Large photo-induced index variations in chalcogenide-on-silicon waveguides

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Nanotechnology

Background:

• Silicon photonics offers advanced optical functionalities but often requires precise postfabrication tuning.
• Existing methods for modifying waveguide properties can be complex or limited in scope.
• Controlling group delay is crucial for optimizing the performance of photonic integrated circuits.

Purpose of the Study:

• To propose and experimentally validate a novel method for postfabrication modification of group delay in silicon-photonic waveguides.
• To investigate the use of photosensitive chalcogenide glass for localized material removal.
• To demonstrate the application of this technique for tuning the spectral response of photonic devices.

Main Methods:

• Utilized a photosensitive As₁₀Se₉₀ chalcogenide glass as an upper cladding layer on silicon-on-insulator waveguides.
• Employed intense green light illumination to induce localized mass transfer and material removal from the cladding.
• Characterized the resulting changes in group delay and the free spectral range of a Mach-Zehnder interferometer.

Main Results:

• Achieved up to 2% group delay variation through photo-induced cladding modification.
• Demonstrated localized removal of the chalcogenide glass cladding from the waveguide core.
• Modified the free spectral range of a chalcogenide-on-silicon Mach-Zehnder interferometer by 1%.

Conclusions:

• The proposed photo-induced material removal technique enables effective postfabrication adjustment of group delay in silicon-photonic waveguides.
• This method provides a precise and localized approach for tuning the frequency response of photonic filters and interferometers.
• The technique holds promise for adaptable and reconfigurable silicon-photonic devices.