ABSTRACT
This condition of total internal reflection writes θi > θc = arcsin (nair/neff), where θi is the angle of incidence of the ray of light. In the case θi > θc, the light escapes the cavity and no resonant mode can be observed. If the condition of total internal reflection is verified, the reflection of light on the disk edges can lead to constructive interferences providing that: eff 02 =p an p (4.1)Where,
p and a is the disk radius. As a result the spectral spacing between two modes is written as:
D p
20eff= an (4.2) This geometric approach is simplified and the resonant modes is described more accurately in the following, using the whispering gallery mode approximation. First, let us calculate the transverse component of the electric field and the effective index.
