Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

On-chip optical vortex-based nanophotonic detectors

An on-chip optical vortex detector based on spin-Hall nanoslits is reported. The detector is sensitive to the spin of the incoming beam and can simultaneously record the polarization and phase singularity. Although the reported device relies on fast decaying surface plasmons, it represents an important step forward in the development of optical vortex-based integrated photonic devices.

The ever-growing demand for compact integration has given rise to integrated photonic devices on different material platforms for emerging applications, including on-chip biosensors, on-chip quantum technologies and, recently, even on-chip optical vortex-based detectors with plasmonic materials1,2,3.

An optical vortex is a beam of light that propagates such that the phase experiences phenomenological singularity and the wavefront has a topological structure with topological charge due to the helicoidal spatial wavefront around this phase singularity. Such a topological structure can be found in many disciplines, including optics, acoustics, and others. To understand the influence of the singularity, one must explore the phase, polarization, and amplitude of the incident beam. While exploring these properties of the special beam, one may discover that both the polarization and the amplitude vanish and the phase cannot be determined. These insights were published as a new concept in wave theory in 1974. In their theoretical work, Nye and Berry reported on the observation of so-called dislocations4.

The first on-chip silicon-integrated optical vortex emitter was reported in the journal Science in 20125. Having an emitter and a detector monolithically integrated on the same chip would be an essential step forward for on-chip optical vortex-based photonic devices. In their experimental work, Feng and coworkers developed a novel on-chip optical detector that allows full characterization of the polarization and phase singularity based on a plasmonic spin-Hall nanograting. Their method of detection is different from that in other state-of-the-art systems6, because it allows for the detection of singularities simultaneously. Interestingly, the detector developed by Feng and coworkers does not require complicated alignment. It is based on an asymmetric metallic array, in which the top and bottom parts of the array have different grating constants. The specific surface topology dictates the angle at which the excited surface plasmon polariton (SPP) will propagate. The asymmetry allows differentiation of the sign of the topological charge (phase), while the spin-Hall slits are sensitive to the spin of the incoming beam. The so-called spin-Hall slits are composed of nanoslits oriented at π/2. This orientation of the nanoslits gives rise to a chiral response of the detector. If the slits are reversed, then the inverted chiral response occurs. This special design allows the authors to distinguish between a left-circularly polarized (LCP) beam and a right-circularly polarized (RCP) beam. Simply put, a beam incident on the detector would excite an SPP that travels at an angle θ to one of the four quadrants, as shown in Fig. 1. The quadrant in which the SPP propagates determines the polarization (RCP/LCP) of the beam and the sign of the topological charge l. The angle θ dictates the magnitude of the topological charge.

Fig. 1: Artistic impression of the on-chip optical vortex detector that records the phase and polarization singularities.
figure1

Two orbital angular momentum beams with opposite polarization states and different topological charges illuminate the on-chip metasurface.

The great advantage of such devices is their ultracompact size and extremely simple operation2,3, which make them easy to integrate with other on-chip components, e.g., modulators and lasers, to form photonic integrated circuits, enabling large-scale integrated photonic applications.

The next milestone to achieve in optical vortex-based integrated photonic devices is to demonstrate the operation by eliminating the inevitable ohmic losses of plasmonic materials and exploring other surface waves such as Bloch waves, which in turn can propagate on lossless dielectric materials. One can expect significant advances in integrated photonics in the coming years in the direction of novel optical vortex-based on-chip devices.

References

  1. 1.

    Karabchevsky, A. et al. On-chip nanophotonics and future challenges Nanophotonics de-Gruyter. https://doi.org/10.1515/nanoph-2020-0204 (2020).

  2. 2.

    Li, S. M. et al. Compact high-efficiency vortex beam emitter based on a silicon photonics micro-ring. Opt. Lett.43, 1319–1322 (2018).

    ADS  Article  Google Scholar 

  3. 3.

    Feng, F. et al. On-chip plasmonic spin-Hall nanograting for simultaneously detecting phase and polarization singularities. Light.: Sci. Appl.9, 95 (2020).

    ADS  Article  Google Scholar 

  4. 4.

    Nye, J. F. & Berry, M. V. Dislocations in wave trains. Proc. R. Soc. A: Math., Phys. Eng. Sci.336, 165–190 (1974).

    ADS  MathSciNet  MATH  Google Scholar 

  5. 5.

    Cai, X. L. et al. Integrated compact optical vortex beam emitters. Science338, 363–366 (2012).

    ADS  Article  Google Scholar 

  6. 6.

    Genevet, P. et al. Holographic detection of the orbital angular momentum of light with plasmonic photodiodes. Nat. Commun.3, 1278 (2012).

    ADS  Article  Google Scholar 

Download references

Author information

Affiliations

Authors

Corresponding author

Correspondence to Alina Karabchevsky.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Karabchevsky, A. On-chip optical vortex-based nanophotonic detectors. Light Sci Appl 9, 115 (2020). https://doi.org/10.1038/s41377-020-00359-8

Download citation

Further reading

Search

Quick links