Non-traditional whispering gallery modes inside microspheres visualized with Fourier analysis

Non-traditional whispering gallery modes are studied in a glass microsphere. Geometrical ray tracing is used to explain and calculate these modes. Thermal emission and Raman scattering are used as an internal light source to excite these modes inside the glass microsphere. The thermal and Raman emission spectra are modified due to the existence of these modes. Fourier analysis is then used to distinguish the individual modes. The understanding of these non-traditional WGM may lead to alternative design strategies for sensor applications or laser cavity configurations.