Adaptive-optics-based simultaneous pre- and post-turbulence compensation of multiple orbital-angular-momentum beams in a bidirectional free-space optical link

Generation of strong cylindrical vector pulses via stimulated Brillouin amplification

“…4 In addition to intensity and phase structures, the polarization of light can also exhibit a non-uniform transverse distribution once the OAM and spin angular momentum (SAM) DOFs are entangled. 5,6 Among them, radially and azimuthally polarized light, two specific members of the so-called cylindrical vector (CV) beam, have received more attention, because their focal a) Zhi-Han Zhu and Peng Chen contributed equally to this work. b) Electronic…”

“…Here, we focus on the radial CV light that can be expressed as a superposition of two Laguerre-Gauss (LG) modes with opposite topological charges and circular polarizations, i.e., . 6 To amplify this CV light via SBA, evidently, a pair of linearly (H+V) or circularly (L+R) polarized pumps with same energy and phase-matching condition is necessary. Figure 1 shows the schematic illustration of this proof-of-principle experiment.…”

Full-duplex bidirectional data transmission link using twisted lights multiplexing over 1.1-km orbital angular momentum fiber

“…There have been lots of efforts to develop bidirectional transmission systems, such as passive optical network, fiber-radio network, fiber-to-the-home link and free-space communication link, which enable the transmission link and the resultant cost of the equipment to be shared between the two directions of traffic in a full-duplex communication link2223242526. Previously, single-mode fiber (SMF) or free space is considered for uplink and downlink transmission between both ends of the architecture.…”

Phase correction for a distorted orbital angular momentum beam using a Zernike polynomials-based stochastic-parallel-gradient-descent algorithm

“…Recently, turbulence compensation for a free-space OAM multiplexed system has been demonstrated in a system that used a Shack-Hartmann sensor to measure the wavefront distortion on a Gaussian beam (l 0) that co-propagated with, but was polarized orthogonally to, the OAM communication beams [16]. It might be desirable to design a sensing method whose probe beam could have a phase singularity (e.g., an OAM beam with l ≠ 0) such that the probe beam would spatially overlap with the information carrying beams during propagation.…”

“…The following points are worth mentioning: (1) given that our phase correction approach was performed in a lab environment and the turbulence was strong enough to replicate ∼1 km of open-air propagation, future implementation of this approach may be applicable in an actual building-to-building or intra-city, link but will require further verification; (2) the proposed method for OAM beam phase correction might be compatible with other schemes, such as a wavefront-sensor-based compensation approach [16]. …”