The use of beams carrying orbital angular momentum (OAM) has become ubiquitous and topical in a variety of research fields. More recently, there has been a growing interest in exotic OAM carrying beams with spatially variant polarisation, so called Poincaré sphere beams. Structuring these beams at the source gives rise to compact solutions for a myriad of applications, from laser materials processing to microscopy. Here we present a visible laser that control's the angular momentum of light by arbitrary spin-orbit (SO) momentum conversion using novel metasurface devices. Further, we outline how to generate high purity OAM states in a deterministic manner with charge up to 100. Finally, we demonstrate the generation of symmetric and non-symmetric vector vortex beams from the same source with a large OAM differential between modes of up to 90. The performance and versatility in design of our approach offers a route to control light's angular momentum at the source.
Twisted light carrying orbital angular momentum (OAM) has given rise to many developments ranging from optical manipulation to optical communications. Generating twisted light from solid-state lasers was initially achieved by amplitude and dynamic phase control, and more recently by manipulating the geometric phase of light. These lasers have been limited to generate superposition of OAM modes as well as scalar modes with OAM ℓ = 10. Here we incorporate a metasurface device into a visible solid-state laser to control the angular momentum of light by arbitrary spin-to-orbit coupling. We demonstrate the generation of pure Laguerre Gaussian modes with OAM up to ℓ = 100. Modal decomposition measurements of the output beams reveal the higher purity of the generated modes can reach up to 96% for ℓ = 1 and 88% for ℓ = 100. our approach offers a new route for high brightness OAM states at the source.
Controlling light with subwavelength-designed metasurfaces (MSs) has allowed for the arbitrary creation of structured light by precisely engineered matter. We report on the purity and conversion efficiency of hybrid orbital angular momentum (OAM)-generating MSs. We use a recently reported method to design and fabricate meta-surfaces that exploit generalized spin-orbit coupling to produce vector OAM states with asymmetric OAM superpositions, e.g., 1 and 5, coupled to linear and circular polarization states, fractional vector OAM states with OAM values of 3.5 and 6.5, and also the common conjugate spin and OAM of ±1 as reported in previous spin-orbit coupling devices. The OAM and radial modes in the resulting beams are quantitatively studied by implementing a modal decomposition approach, establishing both purity and conversion efficiency. We find conversion efficiencies exceeding 75% and purities in excess of 95%. A phase-flattening approach reveals that the OAM purity can be very low due to the presence of undesired radial components. We characterize the effect and illustrate how to suppress the undesired radial modes.
In the avid search for means to increase computational power in comparison to that which is currently available,
quantum walks (QWs) have become a promising option with derived quantum algorithms providing an associated speed
up compared to what is currently used for implementation in classical computers. It has additionally been shown that the
physical implementation of QWs will provide a successful computational basis for a quantum computer. It follows that
considerable drive for finding such means has been occurring over the 20+ years since its introduction with phenomena
such as electrons and photons being employed. Principal problems encountered with such quantum systems involve the
vulnerability to environmental influence as well as scalability of the systems. Here we outline how to perform the QW
due to interference characteristics inherent in the phenomenon, to mitigate these challenges. We utilize the properties of
vector beams to physically implement such a walk in orbital angular momentum space by manipulating polarization and
exploiting the non-separability of such beams.
Beams carrying orbital angular momentum (OAM) are ubiquitous in many experiments carried out today and cover a
wide range of research, from surface microstructure processing to optical tweezers and communications. It follows that
these beams are a significant factor in the outcome of these research areas. They are often generated through the use of
phase-only modulation with elements such as SLMs and q-plates due to the simplicity of the approach. Interesting
consequences result from this generation principal which include the introduction of radial modes as they propagate. We
experimentally demonstrate how this effects the distribution of power where a notable decrease in the desired
fundamental mode power occurs with higher OAM beams in addition to an expansion in the power across these radial
modes. This research additionally affirms their mathematical description as the recently introduced Hypergeometric-