Thermal Self-Focusing of Laser Beams in Lead Glasses

Abstract

Strong thermal self-focusing of an argon laser beam has been observed when the beam passes through lead glass. Focal lengths of less than 20 cm were obtained. The beams showed the effects of spherical aberration and at certain power levels beam trapping occurred. A simple theory is proposed to explain the observed trapping. Computer solutions have been obtained which reasonably agree with experimental determination of focal planes and spot radius.

Solitons in Nonlinear Media with an Infinite Range of Nonlocality: First Observation of Coherent Elliptic Solitons and of Vortex-Ring Solitons

“…or from long-range forces (e.g., electrostatic interactions in liquid crystals [5]) and many-body interactions as with matter waves in BoseEinstein condensates [6] or plasma waves [7]. In nonlinear optics specifically, nonlocality was found in photorefractives [3,[8][9][10], in thermal nonlinear media [11][12][13][14], in atomic vapors [2], and in liquid crystals [5,15]. In principle, nonlocality acts to spread out the effects of localized excitations, and as such it can suppress modulation instabilities of homogeneous states [16].…”

Accessible Light Bullets via Synergetic Nonlinearities

“…Optical solitons have been obtained in a broad range of media and, in spite of the diverse underlying nonlinear responses, share several universal properties [3][4][5]. The main distinguishing feature in this group is the scale of time and space in which the nonlinear mechanisms operate: on one side of this group are those nonlinearities which originate from thermal, molecular, charge drifting mechanisms [6][7][8][9][10][11][12][13], nonlocal in both time and space; on the opposite side are electronic or catalytic nonlinearities, usually treated as local and instantaneous at optical frequencies [14][15][16][17][18]. The instantaneous Kerr effect enables the observation of temporal nonlinear evolution in short optical pulses; in fibers, e. g., several phenomena [self-phase modulation, pulse compression, bright and dark solitons, etc.]…”

Soliton Aided Propagation and Routing of Vortex Beams in Nonlocal Media

“…However, the trajectory comparisons of Figure 6e show that the nematicon trajectories as given by the numerical and modulation solutions are in excellent agreement. The vortex trajectories are in good agreement, unexpectedly; this is because the numerical vortex trajectory is given by the centre of mass position (37), and the agreement is due to total linear momentum being conserved by the vortex governed by Eq. (2).…”

“…This system of equations, however, is generic and applies to a wide range of physical situations, including nonlinear, nonlocal media for which the response to a beam involves some sort of diffusive mechanism [35], for instance thermo-optic media [36] such as lead glasses [37][38][39] and photorefractive crystals [40]. A similar system of equations also arises in the so-called α models of turbulence [41,42].…”

“…The nematicon has been totally restored at z=100, but the vortex has shed a portion on interaction with the interface as it partially entered the region of lower refractive index upon TIR; this shedding can be seen in Figure 2b when the vortex is near the interface. The trajectories of the nematicon, as given by the location of its maximum, and the vortex, as given by its centre of mass position (37), are plotted in Figure 2e. The rapid jumps in the nematicon position are due to its distortion by the interface.…”