为提高光栅的衍射效率，提出了基于主动拉曼效应的超冷原子光栅系统。理论研究表明：通过拉曼增益的空间周期性调节，可有效地将沿垂直光栅方向传播的弱探测光衍射到一级方向，同时零级衍射光将被放大。当系统中引进微波场的原子相干效应时，可以进一步提高光栅的一级衍射效率。在一定的条件下，拉曼增益光栅的一级衍射效率可高于电磁诱导相位光栅的一级衍射效率。该系统可作为高效光开关用于全光网络。

介绍了最近发展的主动拉曼增益介质中快光传播的非线性理论。首先介绍了三能级Λ型和四能级N型主动拉曼增益介质中光的线性传播特性的研究结果，指出两者都可实现群速度为负值的快光传播，但在四能级体系中由于额外耦合光场的引入可导致量子干涉效应，使得信号光场的单峰增益谱线劈裂为双峰结构，利用该特性可实现共振点附近介质增益的有效抑制。其次介绍了在四能级体系中利用主动拉曼增益获得Kerr非线性效应的显著增强。再次介绍了主动拉曼增益体系中弱光的非线性传播。通过体系的色散与Kerr非线性效应的平衡可实现光学厚介质中非线性光脉冲的稳定传播，特别是形成弱光水平下的快光孤子。最后对主动拉曼增益体系中快光的进一步研究提出了展望。

A four-level tripod active-Raman-gain scheme is analyzed for obtaining phase-controlled gain, phase shift, and group velocity at room temperature. The scheme can be used to eliminate significant probe field attenuation or distortion which is unavoidable in the scheme based on electromagnetically induced transparency. It is shown that the intensity gain, phase shift, and group velocity of a probe field can be simultaneously manipulated by changing the relative phase of two pump fields. The scheme is also different from that proposed recently by Deng et al. where a probe-field gain always exists. New features of the scheme presented here raise the possibility of designing rapidly responding optical switches and gates for optical information processing.