Unambiguous identification of waveguide loss and coupling coefficients using add-drop ring resonators.

Area of Science:

• Photonics and Optical Engineering
• Materials Science and Engineering

Background:

• Accurate measurement of waveguide propagation loss and coupling coefficients is crucial for integrated photonic chips.
• Existing methods like the cutback method and all-pass ring resonator method have limitations in accuracy, footprint, or unambiguous parameter identification.

Purpose of the Study:

• To develop a novel, accurate, and robust method for measuring waveguide loss and coupling coefficients in integrated photonics.
• To demonstrate the advantages of the proposed technique over existing methods.

Main Methods:

• Utilizing two spectral measurements of an add-drop ring resonator.
• Performing uncertainty analysis to compare the proposed method with existing techniques.
• Experimental validation on various waveguide platforms.

Main Results:

• The add-drop ring resonator method unambiguously recovers waveguide loss and coupling coefficients.
• This technique offers lower uncertainty compared to alternative methods in many scenarios.
• Demonstrated robustness to defects and applicability across different waveguide platforms.

Conclusions:

• The proposed spectral measurement technique using add-drop ring resonators provides a convenient and accurate tool for integrated photonic process development and fabrication monitoring.
• The method's small footprint and unambiguous results make it highly suitable for routine characterization.