CN100501552C - Compact type pulse dispersion device - Google Patents

Abstract

The present invention relates to a compact pulse disperser. Said disperser is made up by combining two isosceles right prisms. It is worked under the condition of normal incidence of light, it only can utilize the dispersive power of optical material self-body to attain the goal of shaping pulse, and can implement stretching and compression of ultra-short pulse.

Description

Compact type pulse disporsion device

Technical field

The present invention relates to the ultrafast laser technique direction, relate to a kind of compact type pulse disporsion device concretely.

Background technology

Superpower ultrashort laser scientific research is object with the innovation and development of superpower ultrashort laser, superpower ultrashort laser with the interaction and the basis, forward position in cross discipline and relevant high-tech sector of material, is very important science frontier field in current modern physics in the world and even the modern science.In this field, pulse strenching/compress technique is one of them very crucial monotechnics.For example, amplify (CPA) and the optical parameter chirped pulse amplifies in (OPCPA) system at present common Fs chirp pulse, one of them gordian technique is exactly signal pulse to be carried out broadening (from the femtosecond broadening to nearly nanosecond) before carrying out the laser amplification.So both can before the amplification that reaches capacity, avoid the damage of laser effectively, and can improve laser again greatly and amplify efficient, thereby after the pulse shortener compression, obtain the output of superelevation laser pulse power amplification medium.Pulse strenching/compression realizes by frequency chirp, can obtain by material dispersion or the angular dispersion of introducing optical medium, obtains as the effect of dispersion that can utilize grating and prism.Pulse stretcher commonly used at present has two kinds:

The one, the grating pulse stretcher, as shown in Figure 1, the grating pair antiparallel is placed, between grating pair, place two lens, by the confocal telescopic system that is placed to, grating has left telescopical front and back focal plane and close to lens with two lens, and grating is passed through in pulse for four times, produce enough big positive GVD (Group Velocity Dispersion), thereby make pulse obtain broadening.In order to eliminate the astigmatism of the light beam that causes because of grating dispersion, the incident angle of light should be near the Littrow angle.In addition, the aberration that the lens in the grating stretching device are introduced can cause three secondary frequencies dependent phases, and spherical aberration can cause four secondary frequencies dependent phases.Grating stretching/compressor reducer is about 70% to the transmitance of light pulse, and their structure more complicated is adjusted also relatively difficulty.In addition, to use larger-size grating to high power/energy pulses, the price comparison costliness, and be difficult for maintenance, serviceable life is shorter relatively.In addition mechanical part is required also than higher.

The 2nd, traditional prism is right-dispersion compensator, and as shown in Figure 2, when pulse during by prism P1, prism reflects away the light of different wave length according to different angles, enter into second prism P2 again.Because short-wavelength light is bigger than the refraction angle of long wavelength light, the light correspondence of different wave length the different light paths of advancing in the light pulse like this, and the short wavelength becomes the light path of beam split process littler, thereby reaches negative GVD (Group Velocity Dispersion) purpose.By regulating prism, can control required GVD (Group Velocity Dispersion) easily to inserting the degree of depth of light beam.It is operated in Brewster angle, thereby its loss is also less.But faint angular dispersion can cause the distance between two prism apex of requirement far, thereby has limited the dispersion measure that the conventional prism device can produce.

Traditional grating/prism dispersor is adjusted more complicated, and is also relatively more responsive to imbalance.

Summary of the invention

The objective of the invention is at above-mentioned the deficiencies in the prior art part, a kind of compact type pulse disporsion device is provided, this dispersor is constituted by two isosceles right-angle prisms, under light positive incident condition, work, only rely on the chromatic dispersion of optical material own to reach the purpose of shaping pulse, realize broadening/compression ultrashort pulse.

The realization of the object of the invention is finished by following technical scheme:

A kind of compact type pulse disporsion device is characterized in that this dispersor is made of two isosceles right-angle prisms, and the inclined-plane opposing parallel of the two is placed, and one of them can carry out parallel moving along its skewed surface direction, to regulate the dispersion measure of dispersor.Air gap length between the skewed surface of dispersion measure and prism is irrelevant.

In the middle of two prisms, can add one flat plate at least, make that the adjusting of dispersion measure is convenient.

Each prism or the material that each is dull and stereotyped can be different, to regulate the advanced dispersion amount more easily.

Being coated with anti-reflection film on the skewed surface of prism or on the dull and stereotyped logical light face, to reduce the wastage.

If determined required dispersion measure, the in-depth optical cement is glued together passing through between prism and the prism or between prism and the flat board or between flat board and the flat board, the refractive index of in-depth optical cement respectively with the prism of both sides or dull and stereotyped refractive index match, to reduce loss.

Dispersor of the present invention is worked under light positive incident condition.

The invention has the advantages that:

1. the chromatic dispersion that whole device is introduced has only material dispersion, does not have angular dispersion, thereby insensitive to the light path imbalance;

2. simple in structure, good stability is easily adjusted, and cost is low, and is also low to the requirement of mechanical adjustment precision;

3. can reach the purpose of adjusting dispersion measure by adjusting two relative shifts between the prism, flexibility of operation is strong;

4. loss is few.

5. owing to there is not angular dispersion, two prisms can use different materials, this means that many ones degree of freedom remove to control second order and third-order dispersion;

6. if desired, can add one or polylith flat board easily in the middle of two prisms, dull and stereotyped material can be different, thereby make that the adjusting of dispersion measure is convenient;

7. when not plating anti-reflection film, need not readjust light path when changing incident wavelength, its applicable wavelengths scope only is subject to the absorption Spectrum characteristic of material;

8. design size of the present invention is not limited by the spectrum width of incident light pulse.(for grating/prism paired pulses dispersor, the spectrum width of incident light pulse is wide more, requires grating/prism dimensions big more, so have the spectrum width restriction);

9. because normal incidence has only been avoided the generation of aberration;

On the other hand, in the present invention because light has passed through repeatedly reflection, thus its dispersion measure than traditional prism right-dispersion compensator is a lot of greatly.

Summary of drawings

Accompanying drawing 1 grating pair-pulse stretcher structural representation;

Accompanying drawing 2 prisms are right-the dispersion compensator structural representation;

Accompanying drawing 3 structural representations of the present invention;

Accompanying drawing 4 the present invention add the structural representation behind the one flat plate;

The refractive index alternation figure of accompanying drawing 5 in-depth optical cements

Accompanying drawing 6 the present invention add the structural representation behind the n piece flat board;

Accompanying drawing 7 the present invention are used for Fs chirp pulse regneration amplification laser system synoptic diagram;

Accompanying drawing 8 high-repetition-rate Fs chirp pulse regneration amplification laser system synoptic diagram;

Accompanying drawing 9 the present invention are used for Fs chirp pulse parameter amplification laser system synoptic diagram.

Concrete technical scheme

Feature of the present invention and other correlated characteristic are described in further detail by embodiment below in conjunction with accompanying drawing, so that technician's of the same trade understanding:

Shown in Fig. 3-9, label 1-4 represents respectively: between the summit of prism 1, prism 2, dull and stereotyped 3, incident light 4, the right-angle side length L of prism, two prisms apart from d, incident light to the prism edge apart from x.Light pulse enters into the skewed surface of right-angle prism on the left side from right side normal incidence after, through two prisms inside repeatedly back and forth after from the skewed surface output of the right-angle prism on the left side.

Prism to the overall material dispersion that produces is:

$\frac{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="C200510031020E00101.png,C200510031020E00102.png"\; state="\{\{state\}\}">d</figure-callout>}}^2{\mathrm{\&phi;}}_m\left(\mathrm{\&omega;}\right)}{{\mathrm{d\&omega;}}^2}=\frac{{\mathrm{\&lambda;}}^3}{{2\mathrm{\&pi;c}}^2}\frac{d^{2}n\left(\mathrm{\&lambda;}\right)}{{\mathrm{d\&lambda;}}^2}N\left(2\sqrt{2}L\right)=\frac{\sqrt{2L}{\mathrm{\&lambda;}}^3}{{\mathrm{\&pi;c}}^2}\frac{d^{2}n\left(\mathrm{\&lambda;}\right)}{{\mathrm{d\&lambda;}}^2}N---\left(1\right)$

D and N are subject to the hypotenuse length of prism, and its relation can be estimated by following formula:

$N=\left[\frac{\sqrt{2}L/2-x}{d}\right]---\left(2\right)$

So d is big more, N is more little, and the dispersion measure of Yin Ruing is just more little as seen from formula (1).

Embodiment:

Present embodiment is made of two isosceles right-angle prisms 1,2, and the inclined-plane of the two is staggeredly placed relatively, and relative shift is d, and wherein a prism can move along another prism skewed surface direction with perpendicular to the horizontal direction of skewed surface.

During use, as shown in Figure 3, light pulse is from a side normal incidence of prism 1, and incident light center 4 is x to the distance at prism 1 edge, through repeatedly exporting from opposite side after back and forth in prism 1,2 inside.Adjust the back and forth times N of light between two prisms by adjusting two relative shift d between the prism, thereby reach the purpose of adjusting dispersion measure.

In order to reduce loss, can plate anti-reflection film at the skewed surface of prism 1,2, if the skewed surface of two prisms 1,2 plating anti-reflection film, light 10 times back and forth in dispersor the inside, loss only has an appointment 2%.Present embodiment had both made does not have plated film, and loss is also only reflected caused about 4% by luxuriant and rich with fragrance alunite Pu'er tea, and the loss of grating stretching/compressor reducer about about 30%.

In order to reduce loss, if determined required dispersion measure, also available in-depth optical cement (see figure 5) is glued together with two lens 1,2, and the both sides refractive index of in-depth optical cement equals the refractive index of the prism of both sides respectively, thus the alternation of medium refraction index when reaching light and propagating.

Owing to there is not angular dispersion, prism 1,2 can use different materials, this means that many ones degree of freedom remove to control second order and third-order dispersion.And to traditional prism concerning-dispersion compensator, in order to collimate dispersed light beam, two prisms must be that same material is made;

If desired, shown in Fig. 4,6, can add one or polylith optical glass flat board 3 in the middle of two prisms 1,2 in the present embodiment, polylith is dull and stereotyped 3 the time when adding, and the material of each piece flat board can be different, thereby make that the adjusting of dispersion measure is convenient.When carrying out dispersion compensation, except that the compensation GVD (Group Velocity Dispersion), preferably compensate high Jie's chromatic dispersion as far as possible, the GVD (Group Velocity Dispersion) of different materials is different with the ratio of its advanced dispersion, so can carry out the compensation of many Jie chromatic dispersion simultaneously with multiple material.

Present embodiment comprises two isosceles right-angle prisms in a word, as required, can utilize the combination of different materials prism or insert the dull and stereotyped and grating pair pulse shortener cooperation of the optical glass of different materials between two prisms to reach pulse width and minimize.For reducing loss, skewed surface (or optical glass planar surface of insertion different materials) in two prisms can plate anti-reflection film, if perhaps determined required dispersion measure, be connected at the optical cement with refractive index match between prism and the prism or between prism and the flat board or between flat board and the flat board, the refractive index of promptly deepening optical cement respectively with the prism or the dull and stereotyped refractive index match of both sides.

The inclined-plane of two isosceles right-angle prisms of present embodiment is staggeredly placed relatively, behind light pulse normal incidence to one prism surface, between two prisms through repeatedly the reflection after, from another prism surface outgoing (as shown in Figure 3), because prism has different refractive indexes to the light of different wave length, repeatedly reflection prism centering makes the light of different wave length produce GVD (Group Velocity Dispersion) in communication process, thereby has realized the broadening of pulse.

Present embodiment is applied in the Fs chirp pulse regneration amplification laser system (see figure 7): the pulse seed light of a femtosecond of input, is about 200 psecs with the present embodiment product with it broadening, entering titanium jewel regenerative amplifier again amplifies, utilize the grating pair compression at output terminal at last, obtain ultrashort superpower output light laser.

The method that this programme adopts is, the grating stretching device that replaces in the former regenerative amplification device with prism 1,2 carries out broadening with it to the femtosecond laser of incident, and adjustment amount is little, and loss is few, and compact conformation has been saved expense simultaneously.Utilize the combination of multiple prism and grating pair pulse shortener to cooperate to reach pulse width and minimize.

For the Fs chirp pulse regneration amplification laser system of high-repetition-rate (as document Opt.Lett., 29 (22), 2665 (2004) describe), also available traditional prism paired pulses stretcher produces negative warbling, the type pulse disporsion device of present embodiment is as the compressor reducer (see figure 8).

The method that this programme adopts is, to replacing the stretcher in the former OPCPA device, the femtosecond laser of incident carried out broadening with prism, and adjustment amount is little, and loss is few, and has avoided the generation of aberration, and the dispersion measure that its produces is $\frac{\sqrt{2}L{\mathrm{\&lambda;}}^3}{\mathrm{\&pi;}{c}^2}\frac{d^{2}n\left(\mathrm{\&lambda;}\right)}{d{\mathrm{\&lambda;}}^2}N,$ Wherein, λ is the incident light wavelength, and n (λ) is the refractive index of the light of λ for the medium medium wavelength, and c is the light velocity in the vacuum, and N is that light is by the right number of times of prism.

Present embodiment be applied in be applied to OPCPA in the femtosecond optical parameter chirped pulse regenerative amplification laser system cardinal principle as shown in Figure 9.Earlier with 10 femtosecond ultrashort pulse flashlights with this stretcher broadening become 0.5 nanosecond chirped pulse, again with the frequency doubled light of the Nd:YAG laser of 1 nanosecond pumping source as the optical parameter amplifier, utilizing LBO or nonlinear crystals such as BBO, KDP to carry out optical parameter amplifies, utilize the grating pair compression at output terminal at last, obtain ultrashort ultra-intense laser output.

Claims (7)

1, a kind of compact type pulse disporsion device, it is characterized in that this dispersor is made of two isosceles right-angle prisms, the inclined-plane opposing parallel of the two is placed, and one of them can carry out translation along its skewed surface direction, behind light pulse normal incidence to the one prism inclined-plane, between two prisms through repeatedly the reflection after, from another prism inclined-plane outgoing.

2, a kind of compact type pulse disporsion device according to claim 1 is characterized in that can being coated with anti-reflection film on the skewed surface of described prism, to reduce the wastage.

3, a kind of compact type pulse disporsion device according to claim 1 is characterized in that described two prisms can be glued together by the in-depth optical cement, the both sides refractive index of in-depth optical cement respectively with the refractive index match of the prism of both sides.

4, a kind of compact type pulse disporsion device according to claim 1 is characterized in that can adding one flat plate at least in the middle of described two prisms, thereby makes that the adjusting of dispersion measure is convenient.

5, according to claim 1 or 4 described a kind of compact type pulse disporsion devices, it is characterized in that when described each prism or material that each is dull and stereotyped can be different, to regulate the advanced dispersion amount more easily.

6, a kind of compact type pulse disporsion device according to claim 4 is characterized in that can being coated with anti-reflection film on the logical light face of described flat board, to reduce the wastage.

7, a kind of compact type pulse disporsion device according to claim 4, it is characterized in that between described prism and the flat board or can be glued together between flat board and the flat board by the in-depth optical cement, the refractive index of in-depth optical cement respectively with the prism of both sides or dull and stereotyped refractive index match.

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