Electro-Optic Frequency Combs Carrying Orbital Angular Momentum

To date, orbital angular momentum (OAM) and electro-optical frequency combs (EOFCs) are two distinct fields of research without too much association. Herein, we generated the OAM-EOFCs by applying electro-optic phase modulation to the OAM beam. We verified the OAM characteristic of the EOFCs’ sidebands and demonstrated the dispersion-induced spiral fringe rotation in the interference process. Leveraging the optical rotational Doppler effect of the OAM beam and the intermode beat signal of EOFCs, we achieved rotational speed measurement and absolute distance measurement using a single OAM-EOFC. We also demonstrated, for the first time, the simultaneous measurement of rotational speed and absolute distance of rough objects by tuning the repetition rate of EOFCs. Leveraging the large scanning range of the repetition rate of OAM-EOFC’s high-order sidebands of the OAM-EOFC, we obtained an Allan deviation of distance measurement as low as 570.12 μm at an averaged time of 3.87 s under a distance of 17.1664 m, while the error of rotational speed measurement is down to 0.44%. Our study bridges two distinct research fields, EOFCs and OAM, opening the door to various fundamental research avenues and applications, including large-capacity optical communications, high-security optical encryption, and multidimensional photon entanglement.