The measurement of absolute strain (or stress) in the small quartz crystal resonators by a single slit method [observation of vibratory character of a small NS-GT cut resonator]

From the necessity of downsizing devices, the size of quartz crystal resonators has currently been made smaller. If we make a quartz crystal resonator´s size smaller, small external effects will change frequencies or quality factors of the resonator. And those changes make it more difficult to accurately measure stress distributions. In the angle slit vibration diffraction method, by making a single slit (or a pin point hole) and letting a laser beam into the slit, a diffraction pattern is formed which changes slightly with vibration frequency. The diffraction pattern is dynamic but the change itself is very small, therefore we need to detect the change of diffractions using optical fibers. The detected optical signals are converted to an electric signal by a photomultiplier. The patterns of diffractions tell us the changes of the angle slit width and the vibration shift of the resonator. From those results, we can get the absolute values of strain (or stress) and the absolute vibration shift value of the resonator. We experimentally measure the internal strain and the vibration shift value of a small NS-GT cut resonator by this method. Knowing the absolute values, such as strains, and vibration shifts of a small quartz crystal, is very useful in controlling the thickness of vacuum evaporation electrodes and improving the mounting of resonators.