Xiaorui Zheng

In Situ Third‐Order Non‐linear Responses During Laser Reduction of Graphene Oxide Thin Films Towards On‐Chip Non‐linear Photonic Devices

High-quality continuous (GO) thin films are prepared by a self-assembly method. Z-scan measurements during the laser-induced reduction process unveil in situ nonlinear responses in the GO film. Third-order nonlinear responses of the GO film can be tuned dynamically by varying the laser input fluence. GO thin films with tunable nonlinear responses and versatile patterning opportunities by using direct laser writing may serve as promising solid-state materials for novel nonlinear functional devices.

Highly efficient and ultra-broadband graphene oxide ultrathin lenses with three-dimensional subwavelength focusing

Nanometric flat lenses with three-dimensional subwavelength focusing are indispensable in miniaturized optical systems. However, they are fundamentally challenging to achieve because of the difficulties in accurately controlling the optical wavefront by a film with nanometric thickness. Based on the unique and giant refractive index and absorption modulations of the sprayable graphene oxide thin film during its laser reduction process, we demonstrate a graphene oxide ultrathin (∼200 nm) flat lens that shows far-field three-dimensional subwavelength focusing (λ3/5) with an absolute focusing efficiency of >32% for a broad wavelength range from 400 to 1,500 nm. Our flexible graphene oxide lenses are mechanically robust and maintain excellent focusing properties under high stress. The simple and scalable fabrication approach enables wide potential applications in on-chip nanophotonics. The wavefront shaping concept opens up new avenues for easily accessible, highly precise and efficient optical beam manipulations with a flexible and integratable planar graphene oxide ultrathin film.

Tailoring pores in graphene-based materials: from generation to applications

Combining the merits from both porous material and graphene, porous graphene-based materials have received significant attention due to their unique porous structures, large surface areas and prominent electrical conductivity. The access and tuning of both the in-plane pores of a monolayer graphene and the interlayer spacing (interlayered pores) of multilayered graphene-based materials offer additional selective mechanisms. These extraordinary properties enable porous graphene-based materials to serve as critical components in molecular separation, including water desalination, gas separation and bioseparation, and electrochemical energy storage, such as supercapacitors, lithium–O2/ion/sulfur batteries and fuel cells. The state-of-the-art pore-fabrication methods as well as the interlayered pores tuning approach for graphene-based materials are summarized. The insights between structures, properties and the broad applications of these materials are reviewed and discussed. The remaining challenges and future perspectives of porous graphene-based materials for wide implementations are provided.

Giant third-order nonlinearity from low-loss electrochemical graphene oxide film with a high power stability

Giant third-order nonlinear absorption and refraction of electrochemical graphene oxide (EGO) film were investigated in the femtosecond regime using the single beam Z-scan technique. The excellent chemical stability of the EGO film under high-power illumination up to 400 mJ/cm2 is demonstrated, which can be attributed to the low oxidation degree revealed by the optical and Raman spectroscopies. High and broadband linear transmission over 70% has been observed from the visible to the infrared range. The low-loss EGO film with giant third-order nonlinearity, excellent chemical stability, large-scale preparation and flexible integration has a great potential for high-power nonlinear optical applications.

Direct patterning of C-shape arrays on graphene oxide thin films using direct laser printing

Planar C-shape arrays are fabricated on a high quality graphene oxide thin film using the direct laser printing method. Through optimizing the laser fabrication process, the minimum fabricated feature size of the C-shape can be less than 500 nm, making the structures potentially useful for near infrared photonic devices.

Graphene Oxide as Antireflection Coating for Silicon Solar Cells

Graphene oxide thin film is sprayed on the surface of silicon solar cells as an antireflection coating. The reflection loss of the solar cells is significantly reduced leading to enhanced short circuit current and efficiency.