用于光生毫米波的微片激光器研究

发布时间：2018-04-14 20:53

本文选题：双频微片激光器 + 光谱特性　；参考：《杭州电子科技大学》2015年硕士论文

【摘要】：激光二极管端面抽运的双频微片激光器在工业生产、科学研究、信息传输和国防建设等领域应用普遍,尤其是随着无线电频谱资源的日趋紧张,频率更高波段的毫米波频段频谱资源被提上了日程,双频微片激光器作为产生毫米波信号的相对简单和有效的方法,因此近年来各国科学家对双频微片激光器的相关内容表现了持续的研究兴趣。本文主要研究双频微片激光器的特性,包括对LD抽运的双频微片激光器的光谱和频差特性研究和对小信号增益情况下双频激光放大器的理论模型的研究,具体包括以下几方面内容：(1)首先介绍了产生光生毫米波的技术及其工作原理,然后阐述了双频微片激光器的国内外研究现状,最后分析了双频微片激光器的发展趋势和双频微片激光放大的科学意义。(2)阐述了双频微片激光器的基本原理、双频微片激光器常用激光晶体的特性、对微片晶体的选择,并对Nd:YVO4晶体的激光特性进行了详细的介绍。同时,从激光四能级速率方程出发,在近阈值抽运和强光抽运情况下,推导出双频微片激光器的阈值功率、输出功率和斜效率等输出特性。(3)理论分析双频微片激光器谐振腔内的模式,分析单纵模双纵模形成条件,并从实验出发研究了激光二极管(LD)抽运的、频差可调的双频Nd:YVO4微片激光器的光谱特性。对于荧光谱宽固定的激光增益介质,输出激光的光谱特性主要与抽运功率、抽运位置、谐振腔腔长等参数相关；通过控制相关参数,可以调整输出激光不同波长频谱峰之间的相对频差。根据实验结果表明,当LD抽运电流为14.5 A时,抽运光与谐振腔模达到良好的匹配,输出稳定的双纵模双频激光,相应的频差可以达到超过90 GHz：改变抽运参数,相应频差在92.22 GHz-94.24 GHz之间变化；增加谐振腔的腔长时,输出的激光纵模间隔减少并可输出三纵模,其中两频峰之间的最小频差可达到26.5 GHz。(4)建立小信号增益双频放大器理论模型。在小信号增益情况下,从四能级速率方程出发,对经过行波放大器之后的输出谱线和增益谱宽进行研究和分析,建立理论模型,并利用MATLAB软件模拟仿真各个参数,得出如下结论：当增益谱宽不变时,比较放大器增益前后激光频谱的变化发现,通过双频放大器之后输出的光谱包络轮廓比入射光谱包络要窄。当改变增益谱宽时,发现在增益谱宽较大时,输出激光光谱轮廓相对比较平坦,在增益谱宽较小时,输出激光光谱轮廓相对比较陡峭。
[Abstract]:Laser diode end-pumped dual-frequency microchip lasers are widely used in the fields of industrial production, scientific research, information transmission and national defense construction, especially with the increasing shortage of radio spectrum resources.The frequency spectrum of millimeter-wave band in higher frequency band has been put on the agenda. Dual-frequency microchip laser is used as a relatively simple and effective method to generate millimeter-wave signal.In recent years, scientists all over the world have shown a sustained interest in the research of dual-frequency microchip lasers.This paper mainly studies the characteristics of dual frequency microchip laser, including the spectrum and frequency difference characteristics of LD pumped dual frequency microchip laser and the theoretical model of dual frequency laser amplifier with small signal gain.This paper introduces the technology and working principle of generating millimeter wave, and then describes the research status of dual-frequency microchip laser at home and abroad.Finally, the development trend of dual-frequency microchip laser and the scientific significance of double-frequency microchip laser amplification are analyzed. The basic principle of dual-frequency microchip laser, the characteristics of laser crystal commonly used in dual-frequency microchip laser, and the choice of microchip crystal are described.The laser characteristics of Nd:YVO4 crystal are introduced in detail.At the same time, based on the four-level rate equation of laser, the threshold power of dual-frequency microchip laser is derived under the condition of near-threshold pumping and strong light pumping.Output power and skew efficiency.) the mode in resonator of dual-frequency microchip laser is analyzed theoretically, and the forming conditions of single longitudinal mode and double longitudinal mode are analyzed, and the laser diode LD pumped by laser diode is studied based on the experiment.Spectral characteristics of dual frequency Nd:YVO4 microchip laser with adjustable frequency difference.For the laser gain medium with fixed fluorescence spectrum width, the spectral characteristics of the output laser are mainly related to the parameters such as pump power, pump position, cavity length and so on.The relative frequency difference between the spectral peaks of different wavelengths of the output laser can be adjusted.The experimental results show that when the LD pump current is 14.5A, the pump light can match well with the resonant cavity mode, and the output stable dual-longitudinal mode dual-frequency laser can reach a frequency difference of more than 90 GHz.The corresponding frequency difference varies from 92.22 GHz-94.24 GHz to 92.22 GHz-94.24 GHz, and when the cavity length is increased, the output longitudinal mode interval decreases and the three-longitudinal mode can be output, in which the minimum frequency difference between the two frequency peaks can reach 26.5 GHz. 4) the theoretical model of the small signal gain dual-frequency amplifier is established.In the case of small signal gain, starting from the four-level rate equation, the output spectral line and gain spectrum width after traveling wave amplifier are studied and analyzed, the theoretical model is established, and various parameters are simulated by MATLAB software.The following conclusions are drawn: when the gain spectrum width is invariant, compared with the laser spectrum changes before and after the gain, it is found that the spectral envelope profile after the dual-frequency amplifier output is narrower than that of the incident spectral envelope.When the gain spectrum width is changed, it is found that the output laser spectrum profile is relatively flat when the gain spectrum width is large, and the output laser spectrum profile is relatively steep when the gain spectrum width is small.
【学位授予单位】：杭州电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN248

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