CN103105677B - Produce the system and method for the partially coherent Gaussian beam of Laguerre-Gauss association - Google Patents

Abstract

The invention discloses a kind of system producing the partially coherent Gaussian beam of Laguerre-Gauss association, this system places beam expander, spatial light modulator, beam-shrinked mirror, frosted glass plate, lens and gaussian filtering sheet successively along radiation direction.Computed hologram is loaded in spatial light modulator and forms calculation holographic grating, produces the Laguerre-Gaussian beam only having angle modulus; Beam-shrinked mirror is used for the Laguerre-Gaussian beam spot size controlling to incide on rotating ground glass sheet, to adjust the coherence of irradiating light beam; Frosted glass is the partial coherence light beam making Laguerre-Gaussian beam become Laguerre-Gauss association.Lens are to partial coherence light beam collimation, and gaussian filtering sheet becomes Gaussian distribution this light beam light intensity distribution shifts.Due to the dirigibility of computer hologram, can produce by producing different holograms the Laguerre-Gaussian beam that different rank only has angle modulus, thus produce the partially coherent Gaussian beam of the Laguerre-Gauss association of different rank.

Description

Produce the system and method for the partially coherent Gaussian beam of Laguerre-Gauss association

Technical field

The present invention relates to a kind of calculation holographic, system and method that technology that rotating ground glass generating portion is concerned with produces the partially coherent Gaussian beam of Laguerre-Gauss association.

Background technology

Since the graceful invention laser of the many plums in nineteen sixty American Physical scholar Theo, laser, with advantages such as its high strength, high monochromaticity, high coherences, is widely used in the every field such as laser communications, laser ranging, aeroplane mapping.

In the application of reality, find that the complete in other words conj.or perhaps coherent laser that coherence is high has some limitations in some application aspect, when such as, transmitting in a branch of high coherence's laser random medium, the impact being subject to medium is very strong, light beam is just distorted in the very short distance of transmission, and light intensity flicker and drift are very large, and beam quality declines rapidly, this just requires in actual applications, selects to have suitable coherence's laser beam and more contributes to solving practical problems.The research of partially coherent light can relate the sixties in 19th century, does not also have laser at that time, main research be the coherence of finite light source, different 2 P in light field ₁and P ₂the association existed between place's vibration is introduced certain and is measured, and when 2 associations are very high, just saying it is relevant, when not associating, just saying it is incoherent at 2, be between the two be partial coherence.

At present, the model studying partial coherence light beam is the most widely that Schell associates the partially coherent light described in its PhD dissertation by Gauss, namely Gaussian-Schell model beam propagating, scientists under lab can produce Gaussian-Schell model beam propagating, the partial coherence laser subsequently with different correlation form proposes in theory in succession, as first kind Bezier association light source, Equations of The Second Kind Bezier association light source, non-homogeneous Gauss-Xie Er light source, LED light source, many Gauss-Xie Er light sources associate with Laguerre-Gauss or Bezier Gauss associates light source, what mainly can produce experimentally at present is that Gauss-Xie Er light source associates light source with first kind Bezier, the partially coherent light of other associations is also theoretic model, the method that experiment produces does not have report.

In research in sum, the partially coherent light of certain association that what discovery can produce experimentally have is very limited, usually be exactly that Gauss-Xie Er light source associates light source with first kind Bezier, which also limits application in some cases, Gauss-Xie Er light source is Gaussian in the light distribution in far field, first kind Bezier association light source is hollow in certain local place light distribution, find in nearest theoretical research, under suitable Correlation Criteria, far-field intensity distribution is flat-top, or far-field intensity distribution is hollow.Far-field intensity distribution is that hollow light beam all has important application demand in fields such as atom optics, binary optical, particle capture and medical science.

Summary of the invention

In view of this, the invention provides a kind of system and method producing the partially coherent Gaussian beam of Laguerre-Gauss association, the method can produce the partially coherent Gaussian beam of the Laguerre-Gauss association of different rank by producing different holograms.

To achieve these goals, the technical scheme that provides of the application is as follows:

Produce a system for the partially coherent Gaussian beam of Laguerre-Gauss association, comprising:

Light source;

Beam expander, expands the light beam from described light source;

Spatial light modulator, changes into the light beam after expanding the Laguerre-Gaussian beam only having angle modulus;

Beam-shrinked mirror and rotatable frosted glass, only there is the spot size of the Laguerre-Gaussian beam of angle modulus after beam-shrinked mirror regulates, incide on frosted glass, through the scattering of frosted glass, the Laguerre Gao-Si light beam that makes to be concerned with completely is converted into the partial coherence light beam of Laguerre-Gauss association;

Lens, collimate the partial coherence light beam of Laguerre-Gauss association;

Gaussian filtering sheet, is Gaussian hot spot by the partial coherence light beam integer of the Laguerre-Gauss association after collimation, produces the partially coherent Gaussian beam of Laguerre-Gauss association.

As a further improvement on the present invention, described light source is helium-neon laser.

As a further improvement on the present invention, also comprise computing machine, the computed hologram of described Practical computer teaching is loaded in described spatial light modulator and forms calculation holographic grating, to produce the Laguerre-Gaussian beam only having angle modulus.

The invention also discloses a kind of method producing the partially coherent Gaussian beam of Laguerre-Gauss association, comprising:

S1, the light beam from light source to be expanded;

S2, the light beam after expanding is changed into the Laguerre-Gaussian beam only having angle modulus;

S3, by only have the spot size of the Laguerre-Gaussian beam of angle modulus carry out contracting bundle adjustment, be then translated into Laguerre-Gauss association partial coherence light beam;

S4, to Laguerre-Gauss association partial coherence light beam collimate;

S5, the partial coherence light beam integer associated by the Laguerre-Gauss after collimation are Gaussian hot spot, produce the partially coherent Gaussian beam of Laguerre-Gauss association.

As a further improvement on the present invention, in described step s2, the light beam after expanding is changed into the Laguerre-Gaussian beam only having angle modulus by spatial light modulator.

As a further improvement on the present invention, the computed hologram of Practical computer teaching is loaded in described spatial light modulator and forms calculation holographic grating, to produce the Laguerre-Gaussian beam only having angle modulus.

As a further improvement on the present invention, in described step s3, by only there being the spot size of the Laguerre-Gaussian beam of angle modulus to carry out the adjustment of contracting bundle, be then translated into the partial coherence light beam of Laguerre-Gauss association by the scattering of frosted glass.

Compared with prior art, the present invention places light source beam expander, by computer-controlled spatial light modulator, beam-shrinked mirror, rotating ground glass sheet, lens and gaussian filtering sheet successively along the radiation direction of light source.The computed hologram of Practical computer teaching is loaded in described spatial light modulator and forms calculation holographic grating, thus produce the Laguerre-Gaussian beam only having angle modulus.Beam-shrinked mirror regulates the spot size of Laguerre-Gaussian beam, and rotating ground glass is the partial coherence light beam making Laguerre-Gaussian beam become Laguerre-Gauss association.And then by lens, partial coherence Laguerre-Gaussian beam is collimated, by gaussian filtering sheet to light beam integer, make light beam be Gaussian hot spot, produce the partially coherent Gaussian beam of Laguerre-Gauss association.Due to the dirigibility of computer hologram, so can produce by producing different holograms the Laguerre-Gaussian beam that different rank only has angle modulus, thus produce the partially coherent Gaussian beam of the Laguerre-Gauss association of different rank.

Accompanying drawing explanation

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.

Figure 1 shows that the structural representation of system in the specific embodiment of the invention;

Fig. 2 is the single order Laguerre-Gauss associated diagram of theory calculate;

Fig. 3 is high-order (quadravalence) the Laguerre-Gauss associated diagram of theory calculate.

Embodiment

The embodiment of the present invention calculation holographic raster pattern is loaded into spatial light modulator produce the Laguerre-Gaussian beam only having angle modulus, then regulate the spot size of Laguerre-Gaussian beam with beam-shrinked mirror, obtain finally by rotating ground glass sheet and gaussian filtering sheet the partially coherent Gaussian beam that Laguerre-Gauss associates.The method not only experiment condition is simple but also easily manipulate, and is a kind of reasonable method.

Radiation direction along light source places light source beam expander, successively by computer-controlled spatial light modulator, beam-shrinked mirror, rotating ground glass sheet, lens and gaussian filtering sheet.The computed hologram of Practical computer teaching is loaded in described spatial light modulator and forms calculation holographic grating, thus produce the Laguerre-Gaussian beam only having angle modulus.Beam-shrinked mirror regulates Laguerre-Gaussian beam spot size, and rotating ground glass is the partial coherence light beam making Laguerre-Gaussian beam become Laguerre-Gauss association.And then by lens, the partial coherence light beam that Laguerre-Gauss associates is collimated, by gaussian filtering sheet to light beam integer, make light beam be Gaussian hot spot, produce the partially coherent Gaussian beam of Laguerre-Gauss association.

The technical scheme of the present embodiment is:

What adopt in experiment is He-Ne laser beam, can think quasi-monochromatic light, and coherence is very high, and after spatial light modulator and contracting bundle device, the light distribution arriving (before frosted glass scattering) on rotating ground glass face is expressed as:

$I\left(\stackrel{\→}{\mathrm{\ρ}}\right)=I_0{\left(\frac{\sqrt{2}\mathrm{\ρ}}{w_0}\right)}^{2n}{\left|L^n\left(\frac{{2\mathrm{\ρ}}^2}{w_0^2}\right)\right|}^2\exp (-\frac{{2\mathrm{\ρ}}^2}{w_0^2})---\left(1\right),$

the position vector on ground glass surface, w ₀with a relevant amount of spot size on this face, I ₀that these two amounts are all normal numbers with a relevant amount of total light intensity, arrival lens and gaussian filtering unilateral on time, transmission range is the focal distance f of lens ₁, according to VanCittert-Zernike theorem, the secondorder correlation function on lens face:

$\mathrm{\Γ}(r_1,r_2)=\exp \left[(\mathrm{\πi}/{\mathrm{\λf}}_1)(r_1^2-r_2^2)\right]\∫I\left(\stackrel{\→}{\mathrm{\ρ}}\right)\exp [-(2\mathrm{\πi}/{\mathrm{\λf}}_1)\stackrel{\→}{\mathrm{\ρ}}\·(\stackrel{\→}{r_1}-\stackrel{\→}{r_2})]d^2\mathrm{\ρ}---\left(2\right)$

Wherein λ is the wavelength of light beam, and limit of integration comprises all scopes on ground glass surface, light intensity expression in substitution formula, by integration abbreviation, obtain:

$\mathrm{\Γ}(r_1,r_2)=\frac{2{\mathrm{\π}}^3{w}_0^2{f}_1^2{I}_0}{k^2}\mathrm{\Γ}(n+1)\exp \left[(\mathrm{\πi}/\mathrm{\λ}{f}_1)\left(r_1^2\text{-}{r}_2^2\right)\right]$

$\×\exp (-\frac{w_0^2}{2{\mathrm{\λ}}^2{f}_1^2}{|\stackrel{\→}{r_1}-\stackrel{\→}{r_2}|}^2)L_n^0\left(\frac{w_0^2}{2{\mathrm{\λ}}^2{f}_1^2}{|\stackrel{\→}{r_1}-\stackrel{\→}{r_2}|}^2\right)---\left(3\right)$

Because lens and gaussian filtering sheet are close together, then the transmittance function of this device is expressed as: it is the transverse width of gaussian filtering sheet.According to this transmittance function, from the secondorder correlation function of experimental provision light beam be out finally:

$\mathrm{\Γ}(r_1,r_2)=t\left(r_1\right)t^{*}\left(r_2\right)\mathrm{\Γ}(r_1,r_2)=\frac{2{\mathrm{\π}}^3{w}_0^2{z}^2{I}_0}{k^2}\mathrm{\Γ}(l+1)$

$\×\exp [-(r_1^2+r_2^2)/2{{\mathrm{\σ}}_{f_1}}^2]$

$\×\exp (-\frac{w_0^2}{2{\mathrm{\λ}}^2{f}_1^2}{|\stackrel{\→}{r_1}-\stackrel{\→}{r_2}|}^2)L_l^0\left(\frac{w_0^2}{2{\mathrm{\λ}}^2{f}_1^2}{|\stackrel{\→}{r_1}-\stackrel{\→}{r_2}|}^2\right)---\left(4\right)$

The partially coherent Gaussian beam of contrast Laguerre-Gauss association, is easy to obtain following relationship:

$I_1=\frac{2{\mathrm{\π}}^3{w}_0^2{f}_1^2{I}_0}{k^2}\mathrm{\Γ}(l+1)$ $w_1={\mathrm{\σ}}_{f_1}/\sqrt{2}$ $\mathrm{\σ}=\frac{\mathrm{\λ}{f}_1}{w_0}---\left(5\right)$

Wherein: w ₁the amount that target beam spot size is relevant, I ₁be the amount that the total light intensity of target beam is relevant, σ is the lateral coherence length of target beam, and the light beam namely generated is the partially coherent Gaussian beam of Laguerre-Gauss association, and its correlation function is.

$g(r_1,r_2,0)=\frac{T(r_1,r_2)}{\sqrt{T(r_1,r_1)T(r_2,r_2)}}$

$=L_n\left[\frac{{(r_1-r_2)}^2}{2{\mathrm{\σ}}^2}\right]\exp [-\frac{{(r_1-r_2)}^2}{2{\mathrm{\σ}}^2}]---\left(6\right)$

Due to the dirigibility of computer hologram, so can produce by producing different holograms the Laguerre-Gaussian beam that different rank only has angle modulus, thus produce the partially coherent Gaussian beam of the Laguerre-Gauss association with different rank.

Technical scheme in the application is understood better in order to make those skilled in the art person, below in conjunction with the accompanying drawing in the embodiment of the present application, technical scheme in the embodiment of the present application is clearly and completely described, obviously, described embodiment is only some embodiments of the present application, instead of whole embodiments.Based on the embodiment in the application, those of ordinary skill in the art are not making the every other embodiment obtained under creative work prerequisite, all should belong to the scope of the application's protection.

The relative position of each optical device as shown in Figure 1.Radiation direction along the light source 1 produced places beam expander 2, successively by computer-controlled spatial light modulator 3, beam-shrinked mirror 4, rotating ground glass 5, lens 6 and gaussian filtering sheet 7; Gaussian filtering sheet 7 is close to after lens 6.

Light source 1 is preferably helium-neon laser.And then with beam expander 2, light beam is out expanded.Beam orthogonal after expanding incides transmissive spatial photomodulator 3.Spatial light modulator 3 is LC-2002 type transmissive spatial light modulator that German Holoeye produces, and resolution is 800 × 600, and the size of each pixel is 32 microns × 32 microns.Beam-shrinked mirror regulates spot size.The focal length of lens 6 is 400 millimeters.Gaussian filtering sheet.The partially coherent Gaussian beam generally speaking producing Laguerre-Gauss association divides three parts.First is produce the Laguerre Gaussian beam only having angle modulus, and second is the partial coherence light beam being converted into Laguerre-Gauss association, and the 3rd is the partially coherent Gaussian beam converting Laguerre-Gauss association to.

(1) Laguerre-Gaussian beam only having angle modulus is produced

The generation of the Laguerre-Gaussian beam of angle modulus is only had to have a lot of method.The present embodiment adopts the method for calculation holographic to produce the Laguerre Gaussian beam only having angle modulus.So-called calculation holographic method is exactly be loaded on certain equipment with Computer-generated Hologram, then shines on hologram with a branch of reference light, is exactly target beam from hologram light beam out.We load hologram by spatial light modulator under normal circumstances.

(2) the partial coherence light beam of Laguerre-Gauss association is converted into

After regulating spot size by beam-shrinked mirror 4, incide on rotating ground glass sheet, through the scattering of rotating ground glass sheet, the Laguerre Gao-Si light beam that makes to be concerned with completely is converted into the partial coherence light beam of Laguerre-Gauss association.

(3) partially coherent Gaussian beam of Laguerre-Gauss association is converted to

The partial coherence light beam of Laguerre-Gauss association produces Laguerre-Gauss through collimation lens 6 and associates partially coherent Gaussian beam after gaussian filtering sheet 7.

Consult Fig. 2, single order Laguerre Gauss associated diagram (theory calculate) that the embodiment of the present invention obtains.

Consult Fig. 3, quadravalence Laguerre Gauss associated diagram (theory calculate) that the embodiment of the present invention obtains.

In sum, the present invention proposes the partially coherent Gaussian beam experimental program of the generation Laguerre-Gauss association of simple possible.Calculation holographic, rotating ground glass generating portion coherent light beam and the technology of gaussian filtering sheet is utilized to realize the generation of the partially coherent Gaussian beam that Laguerre-Gauss associates.Easily can be produced the partially coherent Gaussian beam of the Laguerre-Gauss association of different rank by the present invention neatly, effectively promote the applied research in other respects of this light beam.Whole technical scheme is simple and have practicality widely, has important experiment and practical value.

To those skilled in the art, obviously the invention is not restricted to the details of above-mentioned one exemplary embodiment, and when not deviating from spirit of the present invention or essential characteristic, the present invention can be realized in other specific forms.Therefore, no matter from which point, all should embodiment be regarded as exemplary, and be nonrestrictive, scope of the present invention is limited by claims instead of above-mentioned explanation, and all changes be therefore intended in the implication of the equivalency by dropping on claim and scope are included in the present invention.Any Reference numeral in claim should be considered as the claim involved by limiting.

In addition, be to be understood that, although this instructions is described according to embodiment, but not each embodiment only comprises an independently technical scheme, this narrating mode of instructions is only for clarity sake, those skilled in the art should by instructions integrally, and the technical scheme in each embodiment also through appropriately combined, can form other embodiments that it will be appreciated by those skilled in the art that.

Claims (7)

1. produce a system for the partially coherent Gaussian beam of Laguerre-Gauss association, it is characterized in that, comprising:

Light source;

Beam expander, expands the light beam from described light source;

Spatial light modulator, changes into the light beam after expanding the Laguerre-Gaussian beam only having angle modulus;

Beam-shrinked mirror and rotatable frosted glass, only there is the spot size of the Laguerre-Gaussian beam of angle modulus after beam-shrinked mirror regulates, incide on frosted glass, through the scattering of frosted glass, the Laguerre Gao-Si light beam that makes to be concerned with completely is converted into the partial coherence light beam of Laguerre-Gauss association;

Lens, collimate the partial coherence light beam of Laguerre-Gauss association;

Gaussian filtering sheet, is Gaussian hot spot by the partial coherence light beam integer of the Laguerre-Gauss association after collimation, produces the partially coherent Gaussian beam of Laguerre-Gauss association.

2. the system of the partially coherent Gaussian beam of generation Laguerre-Gauss association according to claim 1, it is characterized in that, described light source is helium-neon laser.

3. the system of the partially coherent Gaussian beam of generation Laguerre-Gauss association according to claim 1, it is characterized in that, also comprise computing machine, the computed hologram of described Practical computer teaching is loaded in described spatial light modulator and forms calculation holographic grating, to produce the Laguerre-Gaussian beam only having angle modulus.

4. produce a method for the partially coherent Gaussian beam of Laguerre-Gauss association, it is characterized in that, comprising:

Step s1, the light beam from light source to be expanded;

Step s2, the light beam after expanding is changed into the Laguerre-Gaussian beam only having angle modulus;

Step s3, by only have the spot size of the Laguerre-Gaussian beam of angle modulus carry out contracting bundle adjustment, be then translated into Laguerre-Gauss association partial coherence light beam;

Step s4, to Laguerre-Gauss association partial coherence light beam collimate;

Step s5, the partial coherence light beam integer associated by the Laguerre-Gauss after collimation are Gaussian hot spot, produce the partially coherent Gaussian beam of Laguerre-Gauss association.

5. the method for the partially coherent Gaussian beam of generation Laguerre-Gauss association according to claim 4, is characterized in that, in described step s2, the light beam after expanding is changed into the Laguerre-Gaussian beam only having angle modulus by spatial light modulator.

6. the method for the partially coherent Gaussian beam of generation Laguerre-Gauss association according to claim 5, it is characterized in that, the computed hologram of Practical computer teaching is loaded in described spatial light modulator and forms calculation holographic grating, to produce the Laguerre-Gaussian beam only having angle modulus.

7. the method for the partially coherent Gaussian beam of generation Laguerre-Gauss association according to claim 4, it is characterized in that, in described step s3, by only there being the spot size of the Laguerre-Gaussian beam of angle modulus to carry out the adjustment of contracting bundle, be then translated into the partial coherence light beam of Laguerre-Gauss association by the scattering of frosted glass.