Singularity Engineering and Structured Light by Meta-Optics

Metaoptics offer fresh opportunities for structuring light as well as dark. I will discuss metasurfaces that enable light’s spin and OAM to evolve, simultaneously, from one state to another along the propagation direction^1,2, along with nonlocal supercell designs that demonstrate multiple independent optical functions at arbitrary large deflection angles with high efficiency.³ In one implementation the incident laser is simultaneously diffracted into Gaussian, helical and Bessel beams over a large angular range and in another one a compact wavelength-tunable external cavity laser with arbitrary beam control capabilities including hologram lasing is demonstrated. We also propose a new class of computer-generated holograms whose far-fields have designer-specified polarization response, dubbed Jones matrix holograms.³ We provide a simple procedure for their implementation using form-birefringent metasurfaces. In particular, we demonstrate holograms whose far-fields implement parallel polarization analysis and custom waveplate-like behavior. The realization of 2D phase and polarization singularities and the unique applications that they will open will be discussed^{4 ,}along with recent results on the realization of an equally spaced liner array of 0D phase singularities using inversed designed cylindrically symmetric phase only metasurfaces. Finally, a complete, topologically protected polarization singularity has been reported for the first time; it is located in the 4D space spanned by the three spatial dimensions and the wavelength and is created in the focal region of a lens using a metasurface.⁵ The field Jacobian plays a key role in the design of such higher dimensional singularities, which can be extended to multidimensional wave phenomena, and pave the way to novel applications in topological photonics.<br/>1. Ahmed H. Dorrah, Noah A. Rubin, Aun Zaidi, Michele Tamagnone & Federico Capasso<br/><i>Nature Photonics</i> <b>15</b>, 287 (2021)<br/>2. Ahmed H Dorrah, Noah A Rubin, Michele Tamagnone, Aun Zaidi, & Federico Capasso <i>Nature Communications</i> <b>12,</b> 6249 (2021)<br/>3. Noah A. Rubin, Aun Zaidi, Ahmed H. Dorrah, Zhujun Shi, & Federico Capasso <i>Science Advances</i>, <b>7</b>, eabg7488 (2021)<br/>4. Soon Wei Daniel Lim, Joon-Suh Park, Maryna L. Meretska, Ahmed H. Dorrah, & Federico Capasso <i>Nature Communications</i>, <b>12</b>, 4190 (2021)<br/>5. Christina M. Spaegele, Michele Tamagnone, Soon Wei Daniel Lim, Marcus Ossiander, Maryna Meretska, Federico Capasso arXiv:2208.09054 (2022)