Vector Vortex Beam Emitter Embedded in a Photonic Chip

Abstract

Vector vortex beams simultaneously carrying spin and orbital angular momentum of light promise additional degrees of freedom for modern optics and emerging resources for both classical and quantum information technologies. The inherently infinite dimensions can be exploited to enhance data capacity for sustaining the unprecedented growth in big data and internet traffic, and can be encoded to build quantum computing machines in high-dimensional Hilbert space. So far much progress has been made in the emission of vector vortex beams from a chip surface into free space, however, the generation of vector vortex beams inside a photonic chip hasn't been realized yet. Here, we demonstrate the first vector vortex beam emitter embedded in a photonic chip by using femtosecond laser direct writing. We achieve a conversion of vector vortex beams with an efficiency up to 30% and scalar vortex beams with an efficiency up to 74% from Gaussian beams. We also present an expanded coupled-mode model for understanding the mode conversion and the influence of the imperfection in fabrication. The fashion of embedded generation makes vector vortex beams directly ready for further transmission, manipulation and emission without any additional interconnection. Together with the ability to be integrated as an array, our results may enable vector vortex beams become accessible inside a photonic chip for high-capacity communication and high-dimensional quantum information processing.

High‐Dimensional Quantum Communication: Benefits, Progress, and Future Challenges

“…For instance, the polarization of photons needs to be properly addressed in order for integrated chips to be able to carry two orthogonally polarized fields. Furthermore, the generation and propagation of OAM states through waveguides is very demanding as well, but small steps towards the reliable on-chip transmission and source integration of such states have been proved [107,138]. As previously mentioned, frequency and path degrees of freedom are the two that can be more easily controlled and manipulated on integrated devices [139][140][141].…”

“…Finally, although the OAM of light constitutes a natural basis for high-dimensional states, it is very challenging to manipulate on integrated devices, thus it is mainly exploited in bulk optics experiments. Nonetheless, noteworthy results that might open the doors to integrated devices exploiting OAM have been achieved [106,107,138,143].…”

Geometric-phase-based shearing interferometry for broadband vortex state decoding

“…Though vector vortex light also combines polarization and spatial modes, the detection of vector vortex states is rather more complex than scalar vortex states because the spatial and polarization degrees of freedom of this form of structured light are coupled in a non-separable manner 30 , 31 . Through the same holographic method, the generated primary and conjugate waves based on the birefringence-induced spin–orbit optical Hall effect 32 are expressed as …”

Optical Fiber-Integrated Metasurfaces: An Emerging Platform for Multiple Optical Applications

“…Alternatively, the two-photon direct laser writing technique prevails in the aspect of constructing complex three-dimensional (3D) structures which are hardly completed by top-down lithography. The superiorities of two-photon direct laser writing have also enabled complex structure prototyping inside the intra-waveguide structures [ 99 , 100 ].…”