Broadband optical switch for multiple spatial modes based on a silicon densely packed waveguide array.

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Silicon Photonics

Background:

• Mach-Zehnder switches are crucial for optical signal routing.
• Controlling multiple spatial modes simultaneously presents a significant challenge in integrated photonics.
• Broadband operation is essential for high-capacity optical communication systems.

Purpose of the Study:

• To demonstrate a broadband thermo-optic 2x2 Mach-Zehnder switch capable of controlling two spatial modes concurrently on a silicon chip.
• To achieve low insertion loss and high crosstalk suppression over a wide operational bandwidth.
• To enable arbitrary power splitting ratios for both spatial modes.

Main Methods:

• Fabrication of a broadband multimode 3 dB coupler using symmetrically coupled waveguides with a sub-wavelength structure.
• Integration of the multimode coupler with symmetrical delay arms to form the Mach-Zehnder interferometer.
• Utilizing thermo-optic effect via integrated heaters to control the switching functionality.

Main Results:

• Demonstration of a compact (24.2 μm coupler length) broadband multimode 3 dB coupler.
• Experimental realization of optical switching with excess losses < 1.3 dB and crosstalks < -15 dB.
• Achieved operation over a 60 nm bandwidth for both spatial modes, with demonstrated arbitrary splitting ratios.

Conclusions:

• The developed thermo-optic Mach-Zehnder switch effectively controls two spatial modes simultaneously on a silicon chip.
• The device exhibits excellent broadband performance with low loss and high isolation, suitable for advanced optical communication.
• This technology offers a promising solution for mode-division multiplexing and reconfigurable optical networks.