Compact ultrabroad-bandwidth cascaded arrayed waveguide gratings

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Nanophotonics

Background:

• Arrayed waveguide gratings (AWGs) are crucial for wavelength-selective optical signal processing.
• Achieving ultrabroad bandwidths and high resolution in compact AWG devices remains a challenge.
• Silicon nitride (Si3N4) platforms offer advantages for integrated photonic devices due to their low loss and high refractive index.

Purpose of the Study:

• To present a novel compact, high-resolution, and ultrabroad-bandwidth cascaded AWG.
• To demonstrate an innovative design for achieving a 190 nm optical bandwidth with 1 nm spectral resolution.
• To reduce optical loss compared to conventional AWG designs.

Main Methods:

• Realization of a cascaded AWG using a silicon nitride platform.
• Implementation of a 1x3 flat-passband AWG as a primary filter and three 1x70 AWGs as secondary filters.
• Utilizing a multiple-input multi-mode interference (MMI) coupler in the primary AWG for ultrabroad bandwidth.

Main Results:

• Achieved a 190 nm optical bandwidth with 1 nm spectral resolution in a compact 1.1 × 1.0 cm^2 device.
• Demonstrated a cascaded AWG with 210 output channels.
• Reduced optical loss to 4 dB at the central channel, 3 dB lower than conventional designs.
• Proposed a novel low-loss design (∼0.8 dB) for weak light intensity applications.

Conclusions:

• This work presents the first demonstration of an ultrabroad-bandwidth cascaded AWG on a small footprint.
• The innovative MMI-based design significantly enhances bandwidth and reduces loss.
• The proposed low-loss design opens possibilities for sensitive applications like Raman spectroscopy.