Research On 4×4 Thermal Optical Switch And Switch Matrix With Trapezoidal Air Trenches

As the core device of photonic integrated circuits,the optical switch is the basic unit of high-speed data transmission and exchange of the circuits,with one or more optional transmission ports,which can flexibly convert the path of optical signal transmission.Optical switch arrayscasecaded by optical switch units are widely used in applications such as optical path establishment,switch protection and optical packet switching.Optical switches and arrays can be realized by polymer materials since polymer materials have the advantages of high thermo-optical coefficient,low cost,and tunable refractive index.Based on the thermo-optic effect of the polymer material,the refractive index of the optical waveguide can be changed by temperature rise,so the switch states can be changed by controling the shifts of phase shifters.The trapezoidal air trenches are used as thermal isolation structure to reduce heat diffusion to the surrounding area while the heaters are on.In this paper,we used the polymer as the optical switch material,4 × 4 MMI(Multimode interference coupler)as the optical switch structure,thermal tuning to control the state transition of the optical switch,and air trench as the thermal isolation structure.The design of the optical switch unit is optimized by the Beam Propagation Method(BPM)to achieve low loss,small size optical switch and arrays.The main research contents of the paper are as follows:1.Optimal design of 4×4 MMI thermal optical switch with trapezoidal air trenches.A polymer 4 × 4 MMI thermal optical switch with trapezoidal air trenches is proposed to increase the number of portsand and reduce the loss.The excess loss and imbalance of the MMI coupler under different widths and output lengths are analyzed.Then,we analyzed the influence of different sizes of taper waveguide.The required phase shifts while routing the signls between different input ports and output ports are calculated.In order to obtain the relevant structural parameters of the thermal-optical switch with good performance,we analyzed the effect of different parameters of trapezoidal air trenches and different temperature rises on the performance.And the wavelength dependence of the extinction ratio,excess loss,and insertion loss of the optimized thermal-optical switch is analyzed.Simulation results show that the optical switch has a maximum insertion loss of 0.22 d B,a minimum extinction ratio of 21 d B,and a device size of less than 5400 μm.2.Analysis of a 4×4MMI-based optical switch array.In order to reduce the number of optical switch units due to the scaling up of the arrays,optical switch arrays was built on the basis of the proposed 4×4MMI thermal optical switch.The 2×2MMI coupler is used as a cross-waveguide and the structural parameters are optimized to minimize the insertion loss.The differences of insertion loss,number of optical switch units of switch arrys in different network types and sizes are analyzed.In order to reduce the number of optical switch units in the optical switch arrays,the proposed 4×4 MMI thermal optical switchs are used to build non-blocking Spanke arraysand reconfigurable non-blocking Benes arraysrespectively.The simulation results show that the maximum crosstalk of the two arrays is-25 d B and-32 d B,respectively,and the maximum insertion loss is 1.51 d B and 1.47 d B,respectively.