High Diffraction Effeciency Fiber Facet Flat GO Lens with a Large Numerical Aperture

Diffractive devices are essential components in the reduction of the volume of optical systems. The graphene oxide (GO) lens, well-known for its nanoscale thickness, high numerical aperture, one-step laser fabrication, and low fabrication cost, offers a significant advantage in the field of integration with fibers and photonics chips. However, existing research indicates that the diffraction efficiency of GO lenses integrated with fibers and photonics chips is quite low (around 10%). The low diffraction efficiency causes several issues for applications based on GO lenses, including energy dispersion, low signal-to-noise ratio, and low image brightness. In this study, we present the design and fabrication of a femtosecond laser direct writing (FLDW) fiber GO lens with a thickness of 400 nm, which has a diffraction efficiency of 34.7% (more than three times that of former research). Furthermore, the fiber GO lens exhibits a high numerical aperture (NA) of 0.55, rendering it a promising option for a diverse range of applications in optical communications, medical optics, and imaging systems.