Wideband and flat-spectrum chaos generation from a semiconductor laser with strong dispersive light feedback

Abstract

We propose and experimentally demonstrate a method of generating wideband and flat-spectrum chaos from a simple device configuration composed of a semiconductor laser subject to strong dispersive light feedback from a chirped fiber Bragg grating (CFBG). The dispersive feedback light induces external-cavity modes with irregular mode separations which beat with the internal modes of laser. This physical process of beating introduces more high-frequency oscillations and thus removes the domination of relaxation oscillation, widening and flattening the radio-frequency spectrum. Experimental results show that laser chaos with a 3-dB bandwidth of 24GHz can be obtained at a feedback strength of 1.60, which is three times the bandwidth at a feedback strength of 0.35. Effects of the dispersive feedback strength and the wavelength detuning between the laser and the CFBG on the 3-dB bandwidth are studied.