Search

Metasurfaces have proved to possess extraordinary properties and propelled the development of versatile functional devices in the terahertz domain, but the intrinsic dispersion severely impedes their broadband applications. Sporadic studies on achromatic terahertz metasurfaces are either subject to specific polarization operation or challenged in the fabrication process for extended bandwidth and numerical aperture. Herein a novel meta‐atom scheme made up of a silicon–silica–silicon sandwich‐shaped structure is presented that enlarges the propagation phase as well as improves the dispersion engineering capability at low losses. As a classic case, an achromatic metalens is constituted by these meta‐atoms and experimentally demonstrated which shows a remarkable achromatic focusing performance from 0.5 to 1.1 THz with a numerical aperture of 0.47 and an average efficiency as high as 43.1%. Continuous wavelet transformation analysis further proves the metalens has negligible group delay dispersion. This study not only demonstrates an outstanding terahertz achromatic metalens but also provides a novel meta‐atom paradigm for constructing achromatic metasurfaces such as holographic plate, beam deflector, and Bessel axicon, further not limited to THz bands. [ABSTRACT FROM AUTHOR]

Substitutional lanthanide doping of 2D transition metal dichalcogenides (TMDs) is expected to be a promising strategy to engineer optical, electronic, and optoelectronic properties of TMDs. Understanding the interactions between lanthanide dopants and 2D TMDs host is one of the key problems to be resolved for their profound research studies. Herein, the interactions between Ce dopants and monolayer WS2 in a physical vapor deposition grown Ce‐doped WS2 monolayer are studied by combining scanning tunneling microscopy with optical characterizations with high spatial and temporal resolution. It is found that the highly anisotropic crystal field can effectively split the energy levels of the Ce dopants' f orbital. The electrons in the split energy levels can bind the holes in the valence band maximum of the Ce‐doped WS2, forming optical bright excitons. These excitons collide with the free A excitons when increasing the pump fluences, reducing the A exciton's lifetime. This study may be beneficial for the design and fabrication of optical, electronic, and optoelectronic devices based on lanthanide‐doped TMDs. [ABSTRACT FROM AUTHOR]

Upper gastrointestinal (GI) hemorrhage is a common clinical emergency worldwide. Endoscopic hemostasis is the current first line treatment. Nevertheless, for patients with severe active bleeding and challenging anatomy, endoscopic management can be still difficult and usually requires a higher level of surgical expertise. A simple and effective method of endoscopic hemostasis is therefore in acute clinical demand. Herein a hemostatic hybrid hydrogel comprised of hyaluronic acid and polyethylene glycol stabilized by thiourea–catechol coupling and disulfide bonds is reported. The hybrid hydrogels exhibit enhanced mechanical properties, short gelation time, and good blood clotting ability compared with fibrin gels. The in vivo hemostatic efficacy is confirmed in a rat model of arterial bleeding, in which the rapid gelation of hybrid hydrogels after topical application effectively arrests blood loss with no rebleeding occurring during resuscitation when blood pressure approximately recovers to normal. A large animal study further demonstrates the efficacy of hybrid hydrogels to achieve endoscopic hemostasis against upper GI hemorrhage in pigs. Follow‐up observations show that the hybrid hydrogels can remain adherent at the bleeding wound for 48 h, indicating the sustained hemostatic function in vivo. Collectively, this work demonstrates a promising hemostatic hydrogel for endoscopic hemostasis in upper GI hemorrhage. [ABSTRACT FROM AUTHOR]