Abstract
We construct an experimental setup, consisting of conical refraction transformation in two biaxial cascade crystals and 4f-system, to realize Unitary transformation of light beam and the manipulation of Poincaré beams on the different parts of Poincaré sphere. The spatial structure of the polarization can be controlled by changing the polarization of the incident beam or rotating the angle between these two crystals. The beams with different SoPs covering the full-Poincaré sphere, part-Poincaré sphere and one point on the sphere are generated for the different angles between crystals. The Unitary transformation of light beam is proposed in the experiment with the invariant intensity distribution. Subsequently, the spin angular momentum is derived from the distribution of polarization measured in our experiment. Moreover, the conversion between orbital angular momentum and spin angular momentum of light beam is obtained by changing the angle between crystals. And the conversion progress can also be influenced by the polarization of incident beam. We realized the continuous control of the spatial structure of the angular momentum density, which has potential in the manipulation of optical trapping systems and polarization-multiplexed free-space optical communication.
Highlights
We construct an experimental setup, consisting of conical refraction transformation in two biaxial cascade crystals and 4f-system, to realize Unitary transformation of light beam and the manipulation of Poincaré beams on the different parts of Poincaré sphere
One dominant characteristic of full Poincaré (FP) beams is that the states of polarization (SoPs) in the crosssection cover the entire surface of Poincaré sphere
Our studies demonstrate that changing the angle of the crystals and the SoP of incident beam can control the spatial structure of the polarization, making it feasible to tailor the optical force on a particle
Summary
We construct an experimental setup, consisting of conical refraction transformation in two biaxial cascade crystals and 4f-system, to realize Unitary transformation of light beam and the manipulation of Poincaré beams on the different parts of Poincaré sphere. Based on the characters of the conical refraction, in our previous research in 201726, one kind of structured light beam with periodical polarization and phase singularities was theoretically and experimentally obtained from a setup consisting of conical refraction transformation and 4f-system. This beam was verified to be one kind of full Poincaré beams in the r esearch[27], and the effects of using cascade biaxial crystals on the manipulation of polarization was investigated. The beams with different SoPs covering the full-Poincaré sphere, part-Poincaré sphere and one point on the sphere were generated for the different angles between crystals
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