基于透射型电磁感应光栅提高弱光非线性的研究

Studyon Weak Light Nonlinearities Improvement Based on Transmitted-Type Electromagnetically Induced Grating

提出并证明了利用一个强相干驻波场,在一种四能级原子系统产生透射型电磁感应光栅并提高弱探测场交叉相位调制(XPM)及自相位调制(SPM)非线性的设想。探测脉冲的脉宽越短,产生相同相移所需的驻波场以及探测场的强度,与长脉冲或连续光相比需要的强度要大。由于相对传播的共振耦合场形成了驻波电磁感应光栅,探测场在近共振的另一强相干场的共同作用下,在具有大的非线性折射率的相干介质中透明地传播。探测脉冲在介质中传播的群速度受交叉相位调制以及自相位调制非线性调控。

A scheme is proposed to form a transmitted-type electromagnetically induced grating and enhance cross-phase modulation （XPM） and self-phase modulation （SPM） of a probe pulse field using a standing-wave field in a four-level system. The shorter the probe pulse is, the higher intensities of standing-wave field and probe pulse field required to achieve the same phase shifts of XPM and SPM nonlinearities are, comparing with a long pulse or continuous wave （CW）. Because of standing-wave grating generated by counter propagating resonant coupling fields, the resonant probe field can be transparent in the coherence medium with a giant nonlinear refractive index when an additional off-resonant coupling field is added. Group velocity of the probe pulse can be controllable by both XPM and SPM nonlinearities.