Nd：YVO_4小型固体激光器
摘要
激光二极管泵浦的固态激光器被称作：全固态激光器。由于其具有高效、稳定性好、结构简单等特点，被广泛应用于军事、医学和科研中。在本论文中，我们着重讨论了激光二极管泵浦的Nd:YVO_4连续激光器和以Cr:YAG为可饱和吸收体的被动调Q激光器，对a切和45°切割的Nd:YVO_4晶体的激光特性进行了详细的比较。
主要内容如下：
1．概述了LD泵浦固体激光器的发展历史和现状，包括LD泵浦技术和LD泵浦激光器的特点。比较详细的介绍了常见的Nd和Cr离子激光材料，特别是给出了几种广泛使用的Nd离子晶体的参数。
2．我们通过实验比较了a切割和45°切割Nd:YVO_4晶体的连续激光器，发现45°切割的晶体作为增益介质在激光器连续运转的时候，具有某些a切晶体的特性。45°切割的晶体和a切割晶体的激光器都具有较低的泵浦阈值，大约都在20mW。a切晶体对应的连续激光器的斜率效率约为42％，45°切割的约为35％。而且，45°切割晶体激光器出射的激光是线偏振的。
3．在本论文中，我们还比较了两种晶体的使用Cr:YAG被动调Q的激光器的特性，发现此时45°切割的晶体却表现出c切晶体的一些特点。实验证明，相对于a切晶体来说，45°离轴切割Nd:YVO_4比a切晶体更适合被动调Q运转，能够很方便的获得高峰值功率、窄脉宽的激光输出。在被动调Q运转状态下，a切与45°切割晶体激光对应的斜率效率分别为11.3％与8.5％。对于45°切割的晶体，在1340 mW的LD泵浦功率下，我们可以获得峰值功率为1.5kW、重复频率为11.1kHz、脉宽为3.9ns的脉冲。另外，我们还发现45°切割Nd:YVO_4被动调Q激光器处于单纵模运转状态。
4．通过对实验进行分析，我们认为45°切割的晶体表现出同时具有a切和c切晶体的部分特性是因为晶体内部π和σ偏振的受激辐射相互竞争的结果。在所知的范围内，本论文第一次对a切和45°切割的晶体进行了详尽的比较；结合文
中文摘要
献，可以证实450切割的晶体是一种介于a切和c切之间的晶体;进而，提示我
们可以通过改变Nd:YVO;晶体的切割角度来控制被动调Q激光器的输出参数。
本论文的结构如下:第一章中，我们主要介绍了DPsL(diode laser pumped
solid一state laser)背景知识以及一些Nd和C:离子况:体。第二章中，主要描述了
两种晶体的连续运转激光器。第三章中，着重比较了两种晶体在被动调Q运转
状态下的特性差异。第四章对全文做了总结。
Laser-diode-pumped solid-state lasers (DPSL) are named all-solid-state lasers. Due to their advantageous properties such as high efficiency, high stability, compactness, and etc., those lasers have been widely used for many applications in military, medicine and scientific fields. This dissertation is concerned on laser diode (LD) end-pumped continuous wave (cw) and Q-switched Nd:YVO4 laser with Cr4+:YAG as the intracavity saturable absorber.
The main contents are as follows:
1. A brief introduction to DPSL. The development and the characteristics of DPSL were summarized. And the characteristics of Nd and Cr ions laser materials were described in detail; especially, some key parameters of several commonly used Nd ion crystals were also listed.
2. The laser property comparison of off-axially-cut and a-cut Nd:YVO4 lasers in the cw operation domain. We experimentally found the off-axially-cut crystal shared some properties of the a-cut one. Our experiments demonstrated that both 45?off-axially-cut and a-cut crystals could be operated with the low pumping thresholds (20 mW) for the cw lasers. The slope efficiency of the a-cut Nd:YVO4 laser was about 42%, while that of the off-axially-cut Nd:YVO4 laser was about 35%. Furthermore, the light emitted from the off-axially-cut laser was linearly polarized.
3. The laser property comparison of off-axially-cut and a-cut Nd:YVO4 lasers in the passive Q-switched domain. As compared to a-cut Nd:YVO4 lasers, our experiments confirmed that 45-off-axially-cut Nd:YVO4 exhibited better performance for passive Q-switching over a-cut ones, which consequently enabled laser outputs of higher peak powers and narrower pulse widths. For the passively Q-switched laser, slope efficiencies of the a-cut and off-axially-cut lasers were 11.3% and 8.5%, respectively. For the 45-off-axially-cut crystal, we obtained a peak power of 1.5 kW
with a 3.9-ns pulse width and 11.1-kHz repetition rate under the LD pump power of 1340 mW. We also found that the 45-off-axially-cut Nd:YVO4 passively Q-switched laser was easy to operate in the single longitudinal mode.
4. Summary to the previous work. By analyzing the experimental results, we believe that the 45-off-axially-cut Nd:YVO4 exhibited parts of properties both the a-cut and c-cut crystals because of the competition between polarization and polarization simulated emissions. As far as we know, the 45-off-axially-cut and a-cut Nd:YVO4 were compared thoroughly first time in this dissertation. It was confirmed the 45-off-axially-cut Nd:YVO4 was a kind of crystal between a-cut and c-cut one for passively Q-switched laser; furthermore, it implied we could control laser parameters by varying the cutting direction of the laser crystal.
The thesis is organized as follows. In chapter 1, we introduce the background on DPSL and some crystals doped with Nd or Cr ions. Chapter 2 describes the a-cut and off-axially-cut Nd:YVO4 cw lasers. Chapter 3 mainly presents the characteristic difference between a-cut and off-axially-cut Nd:YVO4 lasers in passive Q-switched operation. A brief summary of the whole work is given in chapter 4.
主要内容如下：
1．概述了LD泵浦固体激光器的发展历史和现状，包括LD泵浦技术和LD泵浦激光器的特点。比较详细的介绍了常见的Nd和Cr离子激光材料，特别是给出了几种广泛使用的Nd离子晶体的参数。
2．我们通过实验比较了a切割和45°切割Nd:YVO_4晶体的连续激光器，发现45°切割的晶体作为增益介质在激光器连续运转的时候，具有某些a切晶体的特性。45°切割的晶体和a切割晶体的激光器都具有较低的泵浦阈值，大约都在20mW。a切晶体对应的连续激光器的斜率效率约为42％，45°切割的约为35％。而且，45°切割晶体激光器出射的激光是线偏振的。
3．在本论文中，我们还比较了两种晶体的使用Cr:YAG被动调Q的激光器的特性，发现此时45°切割的晶体却表现出c切晶体的一些特点。实验证明，相对于a切晶体来说，45°离轴切割Nd:YVO_4比a切晶体更适合被动调Q运转，能够很方便的获得高峰值功率、窄脉宽的激光输出。在被动调Q运转状态下，a切与45°切割晶体激光对应的斜率效率分别为11.3％与8.5％。对于45°切割的晶体，在1340 mW的LD泵浦功率下，我们可以获得峰值功率为1.5kW、重复频率为11.1kHz、脉宽为3.9ns的脉冲。另外，我们还发现45°切割Nd:YVO_4被动调Q激光器处于单纵模运转状态。
4．通过对实验进行分析，我们认为45°切割的晶体表现出同时具有a切和c切晶体的部分特性是因为晶体内部π和σ偏振的受激辐射相互竞争的结果。在所知的范围内，本论文第一次对a切和45°切割的晶体进行了详尽的比较；结合文
中文摘要
献，可以证实450切割的晶体是一种介于a切和c切之间的晶体;进而，提示我
们可以通过改变Nd:YVO;晶体的切割角度来控制被动调Q激光器的输出参数。
本论文的结构如下:第一章中，我们主要介绍了DPsL(diode laser pumped
solid一state laser)背景知识以及一些Nd和C:离子况:体。第二章中，主要描述了
两种晶体的连续运转激光器。第三章中，着重比较了两种晶体在被动调Q运转
状态下的特性差异。第四章对全文做了总结。
Laser-diode-pumped solid-state lasers (DPSL) are named all-solid-state lasers. Due to their advantageous properties such as high efficiency, high stability, compactness, and etc., those lasers have been widely used for many applications in military, medicine and scientific fields. This dissertation is concerned on laser diode (LD) end-pumped continuous wave (cw) and Q-switched Nd:YVO4 laser with Cr4+:YAG as the intracavity saturable absorber.
The main contents are as follows:
1. A brief introduction to DPSL. The development and the characteristics of DPSL were summarized. And the characteristics of Nd and Cr ions laser materials were described in detail; especially, some key parameters of several commonly used Nd ion crystals were also listed.
2. The laser property comparison of off-axially-cut and a-cut Nd:YVO4 lasers in the cw operation domain. We experimentally found the off-axially-cut crystal shared some properties of the a-cut one. Our experiments demonstrated that both 45?off-axially-cut and a-cut crystals could be operated with the low pumping thresholds (20 mW) for the cw lasers. The slope efficiency of the a-cut Nd:YVO4 laser was about 42%, while that of the off-axially-cut Nd:YVO4 laser was about 35%. Furthermore, the light emitted from the off-axially-cut laser was linearly polarized.
3. The laser property comparison of off-axially-cut and a-cut Nd:YVO4 lasers in the passive Q-switched domain. As compared to a-cut Nd:YVO4 lasers, our experiments confirmed that 45-off-axially-cut Nd:YVO4 exhibited better performance for passive Q-switching over a-cut ones, which consequently enabled laser outputs of higher peak powers and narrower pulse widths. For the passively Q-switched laser, slope efficiencies of the a-cut and off-axially-cut lasers were 11.3% and 8.5%, respectively. For the 45-off-axially-cut crystal, we obtained a peak power of 1.5 kW
with a 3.9-ns pulse width and 11.1-kHz repetition rate under the LD pump power of 1340 mW. We also found that the 45-off-axially-cut Nd:YVO4 passively Q-switched laser was easy to operate in the single longitudinal mode.
4. Summary to the previous work. By analyzing the experimental results, we believe that the 45-off-axially-cut Nd:YVO4 exhibited parts of properties both the a-cut and c-cut crystals because of the competition between polarization and polarization simulated emissions. As far as we know, the 45-off-axially-cut and a-cut Nd:YVO4 were compared thoroughly first time in this dissertation. It was confirmed the 45-off-axially-cut Nd:YVO4 was a kind of crystal between a-cut and c-cut one for passively Q-switched laser; furthermore, it implied we could control laser parameters by varying the cutting direction of the laser crystal.
The thesis is organized as follows. In chapter 1, we introduce the background on DPSL and some crystals doped with Nd or Cr ions. Chapter 2 describes the a-cut and off-axially-cut Nd:YVO4 cw lasers. Chapter 3 mainly presents the characteristic difference between a-cut and off-axially-cut Nd:YVO4 lasers in passive Q-switched operation. A brief summary of the whole work is given in chapter 4.
引文
1．杨国桢 《略谈我国光物理研究进展》 《物理》1999年11期28卷648-653
2. R.B.Chesher, et.al., Appl.Phys.Lett.23, 235 (1973)
3．陈良惠 《量子阱光电子器件的发展与中国光电子器件》 《中国工程科学》 第1卷第3期75-78
4．王莉 张以谟 吴荣汉 余金中 《半导体激光器的进展》 《激光与红外》第29卷第5期167-270
5．林耀望 潘钟 李联合 张伟 王学宇《GaInNAs／GaAs量子阱激光器的发展与未来》 《光电子技术与信息》第13卷第4期1-6
6．吴雄《激光二极管的发展及其应用前景》《电子与自动化》1998年第1期3-5
7．王德 李学千《半导体激光器的最新进展及其应用现状》《光学精密工程》 第9卷第3期279-283
8. R.J.Keyes, et.al., Phys.Lett., 4, 50 (1964)
9. M.Ross, Pro.IEEE.56,196(1968)
10．李学千 《半导体激光器的最新进展及其应用》 《长春光学精密机械学院学报》第20卷第4期56-63
11．郑权 赵岭 钱龙生《大功率二极管泵浦固体激光器的应用和发展》《光学精密工程》第9卷第1期6-9
12．文建国 吴伟 王石语 蔡德芳《二极管泵浦固体激光器实用化研究》《西安电子科技大学学报》(自然科学版)第30卷第4期539-541
13．朱大勇《美国固体激光雷达技术新进展》《红外与激光工程》第26卷第3期57-61
14．郑权 陈颖新 钱龙生《全固态激光器产业发展的趋势》 《光机电信息》2001年12期17-20
15．许祖彦《光电子晶体与全固态激光器及其应用——光电子技术发展的一个重大方向》 《中国工程科学》第一卷第2期
16．吕百达 马红《二极管泵浦固体激光器研究的一些新进展》《激光与红外》第30卷第2期67-70
17．张思远《稀土激光晶体及其发展》《人工晶体学报》第26卷第3-4期212
18. S. Georgescu etc., Excited-state-absorption in low concentrated Er:YAG crystals for pulsed and cw pumping, Journal of Luminescence 93 (2001) 281-292
19. Takatomo Sasaki etc., Recent development of nonlinear optical borate crystals: key materials for generation of visible and UV light, Materials Science and Engineering, 30 (2000) 1-54
20．杨建虎 戴世勋 姜中宏《稀土离子的上转换发光及研究进展》 《物理学进展》第23卷第3期284-297
21．刘杰 杨济民 何京良《LD抽运Nd：YVO_4、Nd：GdVO_4和Nd：YAG激光特性比较》《激光杂志》2003第24卷第5期28-P30
22．王国富《LD泵浦激光晶体材料的新发展》《人工晶体学报》第27卷第4期1998．11 390-395
23. Y.Kalisky, L.Kravchik, Repetitive modulation and passively Q-switching of diode-pumped Nd-KGW laser C.Labbe, Optics Communications 189(2001) 113-125
24. Voicu Lupei, E.ciency enhancement and power scaling of Nd lasers, Optical Materials 24 (2003) 353 - 368
25. Judith M.Dawes, Peter Dekker, Ying Cai, Q-switching of a diode-pumped Nd:YAG laser with low uniform gain characteristics, Optics Communications 115(1995) 617-625
26. Hailin Wang etc., Experimental study of a high power and high efficiency CW diode-side-pumped Nd:YAG laser, Optics & Laser Technology 36 (2004) 69 - 73
27. Yu.V.Orloveskii etc., Temperature dependencies of excited states lifetimes and relaxation rates of 3-5 phonon (4-6μm) transitions in the YAG, LuAG and YLF crystals doped with trivalent holmium thulium and erbium, Optical Materials 18(2002) 355-365
28．张庆礼 殷绍唐 王爱华 陈长水《Nd：GdVO_4的晶体生长和光谱特性》《量子电子学报》2002．8第19卷 第4期310-313
29．武晓明 张怀金《Nd：GdVO_4晶体的光谱和激光特性》《沈阳电力高等专科学校学报》2001．7第3卷第3期
30. C. Li, J. Song, D. Shen, N.S. Kim, J. Lu, K. Ueda, Diode-pumped passively Q-switched Nd:GdVO4 lasers operating at 1.06μm wavelength, Appl. Phys. B 70, 471-474 (2000)
31．祝俐 秦连杰 孟宪林 杜晨林 刘均海 徐炳超 邵宗书 《新型高效激光物质—Nd：YGdVO_4混晶》《人工晶体学报》2003．4第32卷第2期148-151
32. Z.Hong etl., Laser-diode-pumped Cr4+, Nd3+:YAG self-Q-switched laser with high repetition rate and high stability, Appl. Plays. B 73,205-207 (2001)
33. M.A. Scott, D.L. Russell, B. Henderson, T.P.J. Han, H.G. Gallagher, Crystal growth and optical characterization of novel 3d~2 ion laser hosts, Journal of Crystal Growth 183 (1998) 366-376
34. B. Lipavsky, Y. Kalisky, Z. Burshtein, Y. Shimony, S. Rotman, Some optical properties of Cr~(4+)-doped crystals, Optical Materials 13 (1999) 117-127
2. R.B.Chesher, et.al., Appl.Phys.Lett.23, 235 (1973)
3．陈良惠 《量子阱光电子器件的发展与中国光电子器件》 《中国工程科学》 第1卷第3期75-78
4．王莉 张以谟 吴荣汉 余金中 《半导体激光器的进展》 《激光与红外》第29卷第5期167-270
5．林耀望 潘钟 李联合 张伟 王学宇《GaInNAs／GaAs量子阱激光器的发展与未来》 《光电子技术与信息》第13卷第4期1-6
6．吴雄《激光二极管的发展及其应用前景》《电子与自动化》1998年第1期3-5
7．王德 李学千《半导体激光器的最新进展及其应用现状》《光学精密工程》 第9卷第3期279-283
8. R.J.Keyes, et.al., Phys.Lett., 4, 50 (1964)
9. M.Ross, Pro.IEEE.56,196(1968)
10．李学千 《半导体激光器的最新进展及其应用》 《长春光学精密机械学院学报》第20卷第4期56-63
11．郑权 赵岭 钱龙生《大功率二极管泵浦固体激光器的应用和发展》《光学精密工程》第9卷第1期6-9
12．文建国 吴伟 王石语 蔡德芳《二极管泵浦固体激光器实用化研究》《西安电子科技大学学报》(自然科学版)第30卷第4期539-541
13．朱大勇《美国固体激光雷达技术新进展》《红外与激光工程》第26卷第3期57-61
14．郑权 陈颖新 钱龙生《全固态激光器产业发展的趋势》 《光机电信息》2001年12期17-20
15．许祖彦《光电子晶体与全固态激光器及其应用——光电子技术发展的一个重大方向》 《中国工程科学》第一卷第2期
16．吕百达 马红《二极管泵浦固体激光器研究的一些新进展》《激光与红外》第30卷第2期67-70
17．张思远《稀土激光晶体及其发展》《人工晶体学报》第26卷第3-4期212
18. S. Georgescu etc., Excited-state-absorption in low concentrated Er:YAG crystals for pulsed and cw pumping, Journal of Luminescence 93 (2001) 281-292
19. Takatomo Sasaki etc., Recent development of nonlinear optical borate crystals: key materials for generation of visible and UV light, Materials Science and Engineering, 30 (2000) 1-54
20．杨建虎 戴世勋 姜中宏《稀土离子的上转换发光及研究进展》 《物理学进展》第23卷第3期284-297
21．刘杰 杨济民 何京良《LD抽运Nd：YVO_4、Nd：GdVO_4和Nd：YAG激光特性比较》《激光杂志》2003第24卷第5期28-P30
22．王国富《LD泵浦激光晶体材料的新发展》《人工晶体学报》第27卷第4期1998．11 390-395
23. Y.Kalisky, L.Kravchik, Repetitive modulation and passively Q-switching of diode-pumped Nd-KGW laser C.Labbe, Optics Communications 189(2001) 113-125
24. Voicu Lupei, E.ciency enhancement and power scaling of Nd lasers, Optical Materials 24 (2003) 353 - 368
25. Judith M.Dawes, Peter Dekker, Ying Cai, Q-switching of a diode-pumped Nd:YAG laser with low uniform gain characteristics, Optics Communications 115(1995) 617-625
26. Hailin Wang etc., Experimental study of a high power and high efficiency CW diode-side-pumped Nd:YAG laser, Optics & Laser Technology 36 (2004) 69 - 73
27. Yu.V.Orloveskii etc., Temperature dependencies of excited states lifetimes and relaxation rates of 3-5 phonon (4-6μm) transitions in the YAG, LuAG and YLF crystals doped with trivalent holmium thulium and erbium, Optical Materials 18(2002) 355-365
28．张庆礼 殷绍唐 王爱华 陈长水《Nd：GdVO_4的晶体生长和光谱特性》《量子电子学报》2002．8第19卷 第4期310-313
29．武晓明 张怀金《Nd：GdVO_4晶体的光谱和激光特性》《沈阳电力高等专科学校学报》2001．7第3卷第3期
30. C. Li, J. Song, D. Shen, N.S. Kim, J. Lu, K. Ueda, Diode-pumped passively Q-switched Nd:GdVO4 lasers operating at 1.06μm wavelength, Appl. Phys. B 70, 471-474 (2000)
31．祝俐 秦连杰 孟宪林 杜晨林 刘均海 徐炳超 邵宗书 《新型高效激光物质—Nd：YGdVO_4混晶》《人工晶体学报》2003．4第32卷第2期148-151
32. Z.Hong etl., Laser-diode-pumped Cr4+, Nd3+:YAG self-Q-switched laser with high repetition rate and high stability, Appl. Plays. B 73,205-207 (2001)
33. M.A. Scott, D.L. Russell, B. Henderson, T.P.J. Han, H.G. Gallagher, Crystal growth and optical characterization of novel 3d~2 ion laser hosts, Journal of Crystal Growth 183 (1998) 366-376
34. B. Lipavsky, Y. Kalisky, Z. Burshtein, Y. Shimony, S. Rotman, Some optical properties of Cr~(4+)-doped crystals, Optical Materials 13 (1999) 117-127