Research On Nonlinear Gain Fiber Laser Based On 2?m Band

Due to the inherent advantages,such as good directivity,high brightness and strong monochromaticity,laser has been widely used in military,medical,commercial and many other fields.As the communication band,the 1550nm laser has been extensively used in various industries and attract massive attention at home and abroad.While,as the safe mid-infrared laser for human eyes,the 2?m waveband laser only obtain a few studies in the industrial application fields.The 2?m waveband laser has strong atmospheric penetration,which can be used in the fields of laser radar,laser ranging and spatial optical communication.Furthermore,the laser has a strong water absorption peak near the 2?m waveband,which can make the wound heal quickly,thereby it can be applied to the medical surgery.Finally,the 2?m waveband laser can also be serve as the pumping source for 3-5?m waveband mid-infrared laser.There are many methods to achieve the laser in 2?m waveband,one of which is to use a laser diode as a laser source to pump the doped fiber,which can output the laser of 2?m waveband.In general,the doping ionic are thulium(Tm3+),holmium(Ho3+)and so on.Another method to obtain mid-infrared laser is through nonlinear effects like four-wave mixing.In this paper,we designed and researched several fiber lasers in 2?m waveband.Through utilizing the fiber laser with the properties of compact structure,stable performance,low price and simple operation,and combining with the nonlinear effect in gain fiber,the tunable-broadband laser is output stably.This paper firstly introduces the concept,classification,principles and development history of fiber lasers.Various nonlinear effects in the fiber are briefly described,at the same time,the main design schemes and research progress of 2?m waveband fiber lasers are expounded in detail.It also outlines the work arrangements for each chapter.Then a tunable laser source in 2?m waveband was studied.According to the nature of thulium element and the energy level structure diagram as well as the pumping mode of Tm3+,the gain spectrum characteristics of the thulium-doped fiber were investigated.The advantages and disadvantages of different optical resonant cavities are analyzed and compared.On the basis of the ring cavity,a single longitudinal mode thulium-doped fiber laser based on saturated absorber was designed.The output of single longitudinal mode laser is achieved by saturated absorber,simultaneously,the Fabry-Perot filter makes the wavelength of laser output selectively.The thulium-doped laser achieves a tunable range of wavelength from 1870 nm to 2040 nrm which spans 170 nm,and the output power of the laser is from 17 to 44 mW.The stability of the laser is analyzed based on the data which measured by optical spectrum analyzer,spectrum analyzer and oscilloscope,demonstrating the practicability of the laser.A multi-wavelength thulium-doped fiber laser based on four-wave mixing effect is designed with the 2?m waveband laser source.The multi-wavelength laser uses two-stage thulium-doped fiber amplifier to amplify the pump laser,a high non-linear fiber is used as the gain fiber.Combined with the four-wave mixing effect,the laser in 2?m waveband with spacing-tunable and wide band range was achieved by adjusting the wavelength of pump,which can be applied to the field of fiber-optical communication.The laser continuous to output the new wavelengths which the numbers of wavelengths is over 100 and the scope of the output wavelength is up to 140 nm.It is less likely to be achieved in multi-wavelength lasers in 2?m waveband.Finally,the optical parametric amplifier and optical parametric oscillator based on pulse modulation are studied.The basic principle as well as development and application of them are expounded.The dual-pump optical parametric amplifier is designed according to the principle of optical parametric amplification.With the analysis of theoretical and experimental measurement results,an optical parametric oscillator which has a ring cavity instead of the linear structure is built.According to the influence of dispersion and other factors on nonlinear effects,high-germanium-doped fiber is selected as the gain fiber for the optical parametric oscillator.A high-germanium-parameter oscillator based on pulse modulation is designed for the first time,which can output wide-tunable pulsed laser in 2?m waveband.