In this paper, we present the study on negative refractive index in an inhomogeneously broadened four-level inverted-Y atomic medium based on electromagnetically induced transparency (EIT). The expressions of the relative permittivity and the relative permeability are derived under Doppler broadening. For this four-level system, we have found two frequency bands of negative refractive index in an optical region corresponding to two EIT windows. The influences of coupling and signal laser fields as well as temperature on frequency bands of negative refractive index are investigated. Our research can be convenient for experimental implementation with real atomic media under different temperatures.

中文翻译：

---

非均匀展宽的四能级倒 Y 原子介质中的负折射率

在本文中，我们基于电磁感应透明度 (EIT) 对非均匀展宽的四能级倒 Y 原子介质中的负折射率进行了研究。相对介电常数和相对磁导率的表达式是在多普勒展宽下导出的。对于这个四能级系统，我们在对应于两个 EIT 窗口的光学区域中发现了两个负折射率频带。研究了耦合和信号激光场以及温度对负折射率频带的影响。我们的研究可以方便地在不同温度下用真实的原子介质进行实验实施。