Casimir Force in a One-Dimensional Cavity with Quasimode

We calculate the Casimir force between a perfect reflective wall and a semitransparent wall in the laser cavity. Using the Fox-Li quasimode theory to describe the electromagnetic field in the laser cavity, the vacuum energy and the Casimir force are calculated. We compare our results to the force in the ideal situation and find it smaller in the dissipative cavity. We also find that the Casimir force decreases with the increase of the wall-wall distance and the decay rate of the quasimodes in the laser cavity.