Variation of self-imaging length in multimode waveguides beyond the paraxial approximation

Area of Science:

• Optics and Photonics
• Waveguide Theory

Background:

• Self-imaging is a phenomenon where a periodic structure can reproduce its input field.
• Dielectric slab waveguides are fundamental components in integrated optics.

Purpose of the Study:

• To investigate the precise variation of self-imaging distance with Gaussian beam width.
• To analyze the influence of beam width on excited modes in a dielectric slab waveguide.

Main Methods:

• Simulating a Gaussian input beam centrally fed into a symmetric dielectric slab waveguide.
• Varying the width of the Gaussian beam from paraxial to nonparaxial regimes.

Main Results:

• Self-imaging distance depends on Gaussian beam width, unlike the paraxial case.
• The self-imaging distance changes with the number of excited modes in the waveguide.

Conclusions:

• The observed dependence of self-imaging distance on beam width and excited modes offers new design parameters.
• These findings are valuable for enhancing the efficiency of nanophotonic circuits utilizing self-imaging principles.