Athermal Silicon-on-insulator ring resonators by overlaying a polymer cladding on narrowed waveguides

Area of Science:

• Photonics
• Materials Science
• Optical Engineering

Background:

• Silicon photonics offers miniaturization and high-volume manufacturing potential.
• Temperature fluctuations impact the performance of silicon photonic devices, particularly ring resonators.
• Achieving athermal operation is crucial for reliable silicon photonic integrated circuits.

Purpose of the Study:

• To experimentally demonstrate athermal silicon ring resonators.
• To investigate the effect of polymer cladding on the thermal stability of silicon ring resonators.
• To determine the optimal waveguide dimensions for athermal operation.

Main Methods:

• Fabrication of silicon-on-insulator (SOI) waveguides with a height of 220 nm.
• Narrowing of silicon wires to an ideal width of approximately 350 nm for TE mode.
• Overlaying a polymer cladding layer on the narrowed silicon waveguides.
• Characterization of the wavelength temperature dependence and optical loss of the ring resonators.

Main Results:

• Athermal condition achieved for TE mode in 220 nm-height SOI waveguides with a width around 350 nm.
• Wavelength temperature dependence reduced to less than 5 pm/°C after polymer cladding, an eleven-fold improvement.
• Optical loss of a 350-nm bent waveguide (15 µm radius) reduced to approximately 50 dB/cm.

Conclusions:

• Polymer cladding is an effective method for achieving athermal operation in silicon ring resonators.
• Optimized waveguide dimensions and polymer integration enhance thermal stability and reduce optical loss.
• This advancement is critical for the development of robust and reliable silicon photonic integrated circuits.