Filter-free photonic microwave waveforms generation based on polarization-sensitive Mach–Zehnder modulator

This paper has proposed a photonic microwave waveforms generation scheme based on a dual-polarization Mach–Zehnder modulator (DPol-MZM) at moderate modulation depth without optical filtering. In the scheme, two sub-MZMs are driven by a fundamental frequency and a frequency tripled signal, respectively, to perform the optical carrier suppression modulation along two orthogonal polarization directions. Due to the polarization orthogonality of the tones, there is no cross-beating term in the photocurrent after photodetection. The harmonics power ratio is adjusted by varying the modulation indices and DC biases to obtain the temporal triangular and square waveforms. Frequency-doubled triangular and square waveforms with full duty cycle at repetition rates of 5, 10 and 20 GHz are successfully generated with optimized modulation indices and demonstrated by the simulation.