Study Of Y-Shaped Cavity Orthogonal Polarized Dual-Frequency Laser And Micro-Scale Force Measurement

Dual-frequency laser has a wide application in the fields of interferometry and optical sensing.The accuracy and range of measurement are determined by the stabilit y and magnitude of frequency difference,respectively.Zero frequency difference lock-in,large range of frequency difference,as well as a better stability of frequency difference are the potential advantages of Y-shaped cavity orthogonal polarized dual-frequency laser.Y-shaped cavity orthogonal polarized dual-frequency laser may play an important role in precise measurement.Based on the integration Y-shaped cavity orthogonal polarized dual-frequency laser,the phenomena of frequency difference lock-in,stability as well as the application in nano-scale force measurement has been studied both in theory and experiment.These studies can provide foundations for the application of Y-shaped cavity orthogonal polarized dual-frequency laser in precise force,as well as acceleration measurement.In the first part of this article,the factors which influence the frequency difference lock-in of Y-shaped cavity orthogonal polarized dual-frequency laser were analyzed systematacially.The influences of pump current,operating point as well as the loss of resonator on the lock-in threshold frequency difference are analyzed according to Lamb's semi-classical theory.Various factors,especially pump current and the operating point,are studied in the experiment.The results show that either the pump current increasing or the operating point approaching the gain curve center could cause the lock-in threshold frequency difference to decrease.When the pump current is greater than 2.2mA with its working state at the optimal operating point,the lock-in threshold frequency difference could be less than a few megahertz.The effect of transverse magnetic field's suppressing of frequency difference lock-in was studied.Based on the magnetic-optical effect,the principle of magnetic field's suppressing of frequency difference lock-in was analyzed theoretically.A homogeneous magnetic field is obtained by using a cube coin-pair.The distribution of magnetic field was simulated with Ansoft Maxwell software.Experimental results show that when pump current is 1.8mA,the lock-in threshold frequency difference would be less than tens of kilohertz,provided the magnitude of magnetic field was greater than 10 mT.A comprehensive research was carried out on the stability of Y-shaped cavity orthogonal polarized dual-frequency laser.Stability of the pump current,as well as the distribution of temperature are the main factors which influence the stability of dual-frequency laser.Among all the unstable elements,the heat resource of laser itself is the key factor to limit the improvement of the stability of Y-shaped cavity orthogonal polarized dual-frequency laser.In the end of this dissertation,a precise force measurement system was built.A experimental research of the measurement of static force was developed.Using the large deflection model,the principle of the measurement of micro-scale force was analyzed.Furthermore,the property of the system is studied in experiments.The results demonstrate that the change of frequency difference is proportional to the external force,provided that the external force is smaller than 7mN.The rate is observed as 1.23842×10~9Hz/ N.As the value of external force increase,the relationship between the change of frequency difference and the force become nonlinearity.The stability of dual-frequency laser as well as the action spot of external force are two main factors which influence the accuracy of the micro-scale force measurement system.