Study On Diode-pumped Argon Atoms Continuous Laser And Power Scaling

As considered as an alternative to an alkali vapor laser,diode pumped metastable rare gas laser（DPRGL）is a new hybrid laser that uses a diode laser to pump a discharge gas to output laser.The DPRGL systems are regarded as an important potential laser source for future industrial,medical and military applications due to its many advantages,such as high quantum efficiency,excellent beam quality and good atmospheric transmission characteristics.At the same time,the nonlinear effects of high-power continuous single-mode laser and ultra-fast laser can be prevented.Due to the limitation of bottleneck for the continuous higher power lasers output and the current research status of watt-level power output,the enabled techniques for DRPGL systems are investigated by using the Ar/He mixed gas as the gain medium,and some instructive conclusions have been obtained.The main conclusions of this thesis are summarized as follows:（1）By simplifying the energy level structure of the complex excited state argon atoms generated by the J-l coupling mechanism,the operating mechanism of the more complete five-level structure for DPRGL is determined.The exploratory experimental study of cw DPRGL system was carried out by continuous DC discharge.And the gain output processes were measured by spectrometer.The excited argon atoms transition spectrum in the discharge plasma was determined and the results of measurement were basically the same as the excited state transition of argon atoms in the NIST database.（2）Combined with the pressure broadening mechanism of the metastable argon absorption linewidth,a theoretical model of DL linewidth compression based on Littrow structure is established from the perspective of wave equation,and the factors affecting DL linewidth are analyzed.The results show that DL output with a linewidth of 0.04 nm（20GHz）can be obtained by increasing the length of outer cavity,reducing the reflectance of the output face of DL active region,and increasing the diffraction efficiency of grating,which is basically matched to the absorption linewidth of Ar（1s₅）under an atmospheric pressure Ar/He,and the results verify the easy operation and correct function of DL linewidth compression based on Littrow structure.In addition,due to the shortcomings of traditional end and side pumping structures,the end and side pumping schemes with RF slab structure based on multi-pass pumping processes are exploratorily proposed.（3）Since the total efficiency of DPRGL is limited by the low discharge efficiency and the exciting three-level model cannot fully explain the DPRGL operation mechanism,a five-level model of DPRGL including discharge and optical pumping dynamics is established by the principle of particle number and energy conservation.The impact of the two-stage pumping conditions on the output characteristics of DPRGL and the energy loss mechanism during continuous operation are comprehensively analyzed.And the results show that under the condition of an atmospheric pressure Ar/He,the number density of Ar（1s₅）can be increased by increasing the reduced electric field and the specific gravity of Ar,which is beneficial to overcome the bottlenecks and realize continuous stable output of DPRGL.And a 100 kw DPRGL output with the total efficiency and the opt-opt conversion efficiency of51.5%and 62.5%,respectively,can be achieved by optimizing the parameters.The above conclusions show that high-power and high-efficiency cw DPRGL output can be realized by optimizing the two-stage pumping conditions.（4）Aiming at the current research status of using a single resonant cavity in the process of scaling the output power of DPRGL,a DPRGA scheme based on MOPA structure is firstly proposed in this dissertation,and a DPRGA theoretical model for single-pass amplification process was established and analyzed.The results show that compared with a single oscillator,the appearance of seed laser in DPRGA can accelerate the recycling rate of total particles,increase the utilization rate of particles,and facilitate the output of higher power.And 100 kW or megawatt laser output of DPRGA can be achieved through the parametric optimization.The above conclusions indicate that DPRGA is a potential technical solution to increase the output power of DPRGL.（5）Aiming at the current experimental research on the development of DPRGL systems using end-pumped structure,a model of single-sided with two-way pumping structure for DPRGL is established and analyzed.And an iterative numerical solution process based“end-pumped algorithm”is given.In order to balance the speed and accurate of calculation,the appropriate number of mesh divisions is obtained by iterative algorithm,which lays a foundation for theoretical analysis of the factors affecting the output characteristics of the side-pumped DPRGL.Megawatt-level laser output with high-efficiency and excellent beam quality can be achieved by optimizing the gain medium size and reasonable diode pumping parameters and combining the multi-channel symmetric pumping,multi-fold cavity,heat dissipation by gain medium flow circulation and multi-stage MOPA amplification.In this dissertation,the DPRGL particle transition mechanism is deeply explored.The reasonable discharge structure and optical pumping structure have important academic significance and application prospects for achieving high efficiency and high power DPRGL continuous laser output.