Photocurrent detection of the orbital angular momentum of light
Zhurun Ji, Wenjing Liu, Sergiy Krylyuk, Xiaopeng Fan, Zhifeng Zhang, Anlian Pan, Liang Feng, Albert Davydov, Ritesh Agarwal
Utilizing the orbital angular momentum (OAM) of light is promising for increasing the bandwidth of optical communication networks. However, direct photocurrent detection of different OAM modes has not yet been demonstrated. Most studies on current responses to electromagnetic fields have focused on optical intensity related effects while phase information is lost. Here we design a photodetector based on single-crystalline WTe2 layers with carefully designed electrode geometries that allows the direct characterization of the topological charge of OAM light. This orbital photogalvanic effect, driven by the helical phase gradient, is characterized by a current winding around the optical beam axis, with a magnitude proportional to its quantized OAM mode number. Our approach provides a route to develop on-chip detection of optical OAM modes, which can enable the development of next-generation photonic circuits.