What is the quality factor FOM of laser?

The quality of resonant cavity is described by product quality factor Q, and the definition of Q value is: Q=2πν(E2/E 1). Where v is the resonant frequency of the cavity, E2 is the energy stored in the cavity, and E 1 is the energy lost per second. The more energy stored in the cavity, or the less energy lost per second, the better the quality of the resonator, that is, the higher the value of the quality factor Q.