The tungsten diselenide (WSe₂) layer helps to successfully turn on and off nanolight. The new research proposed a carrier photoexcited gas confined to tungsten carbide bar the layered van der Waals semiconductor WSe₂ plane, and the resulting hyperbolic reaction allows nanolight to pass through.

Recently, researchers at Columbia University in the United States developed a unique platform to program layered crystals, producing imaging capabilities beyond common limits on demand. This discovery is an important step toward control nanolight, which is light that can access the smallest length scales imaginable. The work also provides insights into the field of optical quantum information processing, which aims to solve difficult problems in computing and communications. Related papers were published in Science.

The propagation of light within a material is usually well defined, with the propagation described by scattering and dispersion. In artificially cemented carbide blade designed metamaterials and in anisotropic layered materials, the dispersion can be hyperbolic, giving rise to subwavelength confinement of the light.

Researchers show that the hyperbolic dispersion can be optically switched on and off on demand in the layered transition metal dichalcogenide tungsten diselenide. Illuminating the material with ultrafast pulses of sub-bandgap light creates a transient waveguide, resulting in hyperbolic dispersion in the material. The ability to tune the dispersion characteristics on-demand using optical pumping is an effective approach for developing ultrafast switching photonic devices and controlling the propagation of light on the nanoscale.

Highly anisotropic materials often display nonintuitive optical properties and can permit propagation of subdiffractional waveguide modes, with hyperbolic dispersion, throughout their bulk. The researchers find optically induced electronic hyperbolicity in the layered transition metal dichalcogenide tungsten diselenide. They used photoexcitation to inject electron-hole pairs in WSe₂ and then visualized, by transient nanoimaging, the hyperbolic rays that traveled along conical trajectories inside of the crystal.

Aaron Sternbach, a postdoctoral researcher at Columbia University, said: "We were able to use ultrafast nano-scale microscopy to discover a new way to control our crystals with light, turning elusive photonic properties on and off at will. The effects are short-lived, only lasting for trillionths of one second, yet we are now able to observe these phenomena."

The study demonstrated a new method of controlling the flow of nanolight. Researchers at Columbia University have studied a van der Waals crystal called tungsten diselenide. Due to its unique structure and strong interaction with light, the potential integration of this crystal in electronic and photonic technology has great potential.

When the scientists illuminated the crystal with a Cemented Carbide Blade pulse of light, they were able to change the crystal's electronic structure. The new structure, created by the optical-switching event, allowed something very uncommon to occur: Super-fine details, on the nanoscale, could be transported through the crystal and imaged on its surface.

The report demonstrates a new method of tungsten diselenide to control the flow of light of nanolight. Optical manipulation on the nanoscale, or nanophotonics, has become a critical area of interest as researchers seek ways to meet the increasing demand for technologies that go well beyond what is possible with conventional photonics and electronics.

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