On-chip light trapping in bilayer moiré photonic crystal slabs

Abstract

The optical response of bilayer moiré photonic structures can be precisely controlled by varying the lattice geometry. Bilayer moiré photonic crystal slabs exhibit flat bands in the optical band structure, where the optical modes have zero group velocity. They also give rise to momentum-independent light-trapping of Bloch waves in both transverse and vertical directions, leading to high quality-factors ([Formula: see text]) and small mode volumes ([Formula: see text]). The large Q and small V lead to a large Purcell enhancement ([Formula: see text]), providing opportunities for low-threshold lasing, enhancement of optical nonlinearities, and quantum information processing.

Functionalizing nanophotonic structures with 2D van der Waals materials

“…Stacked 2D vdW heterostructures with a certain precise twist angle have enabled exciting electronic attributes from the interference of Moire ´superlattices. 72,75,404 The deterministic stacking of hybrid 2D and 3D vdW materials 405 or nanophotonic structures [406][407][408][409] may hatch intriguing twist-induced photonic and polaritonic physics as well. 74 Author contributions…”

Experimental probe of twist angle–dependent band structure of on-chip optical bilayer photonic crystal

“…Using a pair of photonic crystal slabs (38) that are twisted relative to each other provides a large number of degrees of freedom-choice of material, lattice symmetry, feature size, twist angle, and interlayer gap-and permits tailoring the optical properties of the material. In particular, recent theoretical work shows that twisted bilayer photonic crystal (TBPhC) structures exhibit slow light (39), facilitating the study of strong light-matter interactions and Purcell enhancement (40) and frequency filtering (41). To date, however, there has not been any demonstration of TBPhC devices in the optical frequency range.…”

GaN Magic Angle Laser in a Merged Moiré Photonic Crystal

“…Simulations suggest these flat band modes can achieve optimal combinations of high-Q values and small mode volumes when compared to more traditional photonic crystal cavities. 6 Beyond these advantages, the twist angle, separation thickness, and layer thicknesses as design parameters present opportunities to actively tune both the wavelength and the spatial distribution of the modes, a capability that is advantageous for many applications, including quantum photonics/light sources 14,15 and on-chip photonic signal processing. 16,17 These exciting properties of moiréphotonic crystals have sparked a specific interest in using them as a new kind of low threshold, microscale laser.…”

“…Moiré photonic crystals, inspired by moiré electronic systems like twisted bilayer graphene, − have recently garnered attention for their potential as novel, light-confining structures. − Consisting of two stacked photonic crystals separated by a subwavelength interlayer separation distance, moiré photonic crystal systems achieve flat photonic bands when the two photonic crystal layers are twisted at a so-called “magic” angle with respect to each other. As shown in Figure a, the bilayer moiré system can also be collapsed into a single photonic crystal layer, which we refer to as a “merged” moiré structure.…”

“…The flat photonic bands in these moiré systems slow light propagation in highly localized regions of the moiré superlattice, forming cavity-like modes. Simulations suggest these flat band modes can achieve optimal combinations of high-Q values and small mode volumes when compared to more traditional photonic crystal cavities . Beyond these advantages, the twist angle, separation thickness, and layer thicknesses as design parameters present opportunities to actively tune both the wavelength and the spatial distribution of the modes, a capability that is advantageous for many applications, including quantum photonics/light sources , and on-chip photonic signal processing. , …”