Phase-dependent amplification switching in a double-Raman system

We experimentally observed phase-dependent optical gain a double-Λ active Raman gain (ARG) system, which may offer potential applications in quantum field amplification as well as bio-imaging techniques. The optical gain in a double-Λ ARG system was conditioned by the relative phase between two probe fields. By detuning the double-Λ ARG system from the optical transition states, spontaneous decay was effectively suppressed, thereby enabling a fully coherent process. By optimizing the multi-photon interaction parameters, we achieved probe field amplification of up to 5 times of their initial intensities. The gain could be all-optically switched off by simply varying the relative phase between the probe fields to π within the loop, demonstrating theoretical analysis of a double-Λ ARG system.