Topological band structure via twisted photons in a degenerate cavity

Abstract

Synthetic dimensions based on particles’ internal degrees of freedom, such as frequency, spatial modes and arrival time, have attracted significant attention. They offer ideal large-scale lattices to simulate nontrivial topological phenomena. Exploring more synthetic dimensions is one of the paths toward higher dimensional physics. In this work, we design and experimentally control the coupling among synthetic dimensions consisting of the intrinsic photonic orbital angular momentum and spin angular momentum degrees of freedom in a degenerate optical resonant cavity, which generates a periodically driven spin-orbital coupling system. We directly characterize the system’s properties, including the density of states, energy band structures and topological windings, through the transmission intensity measurements. Our work demonstrates a mechanism for exploring the spatial modes of twisted photons as the synthetic dimension, which paves the way to design rich topological physics in a highly compact platform.

Realization of exceptional points along a synthetic orbital angular momentum dimension

“…The direct observation of the complex energy bands with EPs in the experiment demonstrates the flexibility of the synthetic platform to characterize the singular properties. Through introducing the synthetic OAM dimension, many more distinguished NH spectra can be investigated, such as the spectra of edge state [30,38] and the spectra with gauge fields [31]. Moreover, as two exceptional points naturally form a point gap exhibiting the non-Hermitian skin effect [39], signatures connected with the accumulation of OAM modes would be interesting to investigate.…”

“…In this work, for the first time, we construct a NH system in a new configuration along the synthetic orbital angular momentum (OAM) dimension [30,31]. We directly measure the real and imaginary parts of the quasienergy near EPs of a periodically driven cavity.…”

Structured Light Laser Based on Intra-Cavity Modulation

“…There were two lenses in the degenerate cavity. High-order modes could be produced through passing a q-plate and a wave plate repeatedly with the input laser beams [86]. Qualified degenerate cavities are required to be high for the fabrication of optical components and the intra-cavity alignment.…”

Realization of exceptional points along a synthetic orbital angular momentum dimension

“…In this work, we construct an NH system in a new configuration along the synthetic orbital angular momentum (OAM) dimension ( 27 , 28 ) in a degenerate cavity. We develop a unique method to explore the band structure along the synthetic OAM dimension, which is referred to as wavefront angle–resolved band structure spectroscopy.…”