Linear and nonlinear spin-orbital coupling in golden-angle spiral quasicrystals.

Abstract

The appealing characteristics of quasi-crystalline nanostructure offer tremendous possibilities to tailor the transmission of the angular momenta. Moreover, the second harmonic generation existing in nonlinear nanostructures also exhibits remarkable potential in the fundamental and applied research areas of the angular momenta conversion. By systematically studying the general angular momenta conservation law, we show that the high-dimensional angular momenta transformation and spin-orbital coupling are realized by the nonlinear sunflower-type quasicrystals, which feature the high-fold rotational symmetry and possess an increasing degree of rotational symmetry in Fourier space. Interestingly, since the sequential Fibonacci numbers are essentially encoded in the distinctive nonlinear sunflower-type patterns, the high-fold angular momenta transformation regularly occurs at both linear and nonlinear wavelengths. The investigations of fundamental physics for the unique quasi-crystals reveal scientific importance for manipulating the angular momenta of nonlinear optical signals, which plays a key role in the promotion and development of modern physics.