Application of the photo-elastic method to measurement of dynamic stress distribution for NS-GT cut quartz crystal resonators
NS-GT cut quartz crystal resonators are widely used as a frequency standard element in consumer products and communication equipment. The vibration mode of the resonators was analyzed by the finite element method (FEM) because they have a complicated shape. As a result, an asymmetrical vibration mode at the main resonant frequency has been obtained by the FEM simulation. But, it is necessary to confirm the asymmetrical vibration mode experimentally because it is just a simulation. In this paper, stress distributions of the NS-GT cut quartz crystal resonators are measured experimentally by using a dynamic photo-elastic method when the resonators are vibrating in the resonant frequency; thereafter, vibration modes of the NS-GT cut resonators are estimated with the experimental data of the stress distributions. This experiment for the NS-GT cut quartz crystal resonators exposes the existence of a twisted asymmetrical vibration mode at the main resonant frequency, with the magnitude of the twisted vibration in proportion to thickness of the resonators.
Analysis of vibrations in AT-cut quartz crystal plates using a light modulated oscillator
A basic study of a quartz crystal oscillator system in which a quartz crystal resonator (or plate) is used as light modulator is reported. In this oscillator system, the quartz crystal plate is used as a three-port network because the light beam modulated by the dynamic stress of the oscillating quartz crystal plate is used as a feedback loop of oscillations. A quartz crystal oscillator system of high quality is realized. Experimental results on the basic characteristic of the plano-convex AT-cut quartz crystal plate used for the light modulator in the present system are described in detail The dynamic stress distributions and the quality factor Q of the plate are measured by means of a laser probe beam modulation method.
Defects in Natural Quartz
X‐ray diffraction topographs show at least two types of defects in natural quartz, planar defects which are parallel to the natural quartz faces and needle‐like defects. The planar defects color when exposed to γ irradiation, indicating these are sheets of substitutional aluminum, with an interstitial alkali ion nearby for charge compensation. The linear defects are similar to macroscopic needles of TiO2 sometimes found in quartz and have previously been associated with dislocations by Lang. Both types of defects show diffraction contrast when observed from different Bragg planes. There does not seem to be a simple relation between either type of defect density and acoustic loss at 300°K in natural quartz.