Resonators are important components used in various fields of Optics. Our research introduces a new type of optical resonator that has unique characteristics compared to traditional ones like Fabry-Perot cavities. We invented a new process called "cascaded-mode conversion" that can produce supermodes in the resonator. This means that one mode transforms into another mode at each reflection. This new type of resonator has different properties that are determined not only by the length and refractive index of the medium, but also by the number of coupled modes and their reflection phases....