Study On Micro-miniature Optical Power Splitters With Slot Waveguide Structure

Optical beam splitter has attracted tremendous interest because it is an important component of optical communication system,optical information processing system,and indispensable part of other optical devices.Traditional optical splitter with large footprint cannot satisfy the needs of optical integrated circuits which require smaller discrete device and tight integration.Recently,optical slot waveguide,a structure of a low-refractive-index sub-?m slot formed between two high-refractive-index waveguides obtain enormous attention because optical beam can be confined into nanoscale slot regions,different materials can be filled in slit and structure is easy to fabricate.In general,there are two types of optical slot waveguide structures,plasmonic slot waveguide(PSWG)and dielectric slot waveguide(DSWG).In this paper,the principle and characteristics of optical power splitter based on T type slot waveguide are analyzed,the structures of T type slot waveguide are designed with optimized parameters.Firstly,subwavelength scale beam splitters based on MIM plasmonic waveguide with simple structure,parallel output ports and low excess loss was proposed.This structure is mainly use standing wave to control the transmission efficiency and the splitting ratio.However,the disadvantage of PSWG is the loss of metal,which is absent in DSWG.In the next place,We investigated the possibility of T type dielectric slot waveguide as an optical power splitter and optimum structural parameters were chosen such as the width of slot Ws and width of dielectric waveguide Wd.Then,new structures based on T type DSWG were proposed where optimized new parameters were chosen.Based on the simulation results,we analyzed transmission mechanism of different types.T-shape splitter composed of DSWG can be optical splitter due to low loss,subwavelength confinement and diffraction at branch point.The results show that the 1:1 splitting ratio and 2.2dB excess loss is achieved in the structure of crossing DSWG with blocked stub.Different structures based on T type dielectric slot waveguide in three dimensions were also designed and investigated.In this research,we investigated the output power of two ports dependent on the slot width,width of cladding dielectric waveguide and thickness and found their influence to the transmission.In the structure of T-type dielectric cross-slot waveguide with right triangles,strong confinement in the slot region for TE and TM polarizations is achieved and splitting ratio is improved by right triangles at branch intersection,which enhance output power of 90 degree bending branch.Finally,an optical power splitter in which splitting ratio is about 1:1 and excess loss is only 0.54dB is obtained.When the slot region is GaN and a dielectric cladding material is Si in T-type dielectric cross-slot waveguide with right triangles,the excess loss is equal to 1.19dB.