Circular polarization-type polarization diversity element, scanning element using same, and lidar

A polarized-light output device for converting a light beam having a spot diameter, incident from a light source, into light having a specific polarization state and outputting the light, comprising:

• first and second polarization gratings disposed with a predetermined spacing therebetween, wherein each polarization grating is oriented along a direction transverse to the incident light beam, comprises a plurality of birefringent directors, and is configured to convert left-handed and right-handed circular polarizations associated with the light beam into reverse circular polarizations, respectively;
• and
• a half-wave plate disposed subsequently to the first and second polarization gratings and configured to reverse one of the circular polarizations,
• wherein
• the plurality of birefringent directors of each polarization grating are configured to rotate at a predetermined period along a rotation axis that extends on a planer direction of the polarization grating,
• the first polarization grating is configured to receive and deflect the incident light beam to generate in separate directions a first light beam with the left-handed circular polarization and a second light beam with a right-handed circular polarization,
• the second polarization grating is configured to receive and deflect the first and second light beams to generate in parallel third and fourth light beams, and
• the half-wave plate is oriented along a direction transverse to the parallel third and fourth light beams, and configured to receive the third light beam and convert the direction of the circular polarization associated with the third light beam into the same direction as the circular polarization associated with the fourth light beam, whereby the third light beam with the converted circular polarization and the fourth light beam are outputted.