| With the rapid growth of ultra-high speed mobile networks and Internet connected devices,as well as the rise of artificial intelligence(AI),network traffic is "explosive" growth.In order to meet the increasing demand of network bandwidth and data capacity,the reliability,miniaturization,sensitivity,power consumption and loss of optoelectronic devices in optical communication are put forward,which makes the advantages of photonic integrated devices and optoelectronic integrated devices gradually prominent.The key technologies involved in photonic integration and optoelectronic integration include material growth,structure design,fabrication process and so on.In the aspect of structure design,some functional passive devices play an important role in photonic integration and optoelectronic integration,such as optical resonators.Optical resonator can be used in laser,optical filter,photodetector,light modulator,sensor and other optoelectronic devices.Therefore,it is very important to design and optimize the structure of optical resonator and apply it to various optoelectronic devices to improve the performance of devices.This paper focuses on the research of micro-nano optical resonators for photonic integration and optoelectronic integration.The main innovations and research results are as follows:1.A new type of roof optical microcavity is proposed.The top mirror of the microcavity is a roof structure,which is composed of two symmetrical distributed Bragg reflectors(DBRs)with proper inclined angle.The bottom mirror is a planar DBR structure.Due to the special design of the top mirror,not only the resonant beam path of the mode light in the cavity is greatly increased,the quality factor is improved,but also the cavity light field is limited in the small central area,which reduces the effective mode volume of the cavity.When the resonance wavelength?=1550nm,the top mirror inclined angle ?=5°,the cavity length is 474.59nm,and the lateral dimension is 2907nm,the proposed optical microcavity can obtain a high quality factor and a small mode volume,with the quality factor of 5762.9 and the effective mode volume of 0.256 ?m3.For the same size F-P optical microcavity,the quality factor is 3988.9 and the effective mode volume is 0.696?m3.Therefore,the quality factor of the roof optical microcavity is increased by 44.7%,the effective mode volume is reduced by 63.2%,and the Q/V is increased by 3.93 times.2.A new type of cone top cylindrical optical microcavity is proposed.The top mirror of the microcavity is cone shaped DBR,and the bottom mirror is a planar circular DBR structure.Due to the special design of the top mirror,the boundary diffraction loss of the microcavity is small,and most of the light energy is limited in the central region of the cavity,which has small mode volume and large quality factor.The simulation results show that the Q value of the microcavity is 52748.6 and the effective mode volume is 0.249 ?m3 when the resonance wavelength ?=1150nm,the top mirror inclined angle ?=4.5°,the cavity length is 4508.7nm and the diameter is 2821.2nm.For the same size cylindrical optical microcavity,the quality factor is 43603.2,and the effective mode volume is 0.512?m3.Therefore,the quality factor of the cone top cylindrical optical microcavity is increased by 21%,while the effective mode volume is reduced by 51%,and the Q/V is increased by 2.48 times.In addition,the tolerance of the cone top and the output beam characteristics are studied.The results show that the microcavity has good beam output characteristics,and the top mirror of the microcavity has high tolerance in the flat top range of 120nm.3.The optical resonator of VCSEL in integrated chip is optimized,and a novel cavity-in DBR structure is proposed.Cavity-in DBR structure is a low Q-value cavity composed of two low reflectivity mirrors,and the cavity contains periodic DBR with high reflectivity.The optical resonator of VCSEL is composed of two cavity-in DBR structures.The simulation results show that the reflectivity of the top mirror and the bottom mirror of VCSEL is close to 99.7%at the emission wavelength of 850nm,and the transmissivity is more than 95%at the detection wavelength of 805nm,and the detection window range of high transmissivity is more than 15nm.4.The fabrication of the above-mentioned integrated chip and the test of VCSEL and PIN photodetector in the integrated chip are completed respectively.Firstly,the test results show that the VCSEL can be successfully lased.The measured threshold current is 9mA,and the slope efficiency is about 0.74W/A.Secondly,the test of PIN photodetector is completed.The test results show that the photodetector works normally with a responsivity of 0.615 A/W,and the detection window of the integrated chip ranges from 801nm to 809nm.According to the literature,the responsivity of GaAs PIN photodetector with 2?m absorption layer thickness is about 0.7A/W,so it can be inferred that the transmittance of VCSEL unit in the detection window is more than 95%.5.A high extinction ratio filter based on silicon-based cascaded microring for single photon detection is designed.Based on the transfer matrix theory,the point coupled third-order,fourth-order and fifth-order microring filters with microring radius(R)of 10?m and 15?m respectively and the racetrack type third-order,fourth-order and fifth order microring filters with R of 10?m and directional coupling length(L)of 10?m are designed under the condition of waveguide loss of 3dB/cm,group refractive index of 3.907 and free spectral range(FSR)of 800GHz?1.2THz.The simulation results show that the designed filters has extinction ratio(ER)of more than 100dB.The width of straight waveguide and microring is 0.5 ?m.The height of microring is 150 nm and that of planar waveguide is 70 nm.At the same time,the racetrack type three-order microring with R of 10?m,L of 10?m and ER between 70dB and 80dB is also designed.6.The high extinction ratio filter based on silicon cascaded microring is tested.The test of the racetrack type three-order microring with ER between 70dB and 80dB was completed without heating adjustment.The test results show that the FSR of the filter is consistent with the theoretical design,and the extinction ratio is more than 55dB.7.The fabrication of the cone top reflector is investigated.The cone top mirror with small inclined angle is approximated by partial arc with large radius.An arc-shaped top mirror with a diameter of 20?m and a height of 1.9?m was fabricated by the photoresist hot-melt method. |
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