Enhanced gain and narrow linewidth of an optical cavity by the Doppler effect in a four-level atomic system

Abstract

A scheme for high gain and narrow linewidth of an optical cavity with a four-level atomic system is proposed by the Doppler effect via active Raman gain (ARG) process. Atomic motion leads to Doppler frequency shift which induces constructive interference for the linear susceptibility. The enhanced normal dispersion greatly narrows the cavity linewidth, and the amplified gain gives rise to a high cavity transmission. Simulation results show that the cavity linewidth based on ARG is about one order of magnitude narrower than that based on electromagnetically-induced transparency under the same conditions, and the cavity transmission intensity could be enhanced by nearly 30 times.

Keywords:

• atomic coherence
• quantum interference
• active Raman gain
• Doppler effect
• dispersion
• gain

Acknowledgments

This work is supported by the National Natural Science Foundation of China (No. 11204162), the Shandong Provincial Natural Science Foundation, China (Nos. ZR2012FQ001 and ZR2012FM011) and the SDUST Research Fund (No. 2012KYTD103).