“…The quantization of the field in a uniform dielectric medium was discussed in [32], [40], [42], [43], [44], [50] (see also [20], [24], [92] and the references therein). Yet the problem of electromagnetic-field quantization in time-dependent nonuniform linear nondispersive media remains an active research topic up to now [2], [7], [12], [13], [20], [33], [39], [41], [58], [60], [67], [77], [78], [79], [80], [92], [96].…”