Generation of a tunable Dual-frequency source by operating a laser at Period-one

A novel method for the generation of a tunable dual-frequency laser source is presented. The proposed system uses a laser diode with optical feedback and operating at period-one (P1) oscillation state. Through investigation on the optical spectra of the laser at this state, dual-frequency components can be obtained and the separation (i.e., the difference) of the two frequencies can be flexibly adjusted from 2.72GHz to 3.12GHz by varying the external cavity length. Such dual-frequency feature and its tunable range have many potential applications for both optical and microwave measurement. The paper also presents an example of application by the proposed system, where a dual-frequency laser Doppler velocimeter (DV) is implemented for high-resolution target detection.