Electro-optic mode-selective switch based on cascaded three-dimensional lithium-niobate waveguide directional...

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Telecommunications

Background:

• Mode-division multiplexing (MDM) is a promising technique for increasing optical communication capacity.
• Efficient and reliable mode-selective switches are crucial for realizing practical MDM systems.
• Lithium niobate (LiNbO3) is a well-established material for electro-optic devices due to its excellent properties.

Purpose of the Study:

• To propose and experimentally demonstrate a novel electro-optic mode-selective switch.
• To achieve switchable (de)multiplexing of different spatial modes (LP01, LP11a, LP11b).
• To investigate the performance of cascaded directional couplers fabricated using annealed proton-exchange.

Main Methods:

• Fabrication of three-dimensional lithium niobate waveguide directional couplers using a single-step annealed proton-exchange process.
• Development of a post-tuning technique involving titanium oxide (TiO2) deposition to compensate for fabrication uncertainties.
• Integration of two cascaded dissimilar directional couplers for experimental demonstration.

Main Results:

• Demonstrated switchable (de)multiplexing of LP01, LP11a, and LP11b modes.
• Achieved >75% switching efficiency for LP11a mode across a 82 nm wavelength range with applied voltages from -9 V to +30 V.
• >90% switching efficiency for LP11b mode across a 43 nm wavelength range with applied voltages from -21 V to 0 V.
• Observed switching times in the range of 230-300 ns.

Conclusions:

• The proposed waveguide platform enables high-performance electro-optic mode-selective switching.
• The post-tuning technique effectively compensates for fabrication variations, enhancing device performance.
• This technology is suitable for developing advanced switches for high-speed spatial mode switching in reconfigurable MDM communication systems.