光丝

当光功率超过自聚焦临界阈值，会伴随自聚焦产生一条等离子体通道，光脉冲在其中能保持几乎不变的直径传输很长一段距离，而不受瑞利长度限制。

• 中文名称 光丝
• 拼音 guāng sī

概述

　　光丝:当光功率超过自聚焦临界阈值，伴随自聚焦产生一条等离子体通道，光脉冲在其中能保持几乎不变的直径传输很长一段距离，而不受瑞利长度限制。光丝中存在一些非常复杂的非线性光学效应:脉冲自聚焦、自相位调制、脉冲自陡峭、多光子吸收电离、锥状辐射、等离子体散焦与时空聚来自焦等，它在远程遥感、激360百科光引雷、脉冲压缩等领域具有光明的应用价值。高功率超快激光脉冲在光学介适歌质中传输引起的成德代商投丝现象是当前科学研究领域的前沿问题。一般认为,激光成丝现象的物理机制主要是光学克尔效应引起的自聚焦与等离子体散焦效应间的动态平衡。激光光丝在远程探测空气污染物、控制闪电、人工造雨雪、远程特别照明等领域有着广泛的运用。

光丝图谱

introductio仍这多县末日早束n

　　ultrashort pulses of several millijoule energy can reach GigaWatt powers that exceed the critical power for self-focusing in air. the critical power is de稳然重边防金fined as the p活皇集断拉相入ower at whic导植的里盐胡议获听字课h self-focusing via the optical Kerr effect balances beam diffraction. Above the critical power, and according to the paraxial wave theory, self-focusing should lead to a collapse singula征即深期普领从守营想洲rity of infinite energy density in 积外后的承推毫土创a finite distance, sinice both diffr例草兴八觉内它action and se编族空lf-focusing increase at the same rate with decreasing 景盟盾beam diameter.

l来自ight filamentation in air

　　a general explanation for the f360百科ormation of light filaments for input peak powers sever想太满轮类一湖盐静al times the cri击走紧货视坏放喜tical power is that, during the initial stages of the propagation, the field breaks up transversely into hot spots of high intens既快ity under the combined actions of the nonlinear Kerr effect 与太振践带好丝过形新动and diffracti节烟散积但on, namely, modulational instability. The high intensities produced in 践其殖乐欢长the hot spots by 船通子滑self-focusing will produce nonlinear absorption via multi-phot很on ionization and electron plasma ge看宗neration, al杆良整冲ong with

　　pl侵别者入课评asma defocusing, which in turn both li敌确以川激它mits the growth of the hot spots and eventually causes them

　　to terminate. This is the basic mechanism of filament formation, and in our case the typical propagation

　　length of f指爱件饭必表领ilaments is of the order of a meter. In addition, due to spatial inhomogenei载头部局ties in the i治演素困首较员结nput

　　field, 放克工围病宪真限集the modulational instability initiates hot 批spots at a range of propagation distances, and filaments are created and disappear along the full propagation distance. It is assumed tha副t static filaments were formed when the self-focusing due to the Kerr effect was balanced by plasma-induced defocusing.

characterization of filaments

　　There has been a controversy as to the filament size, their conductivityw4,5xand even their existence . The main experimental difficulty in the investigation of filaments is that the pulse intensity

　　within the filament far exceeds the damage threshold of any reflectingrtransmissive material. The theoretical studies are equally challenging because of the large range of dimensions involved transverse dimensions over a few microns to several centimeters, longitudinal dimensions over the pulse length, tens of microns, to the total propagation length of tens of meters.. Another difficulty resides in the plethora of nonlinear effects involved at these high intensities, including beam diffraction, group-velocity dispersion, self-phase modulation, multi-photon ionization, and plasma absorption and defocusing, along with the scarcity of known material parameters.