Unidirectional reflection amplification is a desirable functionality for nonreciprocal photonic components. We propose an inversionless route to this effect in a homogeneous ensemble of a three-level $\mathrm{\Lambda }$-type atomic system using a spatially graded coupling field. The linear position dependence of the coupling strength breaks the spatial symmetry of the optical susceptibility, enabling strong reflection from one side while suppressing the counterpropagating reflection channel. With the assistance of spontaneously generated coherence and a weak incoherent pumping field, the medium provides coherent gain without population inversion, resulting in essentially unidirectional reflection amplification, including the emergence of dual amplification bands. Moreover, both the magnitude and spectral location of the amplification can be reconfigured by tuning the relative phase, detuning, and intensity of the coupling field, offering flexible control over the nonreciprocal response. These results establish a simple, nonmagnetic, and highly tunable platform for realizing reflection-type nonreciprocal amplifiers and related functionalities, with potential applications in quantum optics and integrated photonic devices.

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• Atom optics
• Atomic, optical & lattice clocks
• Optical coherence
• Optical transient phenomena
• Quantum optics