Abstract
As a kind of resonant device, the modulation efficiency of the photo-elastic modulator (PEM) is determined by its inherent resonance characteristics, including the resonance frequency and quality factor (Q-factor). The existing methods used to characterize the resonance performance of the PEM are mainly based on the optical method to measure the vibration parameters, but these methods are more complex, have a high cost, and are not able to accurately measure the quality factor. Therefore, this paper proposes an electrical characterization method based on impedance measurement. In this method, an equivalent circuit model for the PEM is established. By measuring the impedance vs. frequency curve of the PEM and using the equivalent circuit model for fitting analysis, we can obtain the parameters of the equivalent circuit model. With these parameters, we can eventually calculate the natural resonance frequency and quality factor. The above method was applied to some commercial PEM products for experimental verification. The experimental results show that this method can accurately measure the natural resonance frequency and quality factor of the PEM, and the error is less than 0.03%.
Highlights
Since the vibration of photo-elastic modulator (PEM) is relatively weak, this method has high requirements for the measurement equipment and measurement environment. This method can only judge whether the measured PEM is in resonance state by the maximum amplitude of vibration, but cannot measure the exact quality factor
For the 2D octagonal PEM, we propose a method based on impedance measurement to obtain the resonance frequency and the exact quality factor of the PEM
Thebandwidth bandwidthofofthe theresonance resonanceregion regionisis only only about about 10 Hz~15 Hz, which means that the deviation between the excitation signal frequency and the natural resonant frequency of a PEM must be small enough to ensure ensure the the stable stable operation operation of of the the PEM
Summary
A common method used to measure the resonance frequencies of PEMs is the use of a Doppler vibrometer [11]. In this method, the vibration status is converted into Doppler frequency shift that is monitored by electrical signals. Since the vibration of PEM is relatively weak, this method has high requirements for the measurement equipment and measurement environment. This method can only judge whether the measured PEM is in resonance state by the maximum amplitude of vibration, but cannot measure the exact quality factor
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
