关于Airy光束衍射及自加速性质的研究

Research on diffraction and self-acceleration of Airy beam

对Airy光束的特性做进一步探讨,一方面对无限宽Airy光束的重心问题给出新的理论说明,另一方面着重对有限宽情形下的Airy光束的奇特性质进行探讨.文中采用反证法给出无衍射的讨论,同时结合数值模拟给出高斯函数及矩形函数限定下的有限宽Airy光束的场分布,并由此得到其重心位置的轨迹:重心位置是不变的,不可能整体自由加速.最终得到有限宽Airy光束既不可能在自由空间加速,也不可能是无衍射光束.

In 1979, Berry and Balazs [M V Berry and N L Balazs 1979 Am. J. Phys. 47 264] obtained a strict solution of the Schrtidinger equation with Airy function used as the initial condition, and described the wave function represented by such solution as the Airy wave-packets. They discovered that infinite Airy wave-packet has unique properties such as non-spreading and free acceleration, proving that it is the only n0ntrivial non-spreading solution of the time-dependent Schr6dinger equation in one dimension. However, the observing of the finite Airy beam seems to be more meaningful since wave,packets in reality is inevitably band limited. A certain form of finite Airy beam was investigated by Siviloglou et al. in 2007 [Siviloglou G A, Broky J, Dogariu A, Christodoulides D N 2007 Phys. Rev. Lett. 99 213901; Siviloglou G A, Christodoulides D N 2007 Opt. Lett. 32 979]. They noted that the Airy wave packet still exhibits its most exotic feature, i.e., its trend toward free acceleration. While in the present paper we discuss the properties of Airy beam in a few steps further and propose several conclusions. On the one hand, a theoretic explanation is given to solve the matter of the centre of mass of infinite Airy beam. On the other hand, deeper research is conducted on the unique properties of finite Airy beam. Another form of finite Airy beam is discussed by reduction to absurdity, and its field distribution is put forward by numerical simulation. We find that the trajectory of the centroid holds its position, which means that the beam cannot accelerate freely as a whole. Ultimately, we have the conclusion that finite Airy beam can neither freely accelerate nor be non-diffractive.