Observation of Chiral Symmetry Breaking in Toroidal Vortices of Light

In this Letter, we explore the intersection of chirality and recently discovered toroidal spatiotemporal optical vortices (STOVs). We introduce “photonic conchs” theoretically as a new type of toroidal-like state exhibiting geometrical chirality, and experimentally observe these wave packets with controllable topological charges. Unlike toroidal STOVs, photonic conchs exhibit unique chirality-related dynamical evolution in free space and possess an orbital angular momentum correlated with all the dimensions of space-time. This research deepens our understanding of toroidal light states and potentially advances various fields by unveiling similar wave phenomena in a broader scope of physics systems, including acoustics and electronics.

Figure 1

(a) TLP. (b) Toroidal STOV. (c) Photonic conch. Insets in (b),(c) show the local field phase (observed by three “observers”) in three radial-temporal planes marked by black circular arrows on the left. (d) Symmetry analysis for toroidal STOV and photonic conch.

Figure 2

(a) Photonic conch generation. (b) Three-dimensional profiles of an anticlockwise photonic conch with ${\ell }_{\mathrm{p}}=5$, wherein lower panels present the local intensity and phase. White dashed boxes in the intensity indicate the regions corresponding to the phase plots. (c) Similar to (b) but for a clockwise photonic conch with ${\ell }_{\mathrm{p}}=-15$. Azimuthal angles $\varphi =0°$ in (b),(c) correspond to the points with radiuses of $r_0$.

Figure 3

(a) Principle of the azimuthal intrinsic dispersion. (b) Ratios ${\beta }_2^{\mathrm{int}}(\varphi )/{\beta }_2^{\mathrm{int}}$ calculated from Eq. (5) and the processed experimental data. (c) Local field evolution for the ${\ell }_{\mathrm{p}}=5$ photonic conch. (d) Similar to (c) but for ${\ell }_{\mathrm{p}}=-10$. The green dashed lines in (c),(d) mark the beam divergence angles at different $\varphi$. Exp.: Experiment.

Figure 4

(a) Calculated integral OAM value of anticlockwise photonic conch and toroidal STOV with ${\ell }_{\mathrm{p}}=5$ as a function of $\varphi$ and $t=z/c$. (b) Similar to (a) but for ${\ell }_{\mathrm{p}}=-10$.