Font Size: a A A

Preliminary Study On Laser Accelerometer Based On Y-shaped Cavity Orthogonal Polarized Dual-frequency Laser

Posted on:2012-02-02Degree:DoctorType:Dissertation
Country:ChinaCandidate:G Z XiaoFull Text:PDF
GTID:1118330362460334Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
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.
Keywords/Search Tags:laser accelerometer, Y-shaped cavity orthogonal polarized dual-frequency laser, resonator sensor, gas sylphon, laser parameters global optimization, finite element transmission matrix method
PDF Full Text Request
Related items