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 necessary position in optical knowledge storage, optical communications, quantum data processing, super-resolution imaging, and optical trapping and manipulation. Nonetheless, the cumbersome quantity and the advanced methods of the traditional OAM beam mills restrict their functions in built-in and miniaturized optical or photonic gadgets.

In a research revealed within the journal Ultrafast Science, Cao and colleagues used ultrafast laser nanoprinting technique to manufacture single ultrathin (200nm) graphene metalenses, which combine OAM era and high-resolution focusing features 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, specifically, metasurfaces, have confirmed helpful in reaching ultrathin and integratable OAM beam mills for high-quality OAM beams. Nonetheless, conventional broadband metasurface lenses typically require time-consuming processing and complicated 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 part of a lightweight beam, permitting excessive flexibility and accuracy within the lens design to attain desired focal depth distributions. Lately, 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 part approach and distinctive optical properties of graphene oxide was developed to design the graphene OAM metalenses, which might independently management the focusing properties and the topological cost of the OAM on the similar time. The broadband capability of the graphene OAM metalens was demonstrated by focusing optical gentle beams at totally different wavelengths.

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

The resultant graphene metalenses are promising for broad functions in built-in optical and photonic gadgets utilizing OAM beams. For these functions, a smaller diameter of the doughnut-shaped spot is desired. The strategies that enhance fabrication, improve the metalens dimension, or use different 2D supplies with larger refractive index distinction are doable 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 cut back the spot dimension, the brand new concept must be proposed, possibly the mixture of tremendous oscillation metalens and spiral part loading is without doubt one of the doable strategies.