Research Of High Performance Waveguide Crossing Unit Based On SOI

With the development of modern photonics technology, the requirements of photonicdevices on the aspects of integration, density, function and capability is getting higher andhigher. This causes the crossing of waveguides on a single chip happen much morefrequently. Meanwhile, the SOI(silicon on isolator) is regarded as the most promisingmaterial of optical integration, which possess the advantages of good light conductivecharacteristics, strong confinement of light and compatible of CMOS crafts. However, thelarge index difference causes the mode’s wide-angle spatial extent, and result in significantscattering in the crossing area. The crossing of SOI waveguides for one time will cause theloss of1~1.5dB and crosstalk of-10~-15dB, so the loss and crosstalk caused by a largeamount of waveguide crossings will be unacceptable of a single chip. To solve the problemsabove, this thesis is attempted to find a strategy of SOI waveguide crossing with few loss,few crosstalk, compact and compatible of semiconductor crafts.The detailed studies of this thesis cover the aspects as follows:(1) Designed the adiabatic taper and adiabatic inverse taper based on SOI, and analysisthe change of the width of fundamental mode and effective refractive index in the inversetaper;(2) Designed the waveguide crossing unit based on the Multi-mode Interferencestructure and ran the simulation with the software Comsol. With the size of13m13m,the loss is0.22dB and the crosstalk is-14.69dB. This scheme has a simple process but itsloss, crosstalk and size are still inacceptable;(3) Designed the waveguide crossing unit based on the bridge structure. An outstandingadvantage of the bridge structure is that the crosstalk can be removed. Simulation shows thatthe loss is0.035dB, the crosstalk is-43.2dB and its size is71.5m1m.This scheme hasachieved the target of few loss and few crosstalk, but it needs at least70mlength andtherefore is not practical for chips highly integrated;(4) To relieve the disadvantage of the bridge structure, the author raises a new schemeto shorten the length. Under the size of10.4m0.5m,simulation results shows that theloss is0.24dB and the loss is-40.5dB. The new scheme only need a10mlength and also has few loss which means a meaningful exploring of the bridge structure.