The Research Of Wavelength Tunable Laser Based On Novel Structure And Its Applications

Continuous-Wave Wavelength Tunable Laser sources(hereinafter referred to as"tunable lasers")are widely used for Wavelength Division Multiplexing(WDM)system,Flexible Optical Switching Network,and Laser Sensing,etc.At present,the new developments of these application scenarios have higher requirements for the tunable lasers which are of high-performance and low-cost.In this context,this thesis explored a set of comprehensive theoretical and experimental researches on novel structure tunable lasers,two kinds of lasers are studied here:first,the micro-ring resonator(MRR)structure external cavity lasers based on heterogeneous silicon photonics integration platform;and second,the tunable fiber laser which is based on multi-mode inference(MMI)structure filter.As a result,a few performance parameters of lasers,which are important for practical applications,were improved;in addition,several practical applications of these lasers were explored.The highlights of this work are summarized as follow:1.We proposed a transmission line model for Widely Tunable Lasers with Micro?ring Resonator External Cavity,for the use of the structure design and the parameters optimization of these kinds of lasers,the validity of this model was verified by experiments.Firstly,the phase noise theory of semiconductor lasers and methods of laser linewidth reduction were summarized,systematically.The principle and mechanism of the linewidth reduction effect for low loss silicon micro-ring resonators structure in the external cavity semiconductor lasers were deeply studied,and the design rules of tunable lasers were reviewed.Secondly,the transmission line model of such kind of lasers was established,and then it was verified by experiments,the model can be used to calculate main performance characteristics of the laser,thus,it is convenient to use it for the laser structure optimization and design parameters design.2.We did a comparison study on the performance characteristics of several types of micro-ring resonator lasers with different external cavity structure design schemes,and we proposed the application scope of these laser designs.And then,we optimized the two designs of laser external cavity:the one with an asymmetric Mach Zehnder auxiliary structure,to further increase laser SMSR;and the other one with parallel three rings,to further reduce laser linewidth.Firstly,several kinds of micro-ring resonator external cavity lasers based on the"add-drop scheme"and"coupled-ring" structures were analyzed theoretically.Secondly,the comprehensive experimental study and data analysis of the fabricated lasers were carried out,for these lasers with different structures,experimental results showed that,single-mode wavelength tuning ranges which are between 20 nm level and 40 nm level,in C+L band for optical communication experiments,3 dB laser linewidths which are between 150 kHz level and 280 kHz level,and laser side mode suppression ratio(SMSR)which are all above 40 dB,were performed.Finally,the performance characteristics,advantages and disadvantages and application scope of these lasers were summarized and compared.Things,mentioned above,provide valuable experiences and inspirations for further optimization for such kind of laser,both in design and characterization.3.We made a deep research on the tuning method for tunable lasers,to meet the laser performance requirements of the photonics microwave generation which is based on heterodyne beating;and then we demonstrated the practical performances of high-frequency microwave tunable generator and microwave tracking generator based on heterogeneous silicon photonics integrated circuits;finally,we completed the performance analysis.For the microwave tracking generator chip,results showed that,two channels of microwave whose frequency interval is a specific value,was performed,the microwave frequency interval can be set,arbitrarily,in the range of 0.01 GHz to nearly 10 GHz.Finally,methods and suggestions for further improving the performance of the microwave generator chip integrated with lasers were summarized,based on experimental results analysis.4.We proposed and fabricated an all fiber tunable laser based on taper coreless fiber multimode interference structure,and then,this proposed tunable laser was applied to refractive index and temperature sensing experiments.Details include:Increasing the sensitivity of“single-mode coreless single-mode"structure by fabricating a taper structure on the coreless fiber.Tactical design and fabrication were done,to make the proposed MMI structure become suitable to be used as the filter for a ring cavity erbium doped fiber wavelength tunable laser.The proposed tunable laser can be used for optical sensing system.In the measurement,the laser SMSRs are higher than 40dB;for RI measurement,the average sensitivity reaches 163.80 nm/RIU,while for temperature measurement,a sensitivity of 10.8 pm/0C is achieved.