Abstract
Submicron tantalum pentoxide ridge and channel optical waveguides and microring resonators are demonstrated on silicon substrates by selective oxidation of the refractory metal, tantalum. The novel method eliminates the surface roughness problem normally introduced during dry etching of waveguide sidewalls and also simplifies fabrication of directional couplers. It is shown that the measured propagation loss is independent of the waveguide structure and thereby limited by the material loss of tantalum pentoxide in waveguides core regions. The achieved microring resonators have cross-sectional dimensions of ~600 nm × ~500 nm, diameters as small as 80 µm with a quality, Q, factor of 4.5 × 10(4), and a finesse of 120.
Highlights
Integrated optical devices, based on microfabrication techniques, have been pursued for over four decades [1,2,3]
It is shown that the measured propagation loss is independent of the waveguide structure and thereby limited by the material loss of tantalum pentoxide in waveguides core regions
We believe that the demonstrated fabrication method allows low-cost and reliable integrated optical devices to be realized for the mentioned host of applications
Summary
Integrated optical devices, based on microfabrication techniques, have been pursued for over four decades [1,2,3]. Among other materials [12,13], oxides of refractory metals, such as tantalum (Ta), are perfect candidates for this purpose They are transparent in visible and infrared wavelengths and have high refractive indices of ~2.2, which allows fabrication of high-index contrast waveguides on low-index cladding layers, such as silicon dioxide (SiO2), on silicon substrates. A novel method for fabrication of high-contrast submicron waveguides based on selective oxidation of a refractory metal (SORM) is introduced. The method eliminates the sidewall surface roughness scattering and at the same time achieves submicron gaps between waveguides without the need of expensive lithographic and etching methods and allows demonstration of high-contrast and low-loss waveguides on silicon substrates. We believe that the demonstrated fabrication method allows low-cost and reliable integrated optical devices to be realized for the mentioned host of applications
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