On-chip mode converter based on two cascaded Bragg gratings

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Waveguide Devices

Background:

• Mode converters are crucial components in integrated photonic circuits for manipulating light propagation.
• Existing methods for mode conversion often face limitations in bandwidth, efficiency, or spectral control.
• Bragg reflection principles, widely used in fiber optics, offer potential for on-chip mode manipulation.

Purpose of the Study:

• To propose and theoretically investigate a novel on-chip mode converter.
• To demonstrate the capability of achieving forward conversion between guided modes using cascaded Bragg reflections.
• To explore methods for controlling the spectral characteristics of the mode converter.

Main Methods:

• Theoretical analysis of light propagation through a structure utilizing two cascaded Bragg reflection processes.
• Rigorous three-dimensional finite-difference time-domain (3D-FDTD) simulations to model device performance.
• Experimental verification of the proposed mode conversion mechanism.

Main Results:

• Successful demonstration of on-chip mode conversion via cascaded Bragg reflections with an auxiliary mode.
• Theoretical and simulation results confirm that bandwidth and central wavelength are adjustable.
• Design of mode converters with specific spectral shapes, including bandpass and sidelobe-reduced spectra, achieved through fiber Bragg grating design principles.

Conclusions:

• The proposed cascaded Bragg reflection approach provides an effective method for on-chip mode conversion.
• The design allows for precise control over spectral properties, enabling tailored device performance.
• This technique offers a promising new avenue for developing mode converters with desired spectral characteristics for integrated photonic systems.