A diode-pumped alkali laser has gained rapid development in recent years. In this study, we take the advantages of high-gain cross section and low upper energy lifetime of an alkali laser to propose, to the best of our knowledge, a novel type of time-domain-modulated alkali vapor amplifier. By using the amplifier, we experimentally demonstrate the power scaling of a modulated seed laser. The study should offer a new methodology to construct a practice high-power and high-modulated laser source for long-distance light detection and ranging systems in the future.