A Simple Photonic Method to Generate Dual-Chirp Microwave Signals Utilizing a Monolithically Integrated Dual-Frequency Laser

Abstract

A novel and simple photonic approach for generating dual-chirp microwave waveforms (DCMWs) by using a monolithic integrated dual-frequency laser is proposed and experimentally demonstrated in this work. The core device is the dual-frequency laser, where the two DFB lasers highly integrated in one laser cavity share the same active layer. By adjusting the integrated dual-frequency semiconductor laser to work in the period-one (P1) state and applying a triangular frequency-modulated microwave waveform to the RF port, DCMWs with two complementarily chirped microwave waveforms can be generated after the photodetector, in which one chirp signal increases similarly and the other decreases with the identical rate. In the experiment, one triangular frequency-modulated microwave signals at 1 GHz with a bandwidth of 2 GHz is modulated and the DCMW with the up-chirp from 13.95 GHz to 17.95 GHz and the down-chirp from 17.95 GHz to 13.95 GHz is successfully realized. The central carrier frequency tunability can be also guaranteed just by tuning the P1 frequency. To my best of knowledge, it is the first time to utilize the frequency up-conversion scheme to generate DCMWs based on the photon integration devices. Especially, no additional external microwave source or signal processing technique is required. Additionally, by making full use of the Reconstruction Equivalent Chirp (REC) technique, the integrated dual-frequency laser can be fabricated easily similar with conventional fabrication process, leading to this system rather compact and a promising candidate for use in radar systems.