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射频强度调制激光作为激光雷达系统的载波可以有效提高系统的抗干扰和抗散射能力,高功率宽带射频强度调制光源是实现高分辨率远距离探测的关键.本文采用在Nd:YAG激光器的耦合腔中插入一对四分之一波片的方法实现了频差调谐范围为30 MHz1.5 GHz的双频激光输出,结合光纤振荡功率放大技术,将双频信号光功率放大为50 W.耦合腔双频种子源具有良好的功率和频率稳定性,输出功率为9.5 mW时,功率标准差为0.145 mW,稳定性为1.52%,输出双频激光的频差为250 MHz时,拍频的标准差为1.6144 MHz.种子光进行三级光纤功率放大,得到50 W双频激光输出.放大后的双频激光功率波动范围小于0.1 W,双频拍频的标准差为1.777 MHz,很好地保持了放大之前的功率稳定性和双频频差稳定性.A high-power wideband radio-frequency (RF) intensity modulated continuous wave light source is demonstrated. The high-power dual-frequency light source is obtained via a dual-frequency laser signal seeding fiber power amplifier. A diode laser pumped dual-frequency laser is built as the seed and a diode laser pumped three-stage Yb3 + doped large mode area fiber power amplifier is used to enhance the output power to 50 W. In the dual-frequency seed laser, a coupled cavity composed of the Nd:YAG gain crystal and output coupler is used as the mode selector and enforces single longitude mode to oscillate. Two quarter wave plates are inserted in the laser cavity to lift the frequency degeneration of the two orthogonally polarized modes. By changing the angle between the fast axes of the two quarter wave plates, the frequency difference between the two orthogonally polarized modes can be tuned from 30 MHz to 1.5 GHz. The standard difference of beat frequency is 1.6144 MHz and stability is 1.52% when a frequency difference of output dual-frequency laser is 250 MHz. This stable dual-frequency seed signal is amplified via a diode pumped Yb3 +-doped fiber power amplifier. In order to suppress amplified spontaneous emission and other nonlinear effects, a three-stage fiber amplification system is used. The first stage is a diode pumped fiber (5 m, 6/125 m, NA = 0.13) power amplifier. The pump power is fixed at 600 mW. The input dual frequency signal is 3.2 mW, and it is amplified to several hundred mW by the first fiber power amplifier. The second fiber amplifier is a diode laser pumped fiber (5 m, 10/125 m, NA = 0.075/0.46) amplifier. The pump power is fixed at 10 W, and the dual frequency signal is amplified to sub watts after the second fiber amplifier. A 5 m large mode area fiber (25/250 m, NA=0.065/0.46) is used in the final amplification. A maximum amplified power of 50.2 W is obtained when the pump power is 70 W in the experiment. The signal-to-noise ratio of the beat note increases from 25 dB to 40 dB via amplification. The output power fluctuation of the amplified signal at 50 W is smaller than 0.1 W during 30 min. The RF frequency stability is well maintained during the amplification, and the beat-note frequency instability is 1.777 MHz. This high-power dual-frequency light source with wide beat note frequency bandwidth has potential applications in dual-frequency coherent lidar system for long distance ranging and imaging or underwater detections after the frequency has been doubled to 532 nm.
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Keywords:
- optically carried radio-frequency signal /
- fiber power amplifier /
- high power /
- widely tunable
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[9] Hu M, Zhang F, Zhang X, Zheng Y Y, Sun X, Xu Y X, Xu W Z, Ge J H, Xiang Z 2014 Acta Opt. Sin. 34 1114003 (in Chinese) [胡淼, 张飞, 张翔, 郑尧元, 孙骁, 徐亚希, 许伟忠, 葛剑虹, 项震 2014 光学学报 34 1114003]
[10] He T, Yang S, Zhao C, Zhang H, Liang Y, Kang Y 2015 Laser Phys. Lett. 12 035101
[11] Du W B, Leng J Y, Zhu J J, Zhou P, Xu X J, Shu B H 2012 Acta Phys. Sin. 61 114203 (in Chinese) [杜文博, 冷进勇, 朱家健, 周朴, 许晓军, 舒柏宏 2012 物理学报 61 114203]
[12] Huang L, Li L, Ma P, Wang X, Zhou P 2016 Opt. Express 24 26722
[13] Li J, Yang S, Zhao C, Zhang H, Xie W 2011 Appl. Opt. 50 1329
[14] Keller U, Knox W H, Roskos H 1990 Opt. Lett. 15 1377
[15] Draegert D 1971 IEEE J. Quantum Elect. 7 300
[16] Tang C L, Statz H, Demars G 1963 J. Appl. Phys. 34 2289
[17] Cheng L J, Yang S H, Zhao C M, Zhang H Y 2017 Acta Opt. Sin. 37 0714002 (in Chinese) [程丽君, 杨苏辉, 赵长明, 张海洋 2017 光学学报 37 0714002]
[18] Wiesenfeld K, Bracikowski C, James G, Roy R 1990 Phys. Rev. Lett. 65 1749
[19] Park J D, Mckay A M, Dawes J M 2009 Opt. Express 17 6053
[20] Leng J Y, Wu W M, Chen S P, Hou J, Xu X J 2011 Acta Opt. Sin. 31 0606007 (in Chinese) [冷进勇, 吴武明, 陈胜平, 侯静, 许晓军 2011 光学学报 31 0606007]
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[1] He Y, Wu J 1998 Laser Optoelectr. Prog. 35 29 (in Chinese) [何毅, 吴健 1998 激光与光电子学进展 35 29]
[2] Li Z G, Sun Z Z, Zhao Z L, Zhu X P 2016 Laser Infrared 46 1467 (in Chinese) [李志刚, 孙泽中, 赵增亮, 竹孝鹏 2016 激光与红外 46 1467]
[3] Zheng Z, Zhao C, Zhang H, Yang S, Zhang D, Yang H, Liu J 2016 Opt. Laser Tech. 80 169
[4] Wang S, Yang S H, Wu X, Zhu Q H 2010 Chin. Phys. Lett. 27 084202
[5] Pellen F, Jezequel V, Zion G, Jeune B L 2012 Appl. Opt. 51 7690
[6] Brunel M, Amon A, Vallet M 2005 Opt. Lett. 30 2418
[7] Maxin J, Molin S, Pillet G, Morvan L 2011 IEEE Photon. Conference 58 479
[8] Xing J H, Jiao M X 2015 Acta Photon. Sin. 44 0214003 (in Chinese) [邢俊红, 焦明星 2015 光子学报 44 0214003]
[9] Hu M, Zhang F, Zhang X, Zheng Y Y, Sun X, Xu Y X, Xu W Z, Ge J H, Xiang Z 2014 Acta Opt. Sin. 34 1114003 (in Chinese) [胡淼, 张飞, 张翔, 郑尧元, 孙骁, 徐亚希, 许伟忠, 葛剑虹, 项震 2014 光学学报 34 1114003]
[10] He T, Yang S, Zhao C, Zhang H, Liang Y, Kang Y 2015 Laser Phys. Lett. 12 035101
[11] Du W B, Leng J Y, Zhu J J, Zhou P, Xu X J, Shu B H 2012 Acta Phys. Sin. 61 114203 (in Chinese) [杜文博, 冷进勇, 朱家健, 周朴, 许晓军, 舒柏宏 2012 物理学报 61 114203]
[12] Huang L, Li L, Ma P, Wang X, Zhou P 2016 Opt. Express 24 26722
[13] Li J, Yang S, Zhao C, Zhang H, Xie W 2011 Appl. Opt. 50 1329
[14] Keller U, Knox W H, Roskos H 1990 Opt. Lett. 15 1377
[15] Draegert D 1971 IEEE J. Quantum Elect. 7 300
[16] Tang C L, Statz H, Demars G 1963 J. Appl. Phys. 34 2289
[17] Cheng L J, Yang S H, Zhao C M, Zhang H Y 2017 Acta Opt. Sin. 37 0714002 (in Chinese) [程丽君, 杨苏辉, 赵长明, 张海洋 2017 光学学报 37 0714002]
[18] Wiesenfeld K, Bracikowski C, James G, Roy R 1990 Phys. Rev. Lett. 65 1749
[19] Park J D, Mckay A M, Dawes J M 2009 Opt. Express 17 6053
[20] Leng J Y, Wu W M, Chen S P, Hou J, Xu X J 2011 Acta Opt. Sin. 31 0606007 (in Chinese) [冷进勇, 吴武明, 陈胜平, 侯静, 许晓军 2011 光学学报 31 0606007]
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