On-chip beam rotators, adiabatic mode converters, and waveplates through low-loss waveguides with variable...

Area of Science:

• Photonics
• Materials Science
• Optical Engineering

Background:

• Integrated photonics requires precise control over waveguide geometry for advanced light manipulation.
• Existing methods often lack the flexibility to arbitrarily control waveguide cross-sections with high precision and low loss.

Purpose of the Study:

• To introduce a new femtosecond laser writing method for fabricating optical-fiber-compatible glass waveguides with arbitrary cross-section control.
• To demonstrate the capabilities of spherical phase-induced multicore waveguides (SPIM-WG) for on-chip light manipulation.

Main Methods:

• Femtosecond laser writing in the heating regime with high scanning speed.
• Precise deformation of waveguide cross-sections in both horizontal and vertical directions.
• Fabrication of SPIM-WG devices within optical glass.

Main Results:

• Achieved waveguides with high refractive index contrast (0.017) and low propagation loss (0.14 dB/cm).
• Demonstrated low coupling loss (0.19 dB) from single-mode fiber.
• Successfully fabricated devices for on-chip beam rotation, polarization manipulation, and arbitrary adiabatic mode conversion.

Conclusions:

• SPIM-WG technology enables precise, arbitrary control over waveguide cross-sections for enhanced light manipulation in integrated photonics.
• The developed waveguides are compatible with optical fibers and operate across ultra-broad wavelength bands (visible to infrared).
• This method paves the way for advanced, packaged photonic integrated circuitry.