignment between the high index silicon waveguide and the metal surface. After the fabrication, we directly measured the propagation and coupling loss of the hybrid waveguide using near-field scanning optical microscope ͑NSOM͒.…”