van der Waals Distributed Bragg Reflectors with Submicron Thickness for Enhanced WSe2 Photodetector Performance

Abstract Distributed Bragg reflectors (DBRs) are essential passive photonic components for spectral selectivity and optical field confinement, yet high-performance DBRs remain largely absent from the van der Waals (vdW) materials platform. Here we report a submicron-thick vdW DBR composed of alternating multilayer tungsten disulfide (WS2) and hexagonal boron nitride (hBN), establishing a compact passive optical building block for all-vdW photonics. Enabled by the large refractive-index contrast between multilayer WS2 and hBN, the 576 nm-thick DBR exhibits an experimental reflectance exceeding 97% and a stopband spanning 660 to 1060 nm. When integrated with tungsten diselenide (WSe2), the vdW DBR increases the layer-resolved absolute absorptance of the ∼4 nm WSe2 layer from 8% to 34% near the excitonic resonance, and photodetectors incorporating the DBR show an approximately 18.5-fold enhancement in responsivity at 750 nm relative to bare devices. Additional molybdenum disulfide (MoS2)/hBN DBR further demonstrates that the design is generalizable across transition metal dichalcogenide (TMD)/hBN material systems. These results show that layered vdW materials can serve not only as active optoelectronic media but also as high-performance passive photonic components, opening a route toward compact, integrable all-vdW optoelectronic and on-chip photonic platforms.