In general, the optical field is elliptically polarized, but there are several combinations of amplitude and phase that are especially important. These are called degenerate polarization states: (1) linearly horizontal/vertical polarized light (LHP/LVP), (2) linear ±45° polarized light (L+45P/L–45P), and (3) right/left circularly polarized light (RCP/LCP). The polarization states along with the mathematical conditions and corresponding figures (polarization ellipses) are as follows.