Realization of "trapped rainbow" in 1D slab waveguide with surface dispersion engineering

Area of Science:

• Photonics
• Materials Science
• Waveguide Optics

Background:

• Dielectric waveguides are crucial for manipulating light.
• Controlling light pulse propagation, especially broadband pulses, is a significant challenge in optics.
• Previous methods for light trapping often involve complex structures or high losses.

Purpose of the Study:

• To design a one-dimensional dielectric waveguide capable of trapping broadband light pulses.
• To achieve a "trapped rainbow" effect where different frequencies are spatially separated.
• To explore the use of silicon gratings for dispersion engineering in SiO(2) waveguides.

Main Methods:

• Engineering the dispersion of a SiO(2) waveguide by incorporating a Si grating.
• Utilizing guided modes with zero group velocity (frozen modes).
• Controlling frozen mode frequencies by adjusting grating parameters (period and duty cycle).

Main Results:

• Demonstrated realization of frozen modes through grating-induced dispersion control.
• Achieved spatial separation of different frequency components of a light pulse, forming a rainbow.
• Showcased that negative Goos-Hänchen shift is key to dispersion control.

Conclusions:

• A novel dielectric waveguide design enables "trapped rainbow" formation for broadband light pulses.
• The device utilizes engineered dispersion via Si gratings on SiO(2) waveguides.
• The planar geometry and dielectric materials promise low loss and reduced fabrication difficulty.