Non-Reciprocal Silicon Magneto-Optical Waveguide With Time-Delay And Buffering Characteristics

Optical buffer plays an important role in optical packet switching network,it can not only provide adjustable buffering time for optical routing control,but also solve the problem of the same port competition,which directly determines the performance of information processing and storage.The reported optical buffers are usually adjusted by optical fiber or waveguide delay line.The accuracy of delay adjustment is low and the product of time-delay and bandwidth is limited,which is difficult to meet the requirements of clock alignment accuracy and bandwidth in high-speed optical network.In this dissertation,the theoretical analysis of buffering mechanism based on non-reciprocal silicon-based waveguide are analyzed,the dispersion relations and delay characteristics of non-reciprocal silicon-based magneto-optical（MO）planar and rectangular waveguides are studied.Two kinds of optical buffers of nonreciprocal silicon-based MO waveguide and microrings array coupled with Sagnac ring are proposed,which can not only break through the product of tine-delay bandwidth,but also have high delay accuracy.Therefore,the study is of great significance and application value.The main innovative results can be summarized as follows:（1）The dielectric constant tensor and the permeability tensor are used to describe gyroelectric semiconductor（GES）and gyromagnetic semiconductor（GMS）materials respectively.The dispersion equations of the non-reciprocal silicon-based MO planar waveguides and C-band rectangular waveguide（GES）are studied.The relationship between the one-way transmission bandwidth,dispersion and time-delay characteristics and the waveguide structural parameters are obtained.The nonreciprocal propagation characteristics of surface magnetoplasmons（SMPs）under external magnetic field are studied.The results show that the slow light effect of rectangular waveguide is better than planar waveguide.The slow light effect of rectangular waveguide is most significant when the cladding material is silver,the minimum group velocity can reach 2.8×10^-3c,and the engineering tolerance is 93.5 nm in C-band.The MO non-reciprocity of terbium gallium garnet（TGG）crystal in optical communication band is investigated experimentally.The non-reciprocal parameters of the TGG dielectric constant tensor ε₂=1.2×10^-6ε₀ are obtained from Verdet constant measured experimentally.（2）An optical buffer structure based on a non-reciprocal silicon rectangular waveguide based on MO material is proposed.The write-in and read-out control of the optical buffer can be realized by adjusting the transmittance of output end（transmission method）or adjusting the magnetic field（reflection method）.According to the evolution of signal light in the buffer,the buffering time of the transmission method is 2.12 ps,and the product of tine-delay bandwidth is 666.3.The buffering time of reflection method is 7.15 ps and the product of tine-delay bandwidth is 2247.2.（3）An optical buffer structure based on non-reciprocal MO microrings array coupled Sagnac ring is proposed.The waveguide of one ring is partially covered with phase change material（PCM）.The write-in and read-out control scheme of optical buffer can be realized by switching the crystalline/amorphous state of the PCM.The transmission equations of 1×n microrings array coupled straight waveguide and 1×3 microring array coupled Sagnac ring are studied.The transmission spectrum,reflection spectrum,phase and group delay of optical buffer based on GST or GSST are obtained respectively.The effective buffering time of signal light in the buffer of 1×3 microrings array coupled Sagnac ring is 119.94 ps,and the product of the time-delay bandwidth of the two PCMs can reach 16.56 and 10.73,respectively.