Study On Two-section Semiconductor Laser Based On Sampled Moiré Grating

With the continuous development of optical communication networks,larger-scale,faster-speed,and higher-capacity information transmission systems are subtly changing people's lives.Traditional discrete photonic devices have some disadvantages like large volume and high power consumption,and no longer meet the needs of optical communication networks.Therefore,the small-sized photonic integrated circuit?PIC?chips appear,and multiple photonic devices can be integrated at the same time.Among a variety of optoelectronic devices,the DFB semiconductor laser has good single longitudinal mode?SLM?characteristics,and is a commonly used light source for optical communication systems and PIC chips.PIC chips are mostly prepared on a silicon-based platform,but the light has a large scattering loss in the silicon waveguide,so the researchers consider increasing the output power of the DFB semiconductor lasers to compensate for the waveguide loss.In addition,DFB semiconductor lasers are also commonly used as light sources for spectral absorption gas detection systems.Because the gas absorption spectrum is very narrow,the requirement for wavelength accuracy is very high.For example,in methane gas detection,the width of the pan band 2?₃ is less than 3.0 nm.Therefore,while pursuing the improvement of the laser output power,the accuracy of the lasing wavelength should also be ensured.In addition,reconstruction equivalent chirp?REC?technology proposes that using sampling grating structure instead of real grating structure,can improve the control accuracy of lasing wavelength by two orders of magnitude.In this paper,from the perspective of improving the output power and wavelength accuracy,we have done some experimental and theoretical research.Firstly,the coupled mode equation and the modified transfer matrix method are combined to analyze the+1sub-grating in the waveguide sampling moirégrating?SMG?,and find that the moiréeffect can be equivalently achieved in the+1 sub-grating.That is to say,through the design of the sampling period,length of SMG,sampling initial phase difference and other parameters of SMG,?phase shift and apodization effect can be introduced simultaneously.Subsequently,we fabricate SMG-DFB semiconductor lasers,which are coated with anti-reflection/high reflection?AR/HR?coatings on both facet to increase the optical power.After encapsulation,the SMG-DFB semiconductor lasers are tested at25.0?and 700.0 m A.Test results show that the output power of the lasers exceed 170.0m W.The average threshold current is 40.0 m A,and the slope efficiency is between 0.26?0.28 m W/m A.In addition,I test the P-I curves at different temperature,the test results show that the threshold current is directly proportional to the temperature,and the slope efficiency is inversely proportional to the temperature.Based on the advantages of SMG,this paper first proposed the use of SMG-GR waveguide grating structure in DFB semiconductor laser.That is,integrating a grating reflector?GR?at one end of SMG to improve the optical feedback for the lasing mode.In the designed SMG-GR-DFB semiconductor laser,the SMG segment is the active region and generates lasing mode.While the GR segment only exists as a reflector,which provides optical feedback for the lasing mode,and does not generate lasing mode itself.AR/AR coatings are used on both facets of the SMG-GR-DFB semiconductor laser,which avoids the introduction of random phases on the facet by HR coating.This paper compares the SMG-GR-DFB semiconductor laser with the SMG-DFB semiconductor laser,and?-EPS?equivalent phase shift,EPS?-GR-DFB semiconductor laser.The simulation results show that the SMG-GR-DFB semiconductor laser has some advantages,such as higher light output power,good SLM characteristics and can be effective avoid the spatial hole burning?SHB?effect.In addition,the preparation of SMG-GR only requires holographic exposure technology and micrometer scale photolithography.The process is mature and the cost is low,which is convenient for large-scale promotion.With so many advangtages,SMG-GR-DFB semiconductor lasers are expected to be widely used in the future optical communication systems and gas detection systems.