All-solid-state Yellow Laser

All-solid-state lasers have the advantages of small scale,high efficiency and long life. Laser sources in 560-600 nm are of interest for many applications in medicine,spectroscopy, information storage,ladar,atmosphere detection and so on.Therefore all-solid-state lasers in the range of 560-600 nm have attracted much attention in recent years.It is difficult to produce laser emission in these spectra efficiently by frequency-doubling Nd-doped lasers for the absence of fundamental lasers that can operate efficiently in the range of 1120-1200 nm, other ways have been investigated intensively.Stimulated Raman Scattering(SRS)in crystals is an effective method to obtain all-solid-state yellow lasers and obvious developments have been made in recent years.SRS is an effective frequency-shift method.The obtained Raman laser wavelengths are determined by the wavelengths of the fundamental pump lasers and the Raman shifts of the Raman-active media.Raman-active media include solids,liquids and gases.The lasers using liquid and gas Raman media have been studied for many decades.Compared with the traditional gas and liquid Raman media,solid-state Raman media offer high gain,high molecule density,good thermal and mechanical properties,and so on.The lasers using crystal Raman media have the advantages of compactness,high efficiency,high stability.They have wide applications in such fields as information,communication,measurement,military affairs,medical treatment,and so on.Solid-state Raman media and all-solid-state Raman lasers have attracted intensive research interests in the fields of laser materials and solid-state lasers in recent years.Scientists from Russia act as the leading role in the regime of Raman crystal growth and research on the solid-state Raman lasers.Researchers from America, Germany,Australia,etc.are taking part actively in the field of the all-solid-state Raman lasers. Particularly the Austrilia scientists have made lots of research in yellow lasers from crystalline Raman lasers.In the Chinese Mainland,the research groups from Shandong University,Shanghai Institute of Optics and Fine Mechanics,Fujian Institute of Research on the Structure of Matter are engaged in the research for solid-state Raman lasers.There are two major routes to yellow/orange laser generation through SRS.In one scheme,the 1.06μm laser is converted into the first-Stokes laser and the first-Stokes laser is frequency-doubled afterwards to generate the yellow laser.In the other scheme,the 1.06μm laser is frequency-doubled prior to the Raman downshifting.In the first choice, diode-pumped actively Q-switched intracavity frequency-doubled Raman lasers benefiting from the high intracavity peak power of the fundamental and Raman lasers,having the advantages of compactness,small scale,high efficiency and so on,have become the most important choice in yellow lasers from Raman crystals.Yellow lasers with different wavelengths can be obtained by selecting different Raman crystals.KTP is an excellent nonlinear crystal,which has the adavantage of large typeâ…¡phase matching effective nonlinear coefficient,low cost,small variation of phase matching angle with temperature and no deliquescence.It is the ideal choice for the intracavity frequency-doubled Raman lasers.In this dissertation,we investigate the characteristics of LD pumped actively Q-switched intracavity frequency-doubled Raman lasers,in which KTP crystal is used as the frequency-doubling crystal and different Raman and self-Raman crystals are employed.The highest yellow laser output is achieved from a diode-side-pumped system and the highest optical-to-optical conversion efficiency is obtained from a diode-end-pumped system.A theoretical model for the actively Q-switched intracavity frequency-doubled Raman laser is built.The main contents of this dissertation are as follows:1.In the rate equations for the Q-switched lasers,the pump beam and intracavity laser beams are considered to be Top-Hat and Gaussian distributions respectively.They are solved numerically.A group of general curves are given and the comparison with the results under Gaussian pump beam distribution and plane-wave approximation is made. The results show that the solutions of the rate equations under Top-Hat pump beam distribution are different from those under Gaussian pump beam distribution,but the difference is very little.The solutions of the rate equations under both situations can give much more precise theoretical results than those under plane-wave approximation.2.The rate equations for actively Q-switched intracavity frequency-doubled Raman lasers are obtained by considering the spatial distributions of the pump beam,fundamental laser and Raman laser,and the thermal effect in laser gain medium.The rate equations can effectively describe the operating of actively Q-switched intracavity frequency-doubled Raman lasers.3.The characteristics of the yellow laser output from a diode-pumped actively Q-switched intracavity KTP frequency-doubled Nd:YAG/GdVO₄ Raman laser is investigated.When the pulse repetition frequency is 15 kHz and the incident pump power is 10.1 W,the obtained average laser power at 587 nm is 763 mW.The conversion efficiency from diode laser to yellow laser is 7.5%.4.A diode-pumped actively Q-switched intracavity KTP frequency-doubled Nd:YVO₄ self-Raman laser and a diode-pumped actively Q-switched intracavity KTP frequency-doubled Nd:YAG/YVO₄ Raman laser are investigated.In the diode-pumped actively Q-switched intracavity KTP frequency-doubled Nd:YVO₄ self-Raman laser, when the pulse repetition frequency is 15 kHz and the incident pump power is 6.7 W,the obtained average laser power at 589 nm is 482 mW.The conversion efficiency from diode laser to yellow laser is 7.2%.In the diode-pumped actively Q-switched intracavity KTP frequency-doubled Nd:YAG/TVO₄ Raman laser,when the pulse repetition frequency is 15 kHz and the incident pump power is 8.2 W,the obtained average laser power at 588 nm is 610 mW.The conversion efficiency from diode laser to yellow laser is 7.4%.5.Diode-pumped actively Q-switched intracavity KTP frequency-doubled Nd:YAG/SrWO₄ Raman lasers with linear-cavity configuration and three-mirror-cavity configuraton are investigated.In the three-mirror-cavity laser,when the pulse repetition frequency is 20 kHz and the incident pump power is 12.6 W,the obtained average laser power at 590 nm is 1.4 W.The conversion efficiency from diode laser to yellow laser is 11.1%.This is the highest conversion efficiency in intracavity frequency-doubled Raman lasers.6.A diode-side-pumped actively Q-switched intracavity KTP frequency-doubled Nd:YAG/BaWO₄ Raman laser is investigated.By using a convex-plane cavity configuration to counteract the thermal effect,the yellow laser output under high pump power is improved.When the pulse repetition frequency is 10 kHz and the incident pump power is 99 W,the obtained average laser power at 590 nm is 3.14 W.This is the highest yellow laser power from a crystalline Raman laser.7.The characteristics of the diode-pumped actively Q-switched intracavity Nd:YAG/ KLu(WO₄)₂ Raman laser is investigated.When the pulse repetition frequency is 20 kHz and the incident pump power is 7.82 W,the obtained average laser power at 1178 nm is 1.33 mW.The conversion efficiency from diode laser to Raman laser is 17%.A diode-pumped actively Q-switched intracavity KTP frequency-doubled Nd:YAG/ KLu(WO₄)₂ Raman laser working at 589 nm is investigated.An average output power of 227 mW at 589 nm from this laser is obtained.The main innovations of this dissertation are as follows:1.The theoretical model for diode-pumped Q-switched lasers in which the pump beam and intracavity photon density are assumed to be Top-Hat and Gaussian spatial distributions respectively is built for the first time.This theoretical model can describe the performance of the diode-pumped actively Q-switched lasers with good accuracy.The rate equations for actively Q-switched intracavity frequency-doubled Raman lasers are obtained for the first time.These rate equations can effectively describe the performance of actively Q-switched intracavity frequency-doubled Raman lasers.2.The efficient diode-side-pumped actively Q-switched intracavity KTP frequency-doubled Nd:YAG/BaWO₄ Raman laser working at 590 nm is obtained for the first time.When the pulse repetition frequency is 10 kHz and the pump power is 99 W,the obtained average laser power at 590 nm is 3.14 mW.This is the highest yellow laser power from crystalline Raman lasers.3.The highly-efficient diode-pumped actively Q-switched intracavity KTP frequencydoubled Nd:YAG/SrWO₄ Raman laser working at 590 nm is obtained for the first time. When the pulse repetition frequency is 20 kHz and the incident pump power is 12.6 W, the obtained average laser power at 590 nm is 1.4 W.The conversion efficiency from diode laser to yellow laser is 11.1%.This is the highest conversion efficiency in intracavity frequency-doubled Raman lasers.4.The efficient diode-pumped actively Q-switched intracavity KTP frequency-doubled Nd:YAG/GdVO₄ Raman laser working at 587 nm is obtained for the first time.When the pulse repetition frequency is 15 kHz and the incident pump power is 10.1 W,the obtained average laser power at 587 nm is 763 mW.The conversion efficiency from diode laser to yellow laser is 7.5%.5.By analyzing the characteristics of intracavity KTP frequency-doubled Raman lasers with different gain media and Raman media,the regulations for the selection of the gain media and their orientations in intracavity KTP frequency-doubled Raman lasers are obtained.