High-precision optical interference in Mach-Zehnder-type photonic crystal waveguide

Area of Science:

• Photonics
• Materials Science
• Optical Engineering

Background:

• Two-dimensional photonic crystals (2DPCs) offer unique light manipulation properties.
• Mach-Zehnder (MZ) interferometers are crucial for optical switching applications.
• GaAs-based materials are suitable for near-infrared photonic devices.

Purpose of the Study:

• To experimentally demonstrate optical interference in asymmetric Mach-Zehnder (MZ) type GaAs-based two-dimensional photonic crystal (2DPC) slab waveguides.
• To validate the performance of directional couplers (DCs) in controlling optical phase and intensity.
• To lay the groundwork for ultra-small symmetrical MZ (SMZ) all-optical switches.

Main Methods:

• Fabrication of asymmetric Mach-Zehnder (MZ) type GaAs-based 2DPC slab waveguides with directional couplers (DCs).
• Experimental manipulation of MZ arm lengths by lattice constant units to observe output intensity changes.
• Utilizing two incident optical beams with externally controlled phase differences to operate DCs and measure output intensities.

Main Results:

• Excellent optical interference was achieved in the near-infrared region.
• Output intensities showed sinusoidal curves with changes in MZ arm lengths, matching coupled-mode theory predictions.
• Sinusoidal changes in output intensities were observed with controlled phase differences in DCs, consistent with DC theory.

Conclusions:

• The study successfully demonstrated optical interference in advanced 2DPC waveguide structures.
• High-quality nano-fabrication enabled precise control over optical phenomena.
• These findings pave the way for the development of ultra-small, symmetrical Mach-Zehnder all-optical switches.