Electrically pumped GaAs-based photonic crystal surface emitting lasers were fabricated using a simple fabrication process by directly capping the indium-tin-oxide transparent conducting thin film as the top cladding layer upon a photonic crystal layer. Optimization of the separate-confinement heterostructures of a laser structure is crucial to improving characteristics by providing advantageous optical confinements. The turn-on voltage, series resistance, threshold current, and slope efficiency of the laser with a 100 × 100 μm2 photonic crystal area operated at room temperature were 1.3 V, 1.5 Ω, 121 mA, and 0.2 W/A, respectively. Furthermore, we demonstrated a single-lobed lasing wavelength of 928.6 nm at 200 mA and a wavelength redshift rate of 0.05 nm/K in temperature-dependent measurements. The device exhibited the maximum output power of approximately 400 mW at an injection current of 2 A; moreover, divergence angles of less than 1° for the unpolarized circular-shaped laser beam were measured at various injection currents. Overall, the low threshold current, excellent beam quality, small divergence, high output power, and high-operating-temperature (up to 343 K) of our devices indicate that they can potentially fill the requirements for next-generation light sources and optoelectronic devices.

We have successfully demonstrated GaAsbased photonic crystal surface emitting lasers with low threshold current density of 0.45 kA/cm 2 by increasing the thickness of indium-tin-oxide (ITO) top cladding layer appropriately. The thicker ITO top cladding layer contributes to lower scattering loss at the surface and more uniform carrier injection. Furthermore, periodic patterns are formed naturally on the surface of ITO layer during the deposition process, resulting in the deflection of the output beam with an angle of 4.5°from the vertical direction and maintaining a small divergence angle. The turn-on voltage, series resistance, and slope efficiency of the laser pumped at room temperature are 2.09 V, 5.10 Ω, and 0.24 W/A, respectively. Lasing wavelengths of different laser devices can be varied from 913.3 to 954.4 nm with several lattice constants designed from 265 to 280 nm. Based on the simple fabrication process, great energy efficiency, small divergence output, and possible beam steering capability by adjusting the periodicity of top cladding layer, such kind of lasers have great potential to be applied in the field of 3D optical sensing, such as vehicle light detection ad ranging, facial identification, environmental sensing, and so on.

Fibrillar materials have gained much attention recently because of their unique properties and potential applications. Although many methods have been developed to fabricate materials, it remains challenging to prepare fibrillar materials containing multicomponent materials or even with complex structures. Here, a facile strategy is developed to fabricate bamboo-shaped fibers by treating electrospun polymer core-shell fibers with solvent vapor annealing. Electrospun polystyrene (PS)/poly(methyl methacrylate) (PMMA) core-shell fibers are first prepared by electrospinning PS/PMMA blend solutions via a phase separation process. When the PS/PMMA core-shell fibers are annealed with the vapor of cyclohexane, which swells and delocalizes the PS domains selectively, the fibers transform into bamboo-shaped structures. The bamboo-shaped structures can be further examined by swelling and delocalizing the PMMA domains selectively, revealing the undulated PS structures. The thermal insulation properties of the fibers with bamboo-shaped structures are observed to be enhanced compared with the original polymer core-shell fibers.

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