Design Of On-chip Filters Based On Grating Slow Light Waveguide

As a functional device,optical filter has a variety of use scenarios,so it has been widely concerned in the research.With the development of integrated optical system,the demand of on-chip filters is increasing.Narrow band devices have broad prospects in the field of DWDM and microwave photonics,and the distribution system and signal processing corresponding to the communication terminal of broadband devices also have great value.Although the application scenarios are different,these on-chip filters often have the problem of too large device size in integrated optical systems.Therefore,on the premise of ensuring the functionality,it is very important to study the integrated design of optical filter on chip.In this study,the on-chip optical filters can be divided into two types:MHz narrow bandwidth filter and GHz wide bandwidth filter.Based on the coupled mode theory,the relationship between filter bandwidth and device size is analyzed.The principle of slow light is introduced into the optimization scheme.The effective refractive index of the device is increased by using one-dimensional grating waveguide,to reduce the size of the filters while maintaining good performance,and realize the integrated design of the on-chip optical filters.In the design and optimization of the ultra-compact on-chip narrow bandwidth optical filters,we propose an implementation scheme for the on-chip narrow bandwidth filters.Based on the one-dimensional grating waveguide,the integration and compactness of the device are greatly improved while the narrow bandwidth is obtained.At the same time,a super compact cascaded microring resonator filter with a wavelength of 1550 nm is designed.Compared with the same structure without optimization,the area of the device unit is reduced by three orders of magnitude.The equivalent 1 d B bandwidth of the filter is only 2.1 pm(263 MHz),the 35 d B bandwidth is 4.04 pm(504 MHz),the roll down speed of the filter band edge is about3.12×10~4 d B/nm,the out band signal rejection ratio is more than 100 d B,and the in band signal fluctuation is less than 0.26 d B.In the design and optimization of compact on-chip wide bandwidth optical filters,we propose a scheme for the realization of on-chip wide bandwidth filters.Based on the low dispersion slow light waveguide,the integration and compactness of the device are improved while the filter characteristics are basically unchanged.A fishbone grating waveguide with a slow light region far away from the edge of Brillouin band is proposed in the study.At the same time,an on-chip optical filter with a band width of GHz near 1550 nm is designed.Compared with the device without optimization,the area is reduced by nearly 50 times.The device has the 1 d B bandwidth of 820 pm(102.34 GHz),the 35 d B bandwidth of 1167 pm(145.64 GHz),the sideband roll down speed of 195.97 d B/nm,the in band fluctuation of about 0.42d B,and the out of band signal rejection ratio of more than 120 d B,which can greatly reduce the interference of out band signals.The integrated optical filters designed in this study can provide the on-chip optical system with smaller and more compact functional devices,and promote the improvement of the integration degree of the photon chip from the device level.At the same time,the proposal of the design scheme also provides ideas for the integrated light and compact work of related devices of the same type,and then promotes the development of the on-chip photon network.