Information processing and communications using optics have undergone significant transformations in the recent years thanks to technological advancement and intensive research in the particular field. With consideration of several optical properties, various solution methods have been proposed for the realization of better results. However, multidimensional splitting has remained a challenge in this field and thus the development of broadband photonic spin hall meta-lens (PSHM) to overcome this problem.
PhD student Junxiao Zhou, Professor Hailu Luo and Professor Shuangchun Wen at Hunan University in China, in collaboration with Professor Zhaowei Liu and his Ph.D. student Haoliang Qian and at the University of California and PhD student Guangwei Hu at the National University of Singapore developed a broadband photonic spin hall meta-lens by integrating geometric and dynamic phase elements. They looked forward towards addressing the challenge of obtaining a multidimensional splitting through simultaneous spinning. This research work has been published in the journal, ACS Nano.
The authors successfully achieved their main object of multidimensional manipulation of photons by allowing more degrees of freedom through the application of the spin-orbit mechanism together with PSHM of very high diffraction efficient. It was also possible to achieve orbital spins in both longitudinal and transverse directions all at the same time at a very high diffraction efficiency of up to 90%. They also compared their experimental results to the available theoretical and found a significant agreement between the two set of results.
As a major contribution of their research work, the authors were able to go beyond the single dimensional photon manipulation that has been practiced by researchers in that area for a long time. Also, they observed that special meta-lens made up of nanoresonator material could be used in cases involving multiple wavelengths. This is because of the dispersion properties of the material which is a key consideration. For instance, it was also observed experimentally that the broadband of the PSHM could be obtained when at least two focusing points that directly depend on the spin meet three requirements. The requirements were that they were to appear at different positions, have opposite transverse shifts and be spin-dependent. Evaluation of the performance of the device is also very simple as it requires at least one significant parameter such as the diffraction efficiencies. The higher the efficiencies, the higher the performance achieved by the device. The obtained efficiency of up to 95% during the experiment is a great achievement by the researchers.
According to the authors, broadband is cost-effective, readily available and has a wide range of properties. This means that it can be used for several applications especially in the field of optical imaging. This is because the employed concept of integration to achieve multi-dimensional operations has resolved the problems of having heavy devices in optics applications. As a result, it will enhance the functionality of the devices in the optical system. This work also reveals useful imaging properties that depend on the polarization effects which the authors see as the next solution move in optical communications, sensing as well as imaging.
Zhou, J., Qian, H., Hu, G., Luo, H., Wen, S., & Liu, Z. (2017). Broadband Photonic Spin Hall Meta-Lens. ACS Nano, 12(1), 82-88.
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