High-Performance Silicon Photonic Filters And Their Applications

At present,a new round of scientific and technological revolution and industrial transformation continue to develop globally,and the reliance on networks in various fields continues to increase.Optical communication systems and data centers,which are their core support,are facing major challenges.Silicon-based optoelectronic chips have attracted much attention due to their unique advantages such as CMOS compatibility,low cost,and small size.Silicon photonic filter is one of its most important components,and as a key component,it is widely used in the fields of wavelength division multiplexing(WDM)and spectral sensing.This article focuses about high-performance silicon photonics filters and their applications.Firstly,we introduce the development of integrated optics,the advantages of silicon phtonics and its typical applications in optical communications,optical sensing and other fields.After that,we summary the research status and development needs of silicon photonic filters,and briefly introduce the simulation design and testing process and equipment of silicon photonic devices on a chip.Secondly,we have done an in-depth study on how to obtain a micro-ring(MRR)-based filter with an ultra large free spectrum range(FSR).First,we propose a single-ring filter based on a multi-mode bent waveguide and a bent directional coupler(DC).The multimode bent waveguide is introduced to reduce the bending loss,and the bent DC is optimized to suppress the exiction of high-order mode.The sub-micron size MRR-based filter has an FSR as large as 93nm,which is the maximum value reported so far.In addition,a high-order ring filter based on a high-order adiabatic ellipse ring(AEM)is further proposed.The ultra-compact microcavity is realized by introducing an elliptical ring whose width and curvature are both adiabatic.A bent DC is introduced to obtain enough coupling,experiment results show that the FSR of high-order ring reaches 37nm,which is the largest record of high-order MRR reported so far.Thirdly,based on the multimode waveguide grating(M WG),two new types of silicon optical filters have been develope.First,for the new communication window and the important sensing band—2?m band,we first proposed and implemented the MWG-based add-drop filter.The demonstrated 2?m silicon optical filter has low loss(?1dB)and high side mode suppression ratio.(>20dB),flexible and adjustable bandwidth(6-26nm)and other excellent performance.In addition,a polarization-insensitive filter based on dual gratings is proposed.The filter is composed of a dual polarization mode demultiplexer and dual gratings(including triangular MWG and rectangular MWG).Through smart structural design and polarization control,we achieve the polarization insensitive characteristics,and introduce a special triangular MWG to reduce reflection and suppress FP resonance.A polarization insensitive filter with a bandwidth of?10nm and unlimited FSR is realized.Fourthly,based on the cascaded MWG structure,by manipulate the spectral characteristics of each MWG,we have developed a variety of multi-channel wavelength division multiplexers,including four-channel coarse wavelength division multiplexer(CWDM),a triplexer and a quadplexer.Utilizing the extremely high flexibility and scalability of the MWG-based filter,the requirements of various multiplexers with different wavelengths and bandwidths are realized.Apodization technology is used to reduce crosstalk.Furthermore,grating tapers and bent waveguides are introduced to suppress FP resonance.Experimental results show that each multiplexer has obtained high performance characteristics of low loss,low crosstalk and flat response,and all meet the requirements of standards.In particular,for the sparse channel wavelengths and nonuniform bandwidths of quadplexer,in the case that other waveguide structure filters are difficult to achieve,the multi-wavelength and multi-channel collaborative design optimizes the structure and spectral characteristics of MWG,and it is the first time to achieve a high-performance quadplexer on the chip.In summary,in terms of high-performance silicon photonic filters and their applications,we have done in-depth and systematic research on filters based on MRR and MWG,and successfully developed a variety of high-performance silicon photonic filters,which will provide an important cornerstone for the future large-scale integration of the silicon photonics.