Making a broadband diffractive graphene orbital angular momentum metalens by laser nanoprinting

Optical beams carrying orbital angular momentum (OAM) appeal to widespread consideration and play an vital function in optical information storage, optical communications, quantum data processing, super-resolution imaging, and optical trapping and manipulation. Nonetheless, the cumbersome quantity and the complicated methods of the traditional OAM beam mills restrict their purposes in built-in and miniaturized optical or photonic gadgets.

In a examine printed within the journal Ultrafast Science, Cao and colleagues used ultrafast laser nanoprinting technique to manufacture single ultrathin (200nm) graphene metalenses, which combine OAM technology and high-resolution focusing capabilities in a broad bandwidth. The broadband graphene OAM matalenses are anticipated to be broadly utilized in miniaturized and built-in photonic gadgets enabled by OAM beams.

New strategies primarily based on periodically organized 2-dimensional nanostructures, particularly, metasurfaces, have confirmed helpful in reaching ultrathin and integratable OAM beam mills for high-quality OAM beams. Nonetheless, conventional broadband metasurface lenses usually require time-consuming processing and sophisticated iterative design strategies to attain correct wave entrance management. Compared, graphene metalenses with easy designs are enabled by a one-step laser nanoprinting.

Graphene supplies can concurrently manipulate the amplitude and section of a light-weight beam, permitting excessive flexibility and accuracy within the lens design to attain desired focal depth distributions. Not too long ago, Cao et al. realized a brand new graphene metalens that may focus broadband OAM beams by ultrafast laser nanoprinting.

A way primarily based on the detour section approach and distinctive optical properties of graphene oxide was developed to design the graphene OAM metalenses, which may independently management the focusing properties and the topological cost of the OAM on the similar time. The broadband capacity of the graphene OAM metalens was demonstrated by focusing optical mild beams at completely different wavelengths.

The experimental focusing depth distributions virtually reproduced the theoretical predictions utilizing the Rayleigh–Sommerfeld diffraction concept. The demonstrated ultrathin graphene metalenses offered a easy and cost-effective method to attain extremely built-in and high-resolution OAM beam focusing. They may discover broad purposes in optical beam and particle manipulations, information storage, quantum data processing, and mode multiplexing communications in built-in photonic gadgets.

The resultant graphene metalenses are promising for broad purposes in built-in optical and photonic gadgets utilizing OAM beams. For these purposes, a smaller diameter of the doughnut-shaped spot is desired. The strategies that enhance fabrication, enhance the metalens dimension, or use different 2D supplies with greater refractive index distinction are potential to cut back the doughnut-shaped spot dimension to a sure extent.

Nonetheless, the minimal diameter of the doughnut-shaped spot of graphene OAM metalens follows the diffraction restrict. To additional scale back the spot dimension, the brand new concept needs to be proposed, perhaps the mix of tremendous oscillation metalens and spiral section loading is likely one of the potential strategies.