【作者】 肖光宗；

【导师】 龙兴武；

【作者基本信息】 国防科学技术大学 ， 光学工程， 2011， 博士

【摘要】 与其它导航方式相比,惯性导航由于能够不受任何外界的干扰,完全自主地提供不间断的导航信号,在军事上具有极其重要的战略意义。作为惯性制导与导航系统中的主要器件,加速度计和陀螺仪一直是世界上各发达国家研究的热点。随着光学陀螺精度和性能的不断提高,加速度计已成为制约我国惯性导航系统性能提高的瓶颈。本文在系统分析我国在高精度加速度计的研制方面总体形势的基础上,结合我国在氦氖激光器的技术和工艺及其在精密测量方面应用的研究基础和优势,独辟蹊径,提出了基于Y型腔正交偏振激光器的激光加速度计方案,并对其开展了初步研究。全面回顾了加速度计,特别是光学加速度计的发展历史和研究现状,重点分析了我军信息化建设对高精度加速度计的迫切需求与我国在高精度加速度计的研制方面总体落后、潜力不足之间的矛盾,指出了我国研制激光加速度计的必要性和紧迫性。系统总结了谐振腔传感器的基本原理和关键技术,对基于谐振腔传感器的加速度测量方案进行了几种探索。详细分析了气体膜盒式激光加速度计和密度梯度盒式激光加速度计的基本原理和影响它们性能的主要因素。理论分析表明,气体膜盒式激光加速度计的比例因子可达针对激光加速度计对Y型腔正交偏振氦氖激光器的输出功率、横模、纵模等物理特征的要求,研究了激光器参数优化和模式分析这两个具有普遍意义的问题。提出了人工神经网络和遗传算法相结合的激光器参数全局优化设计方法,研究表明,该方法可以显著地提高激光器输出功率。研究了谐振腔模式的有限元传输矩阵分析方法(FETM)中有限单元的划分问题,提出了一条新颖而有效的合理确定有限单元划分格数的方法,该方法可以更合理地确定有限单元划分格数,提高FETM方法的计算效率。系统总结了双频激光干涉仪及双频激光器的种类、应用、发展历程和研究现状,详细回顾了国内外双折射效应双频激光器的种类和研究情况。重点对复合腔进行了系统地定义和分类,对其在激光技术中的不同应用进行了总结和比较。成功研制了Y型腔正交偏振激光器,介绍了该激光器的基本原理、结构和特征,测试了激光器的偏振特性,并对其进行了理论分析。通过实验研究了不同频差下共用段调谐过程中,该激光器的光强调谐曲线和相应的拍频变化规律,采用三阶微扰近似下的Lamb半经典气体激光器理论,较为系统、全面地分析和总结了影响光强调谐曲线的各种因素及影响机理。通过实验研究了激光器的频差闭锁现象和闭锁阈值与放电电流之间的关系,并对其进行了理论分析。测试了激光器的频差稳定性,并对其在精密测量中的应用进行了初步探索。从理论和实验上对磁场抑制Y型腔正交偏振激光器的频差闭锁进行了研究。采用Lamb半经典理论建立了磁场中双频激光器两正交偏振纵模间耦合强度的理论模型,定量分析了磁感应强度和频差大小对耦合强度的影响。通过实验验证了横向磁场对频差闭锁具有抑制作用,研究了横向磁场的磁感应强度大小对其抑制频差闭锁效果的影响。理论分析了横向磁场对频差失谐的影响和横向交互磁场对频差失谐的抑制作用,通过实验验证了横向交互磁场对双频激光器频差闭锁和频差失谐的抑制作用。搭建了基于气体膜盒式激光加速度计的微力测量系统和加速度测量系统。实验表明,该测试系统的输入力与拍频变化成正比关系,测量范围为5个量级,最大比例因子为Hz/N,由于拍频不稳定引起的测试系统等效分辨率为10PN。通过优化传感器结构和使用一体化Y型腔正交偏振双频激光器,测试系统的分辨率可达10P-6PN。以MEMS加速度计作为参考,通过实验验证了气体膜盒式激光加速度计的可行性,测试了其性能参数,分析了其性能潜力。实验表明,激光加速度计的输出频差变化与输入加速度成正比关系,比例因子的实验值与理论值基本一致,通过优化激光加速度计结构,其比例因子可达10P9 PHz/g,分辨率可达1Pg,其量程可达±5 g。根据不同方向加速度输入时激光器各输出量的变化规律,提出了基于工作点模式识别的加速度判向方法。更多还原

【Abstract】 Unlike many other types of navigation system, inertial navigation system can affords continuous navigation signals by themselves, possessing immunity to environmental interference, which sustains its important military strategic significance. As the key sensor of inertial navigation system, accelerometer has been under intense research in developed countries. With the rapid development of optical gyro technology, accelerometer has become a bottleneck to hamper the advancement of performance of inertial navigation system in our country. Taking into account the current status of domestic research on high performance accelerometer, and the advantages on the He-Ne laser technique, we propose a novel laser accelerometer based on Y-shaped cavity dual-frequency laser. The primary theoretical and experimental researches on this laser accelerometer have been made and summarized in the dissertation.The dissertation begins with reviewing the history and current status of accelerometer, particularly the optical accelerometer in detail. Conflict between our military equipments’stringent demands for high performance accelerometer, and low level and potential of domestic research on that is studied and analyzed. As a result, the necessity and urgency of laser accelerometer are pointed out.The basic principle and key technology of resonator sensor are summarized detailedly. Then several methods to measure acceleration applying resonator sensor have been proposed and discussed. Especially, the basic principles and characteristics of two laser accelerometers, which are based on gas sylphon and density gradient box respectively, are analyzed and studied. Theoretical analysis shows that the scale factor of the former laser accelerometer is 3.23×10PHz/g and its resolution can reach 4.24×10P-6Pg with measurement range of 10P6P.In view of physical characteristic requirement of Y-shaped cavity dual-frequency laser in the laser accelerometer, including output power, transverse mode, and longitudinal mode, two essential issues, i.e. global optimization method to design laser parameters and finite element transmission matrix method(FETM) for analysis of optical resonator modes, are studied and analyzed. For the first issue, a novel global optimization method based on artificial neural network and genetic algorithm has been proposed for laser parameters design. The output power of laser with parameters optimized by optimization method mentioned above is larger than another laser with the same cavity length, which proves the effectiveness of the above proposed method. For the second issue, the topic of division number of finite elements of cavity mirror has been further investigated. In the end, a novel and effective method to determine the number of finite elements is presented and discussed.The category, application, history and current status of dual-frequency laser and developed birefringence dual-frequency laser is introduced in detail. In addition, the compound cavity is redefined and classified. Comparison and analysis on the different application of compound cavity in laser technology is presented. Applying the Y-shaped cavity, an orthogonal polarized He-Ne laser has been designed and implemented, which is named as Y-shaped cavity dual-frequency laser. The laser’s structure and basic principle are detailed. Afterwards, the transverse model and longitudinal model, the power, the ellipticity of the output light and frequency difference lock-in phenomenon and frequency difference tuning characteristics are experimentally investigated. Based on the Lamb’s semiclassic gas laser theory of three-order perturbation, longitudinal mode competition’s influencing factors and their mechanism are developed and generalized detailedly. The relation between the lock-in frequency difference and discharge current is analyzed through experiment. The frequency difference stability of the laser is tested and estimated. Furthermore, the dissertation makes a primary attempt at several promising applications, such as micro/nano force measurement, refractive index measurement.For overcoming the effect of the lock-in phenomenon in the Y-shaped cavity dual-frequency laser, magnetic field’s suppressing the frequency difference lock-in phenomenon in is experimentally studied and theoretically analyzed. At first the coupling parameter in the magnetic filed strength between two orthogonal polarized modes is derived applying the Lamb’s semiclassic gas laser theory. Experiments show that the transverse magnetic field’s decreasing the frequency difference lock-in effect is valid. The influence of the magnetic filed strength and frequency difference on the coupling parameter is experimentally investigated and quantitatively analyzed according to the coupling parameter derived above. The theories about frequency difference detuning induced by transverse magnetic field and mutually orthogonal transverse magnetic field’s suppressing frequency difference detuning are presented and discussed. Experiments demonstrate that it is feasible to suppress the frequency difference lock-in phenomenon with little frequency difference detuning through adopting the mutually orthogonal transverse magnetic field.In the end, two experiments are carried out and investigated. Firstly, a precise force measurement system based on the Y-shaped cavity dual frequency laser and gas sylphon is built. The experiments are then performed, and demonstrate the force measurement to be proportional to a high degree over almost 5 decades of input signal range. The maximum scale factor is observed as 5.02×10~P9PHz/N with the beat frequency instability equivalent resolution of 10P-5PN. By optimizing the optical and geometrical parameters of the laser sensor, a force measurement resolution of 10P-6PN could be expected. Secondly, an acceleration measurement system based on a Y-shaped cavity dual-frequency laser and gas sylphon is set up and demonstrated. Preliminary experiments confirm the validity of the laser sensor. The experimental results show that the laser sensor in this approach characterizes a nearly linear response to the input acceleration, which is a projection of gravitational acceleration. The experimental values of the scale factors are mostly in good agreement with theoretical ones. By optimizing the optical and geometrical parameters of the laser sensor, an acceleration measurement resolution of P gravitational acceleration (within±5 g measurement range) could be expected. Furthermore, we investigate the principle about the sign of the scale factor in detail, and propose a simple but efficient method to distinguish the direction of the acceleration acted on the laser sensor.更多还原