Design and implementation of a Si₃N₄ three-stigmatic-point arrayed waveguide grating with a resolving power over...

Area of Science:

• Photonics and Optical Engineering
• Astronomy Instrumentation
• Materials Science (Silicon Nitride)

Background:

• Traditional Rowland Arrayed Waveguide Gratings (AWGs) suffer from non-flat focal surfaces, limiting detector coupling and spectral resolution at channel edges.
• This limitation hinders applications requiring precise spectral analysis, such as astronomical spectroscopy.

Purpose of the Study:

• To design and implement a novel three-stigmatic-point arrayed waveguide grating (TSP AWG) that addresses the focal surface curvature issue.
• To achieve high spectral resolving power and demonstrate its suitability for astronomical applications requiring 2D spectral acquisition.

Main Methods:

• Fabrication of a TSP AWG using silicon nitride (Si3N4) on a silicon dioxide (SiO2) platform, leveraging high-index contrast for miniaturization.
• Experimental characterization to measure spectral resolving power and assess focal surface flatness.

Main Results:

• Experimental demonstration of a Si3N4 TSP AWG with a spectral resolving power exceeding 17,000.
• The device exhibits a flat focal surface, enabling direct butt-coupling of detector arrays without performance degradation.
• Achieved a compact device footprint of approximately 9.3 x 9.3 mm2.

Conclusions:

• The developed TSP AWG offers a viable solution for non-flat focal surface issues in AWGs.
• Its high spectral resolution, flat focal surface, and compact size make it highly suitable for astronomical spectrographs and other demanding photonic applications.
• The multi-input design and high-performance platform pave the way for next-generation integrated photonic devices.