On-chip waveguide isolator based on bismuth iron garnet operating via nonreciprocal single-mode cutoff

Area of Science:

• Photonics and Optical Engineering
• Materials Science for Integrated Devices

Background:

• On-chip optical isolators are essential components for preventing back reflections in integrated photonic circuits.
• Existing isolator designs often face challenges with size, efficiency, and material compatibility.

Purpose of the Study:

• To analyze and optimize an on-chip optical isolator based on the principle of direction-dependent single-mode cutoff.
• To achieve high isolation ratios for transverse magnetic (TM) modes using bismuth iron garnet.

Main Methods:

• Analysis in 1D and 2D momentum space.
• Three-dimensional finite difference time domain (FDTD) simulations to demonstrate isolation.
• Magnetization modeled using imaginary off-diagonal permittivity tensor elements.
• Optimization using perturbation theory.

Main Results:

• Successfully predicted increased isolation for rib waveguides and structures with non-magnetic dielectric layers.
• Achieved an isolation ratio of 10.7 dB/mm for TM modes.
• Demonstrated the effectiveness of the proposed design principles.

Conclusions:

• The proposed on-chip optical isolator design based on single-mode cutoff is effective.
• Bismuth iron garnet is a suitable material for achieving high-performance isolators.
• The optimization methodology accurately predicts performance enhancements.