In this work, we compare different methods for implementing a triplicator, a phase grating that generates three equi-intense diffraction orders. The design with optimal efficiency features a continuous phase profile, which cannot be easily reproduced, and is typically affected by quantization. We compare its performance with binary and sinusoidal phase profiles. We also analyze the effect of quantizing the phase levels. Finally, a random approach is adopted to eliminate the additional harmonic orders. In all cases, a liquid-crystal-on-silicon spatial light modulator is employed to experimentally verify and compare the different approaches.

We experimentally demonstrated an approach to generate arbitrary total angular momentum (TAM) states by using two liquid crystal devices. Photons’ TAM, the sum of spin and orbital angular momenta (SAM and OAM) under paraxial approximation, has found many applications in optics and attracted increasing attention in recent years. Our approach is based on the orthogonality of two eigen SAM components, that arbitrary TAM states will be produced through encoding different holograms in one system. The comparison with theoretical predications yields an excellent agreement, including both the separable state and the non-separable state. The proposed scheme takes a step forward for generating complex structured fields and broadens its application to various fields like laser processing and large capacity data transmission.

Multi-ring optical vortices are a kind of structured beams that carry orbital angular momentum (OAM) and have concentrical doughnut intensity distributions. In this Letter, we present both theoretically and experimentally a scheme that employs the dimensions of both the OAM states and radial index of multi-ring optical vortices simultaneously to accomplish high-dimensional free-space data coding/decoding transmissions. Such a scheme can further improve the coding efficiency when limited OAM states are available. In the proof-of-concept experiment, 64-ary coding/decoding employing 16 OAM states and four radial indices are present. Also, the coding/decoding performance when facing various atmosphere turbulences is evaluated. Furthermore, a 64 × 64 gray image (totally, 32,768 bits) is also transmitted through multi-ring optical vortices coding in free-space successfully, showing good transmission performance.

In this Letter, we propose a simple and effective approach for transforming a conventional Talbot array illuminator (TAI) with multilevel phase steps into a binary-phase TAI (BP-TAI) through detour phase encoding. The BP-TAI is a binary (0 π) phase-only diffractive optical element, which can be utilized to generate a large-scale focal spots array with a high compression ratio. As an example, we design a square BP-TAI with the fraction parameter β = 15 for achieving a square multifocal lattice with a high compression ratio β². Theoretical analysis and experimental results demonstrate that the detour phase encoding is efficient for designing the BP-TAI, especially with the high compression ratio. Such results may be exploited in practical large-scale optical trapping and X-ray imaging.

The excitation of high-order Laguerre–Gaussian (LG) modes in a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser resonator was presented by applying the diffraction of a second-order circular Dammann grating (CDG) for annular pumping. In the study, the 808 nm pump light was shaped into a double-ring structure by the CDG and matched spatially with that of an ideal LG₁₁ mode. As a result, the laser resonator generated an LG₁₁ vortex mode, and the laser power reached 204 mW with 14.5% slope efficiency. Also, when the cavity mirror was tilted, the laser output could switch to the LG₀₁ vortex mode. The results showed the convenience and versatility of CDG in an annular-pumped vortex laser.

Separating lights into different paths according to the polarization states while keeping their respective path’s polarizations with high purification is keen for polarization multiplex in optical communications. Metallic nanowire gratings with multi-slits in a period are proposed to achieve polarized beam splitters (PBSs) in reflection and diffraction. The setting of multi-slits largely reduces the reflection of photons with a transverse magnetific field via the plasmonic waveguiding effect, which leads to highly polarized output lights with extinction ratio larger than 20 dB in each channel. The proposed reflection/diffraction PBSs enrich the approaches to control the polarization states with the advantages of wide incident angles and flexible beam splitting angles.