Reduced loss through improved fabrication for single air interface bends in polymer waveguides

Area of Science:

• Photonics and Waveguide Technology
• Materials Science
• Optical Engineering

Background:

• Previous work demonstrated high-efficiency waveguide bends in perfluorocyclobutyl (PFCB) materials.
• Achieving lower loss in optical waveguide bends is crucial for integrated photonic devices.

Purpose of the Study:

• To decrease the optical loss per bend in PFCB waveguide bends.
• To investigate the impact of improved interface accuracy and sidewall smoothness on bend loss.
• To assess the feasibility of using electron-beam lithography for fabricating low-loss bends.

Main Methods:

• Utilized electron-beam lithography (EBL) in a scanning electron microscope (SEM) for waveguide fabrication.
• Focused on enhancing bend interface position accuracy and sidewall smoothness.
• Fabricated 45-degree single air interface waveguide bends.

Main Results:

• Reduced measured loss per bend from 0.33 dB to 0.124 dB for TE polarization (97.2% efficiency).
• Reduced measured loss per bend from 0.30 dB to 0.166 dB for TM polarization (96.2% efficiency).
• Demonstrated that EBL fabrication offers comparable alignment accuracy to high-end stepper tools.

Conclusions:

• Electron-beam lithography significantly reduces optical loss in PFCB waveguide bends.
• Improved fabrication precision leads to higher bend efficiencies.
• The findings suggest that low-loss air trench bends in low refractive index contrast materials are achievable with conventional microfabrication tools.