Recent works of direct light orbital angular momentum (OAM) photodetection based on orbital photogalvanic effect were limited to type-II Weyl semimetals with barely enough OAM resolution. To solve the problem, a team led by Professor Dong Sun at Peking University demonstrated an OAM photodetector based on multilayer graphene (MLG) can detect mid-infrared light OAM with higher resolution capability. This work further advances the OAM photodetection technology and enables diverse practical application like high-capacity communication and super-resolution imaging.
Materials exhibiting orbital photocurrent responses are limited to type II Weyl semimetals previously. The only known material capable of orbital angular momentum detection in the mid-infrared region is TaIrTe4. Its photocurrent response is enhanced by the large Berry curvature near the Weyl nodes, enabling mid-infrared orbital angular momentum detection. This approach was realized in 2022 through collaboration between Professor Dong Sun's group at Peking University and Professor Pei Zhang's group at Xi'an Jiaotong University. However, the instability of TaIrTe4 under ambient conditions and the challenges associated with its large-area epitaxial growth constrain its potential as a material for focal plane arrays and on-chip integration. Furthermore, the signal-to-noise ratio of the orbital photocurrent response in TaIrTe4 remains relatively low, limiting its high-speed applications based on rapid circular polarization modulation techniques.
In a new paper published in Light Science & Application, a team of scientists, led by Professor Dong Sun from International Center for Quantum Materials, School of Physics, Peking University, China and co-workers have achieved direct detection of 4 um light orbital angular momentum in a multilayer graphene (MLG) photodetector with U-shaped electrodes. And as a new orbital angular momentum detection material capable of large-area growth and CMOS compatibility, multilayer graphene exhibits enhanced orbital angular momentum resolution in the mid-infrared range-an order of magnitude greater than that of TaIrTe4 in previous work. Theoretical analysis reveals that the stronger OPGE response in MLG arises from its two-dimensional linear band structure, high Fermi velocity, and low electron scattering rate. Furthermore, unlike TaIrTe4, the angular photocurrent response in MLG does not include OPGE response and is independent of orbital angular momentum, consistent with the symmetry of MLG.
This work discovered that the MLG photodetector can effectively resolve the OAM order of 4-μm scalar vortex beam focused in between the U-shaped electrodes through the circular polarization-dependent component of photocurrent, which shows a linear and steplike dependence on the OAM order. For the same OAM order, the OPGE responsivity of the MLG device is one order of magnitude lager than that of the TaIrTe4 device, leading to the greater OAM resolution capability.
To determine the decisive characteristics of the large OPGE response, this work numerically calculated the OPGE response coefficients based on a simplified analytical model, which captures the basic features of Dirac fermion (DF) for graphene or MLG and the Weyl fermion (WF) for TaIrTe4 or WTe2. And This work discovered that the mid-infrared OPGE response of MLG is strongly enhanced by the divergence of drude-like contribution, due to its reduced dimensionality of the linearly dispersed energy band and reduced scattering rate with high sample quality.
The results of this work can further advance the development of direct mid-infrared orbital angular momentum detection technology and enable diverse practical applications, such as anti-interference infrared sensing, high-capacity optical and quantum communication through orbital angular momentum coupling, super-resolution imaging, and astronomical observation.
Figure | Dimensionality-enhanced mid-infrared light OAM photodetector based on multilayer graphene. a, Schematic of the radial OPGE response collected by an OAM detector with U-shaped electrodes. b, CPGE component JC as a function of the OAM order m. The error bar is the standard deviation of the fit. c, Comparison of the OPGE responsivity and OAM resolution capability. d, OPGE response coefficient of 2D dirac fermions as a function of photon energy together with its drude and other components, and the comparison with that of 3D weyl fermions.
This project was supported by the National Natural Science Foundation of China (Grant Nos. 62250065), the National Key Research and Development Program of China (Grant Nos. 2021YFA1400100 and 2020YFA0308800), the authors also would like to thank the support from the National Natural Science Foundation of China (Grant No: 12404389, 12034001, 62325401, 12034003 and 62227822), the Natural Science Basic Research Program of Shaanxi (Program No. 2024JC-YBQN-0063), and the Open Fund of the State Key Laboratory of Infrared Physics (Grant No. SITP-NLIST-ZD-2023-02).
See the article:
Dehong Yang, Jiawei Lai, Zipu Fan, Shiyu Wang, Kainan Chang, Lili Meng, Jinluo Cheng*, Dong Sun*. Dimensionality-enhanced mid-infrared light vortex detection based on multilayer graphene, Light: Science & Applications 14, 116 (2025). (https://doi.org/10.1038/s41377-024-01735-4)
