Demultiplexer with blazed waveguide sidewall grating and sub-wavelength grating structure.

Area of Science:

• Integrated photonics
• Nanophotonics
• Optical engineering

Background:

• Demultiplexers are crucial for optical communication, enabling signal separation by wavelength.
• Existing devices often face limitations in footprint size and performance trade-offs.
• Silicon-on-insulator (SOI) platform offers advantages for miniaturization and integration.

Purpose of the Study:

• To design and simulate a novel, ultra-compact diffraction grating demultiplexer.
• To achieve high performance, including low crosstalk and broadband operation.
• To leverage the silicon-on-insulator platform for efficient device fabrication.

Main Methods:

• Utilizing a second-order diffraction grating etched into a curved silicon waveguide sidewall.
• Employing a blazed grating design for maximized -1st order diffraction efficiency.
• Incorporating an impedance-matching subwavelength grating (SWG) gradient index (GRIN) antireflective interface for efficient coupling.
• Implementing an apodized and chirped grating design to minimize phase errors and ensure a constant effective index.
• Simulating device performance, including crosstalk and channel spacing.

Main Results:

• Achieved a simulated crosstalk of -30 dB.
• Designed for 15 channels with 25 nm spacing, providing a 375 nm operational bandwidth.
• Demonstrated performance approaching the diffraction limit.
• Realized an ultra-compact footprint of 90 µm x 140 µm, the smallest reported for comparable performance.

Conclusions:

• The proposed diffraction grating demultiplexer represents a significant advancement in miniaturization for photonic integrated circuits.
• The device's small footprint and high performance make it suitable for next-generation optical communication and sensing applications.
• The design methodology provides a pathway for further optimization of compact wavelength-selective devices on the SOI platform.