In order to solve the problem of slow test speed of traditional generalized elliptical mechanical rotation,it is proposed to use a circular elastomeric modulator with better symmetry to replace the electro-optical phase modulator to achieve ultra-high-speed measurement.By decomposing the internal stress standing wave of the elasto-optic crystal into two columns of traveling waves with a phase difference of π/4,it is deduced that when the driving voltage amplitudes of the two piezoelectric actuators are equal and the phase difference is π/2,the fast axis of the elastooptic modulator makes a circular motion with an angular frequency of f/2.However,during the actual experiment,the fast axis direction angle transformation of the photoelastic modulator cannot be seen.Therefore,in order to more vividly verify the pure traveling wave modulation mode,COMSOL software is used for simulation.Using the transient solver in COMSOL,simulations are performed based on the conditions derived from theory to obtain a periodic surface vibration displacement of the photoelastic modulator.The simulation results show that when the elastic optical modulator is in pure traveling wave modulation mode,it can be regarded as a phase modulator that rotates at high speed in the fast axis direction.Since the support structure of the common octagonal elastic optical modulator adopts the chamfer position with the smallest vibration displacement for support and fixation,it is different from the commonly used two-dimensional octagonal elastic optical modulator where the fast axis direction is fixed.In the pure traveling wave mode,the fast axis of the elastomer modulator rotates at high speed,so a new support method is required.By establishing a damped string vibration model and analyzing the three-dimensional vibration displacement of the surface of the elasto-optical crystal at different fast axis angles,a central support method based on the pure traveling wave modulation mode of the elasto-optical modulator is proposed.Then,using the theory of polarization optics,the Mueller matrix of each device is obtained according to the polarization properties of different optical devices,and the Stokes vector of the emitted light is calculated.It is obtained that when the photoelastic modulator is in pure traveling wave modulation mode,there are only double frequency signal.Finally,the pure traveling wave modulation mode is verified experimentally.The signal generator and amplifier are used to provide amplified driving signals to the two piezoelectric drivers.When the photoelastic modulator reaches resonance stability,the detector is used to collect the emitted light,and the signal is processed and displayed and collected on the host computer,and the collected light is the signal undergoes Fourier transformation to obtain the frequency domain signal of the emitted light.The results show that the detected signal has a direct flow and a double frequency,thus verifying the pure traveling wave modulation mode of the elasto-optical modulator.It also proves that the central support method can ensure that the resistance experienced by the elasto-optical modulator after reaching resonance is uniform and minimal,to achieve the best support effect.In the next research,from the perspective of application,we will combine PEM related technology with ellipsometry,and use the Bessel function and the Mueller matrix of each device to obtain the Mueller matrix of the sample,realizing the sample ultra-high-speed measurement of thickness and associated polarization information.
NETL
NSTL
万方数据
