| Popis: |
Light diffracted from a high efficiency, reflective grating may undergo a phase shift which depends strongly on the incident polarization. If the incident wave includes both TE (E // groove) and TM (El groove) polarization, then the diffracted orders may be elliptically polarized. This effect is of special interest in curved-line (holographic) gratings in which the eccentricity of the ellipse may vary across the diffracted wavefront. In this paper the existence of a substantial phase shift between the two polarization is demonstrated in gratings with a period-to-wavelength ratio less than one. Measurements are made at 10.6 µm on both ruled and ion-etched gratings. Comparison with theory shows that the measured effect is due to groove shape rather than to finite conductivity of the substrate. |
