Doppler pulse amplification

The ability to amplify ultrashort pulses has revolutionized modern laser science, driving advances in various fields such as ultrafast optics and spectroscopy. A pivotal development in this field is chirped pulse amplification (CPA), which stretches, amplifies, and recompresses ultrashort optical pulses using dispersive elements to overcome amplification limits. However, CPA faces limitations due to gain narrowing, restricting the final pulse duration. Here we propose Doppler pulse amplification (DoPA), an approach for amplifying ultrashort pulses. While DoPA shares similarities with CPA in that it also stretches, amplifies, and recompresses pulses, it differs in how it achieves this temporal compansion (expansion and compression). Unlike CPA, DoPA exploits Doppler shifts induced by space-time-modulated interfaces through a space-time wedge implementation without chirping. We show that DoPA dynamically shifts the pulse spectrum, effectively mitigating the gain narrowing issue of CPA. Additionally, we show that DoPA enables more compact amplification systems via a space-time Fresnel implementation. This approach may pave the way for more efficient, high-intensity laser systems and expand the potential for applications in both laboratory research and practical environments.