Optical Patterns of Thermally Self-Defocused Light

Abstract

In this Letter we discuss the observation of a pattern of concentric annuli formed as a result of thermal effects upon a light beam. To our knowledge, this is the first time such patterns have been reported. When a beam of light passes through an absorbing medium whose refractive index decreases as a function of temperature, the medium behaves as a negative lens. Gordon et al.1 observed this phenomenon by placing a cell containing an absorbing liquid between the mirrors of a helium-neon laser. The absorption constants for several liquids with very low absorbencies have been determined using this effect.2 Rieckhoff3 measured the increase in the diameter of a light beam that passed through a thermal self-defocusing liquid placed external to the laser inter-ferometer. Recently Leite et al.4 demonstrated that this effect may be used as a power limiting device.

Research of far-field diffraction intensity pattern in hot atomic Rb sample

“…Superior to z-scan which is limited to the measurements of sheet samples with small nonlinear phase shifts, this method can also be applied to those with large nonlinear phase shifts [2]. For its unique properties and potential applications, the far-field diffraction ring pattern has caused much attention since first reported in 1967s [3]. Similar phenomena have been viewed in a variety of materials, including nematic liquid-crystal films [4], photorefractive materials [5], semiconductors [6], atomic vapors [7], carbonaceous materials [8] and other materials [9,10].…”

Investigation of the Nonlinear Optical Response of 3- (Dimethylamino)-7-Aminophenothiazin-5-Ium Chloride Dye

“…Because the laser beam used in the experiment has a Gaussian distribution, the relative phase shift ,   , suffered by the beam while traversing the sample of thickness, L can be written as [8]:…”

“…For the thermal nonlinearity and steady state case, the change nonlinear index, n  , can be expressed as [8]:…”

“…A related phenomenon is the spatial self modulation of a coherent beam, which generates a nested array of concentric intensity ring in the far field. Such diffraction ring have been observed in media with thermally-dependent refractive index change [6][7][8][9] atomic vapours [10][11][12][13], nematic liquid crystals [14][15][16] ,Kerr media [17,18] ,chromophore-substituted silica [19] and photorefractive crystals [20].…”

Diversity and slow dynamics of diffraction rings: a comprehensive study of spatial self-phase modulation in a photopolymer

“…Constructive and destructive interference within the phase-modulated beam generates a set of circular diffraction rings, which are typically observed in the far field. Self-phase modulation has been studied predominantly in thin films of materials that undergo thermally dependent refractive index changes [3][4][5][6], atomic vapours [7][8][9][10][11], nematic liquid crystals [12][13][14], Kerr media [15,16], chromophore-substituted silica [17], and photorefractive crystals [18].…”