Sidelobe suppression in grating-assisted wavelength-selective couplers.

Area of Science:

• Photonics
• Optical Engineering
• Materials Science

Background:

• Vertical codirectional couplers are essential components in optical communication systems.
• Sidelobe suppression is critical for improving device performance and reducing signal interference.
• Phase-matched gratings are widely used in optical devices, but sidelobe levels can impact efficiency.

Purpose of the Study:

• To analyze sidelobe suppression in phase-matched gratings for vertical codirectional couplers.
• To investigate the effectiveness of a tapered duty ratio for sidelobe reduction.
• To determine the feasibility of achieving low cross-talk levels with specific device parameters.

Main Methods:

• Implementation of a tapered duty ratio in a phase-matched grating.
• Utilizing a truncated Gaussian taper profile.
• Analysis of performance at a 830 nm wavelength with a 1-mm coupling length.
• Quantization of the taper into 20 intervals.

Main Results:

• Achieved a cross-talk level below -40 dB with a 5 nm channel spacing.
• Demonstrated the feasibility of sidelobe suppression using the proposed tapered duty ratio method.
• Confirmed that 20 intervals are sufficient for a quantized taper to effectively suppress sidelobes.

Conclusions:

• The tapered duty ratio is an effective technique for sidelobe suppression in phase-matched gratings for vertical codirectional couplers.
• The proposed method enables high performance with low cross-talk, suitable for advanced optical applications.
• Quantized tapers with sufficient intervals can replicate the performance of continuous tapers for sidelobe suppression.