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The valley degree of freedom that results from broken inversion symmetry in two-dimensional (2D) transition-metal dichalcogenides (TMDCs) has sparked a lot of interest due to its huge potential in information processing. In this experimental work, to optically address the valley-polarized emission from three-layer (3 L) thick WS₂at room temperature, we employ a SiN photonic crystal slab that has two sets of holes in a square lattice that supports directional circular dichroism engendered by delocalized guided mode resonances. By perturbatively breaking the inversion symmetry of the photonic crystal slab, we can simultaneously manipulate s and p components of the radiating field so that these resonances correspond to circularly polarized emission. The emission of excitons from distinct valleys is coupled into different radiative channels and hence separated in the farfield. This directional exciton emission from selective valleys provides a potential route for valley-polarized light emitters, which lays the groundwork for future valleytronic devices. 

Abstract There is a great interest in low-cost, versatile microfluidic platforms of which the fabrication processes are rapid, straightforward, and translatable to industrial mass productions. In addition, it is beneficial for microfluidic devices to be reconfigurable in the field, so that multiple functions can be realized by a minimum number of devices. Here, we present a versatile acrylic-tape platform which allows highly accessible rapid prototyping of microfluidic devices, as well as device reconfiguration to realize different functions. The clean-room-free fabrication and sealing process only requires a laser cutter, acrylic, and tapes and can be done by an untrained person in the field. We experimentally characterized the relationship between the capillary flow speed and the channel height, the latter of which can be well controlled by the fabrication process. Reconfiguration of microfluidic functions was demonstrated on a single acrylic-tape device, thanks to the reversible sealing enabled by functional tapes. Different pumping mechanisms, including on-chip pumps for better portability and syringe pumps for precise fluid control, have been employed for the demonstration of two-phase flow and droplet generation, respectively. The low-cost and versatile acrylic-tape microfluidic devices are promising tools for applications in a wide range of fields, especially for point-of-care biomedical and clinical applications.