Optimal angle as a key enabler for efficient electromagnetically induced absorption via laser intensity tuning in a Ξ−V type atomic system

Abstract

We report the key role of the control light’s incident angle in achieving efficient electromagnetically induced absorption (EIA) in the $5S_{1/2}-5P_{3/2}-5D_{5/2}$ transition of the ⁸⁷Rb atom in a $\Xi -V$ type atomic system. By precisely adjusting the control light’s incident angle to 1.7°and subsequently tuning its power, a significant conversion from electromagnetically induced transparency (EIT) to EIA is achieved. Experimental findings reveal that the saturation effect is effectively suppressed at this angle, while constructive interference between dressed states generated by the three-photon coherence greatly improves the EIA signal contrast. Theoretical calculations, employing a dressed perturbation chain approach for a Doppler-broadened four-level atomic model, corroborate our experimental observations. Furthermore, with optimized parameter settings, we observe three EIA signals across various hyperfine transitions concurrently at different detuning frequencies. This work provides a new way for efficient coherent modulation in applications such as precision measurement and optical storage.