Hybrid Wavelength- and Mode-division Multiplexing System Based on Microring Resonators with Mode Splitters [基于带有模式分离器的微环谐振器的波长-模式混合复用系统]

作者：Han X.; Zhang L.; Xue J.; Bao S.; Wu J.; Mi L.

来源：Acta Photonica Sinica, 2022, 51(11): 1113002.

DOI：10.3788/gzxb20225111.1113002

• Hybrid multiplexing
• Microring resonator
• Mode division multiplexing
• Mode splitter
• Optical communication
• Silicon photonics
• Wavelength division multiplexing

The applications of silicon photonics in data bearer networks， data centers and other scenarios will support high-speed data transmission. In order to meet the demand， lots of technologies in silicon photonics have emerged， such as Wavelength Division Multiplexing （WDM），Polarization Division Multiplexing （PDM） and Mode Division multiplexing （MDM）. To further increase the channel capacity， the hybrid multiplexing technology is studied based on the technologies above. Our work is such a hybrid WDM-MDM multiplexer. This paper focuses on the design of a microring resonator with mode splitter. First of all， the effect of mode splitting is better at a longer length， but we need to put the mode splitter into the microring resonator， and such a high mode separation efficiency and coupling efficiency will lead to low efficiency of microring resonance. So， we take the appropriate length. Secondly， an asymmetric structure for the geometry of the mode splitter is designed. One side of the structure is a waveguide with a width of 0.88 nm， allowing high order mode transmission， and the other side is a slot waveguide with a width of 0.86 nm， with an air gap of 50 nm in the middle. The advantage of this structure is that it can effectively split TE0and TE1 modes. In addition， for microring resonators， we can select the desired resonant wavelength by designing appropriate parameters such as radius， waveguide width， coupling region length and gap. By simulating the proposed structure with the finite difference time domain method， the multiplexer and demultiplexer can realize ultra-compact WDM-MDM structure at C band. The microring resonator has a response of -0.66 dB to TE1 mode input， a Q value of 3 692， and an optical bandwidth of 52 GHz. Its free spectral range is 1.03 THz， and the crosstalk generated by TE0 mode is -11.0 dB. The insertion loss of the microring resonator is as low as -0.66 dB. Based on this， we also propose a transmitter-receiver MDM system with dual mode input. The simulation results show that the dual-mode input MDM system based on microring resonator can effectively separate TE0 and TE1 modes， and the microring also has the ability of wavelength selection. In addition， the through ports with fabrication tolerance from -10 nm to +15 nm have responses of less than -20 dB， while the response of the drop ports remains within -1 dB. Compared with other devices， our design has advantages in insertion loss， crosstalk and FSR. In conclusion， proposed system using wavelength-mode multiplexing mircroring can effectively separate the TE0 and TE1 modes and has the ability of wavelength selection， which may be the main device for ultra-compact hybrid multiplexing technology in near future.

• 单位
  中国科学院大学; 瞬态光学与光子技术国家重点实验室