Nonlinear Optical Properties And Application Of Lowdimensional Group-VA Semiconductors

Ultra-fast passive fiber lasers have the advantages of high beam quality,robustness,no collimation,compact system,simple structure,etc.,and have impor ta n t applications in communication,industrial processing,defense,biomedical and othe r fields.The saturable absorber(SA)has a key role in passive mode-locked fiber lasers,which has high requirements for the application of linear materials:large worki ng bandwidth range,ultrafast response,low losses and and stable physicochemi ca l properties.With the rapid development of material preparation and laser technol o g y,the laser can be used in a variety of applications.With the rapid development of material preparation and laser technology,the development of SA has made a quantu m leap from dyes to semiconductor saturable absorption mirrors(SESAMs),while pushing the rapid development of mode-locked lasers towards high power,high beam quality,and ultra-short pulses.However,the complexity of SESAM prepara ti o n process,high cost and narrow application band limit the development of mode-loc k e d lasers.Along with the application needs of high-performance ultrafast fiber lasers,there is an urgent need to find saturable absorption devices with ultra-fast respons e,wide band absorption,and stable performanc e.With the development of material technology,two-dimensional materi al s represented by graphene provide opportunities for the development of ultrafast fiber lasers.Graphene is a two-dimensional material with a hexagonal honeycomb lattic e composed of carbon atoms and sp²hybrid orbitals.Its unique zero-bandgap ener gy band structure gives it wide-band absorption characteristics,and it has been successfully applied to passive applications with different operating waveleng th s.Mode-locked fiber lasers.However,the modulation depth of graphene is limited,which limits the output performance of the mode-locked fiber laser to a certain extent.The structure of black phosphorus is similar to the layered structure of graphene,but is different from the zero band gap of graphene.The two-dimensional black phosph or u s material has a direct band gap energy band structure adjustable from 0.3 to 2 e V,which has been successfully used to modulate different wavelength bands.Mode-locked fiber laser.However,the nature of black phosphorus is unstable,and it is easily hydrol yz e d and oxidized in the air,which makes it difficult to use black phosphorus as a satur a te d absorber to maintain a stable and long-lasting pulse output.Focusing on the applica ti o n requirements of saturable absorbers with ultra-fast response,wide-band absorpti o n,and stable performance,we turned our research focus to other elemental semicondu c to r materials of the same family as black phosphorus,and successfully achieved stable,wide-band ultra-fast fiber laser output.The main contents are as follows:(1)The wide-band nonlinear optical properties of black phosphorous nanosh e e ts have been studied,and ultra-fast fiber laser output has been successfully achieved.A few-layer black phosphorous nanosheets were prepared by the liquid phase lift-o ff method,and the broadband nonlinear optical response of the black phosphor o u s nanosheets was systematically studied by Z-scan technology.Transfer it to the polishe d surface of the side-polished fiber,and build a multi-band ring laser.The black phosp ho r can achieve short-term pulse output.This experiment proves that black phosphor o u s nanosheets can be used as a broadband nonlinear optical modulator to generate pulsed lasers in multiple wavelength bands.However,the experimental results also reveale d that black scales are difficult to stabilize long-lasting output pulses as satur a bl e absorbers.(2)The ultrafast nonlinear optical properties of the antimony film are studied,and the stable optical communicati on band mode-locked fiber laser and mid-infrared Q-switched laser output are realized.The antimony material with a thickness of 12.8nanometers is grown by vapor deposition(VD)method,and the Sb film has a broadband nonlinear saturable absorption charac teristic in the spectral range of 800 to1930 nanometers.The Sb film grown on the substrate is coupled with the side-polis h e d fiber to form a saturable absorber based on evanescent field coupling.The satur a bl e absorber was coupled into an erbium-doped fiber ring laser,and a Q-switched pulse output with a pulse duration of 936 ns and a mode-locked pulse sequence with a duration of 753 fs were realized in the communication band.In addition,by coupli n g the antimony film into an erbium-doped ZBLAN fiber laser,a stable Q-switched pulse with a duration of 824 nanoseconds in the mid-infrared band was successfully obtaine d.The experimental results verify that the Sb film can be used as a very promi si n g broadband optical signal modulator.(3)The broadband ultrafast nonlinear optical properties of the bismuth film are studied,and the stable working optical communication band mode-locked fiber laser and mid-infrared Q-switched laser output are realized.In this work,a highly stable single crystal continuous Bi film was prepared by the vapor deposition(VD)metho d,and its broadband nonlinear optical response in the near-infrared to mid-infr ar e d wavelength range was studied,revealing the broadband nonlinearity of the Bi film for the first time Optical response.In addition,the energy band structure and surface state of the Bi film were theoretically calculated,and the broadband response characteris ti c s of the Bi film as a topological insulator were proved.In addition,we have also successfully achieved a 645 femtosecond fiber laser output,which uses a Bi film-coated D-shaped fiber as a saturable absorber;further,the bismuth film is coupled into an Er³⁺-doped fluoride fiber laser to obtain a pulse A stable Q-switched mid-infr ar e d pulse output with a duration of 1820 ns.Experimental results show that Bi-based thi n film optical devices can indeed become excellent candidates for broadband nonli ne a r optical devices.