Aberration-induced vortex splitting in amplified orbital angular momentum beams.

Here we report the generation and power amplification of higher-order (l = 2) orbital angular momentum (OAM) beams using a compact end-pumped Nd:YAG Master-Oscillator-Power-Amplifier (MOPA) design. We analysed the thermally-induced wavefront aberrations of the Nd:YAG crystal using a Shack-Hartmann sensor as well as modal decomposition of the field and show that the natural astigmatism in such systems results in the splitting of vortex phase singularities. Finally, we show how this can be ameliorated in the far field through engineering of the Gouy phase, realising an amplified vortex purity of 94% while achieving an amplification enhancement of up to 1200%.

Spatially resolved birefringence measurements with a digital micro-mirror device.

We demonstrate a novel technique to measure spatially resolved birefringence structures in an all-digital fashion with a digital micro-mirror device (DMD). The technique exploits the polarization independence of DMDs to apply holographic phase control to orthogonal polarization components and requires only a static linear polarizer as an analyzer for the resulting phase shift polarization measurements. We show the efficacy of this approach by spatially resolving complex polarization structures, including nano-structured metasurfaces, customized liquid crystal devices, as well as chiral L-Alanine and N-Acetyl-L-cystein crystals.

Demonstrating Arago-Fresnel laws with Bessel beams from vectorial axicons.

Two-dimensional Bessel beams, both vectorial and scalar, have been extensively studied to date, finding many applications. Here we mimic a vectorial axicon to create one-dimensional scalar Bessel beams embedded in a two-dimensional vectorial field. We use a digital micro-mirror device to interfere orthogonal conical waves from a holographic axicon, and study the boundary of scalar and vectorial states in the context of structured light using the Arago-Fresnel laws.

Accelerating polarization structures in vectorial fields.

We generate optical fields whose polarization structures not only rotate about their propagation axis but also can be controlled to accelerate independently from their spatial profile. We show that by combining accelerated intensity transport with orthogonal polarization states, we can produce a vector beam that displays optical activity with periodical acceleration and deceleration of the Stokes vector during propagation. We achieve this with orthogonal, scalar fields, represented by weighted superpositions of oppositely charged Bessel beams.