| Since 1960s,lasers have developed rapidly in terms of wavelength diversification,high power(average and peak)and miniaturization,which has promoted the rapid development of manufacturing,life science,information technology,scientific research and national defense.Since the 21st century,with the continuous development of technologies such as ultra-high speed optical interconnection,coherent optical communication,coherent detection and high-precision space exploration,stricter requirements for laser light sources have been put forward.For example,40 g/100 g high-order modulation network in coherent optical communication and the higher-speed coherent wavelength division multiplexing communication systems all require narrow line width lasers with a line width of 300-500 k Hz.In the automotive field,with the development of smart cars to unmanned driving,it is necessary to further reduce the laser linewidth of vehicle-mounted all-solid-state lidar to meet its requirements for imaging distance and object definition.In the field of space exploration,adaptive optics can improve the imaging error of spatio-temporal random optics,and the key to improving the performance of adaptive system is the size of laser linewidth.Considering the large-scale commercial application of this high-coherence technology in the future,the semiconductor narrow-line laser source with direct electric pumping,wafer-level manufacturing and complex integration with other photonic devices will be the most attractive choice.In this paper,the technology of integrated narrow linewidth external cavity semiconductor laser with optical feedback method in butterfly package,as well as the laser coupling package and testing technology are studied.The details are as follows.1.Design the structure of external cavity narrow linewidth laser and analyze the feasibility.Because the micro-ring resonator is simple in structure,easy to manufacture and integrate,the high Q micro-ring resonator and DFB laser butt coupling technology are used to manufacture narrow linewidth lasers.The micro-ring resonator is fabricated in a CMOS compatible doped silicon glass platform with high refractive index,and the Q value is as high as 8.15×10~5.Based on the self-injection locking theory,we theoretically analyze the narrow linewidth laser produced by coupling DFB laser and micro-ring resonator.Substituting the actual parameters,we finally get that the linewidth compression factor of the laser is 470,and theoretically the linewidth of the laser can be compressed by 220900 times.2.Experimental verification of narrow linewidth semiconductor laser with micro-ring.A narrow linewidth laser is fabricated by coupling packaging,and the performance of the laser is tested.In the process of coupling,in order to achieve better coupling effect,the fiber micro-lens is adopted,and the influence of fiber micro-lens structure on the coupling effect is analyzed.In the process of packaging,the butterfly shell is sealed with black glue.Finally,the performance of the narrow linewidth laser is tested on the platform of automatic testing program written by Matlab.The linewidth of narrow linewidth laser is compressed from 2MHz to 6 k Hz by delayed self-heterodyne method. |
