Perfect matching of concave diffraction grating with continuously circular Bragg mirrors on SOI platform

Area of Science:

• Photonics and optical engineering
• Materials science
• Nanotechnology

Background:

• Traditional diffraction gratings suffer from scattering losses at grating teeth junctions.
• Silicon-on-insulator (SOI) platforms offer advantages for integrated optics.
• Dielectric mirrors can improve optical performance by reducing reflection losses.

Purpose of the Study:

• To design and fabricate a novel concave diffraction grating (CDG) using circular Bragg mirrors.
• To minimize scattering losses and enhance reflection efficiency in optical gratings.
• To achieve high dispersion in a compact structure for integrated photonic applications.

Main Methods:

• Construction of a CDG on a 220 nm SOI platform utilizing circular Bragg mirrors.
• Derivation of geometrical parameters by matching Bragg and grating conditions.
• Finite-difference time-domain (FDTD) simulations to analyze optical performance.

Main Results:

• The designed Bragg mirror achieved up to 99.7% reflection over a 330 nm bandwidth.
• The CDG with circular Bragg mirrors demonstrated low insertion loss at a high diffraction order (M=5).
• Suppression of unwanted diffraction orders was observed, leading to high dispersion in a compact design.

Conclusions:

• The novel CDG design effectively reduces scattering losses through continuous dielectric mirrors.
• The integration of circular Bragg mirrors on SOI platforms enables high-performance, compact optical gratings.
• This technology holds potential for advanced integrated photonic devices requiring high dispersion and efficiency.