Wavefront spacing and Gouy phase in strongly focused fields: the role of polarization

The wavefront spacings and the Gouy phases are investigated in the strongly focused fields with four differently polarized incident waves. It is shown that these four incident polarizations will lead to nine axial field components, which are found actually to only have five kinds of wavefront spacings and Gouy phases. The four analytical and one numerical expressions are derived for these five kinds of wavefront spacings in the immediate neighborhood of the focus. Our results show that the polarization state, the semiaperture angle, and beam size influence the wavefront spacings and the Gouy phases in different ways. The difference between two very near wavefront spacings can be bigger than a half wavelength. It is also found that the axial field components with the polarization states orthogonal to that of the incident wave always have larger wavefront spacings.