Studies On Single Longitudinal Mode 589 Nm Laser Based On Crystalline Raman Amplifier

The 589 nm wavelength laser can be used as light source for the sodium guide star system.High power,narrow linewidth sodium yellow light can stimulate the D2 transition of sodium atoms in the atmosphere.By generating resonance fluorescence,it can be used to compensate for the degeneration caused by atmospheric turbulence,and increase the resolution of astronomical telescopes.It plays indispensable role in the fields of astronomy and national defense.In recent decades,sodium guide star lasers have been developed rapidly,and various schemes for implementing sodium guide star lasers have been continuously proposed.Among them,sodium guide star lasers based on crystal Raman amplification technology have great potential,because they can achieve high energy,high power,narrow linewidth,and good beam quality laser output.They also have the advantages of high stability and compactness.In this paper,the Nd:GGG crystal is used as the laser gain medium,and the single longitudinal mode(SLM)passively Q-switched 1062 nm laser was studied theoretically and experimentally using the ring cavity method.The output characteristics of a single frequency Nd:GGG laser amplifier were studied using traveling wave amplification.Using the 1062 nm single frequency laser generated by Nd:GGG laser amplifier as pump source and BaWO4 crystal as Raman medium,single frequency 1178 nm external cavity Raman laser and single frequency 1178 nm Raman laser amplifier were studied.The main research contents are as follows:1.The output characteristics of a quasi-continuous wave LD end-pumped passively Q-switched Nd:GGG single longitudinal mode 1062 nm laser were studied.The single longitudinal mode operation of the laser was realized in the ring cavity.The single pulse energy,pulse duration,and pumping threshold of the passively Q-switched laser were studied in the LD quasi-continuous pump mode.2.The output characteristics of a pulsed amplifier using a Nd:GGG crystal as the gain medium were studied.With a five-stage lamp pump amplifier,the single pulse energy of 140 ?J,pulse duration of 120 ns and repetition rate of 5 Hz single frequency 1062 nm seed source was amplified to 700 mJ with good output beam quality.The amplification ratio is about 5,000.At the same time,using the polarization compensation structure,the final output polarization degree is increased to 83%.3.The output characteristics of a single frequency 1178 nm BaWO4 crystal Raman laser in an external cavity were studied.Using the 1062 nm single longitudinal mode laser with a pulse duration of 130 ns as the pump source,the output characteristics of a Raman laser were investigated when the Raman pump source was above 100 ns.When the pump energy was 59 mJ and pump duration is 130 ns,single frequency 1178 nm Raman laser output with single pulse energy of 3.35 mJ and pulse width of 63 ns was obtained.4.Exploratory work has been done on single frequency crystal Raman amplifiers with the pump pulse duration beyond 100 ns.Single frequency BaWO4 Raman amplifier was designed and built.The Raman amplifier pump source was single frequency 1062 nm laser with pulse duration of 170 ns.The single frequency Raman seed source has maximum energy of 3.35 mJ and pulse duration of 63 ns.Three BaWO4 crystals were connected in series to achieve a total gain length of 12 cm.Through theoretical calculations,the relationship between the amplified Raman output energy and pump energy in this experiment was obtained.