Green’s functions for certain cases in nonlinear electrodynamics

Tvorogov, S. D.

doi:10.1007/bf02766559

Russ Phys J

1998

DOI: 10.1007/bf02766559

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Green’s functions for certain cases in nonlinear electrodynamics

S. D. Tvorogov¹

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“…It is most expedient to convert the image registered in the IR range of the spectrum to the visible range and to investigate it by the standard methods. We note that thermal imaging systems available at present do not allow superfast processes in the IR range of the spectrum to be investigated [1,2].To convert the IR image to the visible range of the spectrum, it makes sense to use nonlinear optical crystals that allow the image to be converted simultaneously in all regions of the crystal with high temporal resolution [3,5]. In this case, the image of the IR-object whose radiation has frequency ω IR is formed in the crystal by the IR objective.…”

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confidence: 99%

“…Pump radiation is chosen so that ω v = ω IR + ω p , where ω v is the circular frequency of radiation converted to the visible range of the spectrum. The spatial spectrum of the IR-image is transformed by a certain method into the visible range of the spectrum [3][4][5][6][7][8][9].The characteristics of the system of IR-image conversion are mainly determined by pump radiation (narrow band laser radiation or wideband non-laser radiation of thermal sources). The method of its formation in the nonlinear optical crystal is also important (a system with tangent matching is used for a collimated laser beam, a system with critical vector matching is used for a laser beam focused by a cylindrical lens, and homocentric radiation beams are used for thermal non-laser radiation focused by a spherical lens) [3][4][5][6][7][8][9].…”

mentioning

confidence: 99%

“…To convert the IR image to the visible range of the spectrum, it makes sense to use nonlinear optical crystals that allow the image to be converted simultaneously in all regions of the crystal with high temporal resolution [3,5]. In this case, the image of the IR-object whose radiation has frequency ω IR is formed in the crystal by the IR objective.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

“…The method of its formation in the nonlinear optical crystal is also important (a system with tangent matching is used for a collimated laser beam, a system with critical vector matching is used for a laser beam focused by a cylindrical lens, and homocentric radiation beams are used for thermal non-laser radiation focused by a spherical lens) [3][4][5][6][7][8][9].…”

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confidence: 99%

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High-speed system of IR-image conversion in a nonlinear crystal pumped by a thermal source

et al. 2011

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The necessity of registration of superfast optical processes in the infrared region of the spectrum has arisen with the development of pico-and femtosecond laser technology. It is most expedient to convert the image registered in the IR range of the spectrum to the visible range and to investigate it by the standard methods. We note that thermal imaging systems available at present do not allow superfast processes in the IR range of the spectrum to be investigated [1,2].To convert the IR image to the visible range of the spectrum, it makes sense to use nonlinear optical crystals that allow the image to be converted simultaneously in all regions of the crystal with high temporal resolution [3,5]. In this case, the image of the IR-object whose radiation has frequency ω IR is formed in the crystal by the IR objective. Pump radiation with frequency ω p is also sent into the same crystal. Pump radiation is chosen so that ω v = ω IR + ω p , where ω v is the circular frequency of radiation converted to the visible range of the spectrum. The spatial spectrum of the IR-image is transformed by a certain method into the visible range of the spectrum [3][4][5][6][7][8][9].The characteristics of the system of IR-image conversion are mainly determined by pump radiation (narrow band laser radiation or wideband non-laser radiation of thermal sources). The method of its formation in the nonlinear optical crystal is also important (a system with tangent matching is used for a collimated laser beam, a system with critical vector matching is used for a laser beam focused by a cylindrical lens, and homocentric radiation beams are used for thermal non-laser radiation focused by a spherical lens) [3][4][5][6][7][8][9].Systems of IR-image conversion to the visible range of the spectrum in nonlinear crystals pumped by laser radiation sources cannot be used for this purpose. Such systems are too sensitive to the degree of focusing and nonmonochromaticity, they do not allow wideband thermal radiation to be registered, and the converted image is compressed compared to the initial image by ω v /ω IR times in the matching plane [3,4,7].The above-indicated disadvantages can be easily excluded by using wideband non-laser thermal pumping in the form of homocentric radiation beams in conversion systems [6,8,9]. In this case, the increased degree of radiation focusing and the increased spectrum width cause the conversion efficiency to increase. During focusing (homocentric beams), the contribution of vector interactions (intersecting beams) to converted radiation increases by 2-3 orders of magnitude [7].The increased width of the spectrum leads to the fact that the frequencies symmetric about the matching frequency contribute to converted radiation, that is, the wider the spectrum, the higher the conversion efficiency. Such type of matching (interaction) is called multifrequency [6-9].The advantage of this system is the possibility of IR image conversion to the visible range of the spectrum without distorting the geometrical sizes of IR images (du...

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mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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High-speed system of IR-image conversion in a nonlinear crystal pumped by a thermal source

et al. 2011

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Additional beams in optically uniaxial crystals

et al. 2007

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Reasons for occurrence of additional beams are established for rays reflected from a tilted prism face and transmitted through the interface between two crystal media.In anisotropic media, an arbitrarily polarized light wave is split into two linearly polarized waves. When passing through the interface between two crystal media or reflecting from this interface, each linearly polarized light wave is split into two linearly polarized waves. In the second medium, four light waves are formed [1][2][3].A reason for occurrence of additional waves in the second anisotropic medium is noncoincidence of planes of the main crystal cross sections for incident rays and rays transmitted into the second medium [1,2]. However, in [4-6] cases were described in which the planes of the main cross section seemed to be coinciding for the incident, transmitted, and reflected beams; nevertheless, four beams passed into the second medium or were reflected from the interface. Attention is drawn to the fact that in all cases examined in [4][5][6], beams in one anisotropic medium were propagated at small angles to the optical axis, and in another medium, they were propagated in the vicinity of the normal to it (Fig. 1).Four beams also arise when the ray is reflected from faces of a prism, for example, of the Fresnel rhombic prism (Figs. 1c and 2а) [7,8]. In all cases (Figs. 1 and 2), the plane of the main crystal cross section lies in the figure plane. It would seem that if the ordinary (extraordinary) beam arose in medium 1, it would remain ordinary (extraordinary) in medium 2 or 3 because the planes of the main crystal cross sections for the incident, transmitted, and reflected rays coincide.The present work considers the given anomalies and explains reasons of their occurrence. Experimental investigations demonstrated that generally, four rays each pair of which is polarized in mutually perpendicular directions leave polarization devices like bifocal lenses, Senarmont prisms, and Fresnel rhombs. In a particular case, for a certain position of the prism, only two rays leave it.Results of observations of four split rays leaving the Fresnel rhombic prism fabricated from the lithium niobate crystal (Fig. 2) are presented below. The sizes of the input prism slit were 18 × 5 mm. The prism faces were tilted at an angle of 45° to the optical crystal axis. A ray of unpolarized radiation of a helium-neon laser was incident on input face 1 and then propagated as ordinary and extraordinary rays. These rays were incident at angles α on lateral face 2 from which two rays polarized in mutually orthogonal directions were reflected at angles α o and α е .The rays reflected from face 2 propagated in the vicinity of the optical crystal axis and were incident on opposite lateral face 4. Angles of ray incidence on face 4 were equal to α o and α е , respectively. Because n е < n о (the uniaxial negative crystal), α е < α o in accordance with the reflection law.We note that rays reflected from face 2 are considered ordinary and extraordinary only when they p...

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Green’s functions for certain cases in nonlinear electrodynamics

Cited by 2 publications

References 1 publication

High-speed system of IR-image conversion in a nonlinear crystal pumped by a thermal source

High-speed system of IR-image conversion in a nonlinear crystal pumped by a thermal source

Additional beams in optically uniaxial crystals

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