How to design a flat lens

Flat lenses theoretically are able to eliminate optical aberrations, astigmatism, and coma, so the resulting images or signals are accurate and do not require any complicated correction techniques. This prediction is based on the ability to accurately design a flat lens. However, the accurate design of flat lenses remains a challenge. Existing design methods of the planar lens based on the Fresnel approximation diffraction theory are unable to accurately describe the imaging and focusing processes of a flat lens due to paraxial approximations associated. So errors are introduced in the design process, and the outstanding performance of the expected flat lenses cannot be achieved. 

    The research team led by Prof. Baohua Jia from the Center for Micro-Photonics of the Swinburne University of Technology in Australia is dedicated to study graphene optoelectronic devices, represented by graphene flat lenses. In this work, Prof. Baohua Jia, PhD student Mr. Guiyuan Cao and co-authors solve this problem by directly using the fundamental principle and employing the more accurate Rayleigh-Sommerfeld diffraction theory to design and analyze flat lenses. In addition, the accuracy of the designed lenses is experimentally verified by fabricating and characterization. It is found that the focal length of the designed flat lens based on the Rayleigh Sommerfeld theory is accurate and the imaging resolution is in an excellent agreement with the theory. The demonstrated design method is expected to find broad applications in designing and analyzing other ultrathin flat lenses, including metasurface lenses and lenses made of other 2D materials. With this design tool, accurate flat lenses can be designed and applied as camera lenses for cell phones or digital cameras, to minimize the thickness and weight of the module and improve imaging quality. 

GO lens designed by the RS model. (a)Topographic profile of the graphene oxide ultrathin flat lens measured by an atomic force microscope. (b) Intensity distributions in focal plane calculated by Rayleigh-Sommerfeld diffraction theory. (c) Intensity distributions in r-z plane calculated by Rayleigh-Sommerfeld diffraction theory.

About Team
The Laser Nanomaterials Interactions (LNI) group led by Professor Baohua Jia investigates the fundamental light interactions with nanomaterials, in particular 2D materials. They aim at unveiling the exotic physical properties of atomic materials and 2D materials for the development of next-generation optoelectronic integrated devices for broad applications in energy, biomedical and communications. The LNI group is currently supported by the Australian Research Council, Defense Science Institute, and industrial funds. The team has published more than 100 academic papers in internationally renowned academic journals and holds more than 10 patents and patent applications. Professor Jia is a life member of the International Society for Optics and Photonics (SPIE) and Optical Society of America (OSA). She is also the President of Australian-China Advanced Materials and Manufacturing Association (ACAMMA). She has been awarded numerous prizes and grants in her academic career.

Cao G Y, Gan X S, Lin H, Jia B H. An accurate design of graphene oxide ultrathin flat lens based on Rayleigh-Sommerfeld theory. Opto-Electronic Advances 1, 180012 (2018).
DOI: 10.29026/oea.2018.180012