Editing Optical ring resonators (section)

=== Total internal reflection ===
{{Main|Total internal reflection}}
The light travelling through the waveguides in an optical ring resonator remains within the waveguides due to the [[ray optics]] phenomenon known as total internal reflection (TIR). TIR is an optical phenomenon that occurs when a ray of light strikes the boundary of a medium and fails to refract through the boundary. Given that the [[angle of incidence (optics)|angle of incidence]] is larger than the critical angle (with respect to the normal of the surface) and the [[refractive index]] is lower on the other side of the boundary relative to the incident ray, TIR will occur and no light will be able to pass through. For an optical ring resonator to work well, total internal reflection conditions must be met and the light travelling through the waveguides must not be allowed to escape by any means.