Complex traversal time for optical pulse transmission in a Fabry-Perot cavity

We show that the physical clock approach can be applied to the problem of optical pulse transmission in the Fabry-Perot cavity. Our theoretical analysis leads directly to a complex-valued traversal time for the pulse. Real and imaginary parts of the traversal time, referred to as the phase time and the loss time, are associated, respectively, with the rotation angle of polarization and the change in the polarization ellipticity of the outgoing pulse in the presence of a magnetic clock. The physical significance of the phase time and the loss time is discussed in relation to the superluminal group velocity and the spectral shift of the pulse.