Efficient frequency conversion based on resonant four-wave mixing

Efficient frequency conversion of photons has important applications in optical quantum technology because the range suitable for photon manipulation and communication usually varies widely. Recently, an efficient system using a double-$\Lambda$ four-wave mixing (FWM) process based on electromagnetically induced transparency (EIT) attracted considerable attention its potential to achieve nearly 100% efficiency (CE). To obtain such high CE, spontaneous emission loss this resonant-type FWM must be suppressed considerably. A simple solution is arrange applied laser fields backward configuration. However, phase mismatch due configuration can cause significant decrease CE. Here, we demonstrate that effectively compensated by introducing shift obtained two-photon detuning. Under optimal conditions, observe wavelength from 780 795 nm with maximum CE 91.2(6)% at depth 130 cold rubidium atoms. The current work represents step toward achieving low-loss, high-fidelity EIT-based conversion.