Quality Factor Measurements for PMMA WGM Microsphere Resonators Using Fixed Wavelength Laser and Temperature Changes

The whispering gallery modes (WGM) resonators are based on spherical objects, which are made from optically transparent materials, and are capable of maintaining circulating optical waves, inside the sphere, using total internal reflection. If there is a monochromatic light source which supplies the sphere with a constant intensity, the wave moving along the perimeter of sphere starts to constructively interfere. In this case the resonance happens, which is called whispering gallery mode (WGM). The current work explores the possibility of using temperature changes to measure polymethyl methacrylate (PMMA) WGM microsphere resonator quality factor (Q) and thermal expansion parameters. Different diameter and material spheres are used in the experiments for equipment testing and calibrating. The following work opens up opportunities to create a simple and low cost Q factor measurement systems, that could be useful in laboratories that are working with low cost polymer WGM resonators.