Research On Micro-nano Optical Resonator In Optical Communication System

With the arrival of the 5G commercialization era,global data traffic is experiencing explosive growth,which provides new opportunities for the development of optical communication and also puts forward higher requirements for the performance of various optoelectronic devices in optical communication systems.In the optical communication system,some functional passive components play a very important role in many key components of the system,such as optical resonators.Moreover,with the continuous maturity of micro-nano fabrication technologies,optical resonators are gradually developing towards high performance,small size and integration.The focus of research has shifted from the traditional open optical resonator to the optical microcavity.Optical microcavities have various structures,among which F-P microcavities and microring resonators are widely used in optoelectronic devices such as lasers,filters,photodetectors,and sensors due to their relatively simple structures.Therefore,it is particularly important to design and optimize the structure of optical microcavities to further improve the performance of photoelectric devices.This dissertation focuses on theoretical and experimental research on micro-nano optical resonators in optical communication systems.The main research contents and innovations are as follows:1.A novel optical microcavity based on nonperiodic high index contrast subwavelength gratings(HCGs)is proposed.The bottom mirror of the the proposed microcavity is composed of two symmetrical nonperiodic HCGs with small angle beam steering ability.The top reflector consists of multiple pairs of distributed Bragg reflectors(DBRs),and the cavity is filled with air.The theoretical analysis shows that the microcavity can not only greatly increase the one-period-length for the mode light ray inside the microcavity to improve the quality factor,but also limit the oscillating light field to the center of the cavity to reduce the effective mode volume.2.The structure of the proposed nonperiodic HCG microcavity is designed and optimized by rigorous coupled wave analysis and finite element method.When using a high reflectivity HCG reflector with a steering angle of 1° as the bottom mirror of the microcavity,the microcavity has the best performance.At a wavelength of 1550 nm,the quality factor of the microcavity with a cavity length of 1549.88 nm and a cavity width of about 24 μm is 4379,and the effective mode volume is 1.361 μm2·d.Compared with the ordinary F-P microcavity with the same size,the quality factor is increased by 2.5 times and the effective mode volume is reduced by 17.67 times.3.A novel optical microcavity based on nonperiodic HCG-DBR is proposed.The top reflector of the microcavity is DBRs,and the bottom reflector is a combination of nonperiodic HCGs and DBRs.The medium filled in the cavity is air.The incident wavelength is 1550 nm,and the steering angle of the bottom HCG reflector is 1°.When the width of the microcavity is about 24 μm,and the cavity length is 1549.88 nm,the maximum quality factor of the cavity can reach 8857.Compared with nonperiodic HCG microcavity of the same size,the quality factor of the novel F-P microcavity is increased by about 2 times,and the effective mode volume remains about 1.36μm2·d.4.The high extinction ratio filter based on silicon cascaded microrings is experimentally tested.The transmission spectrum and temperature characteristics of the device are tested in cooperation with others.First of all,the test of the transmission spectrum characteristics of the runway-type three-level microring with the theoretical extinction ratio between 70 dB and 80 dB is completed.The test results show that the free spectrum range of the device is consistent with the theoretical value,and the extinction ratio is greater than 60 dB.Then,the influence of temperature on the resonant wavelength of the point coupled three-level microring is investigated.The test results show that the resonance wavelength has good linearity in the temperature range of 30℃-55℃,and the temperature sensitivity coefficient is 56 pm/℃.