Achieving high-quality radar forward-looking imaging (FLI) presents significant challenges due to the poor azimuth resolution, which is constrained by the physical antenna aperture size and specific imaging geometry. In this paper, an efficient super-resolution FLI method that integrates wavefront modulation with beam scanning is proposed. Without resorting to complex super-resolution algorithms to solve the imaging equation, this method generates a distinct echo structure and then enhances resolution by extrapolating the azimuth information of the targets. First, a novel chirp-modulated beam is developed, functioning as a chirp pulse propagating along the azimuth direction during scanning. By leveraging the flexibility of modulation, chirp beams with varying azimuthal chirp rates are produced and employed successively in the scanning process, resulting in a series of two-dimensional (2-D) echo matrices. Subsequently, these matrices are compiled into a threedimensional (3-D) echo cube, which provides three degrees of freedom derived from the transmitting signal's bandwidth, beam scanning, and modulation parameters. Moreover, a maximum a posteriori (MAP)-based signal extrapolator is applied along the modulation dimension to augment target's azimuth information and enlarge the separability between different targets. Finally, super-resolution azimuth profiles are obtained through applying the Fourier transform (FT) along the scanning dimension to the extrapolated signal. Simulation results verify the effectiveness of the proposed method, showing a twofold to fourfold enhancement in azimuth resolution. Furthermore, a case study on sea-surface target imaging confirms its practical utility.