Interferometric method for determining the losses of spatially multi-mode nonlinear waveguides based on second...

Area of Science:

• Nonlinear optics
• Waveguide characterization
• Materials science

Background:

• Optical waveguide loss characterization is crucial for device performance.
• Existing interferometric methods are limited to single-mode waveguides.
• Characterizing losses in multi-mode nonlinear waveguides remains challenging.

Purpose of the Study:

• To introduce a Fabry-Pérot-based scheme for estimating losses in multi-mode nonlinear optical waveguides.
• To enable loss characterization at wavelengths where waveguides support multiple spatial modes.
• To extend loss measurement capabilities beyond single-mode limitations.

Main Methods:

• Utilizing a Fabry-Pérot resonator to measure second harmonic (SH) power.
• Scanning the pump wavelength across the phase-matching region to analyze SH generation.
• Analyzing separated phase-matching spectra to infer losses of different SH spatial modes.

Main Results:

• The proposed method successfully estimates losses in nonlinear waveguides operating in a multi-mode regime.
• Losses of individual second harmonic spatial modes can be inferred by scanning the pump field.
• Accurate estimation of second harmonic losses for single spatial modes in multi-mode waveguides was demonstrated.

Conclusions:

• The Fabry-Pérot-based scheme provides a viable method for characterizing losses in multi-mode nonlinear waveguides.
• This technique overcomes limitations of traditional methods, enabling broader waveguide analysis.
• The study demonstrates the ability to estimate SH losses of single spatial modes within multi-mode waveguides.