Experimental Techniques

Abstract

In order to have a testing station for our mechanical devices, we built a simple, fiber-based interferometer. It had several advantages over the actual Fabry-Pérot setup—it was easy to use, i.e. it did not require any active stabilization, the chips with the mechanical resonators could be easily swapped, the travel on the piezo-stage was larger and hence allowed for measuring a full chip at once and most importantly, in contrast to the actual setup, the radiation-pressure backaction was negligible and hence it did not have to be taken into account when determining the mechanical frequency and $Q$. The working principle is to use a cleaved fiber, put it above the chip with the mechanical devices, and measure the interference between the light that is directly reflected off the fiber-tip (which is approx. 4 $\%$) and the light being reflected by the mechanical device, which imparts a phase modulation due to its mechanical motion (see Fig. 3.1).