研究目的
To demonstrate a compact silicon photonic 4-channel optical add-drop wavelength multiplexer using subwavelength-grating-based contra-directional couplers for coarse wavelength division multiplexing in short-reach optical interconnects.
研究成果
The 4-channel OADM demonstrated on-chip insertion losses below 1.3 dB and 3 dB bandwidths of approximately 6.7 nm, making it suitable for CWDM in short-reach optical interconnects. The use of gap-apodized SWG-based contra-DCs provided a compact design with good performance balance between transmission isolation and cross-talk. Future work could explore scaling to more channels or enhancing thermal stability.
研究不足
The device may have constraints related to fabrication imperfections, thermal sensitivity, and potential cross-talk between channels. Optimization could focus on further reducing insertion loss and improving sidelobe suppression without compromising other performance metrics.
1：Experimental Design and Method Selection:
The experiment involved designing and fabricating a 4-channel optical add-drop multiplexer (OADM) on a silicon-on-insulator (SOI) platform using cascaded gap-apodized subwavelength grating (SWG)-based contra-directional couplers (contra-DCs). The design aimed to achieve low insertion loss, wide bandwidth, and good transmission isolation for coarse wavelength division multiplexing (CWDM) applications. Theoretical models for contra-directional coupling and gap apodization were employed, as referenced from previous work [6,7].
2：7].
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: The device was fabricated on an SOI wafer with specific dimensions: strip waveguides of 220 nm height and 500 nm width, on a 3 μm thick buried oxide (BOX) layer, with a 2.5 μm thick SiO2 cladding. The SWG waveguides had duty cycles fixed at 50% with periods of 370, 374, 378, and 382 nm for different channels.
3：5 μm thick SiO2 cladding. The SWG waveguides had duty cycles fixed at 50% with periods of 370, 374, 378, and 382 nm for different channels.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment included an 8-port fiber ribbon array for light coupling, a tunable laser for spectral scanning (steps of 50 pm), and a power meter for optical power measurement. Materials involved SOI wafers, SiO2 for cladding, and components fabricated using electron beam lithography and plasma etching.
4：Experimental Procedures and Operational Workflow:
Light was coupled into the input and add ports using vertical grating couplers (VGCs) optimized for TE operation. The tunable laser scanned wavelengths, and the power meter measured output from drop and through ports. Spectra were normalized to back-to-back insertion loss of VGC test pairs.
5：Data Analysis Methods:
Measured spectra for drop and add operations were analyzed to determine insertion loss, 3 dB bandwidth, transmission isolation, and center wavelengths. Data were compared using Lorentz reciprocity theorem to ensure symmetry and repeatability.
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