双纵模四频激光陀螺自偏频机理与技术研究

Biasing is one of the key technologies of laser gyroscope. The new self-biasing phenomenon is experimentally found by applicant: In the mode-hop process in single longitudinal mode operating and mechanical dithering prisms laser gyroscope, if we remove the mechanical dithering, the double-longitudinal modes and four frequencies oscillation will realize in a short time, the gyroscope can detect the earth rotation angular velocity without dithering, the lock disappears, and the self-biasing state is induced in gyroscope. The project research on the self-biasing technology in double-longitudinal modes and four frequencies laser gyroscope, using the semi-classical theory to establish the self-consistent equations of circular cavity operation under double longitudinal modes and four frequencies with the same polarization, according to the theory of gas plasma dispersion, etc, deductive the operating characteristic of laser longitudinal modes oscillation, gain of frequency stabilization laser, and the coupling characteristic of four frequencies with same polarization, the theoretical model of self-biasing is established. Experimentally, the double longitudinal modes frequency stable oscillation, the double longitudinal modes tuning and the experiment platform for the self-biasing are planed to be established, make the self-biasing state steady and take an experimental research. The results will reveal the generation mechanism, stable condition and key technologies of self-biasing, and lay a foundation for developing a new self-biasing laser gyroscope. The gyroscope has the benefits such as zero lock, solid state and low loss, so it has the potential for challenge the strategic level precision, and has a broad application prospect in strategic missile, rocket, ship, submarine and other important fields.

偏频技术是激光陀螺的关键技术之一。申请人在实验中发现了全新的自偏频现象：单纵模机抖偏频棱镜式激光陀螺跳模过程中，去掉机抖偏频，短时间内能够实现激光双纵模四频振荡，并且无偏频地检测出地球自转角速度，此时闭锁消失，陀螺处于自偏频状态。本项目以双纵模四频激光陀螺自偏频技术为研究对象，通过半经典理论建立环形激光器同偏振双纵模四频工作自洽方程，根据气体等离子体色散等理论推演激光器纵模工作特性及稳频激光器增益特性，研究自偏频状态下同偏振四频间的耦合效应，获得自偏频理论模型；实验上，建立激光陀螺双纵模稳频、双纵模频率动态调谐系统，以及陀螺自偏频工作实验平台，实现稳定自偏频，并实验研究。揭示自偏频技术的产生机理、稳定工作条件和关键技术，为研制一种新型双纵模自偏频陀螺奠定基础。这种陀螺具有零闭锁、全固态、低损耗等优点，性能上具备挑战战略级的潜力，在战略导弹、运载火箭、舰船、潜艇等重要领域拥有广阔的应用前景。

激光陀螺的闭锁效应，即它对微小转动角速度的不敏感性，是诸多误差中对陀螺性能影响最大的。为了克服闭锁而采取的各种偏频措施，均会不同程度地影响陀螺的精度及稳定性。本项目基于实验发现，棱镜式激光陀螺在双纵模四频体制下工作，表现出自偏频现象：单纵模机抖偏频激光陀螺跳模过程中，去掉机抖偏频，短时间内实现了激光双纵模四频振荡，并可无偏频地检测出地球自转角速度的天向分量，此时闭锁消失，陀螺处于自偏频状态。本项目在前期研究基础上进一步探索，首先，理论上采用激光半经典Lamb理论，分析自偏频状态下双纵模四频间的耦合关系，建立激光陀螺双纵模自偏频数学——物理模型。其次，实验上搭建激光陀螺自偏频实验系统和激光陀螺闭锁阈值检测系统，研究自偏频状态的产生机理和稳定条件。.本项目完成的主要工作包括五部分：(1)基于对兵器工业集团从俄罗斯引进技术：单纵模工作、机械抖动偏频棱镜式激光陀螺结构的分析和复算，重点研究了环境温度、棱镜角度、腔体塔差、光学非共面等因素对陀螺工作稳定性的影响。在此基础上，自主设计了双纵模四频工作体制的棱镜式环形谐振腔。(2)基于数字电路技术，设计并制造了双纵模四频激光陀螺测试平台。根据自偏频实验需要，编写了新的调测控制软件。(3)搭建激光陀螺双纵模自偏频实验平台，基于光学腔长为0.47m的棱镜式环形谐振腔，复现了激光陀螺双纵模自偏频实验现象。实验获得陀螺自偏频现象的模态特点：强、弱纵模分立于增益曲线中心频率两侧，强、弱纵模振荡强度比约为1.4:1。(4)理论上，从双纵模四频环形激光器行波方程出发，运用半经典Lamb理论、等离子体色散理论、三阶微扰理论，分析四频间的频率耦合效应，总结获得激光陀螺双纵模自偏频状态产生的机理和条件：激光陀螺内部振荡的四频间相互耦合，特别是弱模的频率推斥效应为陀螺的拍频输出提供了偏置项，是自偏频现象产生的关键因素。(5)搭建激光陀螺闭锁阈值检测实验系统。在双纵模频率调谐状态下，实现陀螺闭锁阈值实时检测。该实验结果为定量研究Lamb系数与环形谐振腔振荡纵模的联系提供依据，进而探索自偏频状态稳定的关键因素。本项目为研制一种全新的、无需任何偏频技术、实现光学自偏频的高精度激光陀螺奠定基础，具有科学价值和工程应用价值。