“…As for the birefringence in a cavity, several experiments were performed, i.e., the PVLAS (Polarizzazione del Vuoto con LASer) [12][13][14][15][16], BMV (Biréfringence Magnétique du Vide) [17], and OVAL (Observing VAcuum with Laser) [18] experiments. A cavity system is often considered in theoretical studies [19][20][21][22][23][24][25]. Several other systems have also been studied, for example, a waveguide [20,26,27], a ring laser [28], the Michelson interferometer [29], and a propagation between two mirrors [30,31].…”