Single-mode lasing in whispering-gallery mode (WGM) microresonators is challenging to achieve. In bottle microresonators, the highly non-degenerated WGMs are spatially well-separated along the long-axis direction and provide mode-selection capability. In this work, by engineering the pump intensity to modify the spatial gain profiles of bottle microresonators, we demonstrate a simple and general approach to realizing single-mode WGM lasing in polymer bottle microresonators. The pump intensity is engineered into an interference distribution on the bottle microresonator surface. By tuning the spacing between axial positions of the interference pump patterns, the mode intensity profiles of single-bottle WGMs can be spatially overlapped with the interference stripes, intrinsically enabling single-mode lasing and selection. Attractive advantages of the system, including high side-mode suppression factors >20 dB, large spectral tunability >8 nm, low-lasing threshold and reversible control, are presented. Our demonstrated approach may have a variety of promising applications, ranging from tunable single-mode lasing and sensing to nonlinear optics.

Chemically synthesized metal nanowires are promising building blocks for next-generation photonic integrated circuits, but technological implementation in monolithic integration will be severely hampered by the lack of controllable and precise manipulation approaches, due to the strong adhesion of nanowires to substrates in non-liquid environments. Here, we demonstrate this obstacle can be removed by our proposed earthworm-like peristaltic crawling motion mechanism, based on the synergistic expansion, friction, and contraction in plasmon-driven metal nanowires in non-liquid environments. The evanescently excited surface plasmon greatly enhances the heating effect in metal nanowires, thereby generating surface acoustic waves to drive the nanowires crawling along silica microfibres. Advantages include sub-nanometer positioning accuracy, low actuation power, and self-parallel parking. We further demonstrate on-chip manipulations including transporting, positioning, orientation, and sorting, with on-situ operation, high selectivity, and great versatility. Our work paves the way to realize full co-integration of various functionalized photonic components on single chips.

Although monolayer transition metal dichalcogenides (TMDs) have direct bandgaps, the low room-temperature photoluminescence quantum yields (QYs), especially under high pump intensity, limit their practical applications. Here, we use a simple photoactivation method to enhance the room-temperature QYs of monolayer MoS₂ grown on to silica micro/nanofibers by more than two orders of magnitude in a wide pump dynamic range. The high-density oxygen dangling bonds released from the tapered micro/nanofiber surface are the key to this strong enhancement of QYs. As the pump intensity increases from 10⁻¹ to 10⁴ W cm⁻², our photoactivated monolayer MoS₂ exhibits QYs from ~30 to 1% while maintaining high environmental stability, allowing direct lasing with greatly reduced thresholds down to 5 W cm⁻². Our strategy can be extended to other TMDs and offers a solution to the most challenging problem toward the realization of efficient and stable light emitters at room temperature based on these atomically thin materials.

In this work, we show that both A-excitonic and B-excitonic photoluminescence of the CVD-grown monolayer MoS₂ can be tuned by electrostatic doping in air by applying a gate voltage.

Subwavelength diameter micro/nanofiber (MNF) provides excellent platform for many applications. In this work, we fabricate subwavelength diameter MNFs with ultra-long waist and analyze the propagation loss origin for such fibers. Transmittance as high as 99.4% is measured for MNF with a waist length of 10 cm and diameter of $1.2\mu \text{m}$ , and the loss is mainly resulted from the modal leakage of the taper. However, when the MNF is getting longer and thinner, the intrinsic surface roughness induced during the fabrication process overrides the modal leakage and plays a major role in the propagation loss. Our study reveals existence of an ultimate transmission limitation for ultra-long MNFs.

We report a simple electrospinning method to fabricate polymer bottle microresonators, which are doped with a lasing gain material and supported by electrospun polymer micro/nanofibers on a flexible grooved polymer substrate. The fabricated bottle microresonators have smooth outer surfaces and high quality. By using an interference light pump approach, single whispering gallery mode lasing is obtained, with a side-mode suppression factor over 20 dB. By mechanically stretching the grooved substrate, tunability of the lasing peaks is demonstrated. Our method has the advantages of saving time and being low in cost and may have promising applications in stretchable lasing and sensing devices.