A Modulator-Free Photonic Triangular Pulse Generator Based on Semiconductor Lasers

A modulator-free photonic triangular pulse generator is proposed and demonstrated based on two semiconductor lasers. In this method, a direct-modulated semiconductor laser is employed to generate a fundamental frequency component. Meanwhile, a third-order harmonic signal is generated by external optical injection together with 1/3 subharmonic microwave modulation of another semiconductor laser. After properly setting the amplitude and time delay between the fundamental and third-order harmonics, the combined signal composes a triangular waveform. The generation of a 11.4-GHz triangular pulse train is experimentally demonstrated. Without using any modulator, the proposed approach is a promising method for triangular pulse generation with low cost and simple structure.