Dynamics of two-photon paired superradiance
Dynamics of two-photon paired superradiance
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DOI：
10.1103/physreva.86.013812
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发表时间：
2012-03
影响因子：
2.9
通讯作者：
M. Yoshimura;N. Sasao;M. Tanaka
中科院分区：
文献类型：
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作者：
M. Yoshimura;N. Sasao;M. Tanaka
我们发展了双光子成对超辐射(PSR)的双光子成对超辐射动力学理论。这是一个合作的过程，其特征是两个光子以相等的能量背靠背发射。通过从两个靶端照射触发激光，并将其频率调谐到两个能级之间的一半能量，随着时间的推移，介质和场的宏观相干态动态出现，并产生具有时延的放大输出的大信号。导出了描述整个系统时空演化的1+1时空维基本半经典方程，并用数值解证明了松弛项存在时，爆炸现象和弱PSR现象的存在。爆炸性的PSR事件终止，伴随着储存在目标中的大部分能量的突然释放。我们的数值模拟是使用对-H-2分子的振动跃迁X-1Sigma(+)(G)upsilon=1->；0进行的，并采用许多不同的激发原子数密度和亚稳态和基态之间不同的初始相干。在数密度接近O(10(21)cm(-3))和高初始相干性的例子中，当采取大于O(10 Ns)的相位松弛时间时，爆炸事件在触发照射后几纳秒终止。在PSR事件发生后，系统将遵循由具有拓扑稳定性的多个场凝聚对象组成的、由解析方法获得的稳态解。
We develop for dipole-forbidden transition a dynamical theory of two-photon paired superradiance (PSR). This is a cooperative process characterized by two photons emitted back to back with equal energies. By irradiating the trigger laser from two target ends, with its frequency tuned at the half energy between two levels, a macroscopically coherent state of medium and fields dynamically emerges as time evolves, and a large signal of amplified output occurs with a time delay. The basic semiclassical equations in 1 + 1 space-time dimensions are derived for the field-plus-medium system to describe the space-time evolution of the entire system and are numerically solved to demonstrate the existence of both explosive and weak PSR phenomena in the presence of relaxation terms. The explosive PSR event terminates accompanying a sudden release of most of the energy stored in the target. Our numerical simulations are performed using the vibrational transition X-1 Sigma(+)(g)upsilon = 1 -> 0 of a para-H-2 molecule and taking many different excited atom number densities and different initial coherences between the metastable and the ground states. In an example with a number density close to O(10(21) cm(-3)) and a high initial coherence, the explosive event terminates several nanoseconds after the trigger irradiation, when the phase relaxation time larger than O(10 ns) is taken. After PSR events the system is expected to follow a steady-state solution which is obtained by analytic means and is made of many objects of field condensates endowed with a topological stability.