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Two-Dimensional Optical Bistability

二维光学双稳定性

基本信息

批准号：
62460065
负责人：
YABUZAKI Tsutomu
金额：
$ 4.61万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1989
项目状态：
已结题

项目摘要

We Proposed and studied on a new type optical bistability, which is largely different from the ordinary one behaving with hysteresis. The optical system is very simple, which consists of a cell containing atoms with spin in the ground state, a lambda/8 plate and a mirror. This system has a positive feedback loop with respect to the spin polarizatim, so even if the incident light is linearly polarized with no angular momentum, atoms begin to have spin polarization when the incident light intensity exceeds a exceeds a critical value. In the present work, we have studied experimentally and theoretically on the behavior of specially coupled bistable systems, the coupling being through(1) light it self and (2) diffusion of spin-soarized atoms. At first we studied about the coupling of two systems, and found that the coupled system behaves with pitchfork bifurcation (symmetry breaking) at two different values of incident light intensity and it has four stable states in the strong intensity region. Next, the behavior of the system with continuously distributed bistable system has been studied. A laser beam with a large cross section is applied to the cell, and observed the spontaneously produced spin-polarization at each position of the cell, by detecting the special tribution of the Faraday rotation. We have found the existence of magnetic domain, in which all of spins are oriented to the same direction. It is also found that the steady state distribution of spin-polarization has spatial modes particularly in case of (1). All of experiments have been carried out with sodium vapor. Computer simulation with a simplified model was found to explain well the experimental results mentioned above.

提出并研究了一种新型的光学双稳态，它与普通的具有迟滞特性的光学双稳态有很大的不同。光学系统非常简单，它由一个包含基态自旋原子的单元、λ/8板和反射镜组成。该系统具有关于自旋极化的正反馈回路，因此即使入射光是无角动量的线极化，当入射光强度超过临界值时，原子开始具有自旋极化。本文从实验和理论两方面研究了特殊耦合双光子系统的行为，这种耦合是通过（1）光自身和（2）自旋极化原子的扩散实现的。首先我们研究了两个系统的耦合，发现耦合系统在两个不同的入射光强下都表现出对称性破缺，在强光强区有四个稳定态。其次，研究了具有连续分布时滞系统的系统的行为。用大截面激光束照射细胞，通过检测细胞内法拉第旋转的特殊方向，观察细胞内各个位置自发产生的自旋极化。我们发现了磁畴的存在，其中所有的自旋都指向同一方向。研究还发现，自旋极化的稳态分布具有空间模式，特别是在（1）的情况下。所有的实验都是在钠蒸气中进行的。用简化的模型进行了计算机模拟，很好地解释了上述实验结果。