| High power Yb-doped nanosecond lasers have the characteristics of high peak power and large single pulse energy.In recent years,along with the advance of laser technology,the demand for high power nanosecond lasers is increasing worldwide,and the application fields are very wide,so they have the huge development potential and application value.At present,the demand for 1μm high power nanosecond lasers in the industrial field is expanding.The 1μm high power nanosecond lasers are mainly composed of fiber laser and solid state laser.Compared with solid state lasers,fiber lasers have many advantages,such as compact structure,low cost,and so on.The high power and large energy pulse fiber lasers are considered to be the development trend of the future pulse lasers.At present,the traditional laser has been gradually replaced in the field of processing.Therefore,purposeful study of high power pulse lasers is of great significance for promoting the development of laser processing in China.The main research content is high power Yb-doped nanosecond pulse laser based on all-fiber structure.First of all,we study high power nanosecond pulse fiber laser based on diode-modulated technology.Its main technology are diode-modulated technology and main oscillation power amplification(MOPA)technology.Secondly,we will research combination dual-cavity nanosecond pulse all-fiber laser,and we use two pairs of fiber Bragg gratings(FBG)and two segment doped fibers to achieve high power nanosecond pulse output.The main research contents were as follows:1.The basic principle of high power Yb-doped nanosecond pulse fiber laser was analyzed.Combining with the energy level structure and luminescence properties of Yb-doped fiber,the characteristics of 1μm band Yb-doped fiber laser was introduced in detail.The main technology and working mechanism of nanosecond pulse fiber laser were described,including Q-switching,gain-switching,and diode-modulated technologies.2.The principle and the modulation characteristic of the semiconductor laser were studied.The principle and the nonlinear effects of the fiber amplifier were analyzed according to the rate equation of laser.The principle of using Yb-doped fiber as a saturable absorber was introduced in detail.The theoretical model of combination dual-cavity fiber laser was developed.3.The experimental research of all-fiber high power Yb-doped laser based on diode-modulated.The seed laser was a 1064 nm diode-modulated laser,which generated 510μW average output power,and the pulse width is 44 ns at the repetition rate of 20 kHz.The amplifier adopted master oscillator fiber power amplifier(MOPA)configuration,which generated 20.11 W output average power.The laser pulse width was 8.8 ns and center wavelength was 1064.2 nm,M~2 was less than 1.8.The single pulse energy and peak-power after the amplification were 1 mJ and 113 kW.4.The experimental research of all-fiber combination dual-cavity nanosecond laser.The inner cavity used Yb-doped fiber with a core diameter of 10μm as a saturable absorber.The outer cavity used Yb-doped fiber with a core diameter of 20μm as the gain fiber.These two different fibers were connected by transition fiber.Finally,the combination dual-cavity fiber laser could achieve the minimum pulse width of 36 ns,the maximum average power of 21.8 W,the repetition rate varied from9.5 kHz-67 kHz. |
