Twisted Nanotubes of Transition Metal Dichalcogenides with Split Optical Modes for Tunable Radiated Light Resonators

Synthesized micro‐ and nanotubes composed of transition metal dichalcogenides (TMDCs) such as MoS2 are promising for many applications in nanophotonics because they combine the abilities to emit strong exciton luminescence and to act as whispering gallery microcavities even at room temperature. In addition to tubes in the form of hollow cylinders, there is an insufficiently studied class of twisted tubes, the flattened cross‐section of which rotates along the tube axis. As shown by theoretical analysis, in such nanotubes the interaction of electromagnetic waves excited at the opposite sides of the cross‐section can cause splitting of the whispering gallery modes. By studying micro‐photoluminescence spectra measured along individual MoS2 tubes, it has been established that the splitting value, which controls the energies of the split modes, depends exponentially on the aspect ratio of the cross‐section, which varies in “breathing” tubes, while the relative intensity of the modes in a pair is determined by the angle of rotation of the cross‐section. These results open up the possibility of creating multifunctional tubular TMDC nanodevices that provide resonant amplification of self‐emitting light at adjustable frequencies. Whispering gallery mode splitting is observed in MoS2 nanotubes with a flattened cross‐section. The energy and intensity of the split peaks depend on the flattening degree of the cross‐section and its orientation with respect to the excitation electric vector. These results open the way to the creation of multifunctional tubular transition metal dichalcogenide nanodevices providing resonant amplification of self‐emitting light at controlled frequencies.