“…Quantization of the electromagnetic field in dielectrics with real and frequency-independent permittivity has been treated extensively [1,2,3,4,5,6,7,8,9,10,11,12,13]. In the same context, dispersive dielectrics have been considered [14,15,16,17,18,19,20]. However, it is well known that the permittivity is a complex function of frequency which has to satisfy the Kramers-Kronig relations which state that the real part of the permittivity (responsible for dispersion) and the imaginary part (responsible for absorption) are necessarily connected with each other.…”