| Nonlinear frequency conversion technology is an important way to widen the spectral range,and plays an important role in the optical field.Common nonlinear effects include the second-order nonlinear effects and third-order nonlinear effects.The second-order nonlinear effects contain of the double-frequency,the sum-frequency,the difference-frequency,the optical parametric oscillation and so on.The third-order nonlinear effects contain of the stimulated Raman scattering(SRS),the Brillouin scattering and four-wave mixing.The SRS is the high laser interaction with molecular vibrations or coupled to the crystal lattice.The SRS is with strong direction and high scattering intensity.So it is widely used in the medical,measurement,information and transportation.Laser guided technology to create artificial beacons of light,can effectively solve the problem that the natural beacon is limited in adaptive optics.589 nm sodium lasers can effectively stimulate sodium atom.With the development of the diode-pumped technology and crystal growth,the 589 nm sodium lasers which based on the crystal Raman technology have attracted more and more attention.With the development of the laser technology,the requirement for the laser was higher.But sometimes,the output parameter is contradictory,for example,high power may lead to a poor beam quality,so the laser amplifier technology came into being.Based on the pulse width of the output laser,the amplifiers can be divided into ultrashort pulse amplifier,pulse amplifier and long wave amplifier.In addition,in accordance with the different modes of amplifiers,they can be divided into traveling-wave amplifier,multiple amplifier and regenerative amplifier.Content of this dissertation is divided into two parts.One part studied the SrWO4 and BaWO4 Raman laser output properties based on the Nd:YLF crystal performed as the laser gain media.We realized a four-wavelength laser using Nd:YLF and BaWO4 crystals.The output powers of the four wavelengths were in the same level.Another part of the dissertation we studied two methods to obtain a quasi-continuous-wave(QCW)589 nm yellow laser.One is through an intracavity double frequency Nd:GGG/BaWO4 Raman laser.Another one is by amplifications and double frequency to obtain a single longitudinal mode 532 nm laser,then we can obtain a 589 nm laser by external cavity Raman laser.Specific contents are as follows:1.With the Nd:YLF crystal and SrWO4 crystal as the fundamental gain medium and Raman gain medium,respectively,we observed the output properties of the diode pumped actively Q-switched Raman laser.The fundamental wavelength was 1047.0 nm and the corresponding first stokes wavelength was 1158.7 nm.At the pumping power of 10.5 W,the average output power of the Raman laser was about 2.2 W,with a corresponding conversion efficiency of 20.9%.The pulse width was 8.7 ns.2.With the Nd:YLF crystal and BaWO4 crystal as the fundamental gain medium and Raman gain medium,we demonstrated a four-wavelength laser.The two laser cavity was jointed with a Brewster plate.The two fundamental wavelengths were 1047.0 nm and 1053.0 nm,and their corresponding first stokes waves were 1159.4 nm and 1166.8 nm,respectively.With the pulse synchronized,we obtained the output powers of four wavelengths.And the output powers were in the same level.Five sum-frequency wavelengths were obtained with KTP and LBO crystals.3.With the Nd:GGG crystal as the fundamental gain medium,the BaWO4 crystal as the Raman gain medium,and the KTP as the double-frequency medium,we studied a QCW actively Q-switched 589 nm laser.With a pump frequency of 300 Hz,a pump width of 300 ?s,the average output power of 589 nm laser was about 4.2 W.The pulse width was 13.6 ns and the repetition rate was 33.3 kHz,so the peak power can be calculated to 68.1 kW.4.A twisted optical cavity was used to obtain a single frequency 1064 nm laser.The laser medium was a Nd:YAG crystal.The repetition rate was 50 kHz.The maximum average output power was about 600 mW.The corresponding pulse width was 40 ns,and the value of the beam quality were M2x=1.08,M2y=1.10.5.The seed laser was a single frequency 1064 nm laser.We studied the amplification of the seed laser with a Nd:YAG single crystal fiber.The variation of the spot sizes in the Nd:YAG single crystal fiber were 500-450-500 ?m.At an average pumping power of 5.5 W.the output power of 0.99 W was obtained.And other parameters of the laser was same of seed laser.6.With three diode-side-pumped Nd:YAG modulators as the amplification,we observed the single frequency 1064 nm laser output.In the end,the average output power was about 40 W.And other parameters of the 1064 nm laser were same as the seed laser.7.With a LBO crystal,we accomplished the double-frequency process.A single frequency 532 nm was obtained.The average power was about 20 W.The pulse width was 28 ns,which was smaller than the 1064 nm laser.The value of beam quality in the two directions were 1.30 and 1.42,respectively.The main innovations of this dissertation:1.With the Nd:YLF crystal and SrWO4 crystal as the fundamental gain medium and Raman gain medium,respectively,we observed the output properties of the diode pumped actively Q-switched Raman laser.The fundamental wavelength was 1047.0 nm and the corresponding stokes wavelength was 1158.7 nm.At the pumping power of 10.5 W,the average output power of the Raman laser was about 2.2 W,with a corresponding conversion efficiency of 20.9%.The optical conversion efficiency was higher than previous works.2.For the first time.With the Nd:YLF crystal and BaWO4 crystal as the fundamental gain medium and Raman gain medium,we demonstrated a four-wavelength laser.The two laser cavities were jointed with a Brewster plate.The two fundamental wavelengths were 1047.0 nm and 1053.0 nm,and the corresponding stokes waves were 1159.4 nm and 1166.8 nm.respectively.With the pulse synchronized,we obtained the output powers of four wavelengths.And the output powers were in the same level.Five sum-frequency wavelengths were obtained with KTP and LBO crystals.3.For the first time.With the Nd:GGG crystal as the fundamental gain medium,the BaWO4 crystal as the Raman gain medium,and the KTP as the double-frequency medium,we studied a QCW actively Q-switched 589 nm laser.With a pump frequency of 300 Hz,a pump width of 300 ?s,the average output power of 589 nm laser was about 4.2 W.The pulse width was 13.6 ns and the repetition rate was 33.3 kHz,so the peak power can be calculated to 68.1 kW.4.For the first time,a QCW single frequency 1064 nm obtained by a twisted optical cavity was used as the seed laser.Through four amplification processes and double-frequency process,a high average power,single frequency 532 nm laser was obtained.The value of the beam quality was about 1.3.This laser can be used as the pumping source of a Raman laser to get a 589 nm sodium laser. |
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