CN102681288B - Silicon-based optical amplitude limiter - Google Patents
Silicon-based optical amplitude limiter Download PDFInfo
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- CN102681288B CN102681288B CN201210162942.0A CN201210162942A CN102681288B CN 102681288 B CN102681288 B CN 102681288B CN 201210162942 A CN201210162942 A CN 201210162942A CN 102681288 B CN102681288 B CN 102681288B
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Abstract
The invention discloses an optical amplitude limiter, which comprises a nonlinear optical medium and a silicon thin film, wherein the nonlinear optical medium has a positive nonlinear refraction coefficient; a crystallized region which is crystallized by laser is formed on the silicon thin film; an absorption coefficient of the silicon thin film is gradually increased on the cross section of the crystallized region from the edge of the crystallized region to the center of the crystallized region; an incident laser beam sequentially penetrates through the nonlinear optical medium and the crystallized region of the silicon thin film; when the light intensity of the incident laser beam is greater than or equal to that of a self-focusing threshold value, the incident laser beam is focused and projected to the crystallized region after penetrating through the nonlinear optical medium so as to be absorbed; and therefore, an effect of optical amplitude limitation is achieved. The optical amplitude limiter has a simple structure, is low in cost and can be used in multiple different occasions, so that a precise optical device (eyes included) can be used safely.
Description
Technical field
The present invention relates to a kind of optical limiter, particularly relate to a kind of optical limiter for lasing safety.
Background technology
Since the sixties in 20th century, laser instrument came out, along with the progressively development of science and technology, the power output of laser instrument is increasing, and the intensity of its laser exported is also more and more higher.Laser has become an importance of photoelectronic warfare in modern war, has the research about laser protection to be also subject to people's attention gradually thus.This be due to light laser be easy to damage human eye, optical instrument etc., so certain safeguard procedures must be taked, and optical limiter be exactly a kind of can restricted passage its light beam intensity with reach protection object device.
For a desirable optical limiter; it should have following characteristic: for more weak incident light; it has relatively high transmitance; and along with the increase gradually of incident intensity; its transmitance can reduce gradually; thus output intensity is stable at a certain threshold value, and then to play in Backup lightpath the effect of optics after which.Broadly optical limiter can be divided into initiatively limiter and passive limiter two class.Wherein, initiatively limiter utilizes active feedback to complete optics amplitude limit.Such as, control diaphragm bore with the signal that photodetector obtains and enter optical system to stop high light.Passive limiter be utilize nonlinear optical medium itself to have nonlinear optical property to realize optics amplitude limit function.The research of current optical limiter mainly concentrates on passive limiter, needs to find new material (as: nano material and organic material etc.) and apply new principle (as: reverse saturated absorption, two-photon absorption, nonlinear refraction and nonlinear scattering etc.) to make optical limiter that is novel, stable optical performance.
Self-focusing effect is a kind of optical phenomena that light beam shows through the nonlinear optical medium with larger positive nonlinear refractive index, when this kind of nonlinear optical medium is (as carbon disulfide (CS
2) solution) be subject to stronger illumination when penetrating, there is the change relevant to light intensity in the refractive index of medium, when the distribution of intensity on the cross section of light beam of the light beam irradiated is Gaussian (i.e. bell), and when this intensity enough produces nonlinear effect, now the cross direction profiles of refractive index is also Gaussian, and therefore this medium can convergent beam just as convergent lens.There is the optical limiter utilizing nonlinear optical medium to prepare at present, such as arrange in the optical path nonlinear optical medium and its after mechanism of diaphragm to realize the function of optics amplitude limit, but their most structures are more complicated, cost of manufacture is higher, are therefore unfavorable for industrially scalable processing.
Therefore, those skilled in the art is devoted to develop a kind of optical limiter, by arranging nonlinear optical medium in the optical path, and after this medium, arranges the silicon thin film through laser crystallization process, realize the function of the light intensity limiting transmitted light, reach the effect of optics amplitude limit.
Summary of the invention
Because the above-mentioned defect of prior art, technical problem to be solved by this invention is to provide a kind of optical limiter, focusing to the stronger incident laser of light intensity is achieved by arranging nonlinear optical medium in the optical path, by arranging the silicon thin film through laser crystallization process after this nonlinear optical medium, achieve the absorption of the incident laser after to focusing to reach the effect of optics amplitude limit.
For achieving the above object, the invention provides a kind of optical limiter, it is characterized in that, comprise nonlinear optical medium and silicon thin film, described nonlinear optical medium has positive nonlinear refractive index, described silicon thin film has the crystalline areas through laser crystallization process; The absorption coefficient of described silicon thin film being distributed as on the cross section of described crystalline areas increases progressively along the edge of described crystalline areas to the direction at the center of described crystalline areas; Incoming laser beam passes through the described crystalline areas of described nonlinear optical medium and described silicon thin film successively.
Further, described nonlinear optical medium is carbon disulfide solution.
Further, described carbon disulfide solution is encapsulated in quartz colorimetric utensil.
Further, described incoming laser beam is Gaussian beam.
Alternatively, the light intensity of described incoming laser beam is more than or equal to self focusing threshold light intensity, described incoming laser beam is by being focused after described nonlinear optical medium and being incident upon on the described crystalline areas of described silicon thin film, and the diameter of the described crystalline areas of 2 times is less than through the diameter of the hot spot of described incoming laser beam on described silicon thin film of described focusing, the deviation between the position at the position at the center of described hot spot and the described center of described crystalline areas is not more than 10%.
Alternatively, the light intensity of described incoming laser beam is less than self focusing threshold light intensity, described incoming laser beam is by being projected on described silicon thin film after described nonlinear optical medium, and the diameter of the hot spot of described incoming laser beam on described silicon thin film is greater than the diameter of the described crystalline areas of 2 times.
Further, carrying out the laser beam that described laser crystallization process adopts is Gaussian beam, and the diameter of the hot spot of described laser beam is less than described incoming laser beam at 1/2nd of the diameter by the hot spot before described nonlinear optical medium.
Further, described silicon thin film is amorphous silicon membrane or Nano thin film.
Further, the described absorption coefficient of described silicon thin film is Gaussian Profile on the described cross section of described crystalline areas.
In a better embodiment of the present invention, provide a kind of optical limiter, comprise nonlinear optical medium and silicon thin film.Wherein, nonlinear optical medium is the carbon disulfide solution be encapsulated in quartz colorimetric utensil, and silicon thin film is Nano thin film, silicon thin film has the crystalline areas through laser crystallization process.The laser beam adopted when carrying out laser crystallization process is Gaussian beam, and the absorption coefficient of the silicon thin film after process is Gaussian Profile on the cross section of crystalline areas.During use, if the light intensity of incoming laser beam is more than or equal to self focusing threshold light intensity, incoming laser beam is by being focused after carbon disulfide solution and being incident upon on the crystalline areas of silicon thin film, and substantially drop on crystalline areas through the hot spot of incoming laser beam on silicon thin film focused on, therefore its light intensity is significantly absorbed, and so just reaches the effect of optics amplitude limit; If the light intensity of incoming laser beam is less than self focusing threshold light intensity, described incoming laser beam is by being projected on silicon thin film after carbon disulfide solution, because the size of the hot spot of incoming laser beam on silicon thin film is more much bigger than the size of crystalline areas, therefore can ensure that it keeps higher transmitance.
Visible, optical limiter of the present invention is provided with nonlinear optical medium (CS in the optical path
2), and after this medium, be provided with the silicon thin film through laser crystallization process, pass through CS by utilizing comparatively intense laser beam
2time self-focusing effect and silicon thin film crystalline areas in the absorption coefficient of Gaussian Profile, achieve the function of the optics amplitude limit to incoming laser beam.Structure of the present invention is simple, with low cost, and material of the present invention can realize industrial-scale production at present.The present invention can be used for multiple different occasion, thus provides safeguard for the safe handling of precision optics (comprising human eye).
Be described further below with reference to the technique effect of accompanying drawing to design of the present invention, concrete structure and generation, to understand object of the present invention, characteristic sum effect fully.
Accompanying drawing explanation
Fig. 1 is the structural representation of optical limiter of the present invention.
Fig. 2 is the schematic diagram of the silicon thin film through laser crystallization process of optical limiter of the present invention.
Fig. 3 is the distribution map of absorption coefficient on the cross section of crystalline areas of the silicon thin film measuring the optical limiter of the present invention obtained.
Fig. 4 is the experimental result curve map of the optics amplitude limiting characteristic experiment of optical limiter of the present invention.
Detailed description of the invention
As shown in Figure 1, optical limiter 40 of the present invention comprises the carbon disulfide (CS be encapsulated in quartz colorimetric utensil 10
2) solution 11 and the silicon thin film 20 through laser crystallization process.Wherein, the wall thickness of quartz colorimetric utensil 10 is 1mm, silicon thin film 20 has the crystalline areas 21 (see Fig. 2) through laser crystallization process.Quartz colorimetric utensil 10 is fixed on base plate 30 by support 12, and silicon thin film 20 is on a surface of transparent substrate 22, and substrate 22 is fixed on base plate 30 by support 23.During use, incoming laser beam 51 enters optical limiter 40, passes through the crystalline areas 21 of carbon disulfide solution 11 and silicon thin film 20 successively, becomes shoot laser bundle 52 and leave optical limiter 40.In the present embodiment, optical limiter 40 of the present invention has shell, quartz colorimetric utensil 10 (comprising the carbon disulfide solution 11 be encapsulated in wherein), substrate 22 (be included in the silicon thin film 20 in one surface, silicon thin film have crystalline areas 21), support 12, support 23 and base plate 30 are encapsulated in this shell after accurately setting position to each other.Incoming laser beam 51 enters from one end of this shell, passes through the crystalline areas 21 of carbon disulfide solution 11 and silicon thin film 20 successively, becomes the other end outgoing of shoot laser bundle 52 from this shell.
In the present embodiment, silicon thin film 20 is Nano thin film, using plasma strengthens chemical gaseous phase depositing process (PECVD) growth on a surface of substrate 22, thickness about 1 micron, crystalline ratio (total volume percent of film shared by the crystalline state composition namely in film) is about 37%.Substrate 22 is transparent substrates.To the parameter of the laser crystallization process that silicon thin film 20 carries out be: the centre wavelength of laser instrument is 800nm, and pulse width is 100fs, and repetition rate is 82MHz, and power is about 200mW; Laser beam is Gaussian beam, and the size of the hot spot of laser beam is relevant to the size of the hot spot of incoming laser beam 51, and the diameter of the hot spot of such as laser beam is less than incoming laser beam 51 at 1/2nd of the diameter by the hot spot before carbon disulfide solution 11.In the present embodiment, the diameter of the crystalline areas 21 obtained after above-mentioned laser crystallization process is about 50 microns.After laser crystallization process, the energy gap of silicon thin film will reduce, and material surface roughness increases, and the absorption coefficient therefore through the silicon thin film of laser crystallization process can change.As shown in Figure 3, the direction of absorption coefficient along the edge of crystalline areas 21 to the center of crystalline areas 21 on the cross section of crystalline areas 21 of silicon thin film 20 increases progressively, and in Gaussian Profile.In figure, r puts the distance at the center of crystalline areas 21, in edge r ~ 25 μm of crystalline areas 21, at the center r=0 of crystalline areas 21 for institute's location on silicon thin film 20.It should be noted that, the silicon thin film 20 used in the present embodiment is Nano thin films, also can use amorphous silicon membrane in other embodiments.
Carbon disulfide solution 11 is nonlinear optical mediums, has larger positive nonlinear refractive index.Through this kind of nonlinear optical medium, can self-focusing effect be there is in the enough large laser beam of intensity.Wherein, for a certain nonlinear optical medium, laser beam is self focusing threshold light intensity by wherein there is the minimum intensity of light of self-focusing effect.Therefore, for carbon disulfide solution 11, when the light intensity of incoming laser beam 51 is more than or equal to self focusing threshold light intensity, there is self-focusing effect by carbon disulfide solution 11 in incoming laser beam 51, and incoming laser beam 51 is focused and is incident upon on the crystalline areas 21 of silicon thin film 20.The hot spot of incoming laser beam 51 on silicon thin film 20 through focusing on drops on crystalline areas 21 substantially, such as the diameter of the hot spot of incoming laser beam 51 on silicon thin film 20 is less than the diameter of the crystalline areas 21 of 2 times, and the deviation between the position at the position at the center of this hot spot and the center of crystalline areas is not more than 10%.Namely incoming laser beam 51 is focused to the high absorption coefficient region, center of silicon thin film 20, thus the transmitance of laser beam reduces gradually, reaches the effect of optics amplitude limit.When the light intensity of incoming laser beam 51 is less than self focusing threshold light intensity, self-focusing effect is there is not in incoming laser beam 51 by carbon disulfide solution 11, incoming laser beam 51 is projected on silicon thin film 20, diameter due to the hot spot of incoming laser beam 51 on silicon thin film 20 is greater than the diameter of the crystalline areas 21 of 2 times, therefore the absorption of the 21 pairs of incoming laser beams 51 in crystalline areas is less, can ensure that the change of its light intensity is less.
Fig. 4 gives the experimental result to the optics amplitude limiting characteristic experiment that optical limiter 40 of the present invention carries out, during experiment, the distance between quartz colorimetric utensil 10 and silicon thin film 20 is regulated to be 5 centimetres, the parameter of the incoming laser beam 51 used is: the centre wavelength of laser instrument is 800nm, pulse width is 100fs, repetition rate is 82MHz, and peak power output is about 250mW, and laser beam is Gaussian beam.Use laser power meter to measure the power (incident laser power namely in Fig. 4) of incoming laser beam 51 and the power (the shoot laser power namely in Fig. 4) of shoot laser bundle 52 respectively, the variation relation of power with the power of incoming laser beam 51 of shoot laser bundle 52 can be obtained.As can be seen from Figure when incoming laser beam 51 power is less than 100mW, there is not self-focusing effect substantially by carbon disulfide solution 11 in incoming laser beam 51, and light transmission rate (ratio of shoot laser power and incident laser power) is constant; When incoming laser beam 51 power reaches 100mW and continues to increase, CS
2the self-focusing effect of solution starts to have an effect, the hot spot that then incoming laser beam 51 projects on silicon thin film 20 reduces gradually, focus on the crystalline areas 21 of high absorption coefficient, thus light transmission rate reduces gradually, the light intensity of outgoing laser beam 52 is restricted under certain numerical value (i.e. threshold value light intensity).
In the present embodiment, use carbon disulfide solution 11 as the nonlinear optical medium with larger positive nonlinear refractive index, but also can use other the nonlinear optical medium with larger positive nonlinear refractive index in other embodiments.In the present embodiment, carbon disulfide solution 11 is encapsulated in quartz colorimetric utensil 10, but also can use other packaged type in other embodiments.In addition, the threshold value light intensity by regulating the thickness of quartz colorimetric utensil 10 and the distance between quartz colorimetric utensil 10 and silicon thin film 20 can also regulate optical Limiting within limits.
More than describe preferred embodiment of the present invention in detail.Should be appreciated that those of ordinary skill in the art just design according to the present invention can make many modifications and variations without the need to creative work.Therefore, all those skilled in the art, all should by the determined protection domain of claims under this invention's idea on the basis of existing technology by the available technical scheme of logical analysis, reasoning, or a limited experiment.
Claims (7)
1. an optical limiter, is characterized in that, comprises nonlinear optical medium and silicon thin film, and described nonlinear optical medium has positive nonlinear refractive index, described silicon thin film has the crystalline areas through laser crystallization process; The absorption coefficient of described silicon thin film being distributed as on the cross section of described crystalline areas increases progressively along the edge of described crystalline areas to the direction at the center of described crystalline areas; Incoming laser beam passes through the described crystalline areas of described nonlinear optical medium and described silicon thin film successively; Described nonlinear optical medium is carbon disulfide solution; Described incoming laser beam is Gaussian beam.
2. optical limiter as claimed in claim 1, wherein said carbon disulfide solution is encapsulated in quartz colorimetric utensil.
3. optical limiter as claimed in claim 2, the light intensity of wherein said incoming laser beam is more than or equal to self focusing threshold light intensity, described incoming laser beam is by being focused after described nonlinear optical medium and being incident upon on the described crystalline areas of described silicon thin film, and the diameter of the described crystalline areas of 2 times is less than through the diameter of the hot spot of described incoming laser beam on described silicon thin film of described focusing, the deviation between the position at the position at the center of described hot spot and the described center of described crystalline areas is not more than 10%.
4. optical limiter as claimed in claim 2, the light intensity of wherein said incoming laser beam is less than self focusing threshold light intensity, described incoming laser beam is by being projected on described silicon thin film after described nonlinear optical medium, and the diameter of the hot spot of described incoming laser beam on described silicon thin film is greater than the diameter of the described crystalline areas of 2 times.
5. the optical limiter as described in claim 3 or 4, wherein carrying out the laser beam that described laser crystallization process adopts is Gaussian beam, and the diameter of the hot spot of described laser beam is less than described incoming laser beam at 1/2nd of the diameter by the hot spot before described nonlinear optical medium.
6. optical limiter as claimed in claim 5, wherein said silicon thin film is amorphous silicon membrane or Nano thin film.
7. optical limiter as claimed in claim 6, the described absorption coefficient of wherein said silicon thin film is Gaussian Profile on the described cross section of described crystalline areas.
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| CN1218367C (en) * | 2000-06-12 | 2005-09-07 | 精工爱普生株式会社 | Manufacture of film semiconductor device |
| CN1971395A (en) * | 2006-12-13 | 2007-05-30 | 中国科学院光电技术研究所 | A manufacturing method of optical limiter of photon crystal |
| CN1996685A (en) * | 2006-12-27 | 2007-07-11 | 中国科学院上海技术物理研究所 | Te, cadmium and Hg optical range limiter with the continuously adjusting output light intensity of the passive saturated clamp |
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Inventor after: Shen Wenzhong Inventor after: Zheng Daqi Inventor after: Zeng Yang Inventor after: Ma Yangjin Inventor after: Ye Qinghao Inventor after: Wu Zhengri Inventor before: Shen Wenzhong Inventor before: Zheng Daqi Inventor before: Ma Yangjin Inventor before: Ye Qinghao Inventor before: Wu Zhengri |
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