Figure 1
Preparation of modulated CPL beams that periodically alternate between LCPn and RCPn.
(a) CPL modulation with a PEM adopted in commercial CD spectrometers. (b) Discrete CPL modulation with a pair of polarization BDs proposed in this study. The modulated light with the PEM in (a) unavoidably involves LP components when the polarization transits between LCPn and RCPn. In the discrete modulation in (b), the BD1 divides an incident LP beam, with a polarization angle of 45 degrees from the y-axis, into horizontally and vertically polarized beams. A rotatory chopper blade with a 25% duty cycle always blocks one of the split two beams, and horizontally and vertically polarized beams are alternately delivered to the subsequent optical system. The split beams are recombined with another BD into one beam. By converting the modulated light beam into CPL through a quarter waveplate, the discrete CPL modulation is obtained, for which the LP components are not involved.
