A freestanding dye-doped polymethylmethacrylate microbubble laser based on high-Q whispering gallery mode (WGM) is demonstrated. Low threshold tunable laser emissions are observed in microbubbles with different sizes fabricated by a volumetric pipette. The whispering gallery mode laser emissions in the 944 nm diameter microbubble have a low laser threshold of about 15 µJ pulse −1 and a 0.083 nm free spectral range. The smooth wall of the microbubble ensures a high quality factor of approximately 24 120. In addition, 590 nm-610 nm laser emission is achieved by the reabsorption effect of the dye. This work provides an efficient way to implement a freestanding,easily doped and low cost tunable WGM micro-laser.

Vanadium dioxide (VO2) is an attractive thermal-control material exhibiting low thermal hysteresis and excellent temperature cycling performance. However, the deficiencies including weak spectral shift and narrow-band absorption during insulating-metallic transitions hinder its application in optoelectronics. The transition metal dichalcogenides (TMDs) can provide a promising solution with their high dielectric properties and robust optical coupling. Here, we report a MoS2/VO2/Au/Si metasurface and investigate the dynamic tunability of its optical absorbance and structural color upon heating via spectroscopic ellipsometry measurements and numerical simulations. The first-principles calculations reveal that the dielectric absorptions of metallic and insulating VO2 oppositely response to temperature, closely related to the difference in the transitions of O-2p states. Finite-element simulations reveal that the introduction of MoS2 nanostructure induces more absorption peaks by 2∼3 and achieves strong absorption in the full wavelength range of visible light. The Fabry–Perot (F–P) resonance is the critical factor for the optimized optical absorption. The structural color is sensitive to environmental perturbations at high-ε state of VO2, lower oblique incidence angles, and heights of MoS2. This work seeks to facilitate the spectral modulation of phase change metamaterials and can be extended to photoelectric detection and temperature sensing applications.

We report a voltage-tunable reflective gold wire grid metasurface on vanadium dioxide thin film, which consists of a metal-insulator-metal (MIM) structure. We excite surface plasmon polariton (SPP) modes on the gold surface by fabricating a one-dimensional structured gold wire grid. Joule heating of laser-induced graphene (LIG) can be controlled by the voltage at the bottom, allowing vanadium dioxide in the structure to complete the transition from the insulating state to the metallic state. The phase transition of vanadium dioxide strongly disrupts the plasmon modes excited by the gold wire grid above, thereby realizing a huge change in the reflection spectrum. This acts as a tunable metasurface optical switch with a maximum modulation depth (MD) of over 20 dB. We provide a more effective and simple method for creating tunable metasurfaces in the near-infrared band, which can allow metasurfaces to have wider applications in optical signal processing, optical storage, and holography.

A sensing enhancement sensor based on hybrid film fiber has been proposed to detect ammonia. The hybrid film coated on the MMF-SMF-MMF (Multimode Fiber–Single-mode Fiber–Multimode Fiber) structure is composed of single-walled carbon nanotubes with carboxylic acid groups (SWCNTs-COOH) self-assembled film and the silver film that was used to excite surface plasmon polariton (SPP) which contribute to enhancing the sensitive for refractive index (RI). The presence of free carboxylic acid functional groups and large surface area on the SWCNTs-COOH leads to high adsorption and selectivity toward amine compounds. The sensor works under a wavelength modulation scheme. And the resonance wavelength showed a red shift with an increase of the effective RI of the SWCNTs-COOH self-assembled film affected by ammonia concentration. The experimental results show that the sensor coated with hybrid film has high sensitivity and selectivity to ammonia gas. The proposed sensor is linearly responsive to ammonia concentration in the range 0 - 30 ppm, with a maximum sensitivity of 0.8 nm/ppm, the resolution 0.375 ppm, and the measured response 30 s, respectively. Finally, the sensor also has the advantages of simple structure and compact size, excellent stability, and low cost.

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