Improved sensing performance of D-fiber/planar waveguide couplers

Area of Science:

• Optoelectronics
• Materials Science
• Optical Engineering

Background:

• Optical fiber sensors rely on precise control of light-matter interactions.
• D-shaped fibers offer unique evanescent field access for coupling.
• Planar waveguides provide a platform for integrated optical devices.

Purpose of the Study:

• To demonstrate wavelength selective coupling between D-shaped optical fibers and multimode planar waveguides.
• To develop a fabrication process for creating such coupled structures.
• To characterize the performance of the resulting optical filter and its sensitivity.

Main Methods:

• Fabrication involved wet chemical etching of D-shaped fibers.
• Planar waveguides were produced using spin coating or molding techniques.
• Wavelength-dependent transmission spectra were measured to analyze coupling and filter characteristics.

Main Results:

• Achieved weak coupling and long interaction length, leading to narrow transmission dip linewidths.
• Demonstrated a comb filter with 12nm peak separations, -20dB transmission dips, and 0.25nm linewidths.
• Exhibited high temperature sensitivity with a transmission dip shift of -3.16 nm/degree C.

Conclusions:

• The demonstrated fabrication process enables efficient wavelength selective coupling for optical filtering.
• The resulting device functions as a narrow-linewidth comb filter with potential for integrated optics.
• The high temperature sensitivity indicates suitability for optical sensing applications.