Low-loss silicon core fibre platform for mid-infrared nonlinear photonics

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Nonlinear Optics

Background:

• Broadband mid-infrared (mid-IR) light sources are crucial for applications like communications and spectroscopy.
• Silicon waveguides offer low loss and high stability for nonlinear optical wavelength conversion in the mid-IR.
• Existing silicon-on-insulator platforms are limited by silica cladding absorption beyond 3 µm.

Purpose of the Study:

• To design and demonstrate a compact silicon core, silica-clad waveguide with low losses across the silicon transparency window.
• To enable efficient nonlinear propagation of mid-infrared light with minimal cladding interaction.
• To generate high-brightness, coherent mid-infrared supercontinuum spectra.

Main Methods:

• Fabrication of waveguides from a silicon core fiber.
• Tapering the silicon core fiber to engineer mode properties for efficient nonlinear propagation.
• Utilizing a compact silicon core, silica-clad waveguide design.

Main Results:

• Demonstrated a waveguide platform with low losses across the entire silicon transparency window.
• Achieved efficient nonlinear propagation in the silicon core, minimizing mid-IR light interaction with the silica cladding.
• Generated bright and coherent mid-infrared supercontinuum spectra spanning nearly two octaves (1.6–5.3 µm).

Conclusions:

• The developed silicon core fiber waveguide platform effectively overcomes limitations of previous designs.
• This platform offers high coupling efficiency and power handling capabilities, characteristic of fiber platforms.
• Enables generation of broadband, coherent mid-IR supercontinuum for advanced optical applications.