Photonic Generation of High-Sampling-Rate Arbitrary Waveforms in a Temporal Synthetic Dimension Created by Two Polarimetric Subspaces

We propose and experimentally demonstrate a novel approach to the photonic generation of high-sampling-rate arbitrary microwave waveforms in a temporal synthetic dimension created by two polarimetric subspaces. The two polarimetric subspaces are established based on a polarization-maintaining fiber (PMF) loop incorporating a polarization modulator (PolM). Due to the different refractive indices along the two orthogonal axes of the PMF, one physical PMF loop is equivalent to two dynamically coupled loops with different time delays and a variable coupling ratio controlled by the PolM. If a single linearly polarized pulse is injected into the PMF loop, it is split into two pulses with orthogonal polarizations and with different amplitudes controlled by the PolM. After multiple round trips, a pulse burst with a tailored amplitude profile is produced in the temporal synthetic dimension. The temporal interval between two adjacent pulses in the pulse burst, or the sampling rate of the generated waveform, is determined by the birefringence and the length of the PMF. The proposed approach is evaluated by an experiment. Arbitrary waveforms with different sampling rates of 16.7, 62.5, and 250 GSa/s are generated. The fidelity of the generated waveforms is evaluated by calculating the average root mean square error (RMSE). For the generated waveforms, the RMSE is as low as 0.0596, conforming a good fidelity of the generated waveforms.