RU2350991C1 - Monoblock arrester of laser radiation intensity - Google Patents

Abstract

FIELD: physics, optics.

SUBSTANCE: invention is related to the field of optical equipment. In monoblock arrester body comprises internal cavity filled with limiting substance that possesses non-linear absorption. Limiting substance used may be flaking solution with lower critical point, in particular water solution of triethylamine with concentration of C_work.=(32±2) wt %, at working temperature of solution that is less than critical temperature (t_work.<t_crit.=18.163°C) or water solution of 2-butoxyethanol with concentration of C_work=(30±2) wt %, when working temperature of solution is less than its critical temperature (t_work.<t_crit.=48.272°C).

EFFECT: creation of laser radiation arrester with high initial transmission and wide range of waves working lengths that provides for neutral coloring of optical instruments field of view.

3 cl, 2 dwg

Description

The invention relates to the field of optical technology, namely, to limit the intensity of laser radiation, and can be used to protect the organs of vision and sensitive radiation receivers from the damaging effects of high-intensity incident radiation.

The development of laser technology, which penetrated into various spheres of human activity, revealed the likelihood of the harmful effects of powerful radiation, which made it important to develop means of protecting the organs of vision and optical systems from the effects of laser radiation. The relevance of this problem is caused by a noticeable increase in the radiation intensity of laser devices operating in a wide spectral region.

When developing working materials for laser radiation intensity limiters (limiters) (limiting substances), the following characteristics are most important:

1. High initial (linear) transmission of radiation T ₀ (λ) and a wide linear transmission band of the limiter in the working region of the spectrum (the sensitivity curve of the eye or the sensitivity region of the radiation detectors), which provides neutral coloring of the field of view of optical instruments.

2. A high degree of attenuation of the intensity of the input radiation ω is the coefficient of limitation (attenuation) of radiation (CO), which is understood as the ratio of the intensity of the incident radiation to the intensity of the radiation transmitted through the limiter.

3. High speed switching on of the limiting device.

The effect of limiting laser radiation is achieved in various ways. The most convenient passive types of limiters are based on nonlinear dynamic absorption, in particular, reverse saturated absorption (RSA), multiphoton absorption of radiation, its thermal defocusing, and photorefraction [1].

A known limiter of the intensity of laser radiation, the body of which contains a limiting substance with reverse saturated absorption of high-intensity optical radiation - the organometallic complex bis (trimethyl) phosphine-decacarbonyl-iron-tricobalt, and external collective lenses focusing the incident radiation into the substance of the limiter [2].

The disadvantages of such a limiter are the low initial transmission of radiation and a narrow band of linear transmission of the material of the limiter, as well as the non-monolithic nature of its housing, which allows contamination of the optical parts of the device, which sharply reduces its efficiency.

Also known is a light filter for protecting the observer's eyes and optoelectronic devices from powerful light radiation, which is a transparent sealed cuvette filled with a liquid that absorbs incident radiation [3].

The disadvantages of such a filter include an extremely low initial transmission, independent of the intensity of the incident radiation, which excludes its use in optical devices.

The closest set of essential features to the claimed device is a monolithic limiter of the intensity of laser radiation, consisting of a housing oriented along the direction of propagation of incident radiation, with collective lenses placed on the ends of the housing, which is selected as a prototype [4]. The limitation of the high-intensity optical limiter is achieved due to two-photon absorption in the material of the limiter case — ZeSe and ZnS in the visible spectrum, copper dichloride in the UV spectrum, and HgCdTe in the IR spectrum.

The disadvantages of the prototype are the high toxicity of the substances used, a small linear transmission and a narrow linear transmission band in the working region of the spectrum of the solid-state materials of the limiter and their low radiation strength: when focused radiation entered the peripheral parts of the limiter, it was probably its optical destruction [5].

These disadvantages can be overcome due to the fact that the housing of the limiter contains an internal cavity filled with a limiting substance, which has a nonlinear dynamic absorption. A limiting solution with a lower critical point can be used as a limiting substance, in particular, an aqueous solution of triethylamine with a concentration of C _slave = (32 ± 2) wt.%, At a working temperature of the solution less than its critical temperature (t _slave <t _cr = 18.163 ° C ) or an aqueous solution of 2-butoxyethanol (butyl cellosolve) concentration С _work = (30 ± 2) wt.%, at a working temperature of the solution less than its critical temperature (t _work <t _cr = 48.272 ° С).

Light-induced spinodal decomposition was detected in stratified solutions with a lower critical separation point of water-triethylamine and water-butyl cellosolve [6]. The optothermodynamic transfer of solutions through a critical point under the action of laser radiation leads to the creation of a labile state in them, whose relaxation to a stable state occurs with the formation of microheterophase concentration inhomogeneities and subsequent separation. The bulk growth of the new phase is accompanied by the appearance of inhomogeneities in the refractive index, which causes an increase in the scattering of radiation near the critical temperature. The concentration of the solution near its critical value can vary over a wide range, for example, with C _work = (32 ± 2) wt.% For an aqueous solution of triethylamine and C _work = (30 ± 2) wt.% For an aqueous solution of 2-butoxyethanol (butyl cellosolve )

The aim of the present invention is to provide a laser radiation limiter with a high initial transmission and a wide range of operating wavelengths, providing neutral coloring of the field of view of optical devices.

The goal of expanding the range of working wavelengths in which laser radiation is limited is achieved by using a portable monoblock laser radiation limiter with an internal cavity filled with a limiting substance that has nonlinear dynamic absorption. The choice of overall dimensions depends on the application conditions of the monoblock limiter (required focal length, focus spot size). The use of such a monoblock limiter eliminates the influence of the external environment, since the entire process of limiting laser radiation occurs in a limiting substance located in the internal cavity of the housing.

Figure 1 shows the design of the proposed one-piece limiter for the intensity of laser radiation, the housing 1 of which is oriented along the direction of propagation of the incident radiation 2, with collective lenses 3, 4 located on the ends of the housing 5, and a limiting substance 6 placed in the inner cavity 7 of the limiter housing. If the focal lengths of lenses 3 and 4 are equal to F ₁ and F _2, respectively, and the lenses are at a distance L from each other, then at L = F ₁ + F ₂ low-intensity incident radiation freely passes through the limiter, and lens 3 focuses the incident radiation into the working the substance 6 of the limiter, and the lens 4 gives the output radiation 8 its original shape.

In the case of a high-intensity radiation incident on the limiter, the lens 3 focuses the incident radiation on the limiter substance 6, increasing the power density (and the incident radiation energy) to the level at which the laser radiation is absorbed dynamically, which creates conditions for limiting its intensity in the limiter substance.

Figure 2 presents the installation diagram for measuring KO. The solutions were introduced into the phase lability region as a result of light-induced heating while absorbing the radiation of a neodymium glass laser 9 acting on them with a radiation pulse duration τ = 1.5 ms at a radiation power density (intensity) of ω≤250 kW / cm ² . To cut off the unnecessary part of the radiation, we used a diaphragm 11. We measured the radiation intensity at the input using a laser plate deflecting laser radiation 13 and an energy meter 12. We also measured the radiation intensity after passing the monoblock limiter 14 at the output using an energy meter 15. The values of ω could vary with using a set of neutral filters 10.

The possibility of attenuation of high-power optical radiation can be associated with the phenomenon of strong scattering of incident high-intensity radiation under the effect of light-induced spinodal decay in a layering solution with a lower critical point located in a closed volume of the internal cavity of the limiter case. In this case, an aqueous solution of triethylamine of critical concentration (C _cr = 32.118 wt.%, T _cr = 18.163 ° C) or an aqueous solution of 2-butoxyethanol (butyl cellosolve) of critical concentration (C _cr = 30.140 wt.%, Can be used as a limiting substance, t _cr = 48.272 ° C). These substances are practically transparent in the visible and near infrared spectral regions (the working region of the limiter spectrum).

The solution concentration does not require exact observance of the critical concentration of the solutions, so that the working concentration of the limiting solutions can be C _work = (C _cr ± 2) wt.%, And the working temperature of the limiting solutions must be less than their critical temperature (t _work <t _cr ) The response time of limiting exfoliating solutions with a lower critical point can be from several ns to several microseconds, which ensures a high switching speed of the limiting device on such limiting substances.

The use of liquid limiting substances provides resistance to optical damage (optical strength) of a monoblock limiter, since, in contrast to a solid limiting substance in a liquid, restoration of its strength properties between the cycles of the limiter due to convection of the limiting liquid is achieved.

Examples

Example 1. Measurements were made of the attenuation coefficient of the CO of radiation from a neodymium glass laser with a radiation pulse duration of τ = 1.5 ms at a radiation power density (intensity) of ω≤250 kW / cm ² , using a one-piece limiter with an optical glass casing, the inner cavity of which was an aqueous solution of triethylamine concentration C _work = 30% at a temperature t _work = 15 ° C.

The resulting value of KO (ω = 150 kW / cm ² ) = 5.

Example 2. Measurements were made of the attenuation coefficient of CO radiation of a neodymium glass laser (τ = 1.5 ms, ω≤150 kW / cm ² ) using a one-block limiter with an optical glass case, in the inner cavity of which there was an aqueous solution of concentration triethylamine With _slave = 32% at a temperature of t _slave = 18 ° C. The installation diagram for measuring KO is presented in figure 2.

The resulting value of KO (ω = 100 kW / cm ² ) = 10.

Example 3. Measurements were made of the attenuation coefficient of CO radiation of a neodymium glass laser (τ = 1.5 ms, ω≤150 kW / cm ² ), using a one-block limiter with an optical glass case, in the inner cavity of which there was an aqueous solution of concentration triethylamine With _slave = 34% at a temperature t _slave = 17 ° C. The installation diagram for measuring KO is presented in figure 2.

The resulting value of KO (ω = 150 kW / cm ² ) ≈5.

Example 4. Measurements were made of the attenuation coefficient of CO radiation of a neodymium glass laser (τ = 1.5 ms, ω≤150 kW / cm ² ), using a monoblock limiter with an optical glass case, in the inner cavity of which there was an aqueous solution of 2- butoxyethanol concentration C _work = 28% at a temperature t _work = 45 ° C. To measure KO, the setup shown in FIG. 2 was used.

The resulting value of KO (ω = 230 kW / cm ² ) = 5.

Example 5. Measurements were made of the attenuation coefficient of CO radiation of a neodymium glass laser (τ = 1.5 ms, ω≤150 kW / cm ² ), using a monoblock limiter with an optical glass case, in the inner cavity of which there was an aqueous solution of 2- butoxyethanol concentration C _work = 30% at a temperature t _work = 48 ° C. To measure KO, the setup shown in FIG. 2 was used.

The resulting value of KO (ω = 170 kW / cm ² ) = 10.

Example 6. Measurements were made of the attenuation coefficient of the CO radiation of a neodymium glass laser (τ = 1.5 ms, ω≤150 kW / cm ² ), using a one-piece limiter with an optical glass case, in the inner cavity of which there was an aqueous solution of 2- butoxyethanol concentration C _work = 32% at a temperature t _work = 47 ° C. To measure KO, the setup shown in FIG. 2 was used.

The resulting value of KO (ω = 230 kW / cm ² ) = 5.

This technical solution is new, and the combination of distinctive features does not follow from the known technical solutions. Such a laser radiation limiter is universal, since it limits the intensity of radiation by easily replacing the working substance.

The inventive monoblock limiter of the intensity of laser radiation can be used, for example, with binoculars or another optical device to protect photodetectors and organs of vision from destruction and blinding by high-intensity radiation.

Information sources

1. L.W. Tutt, T.F. Boggess - Prog. Quantum Electron., 1993, v. 17, p. 299-338.

2. US patent No. 5.080.469.

3. RF patent No. 2110817.

4. US patent No. 4.846.561.

5. E.W. Van Stryland, Y. Y. Wu, DJ. Hagan and all. - JOSA, 1988, v.5, No.9, p.1980-1988.

6. F.V. Bunkin, V.M. Podgaetsky, V.N. Semin - Letters to the ZhTF, 1988, v.14, No. 2, p.162-164.

Claims (3)

1. A monoblock laser radiation intensity limiter, consisting of a housing oriented along the direction of propagation of incident radiation, with collective lenses located on the ends of the housing, characterized in that the housing contains an internal cavity, the volume of which is filled with a limiting substance having non-linear absorption, the quality of which used exfoliating solution. 2. The monoblock limiter according to claim 1, characterized in that an aqueous solution of triethylamine with a concentration of C _slave = (32 ± 2) wt.% Is used as the limiting substance, at a working temperature of the solution less than its critical temperature (t _slave <t _cr = 18.163 ° C). 3. The monoblock limiter according to claim 1, characterized in that an aqueous solution of 2-butoxyethanol of a concentration of C _slave = (30 ± 2) wt.% Is used as the limiting substance, at a working temperature of the solution less than its critical temperature (t _slave <t _cr = 48.272 ° C).

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