Investigation Of Thermal Effects In Tunable Semiconductor Photonic Integrated Devices

With the rapid development of optical communication,the higher demand of dynamic flexibility and functionality of optical communication network is proposed.To meet people's diverse communication needs,there have been various integrated photonic devices developed with innovations.Tunable semiconductor photonic devices are playing important roles in wavelength division multiplexing(WDM)network systems and next-generation dynamic optical networks.However,such semiconductor devices may be influenced by the thermal effects with different levels,since semiconductor meterials are very temperature-sensitive.In this thesis,thermal effects of typical tunable photonic devices,such as semiconductor optical amplifier integrated with sampled grating-distributed Bragg reflector(SOA-SG-DBR)laser module and array,thermally tuned multimode interference(MMI)power splitter,are investigated.Thermal managements and optimizations are proposed to suppress or use the thermal effects.The main content of this thesis are organized as follows:(1)Based on the thermal generation mechanisms,thermal model of SOA-SG-DBR laser module is developed by using finite element method(FEM).Then the temperature distribution,thermal crosstalk between adjacent elements and dynamic temperature changes are analyzed.Based on the dynamic transfer matrix method(DTMM),the optical model of SOA-SG-DBR laser module is developed further.Using this temperature-dependent DTMM optical model,the influences of dynamic thermal effects on the optical output properties are examined in detail.(2)Suppression and compensation method of the thermal effects in the SG-DBR laser modules are investigated,then corresponding implementing schemes are proposed.An optimized wavelength drift compensation method based on the dynamic phase section's injection currents is proposed,moreover,realized by field programmable gate array(FPGA).Next,the analyzed object is extended to the SOA-SG-DBR laser array,by using FEM,the corresponding thermal model is developed.According to the calculated temperature distributions,the minimum value of the spacing of the laser array is obtained to make sure there is no thermal crosstalk between the adjacent submodules.Finally,we propose a thermal model of SOA-SG-DBR laser array integrated with thermoelectric cooler(TEC),disscuss the TEC's power consumptions when the ambient temperature varies and select a better scheme of submount's material and TEC stages respectively.(3)Mechanisms of thermally induced wavelength tuning,related numerical modeling and optimization of thermal design are discussed.A more comprehensive thermal model of thermal tuning SG-DBR laser is proposed,including a thermal conduction model and a thermoelasticity model.By using the thermal conduction model,the temperature distributions of laser without/with thermal isolations(air trench)is studied and compared,then,thermal tuning efficiency problems are discussed.By using the thermoelasticity model,thermal stress distributions when thermal isolations' geometry changes are obtained.Then considering the temperature and the thermal stress distribution,the geometry of air trenches is optimized,and the thermal tuning efficiency is clearly improved.Finally,based on temperature-dependent TMM optical model of the thermal tuning SG-DBR laser,the optical output properties are calculated,including wide wavelength tuning ranges and narrow linewidths.(4)Structure optimizations of the thermally tuned reconfigurable MMI power splitter are investigated.Based on beam propagation method(BPM),a thermal model of thermal tuning MMI power splitter is proposed.Then,to achieve the needed reconfigurable function,the corresponding refractive index changes and phase shifts are discussed.Next,based on FEM,a thermal model of the MMI splitter is developed.Different temperature distributions under different heating powers are calculated.To further improve the thermal tuning efficiency of this device,some thermal isolations are designed in specific regions of the multimode waveguide.By comparing the temperature distributions of differnet thermal tuning regions,the influence of the isolations' geometry on thermal crosstalk is examined in detail.Finally,by using the thermo-optics model of thermal tuning MMI splitter,from the angles' of thermal tuning efficiency and optical output properties,the geometry of the thermal isolations are optimized.