Integrated silicon nitride devices via inverse design.

Area of Science:

• Photonics
• Materials Science
• Integrated Optics

Background:

• Silicon nitride photonics offers integration potential but faces challenges with low refractive index contrast, limiting device miniaturization.
• Existing silicon nitride devices often require larger footprints compared to silicon-based counterparts.

Purpose of the Study:

• To demonstrate the effectiveness of inverse design for creating compact and efficient freeform silicon nitride photonic devices.
• To benchmark the design capabilities, fabrication repeatability, and robustness of inverse-designed silicon nitride components.

Main Methods:

• Utilized inverse design to create three freeform silicon nitride devices: a coarse wavelength-division multiplexer, a five-mode mode division multiplexer, and a polarization beam splitter.
• Systematically evaluated the performance and fabrication characteristics of these inverse-designed devices.

Main Results:

• Achieved up to a 1200× reduction in device footprint compared to conventional designs.
• Maintained relatively large minimum feature sizes of up to 160 nm, demonstrating design robustness.
• Showcased that inverse-designed silicon nitride devices can rival the compactness of silicon-based devices.

Conclusions:

• Inverse design successfully overcomes the limitations of low refractive index contrast in silicon nitride photonics, enabling highly compact devices.
• These findings pave the way for high-density integration in silicon nitride photonics.
• The inverse design methodology is applicable to various silicon nitride thicknesses and potentially other low- and mid-index contrast platforms, supporting multidimensional data transmission and quantum applications.