CN110632761A - Partially coherent beam splitter, working method and optical device - Google Patents

Abstract

The present disclosure provides a partially coherent beam splitter, a working method, and an optical device, including a first lens, a second lens, and a phase plate, the first lens and the second lens constitute an optical 4f system, and the phase plate is set In the middle position between the first lens and the second lens, the number, distribution form and sub-beam spacing of the split sub-beams can be controlled by adjusting the parameters of the phase plate; this disclosure can flexibly split any incident partial coherent beams, using the The equipment is simple, the cost is low, and it is easy to build. The quality of the split beam produced is high, and it can be applied to the incident light with high power. It has broad application prospects in the fields of industry, scientific research, national defense and military affairs.

Description

Partially coherent beam splitter, working method and optical device

technical field

The present disclosure relates to the technical field of optical devices, in particular to a partially coherent beam splitter, a working method and an optical device.

Background technique

The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.

The beam splitter (Beam Splitter, BS) is the most basic device in the laboratory. The most common BS is a cubic crystal that is glued together by two triangular prisms through polyester, epoxy resin or polyurethane adhesives. The beam of light is split into two beams. This type of beam splitter is generally divided into two types: one is the polarization-dependent beam splitter (PBS), which divides the incident beam into a transmitted beam and a reflected beam, and the polarization directions of the outgoing beams And the transmission direction are perpendicular to each other, the most common PBS are Nicol prism, Glan prism, Wollaston prism and so on. The other is a polarization-independent beam splitter, which is still bonded by two triangular prisms, and the contact surface is coated with a thin film of metal material. By controlling the thickness of the film, the light incident at 45° and not absorbed by the coating Partial transmission and partial reflection occur, and the incident beam can be split into two beams whose transmission directions are perpendicular to each other.

All the real light beams in nature must have certain fluctuations in their amplitude, and the light spectrum has a certain width, which will lead to the fact that idealized completely coherent light and completely incoherent light do not really exist, so the current contact Strictly speaking, all beams are called partially coherent beams, whose coherence is between fully coherent and completely incoherent. The research results show that: compared with fully coherent beams, partially coherent beams have unique advantages in many practical applications. For example, partially coherent beams have anti-disturbance effects during transmission in complex environments; the reduction of coherence will lead to more uniform beams. It has important applications in the heat treatment of materials. In addition, by adjusting the coherence of the partially coherent beam source, the transmission properties of the beam can be adjusted, which has important applications in optical communication, particle capture, imaging, etc.

The inventors of the present disclosure found in the research that the following problems generally exist in the existing BS: (1) the incident beam can only be divided into two beams, and the number and distribution of the beams cannot be controlled; (2) as the laser beam In the field of application, array (multiple) beams have important applications in confocal microscopic imaging, multi-particle capture, optical communication multiplex technology, real-time three-dimensional imaging, human blood flow velocity measurement, etc. However, the current beam splitter after beam splitting The transmission directions of the two beams can only be orthogonal, resulting in an uncompact optical path structure and unable to meet the control requirements for the number, distribution and spacing of the split beams.

Contents of the invention

In order to solve the deficiencies of the prior art, the present disclosure provides a partially coherent beam splitter, a working method and an optical device, which have a simple structure and can split any partially coherent beam, and the number, distribution and The spacing can be flexibly adjusted.

In order to achieve the above purpose, the present disclosure adopts the following technical solutions:

In a first aspect, the present disclosure provides a partially coherent beam splitter;

A partially coherent beam splitter comprising a first lens, a second lens and a phase plate, the first lens and the second lens constitute an optical 4f system, and the phase plate is arranged in the middle of the first lens and the second lens By adjusting the parameters of the phase plate, the number, distribution and spacing of sub-beams can be controlled.

As some possible implementation manners, the focal lengths of the first lens and the second lens are both f, the front focal plane of the first lens is an incident light source plane, and the rear focal plane of the second lens is a receiving plane.

As a further limitation, the cross density function of any partially coherent beam at the incident light source surface is W(r ₁ , r ₂ ), after the beam passes through the first lens, the phase plate and the second lens, it is The cross spectral density function of is:

W(ρ ₁ ,ρ ₂ )＝∫W(r ₁ ,r ₂ )h ^* (r ₁ ,ρ ₁ )h(r ₂ ,ρ ₂ )d ² r ₁ d ² r ₂

The vectors r ₁ =(x ₁ ,y ₁ ), r ₂ =(x ₂ ,y ₂ ) and ρ ₁ =(ρ _x1 ,ρ _y1 ), ρ ₂ =(ρ _x2 ,ρ _y2 ) represent the incident light source surface respectively and the vector coordinates of any two points on the receiving surface, ∫∫d ² r ₁ d ² r ₂ represents the multiple integral of the integrand, h(r ₁ ,ρ ₁ ) and h(r ₂ ,ρ ₂ ) are the optical The response function of the system, * stands for complex conjugate.

As a further limitation, the response function of the optical system composed of the first lens, the phase plate and the second lens is:

k=2π/λ is the wave number, λ is the wavelength of the incident light source, ξ=(ξ _x ,ξ _y ) represents the vector coordinates at the frequency plane where the phase plate is located, and P(ξ) is the phase function corresponding to the phase plate.

As a further limitation, the phase function of the phase plate is:

Wherein, i is an imaginary number symbol, satisfying i ² =-1, a _n , b _n and M, and N is a parameter of the phase plate.

By adjusting the values of the constants a _n and b _n , the spacing of the split sub-beams can be adjusted. N and M are the number of horizontal and vertical sub-beams after beam splitting, and the beams obtained at the receiving surface are the light intensity and coherence The degrees are distributed in an N×M array.

As a further limitation, combining the phase function of the phase plate with the response function of the optical system, the specific response function of the optical system is obtained as:

where δ is the Dirac function.

As a further limitation, the phase function of the phase plate, the response function of the optical system and the cross spectral density function at the receiving surface of the second lens are combined, and the sampling property of the delta function is used to obtain the The actual cross-spectral density function is:

As a further limitation, calculate the light intensity and coherence of each sub-beam;

Among them, let ρ ₁ =ρ ₂ =ρ to obtain the light intensity at point ρ as:

I(ρ)=W(ρ,ρ)

The degree of coherence between two points ρ ₁ and ρ ₂ is:

In the second aspect, the present disclosure provides a working method of a partially coherent beam splitter, using the partially coherent beam splitter described in the present disclosure, the steps are as follows:

establishing a partially coherent beam splitter through a first lens, a phase plate, and a second lens;

By setting the parameters N and M in the phase function of the phase plate to determine the number of sub-beams in the horizontal and vertical directions and the distribution form of the sub-beams after beam splitting;

After the N and M parameters are determined, the control of the sub-beam spacing of the beam splitting is realized by adjusting the values of the constants a _n and b _n .

In a third aspect, the present disclosure provides an optical device, including the partially coherent beam splitter described in the present disclosure.

Compared with the prior art, the beneficial effects of the present disclosure are:

1. The partially coherent beam flexible beam splitter described in this disclosure can flexibly split any incident partially coherent beam, and adjust the number, distribution form and distribution distance of the beams by changing the parameters of the phase plate.

2. The partial coherent beam flexible beam splitter described in this disclosure adopts simple equipment, low cost, easy to build, and the quality of the generated beam split is high, and can be applied to incident light with relatively high power. It is used in industry, scientific research and national defense military and other fields have broad application prospects.

Description of drawings

FIG. 1 is a schematic structural diagram of a partially coherent beam splitter according to Embodiment 1 of the present disclosure.

Figure 2(a) and Figure 2(b) are the light intensity distribution diagram and coherence distribution diagram of the Gaussian Shell mode beam at the incident light source plane, respectively.

FIG. 3( a1 ) is a phase distribution diagram of the phase plate when N=M=3 in Embodiment 1 of the present disclosure.

FIG. 3( b1 ) and FIG. 3( c1 ) are respectively the light intensity distribution diagram and the coherence distribution diagram of the light beam obtained on the receiving surface when N=M=3 in Embodiment 1 of the present disclosure.

Figure 3(a2) shows N=5, M=3, a ₁ =-2×10 ⁵ m ^-1 , a ₂ =-10 ⁵ m ^-1 , a ₃ =0m ^-1 , a in Example 1 of the present disclosure. Phase distribution of the phase plate when ₄ = 10 ⁵ m ^-1 , a ₅ = 2×10 ⁵ m ^-1 , b ₁ = -10 ⁵ m ^-1 , b ₂ = 0m ^-1 , b ₃ = 10 ⁵ m ^-1 picture.

Figure 3(a3) shows N=5, M=5, a ₁ =b1=-2×10 ⁵ m ^-1 , a ₂ =b2=-10 ⁵ m ^-1 , a ₃ =b3 in Example 1 of the present disclosure =0m ^-1 , a ₄ =b4=10 ⁵ m ^-1 , a ₅ =b5=2×10 ⁵ m ^-1 phase distribution diagram of the phase plate.

Figure 3(b2) and Figure (c2) are N=5, M=3, a ₁ =-2×10 ⁵ m ^-1 , a ₂ =-10 ⁵ m ^-1 , a ₃ = 0m ^-1 , a ₄ = 10 ⁵ m ^-1 , a ₅ = 2×10 ⁵ m ^-1 , b ₁ = -10 ⁵ m ^-1 , b ₂ = 0m ^-1 , b ₃ = 10 ⁵ m ^-1 The light intensity distribution diagram and the coherence distribution diagram of the light beam obtained on the receiving surface.

Figure 3(b3) and Figure (c3) show N=5, M=5, a ₁ =b1=-2×10 ⁵ m ^-1 , a ₂ =b2=-10 ⁵ m ^-1 in Example 1 of the present disclosure , a ₃ =b3=0m ^-1 , a ₄ =b4=10 ⁵ m ^-1 , a ₅ =b5=2×10 ⁵ m ^-1 the light intensity distribution and coherence distribution of the light beam obtained on the receiving surface.

Fig. 4(a) and Fig. 4(b) are respectively the light intensity distribution diagram and the coherence distribution diagram of the Gaussian Schell mode beam on the receiving surface after being split by the beam splitter in Embodiment 1 of the present disclosure.

Fig. 5(a1) and Fig. 5(b1) are the light intensity distribution diagram and the coherence distribution diagram of the partially coherent elegant Hermegaussian beam in Embodiment 1 of the present disclosure.

Fig. 5(a2) and Fig. 5(b2) are diagrams of light intensity distribution and coherence distribution of the Hermitian-Gaussian correlated Sher mode beam in Embodiment 1 of the present disclosure.

Fig. 6(a1) and Fig. 6(b1) are the light intensity distribution diagram and the coherence distribution diagram of the partially coherent elegant Hermitian Gaussian beam split by the beam splitter in Embodiment 1 of the present disclosure, respectively.

Fig. 6(a2) and Fig. 6(b2) are respectively the light intensity distribution diagram and the coherence distribution diagram of the Hermitian-Gaussian correlated Sher mode beam split by the beam splitter in Embodiment 1 of the present disclosure.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the present disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

It should be noted that the terminology used herein is only for describing specific embodiments, and is not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

Example 1:

As shown in FIG. 1 , Embodiment 1 of the present disclosure provides a partially coherent beam splitter, including a first lens, a second lens, and a phase plate, the first lens and the second lens constitute an optical 4f system, and the The phase plate is arranged in the middle of the first lens and the second lens, and the number, distribution form and spacing of the sub-beams of the split beams can be controlled by adjusting the parameters of the phase plate.

The focal lengths of the first lens and the second lens are both f, the front focal plane of the first lens is an incident light source plane, and the rear focal plane of the second lens is a receiving plane.

In the space-frequency domain, the second-order statistical properties of partially coherent beams can be described by the cross spectral density function. The cross density function of any partially coherent beam at the incident light source surface is W(r ₁ ,r ₂ ). After the lens, the phase plate and the second lens, the cross spectral density function at the receiving surface of the second lens is:

W(ρ ₁ ,ρ ₂ )＝∫W(r ₁ ,r ₂ )h ^* (r ₁ ,ρ ₁ )h(r ₂ ,ρ ₂ )d ² r ₁ d ² r ₂ (1)

The vectors r ₁ =(x ₁ ,y ₁ ), r ₂ =(x ₂ ,y ₂ ) and ρ ₁ =(ρ _x1 ,ρ _y1 ), ρ ₂ =(ρ _x2 ,ρ _y2 ) represent the incident light source surface respectively and the vector coordinates of any two points on the receiving surface, ∫∫d ² r ₁ d ² r ₂ represents the multiple integral of the integrand, h(r ₁ ,ρ ₁ ) and h(r ₂ ,ρ ₂ ) are the optical The response function of the system, * stands for complex conjugate.

The response function of the optical system composed of the first lens, phase plate and second lens can be described as:

Among them, k=2π/λ is the wave number, λ is the wavelength of the incident light source, ξ=(ξ _x ,ξ _y ) indicates the vector coordinates of the phase plate at the frequency plane, and P(ξ) is the phase function corresponding to the phase plate.

In order to realize the beam splitting effect here, define: the phase function of described phase plate is:

Among them, i is an imaginary number symbol, satisfying i ² =-1, a _n , b _n and M, N is the parameter of the phase plate, and the sub-beam spacing of the beam splitting is realized by adjusting the values of the constants a _n and b _n N and M are respectively the number of horizontal and vertical sub-beams after beam splitting, and the beams obtained on the receiving surface are distributed in an array with both light intensity and coherence of N×M.

Combining the phase function of the phase plate (Formula 3) with the response function of the optical system (Formula 2), the specific response function of the optical system is obtained as:

where δ is the Dirac function.

Combining the phase function of the phase plate (Equation 3), the response function of the optical system (Equation 2) and the cross-spectral density function (Equation 1) at the receiving surface of the second lens, using the sampling property of the delta function, the second The actual cross-spectral density function at the receiving face of the lens is:

By the actual cross spectral density function (formula 5) at the receiving surface, the light intensity and coherence of each sub-beam sub-beam are calculated;

Among them, let ρ ₁ =ρ ₂ =ρ to obtain the light intensity at point ρ as:

I(ρ)=W(ρ,ρ) (6)

The degree of coherence between two points ρ ₁ and ρ ₂ is:

The following example illustrates:

For the incident beam selected as a Gaussian Schell mode (GSM) laser beam with a wavelength of λ=632nm, the cross spectral density is:

Wherein, the spot width ω ₀ =0.5 mm, and the coherence width σ ₀ =0.5 mm. Figure 2(a) and Figure 2(b) are the light intensity distribution diagram and coherence distribution diagram of the Gaussian Shell mode beam at the incident source plane, respectively. Also the focal length of the thin lens is f=400mm. As for the phase function corresponding to the phase plate (see formula (3)), N=M=3, a ₁ =b ₁ =-10 ⁵ m ^-1 , a ₂ =b ₂ =0m ^-1 , a ₃ = b ₃ =10 ⁵ m ^-1 , and its phase distribution is shown in Fig. 3(a1).

After the Gaussian Schell mode beam passes through the beam splitter described in this embodiment, an array distribution of 3×3 light intensity and coherence is obtained on the receiving surface, and the light intensity distribution is shown in Figure 3 (b1), and the coherence distribution is shown in Figure 3(b1). Fig. 3(c1), compared with Fig. 2(a) and (b) respectively, it is found that each beam after beam splitting is still an independent Gaussian Schell mode beam, so the beam splitter described in this embodiment can indeed correct the incident light Perform beam splitting.

In addition, the parameters of the phase plate are respectively changed to N=5, M=3, a ₁ =-2×10 ⁵ m ^-1 , a ₂ =-10 ⁵ m ^-1 , a ₃ =0m ^-1 , a ₄ =10 ⁵ m ^-1 , a ₅ =2×10 ⁵ m ^-1 , b ₁ =-10 ⁵ m ^-1 , b ₂ =0m ^-1 , b ₃ =10 ⁵ m ^-1 and N=5, M=5, a ₁ =b1=-2×10 ⁵ m ^-1 , a ₂ =b2=-10 ⁵ m ^-1 , a ₃ =b3=0m ^-1 , a ₄ =b4=10 ⁵ m ^-1 , a ₅ =b5 =2×10 ⁵ m ^-1 , other parameters remain unchanged, the phase distribution diagrams are shown in Fig. 3(a2) and Fig. 3(a3), and a 5×3 array beam and a 5×5 array are respectively obtained at the receiving surface The light beam, its light intensity distribution diagram and coherence degree distribution diagram are Fig. (b2), Fig. (b3) and Fig. (c2), Fig. (c3) respectively.

It can be seen that the beam splitter described in this embodiment can control the number and distribution form of the split beams by adjusting the phase plate parameters N and M.

Next, change the parameters a _n and b _n of the phase plate with N=M=3 as: a ₁ =b ₁ =-10 ⁵ m ^-1 , a ₂ =b ₂ =0, a ₃ =b ₃ =2 ×10 ⁵ m ^-1 , Figure 4(a) and Figure 4(b) are respectively the light intensity distribution diagram and the coherence distribution diagram of the Gaussian Shell mode beam on the receiving surface after being split by the beam splitter described in this embodiment, As can be seen from the figure, the lateral distribution spacing of the light intensity and coherence of the split beams has changed, and the distance d ₁₂ between the measured beams (1, 1) and the beams (1, 2) is 8mm, and the beams (1, 2) 2) The distance d ₂₃ from the beam (1, 3) is 4mm. Therefore, the beam splitter described in this embodiment can adjust the transverse and longitudinal sub-beam spacings respectively by adjusting the phase plate parameters a _n and b _n .

In order to verify that the beam splitting device can achieve flexible beam splitting for any partially coherent beam, a beam with a more complex structure is selected as the incident beam, which is respectively selected as a partially coherent elegant Hermegaussian beam (the light intensity and coherence are shown in Fig. 5(a1 ) and Figure 5(b1)) and Hermitian-Gaussian correlated Sher mode beams (intensity and coherence are shown in Figure 5(a2) and Figure 5(b2) respectively), where the cross-spectral density function of a partially coherent elegant Hermitian-Gaussian beam for:

The cross-spectral density function of a partially coherent Hermitian-Gaussian correlated Sher mode beam is:

Wherein H _n represents an n-order Hermitian polynomial, and here, n=m=2 is selected. In addition, the wavelength, spot width and coherence width of the two incident beams are the same as the corresponding parameters of the Gaussian Schell mode beam, and the focal length of the thin lens is still selected as f=400mm. The selection of phase plate parameters is the same as that in Figure 3(a1).

After the above-mentioned complex laser beam is split by the beam splitting device, its light intensity distribution diagram and coherence distribution diagram on the receiving surface are shown in Figure 6, where Figure 6(a1) and Figure 6(b1) are partial coherence elegant The light intensity distribution diagram and coherence distribution of the Hermitian-Gaussian beam after being split by the beam splitter described in this embodiment, Fig. 6 (a2) and Fig. 6 (b2) respectively show the Hermitian-Gaussian correlation Sher mode beam passed through this embodiment The light intensity distribution diagram and the coherence distribution diagram of the beam splitter after beam splitting can be seen from the comparison with FIG. 5 that the beam splitter described in this embodiment can indeed flexibly split complex laser beams.

In summary, the partially coherent beam flexible beam splitter described in this embodiment can flexibly split any incident partially coherent beam, and adjust the number, distribution form and distribution distance of the beam by changing the parameters of the phase plate, and The equipment used in this device is simple, low in cost, easy to build, and the quality of the split beam generated is high, which can be applied to incident light with high power, so it has broad application prospects in the fields of industry, scientific research, national defense and military affairs.

Example 2:

Embodiment 2 of the present disclosure provides a working method of a partially coherent beam splitter. Using the partially coherent beam splitter described in Embodiment 1 of the present disclosure, the steps are as follows:

establishing a partially coherent beam splitter through a first lens, a phase plate, and a second lens;

By setting the parameters N and M in the phase function of the phase plate to determine the number of sub-beams in the horizontal and vertical directions and the distribution form of the sub-beams after beam splitting;

After the N and M parameters are determined, the control of the sub-beam spacing of the beam splitting is realized by adjusting the values of the constants a _n and b _n .

Example 3:

Embodiment 3 of the present disclosure provides an optical device, including the partially coherent beam splitter described in Embodiment 1 of the present disclosure.

The above descriptions are only preferred embodiments of the present disclosure, and are not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included within the protection scope of the present disclosure.

Claims (10)

1. The partial dry beam splitter is characterized by comprising a first lens, a second lens and a phase plate, wherein the first lens and the second lens form an optical 4f system, the phase plate is arranged in the middle position of the first lens and the second lens, and the quantity, the distribution form and the sub-beam distance of the split sub-beams are controlled by adjusting the parameters of the phase plate.

2. The partially coherent beam splitter of claim 1, wherein the first and second lenses each have a focal length f, the first lens having a front focal plane that is an incident light source plane and the second lens having a back focal plane that is a receiving plane.

3. The partially coherent beam splitter of claim 2, wherein the cross-over density function of any partially coherent beam at the plane of the incident light source is W (r)₁,r₂) After the light beam passes through the first lens, the phase plate and the second lens, the cross spectral density function at the receiving surface of the second lens is as follows:

W(ρ₁,ρ₂)＝∫W(r₁,r₂)h^*(r₁,ρ₁)h(r₂,ρ₂)d²r₁d²r₂

wherein the vector r₁＝(x₁,y₁)、r₂＝(x₂,y₂) And ρ₁＝(ρ_x1,ρ_y1)、ρ₂＝(ρ_x2,ρ_y2) Denotes the vector coordinates of any two points of the incident light source surface and the receiving surface, respectively, [ integral ] d²r₁d²r₂Representing multiple integrals, h (r), of an integrand₁,ρ₁) And h (r)₂,ρ₂) The response function of the optical system represents the complex conjugate.

4. The partially coherent beam splitter of claim 3 wherein the response function of the optical system of the first lens, the phase plate and the second lens is:

k 2 pi/lambda is wave number, lambda is wavelength of incident light source, xi is xi_x,ξ_y) And P (xi) is a phase function corresponding to the phase plate.

5. The partially coherent beam splitter of claim 4, wherein the phase plate has a phase function of:

wherein i is an imaginary symbol satisfying i²＝-1，a_n、b_nAnd M, N are parameters of the phase plate.

By adjusting the constant a_nAnd b_nThe adjustment and control of the sub-beam distance of the beam splitting are realized by the value size, N and M are the number of the sub-beams in the transverse direction and the longitudinal direction of the beam splitting respectively, and the light beams obtained at the receiving surface are in array distribution with the light intensity and the coherence degree of NxM.

6. The partially coherent beam splitter of claim 5, wherein combining the phase function of the phase plate with the response function of the optical system results in a specific response function of the optical system that is:

where δ is the dirac function.

7. The partially coherent beam splitter of claim 6, wherein the phase function of the phase plate, the response function of the optical system, and the cross spectral density function at the receiving face of the second lens are combined to obtain an actual cross spectral density function at the receiving face of the second lens using a sampling property of the delta function as:

8. the partially coherent beam splitter of claim 7 in which the intensity and coherence of each split sub-beam is calculated;

let ρ be₁＝ρ₂The light intensity at the ρ point is obtained as ρ:

I(ρ)＝W(ρ,ρ)

ρ₁and ρ₂The degree of coherence between them is:

9. a method of operating a partially coherent beam splitter, using a partially coherent beam splitter as claimed in any one of claims 5 to 8, comprising the steps of:

creating a partially coherent beam splitter by a first lens, a phase plate and a second lens;

determining the number of transverse and longitudinal sub-beams after beam splitting and the distribution form of the sub-beams by setting parameters N and M in a phase function of the phase plate;

after the N and M parameters are determined, the constant a is adjusted_nAnd b_nThe value size realizes the control of the sub-beam spacing of the beam splitting.

10. An optical device comprising a partially coherent beam splitter according to any one of claims 1 to 8.

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