CN102967928B - The production method of the tight focal beam spot of a kind of post polarization vector light beam and device - Google Patents

Abstract

The invention discloses a kind of production method and device of the tight focal beam spot array of post polarization vector light beam that can rotate arbitrarily.According to prior art on the basis producing post polarization vector light beam, come the polarization direction of column spinner polarization vector light beam by allowing light beam by the method for two half-wave plates.Finally allow this light beam tightly be focused on by high-NA microcobjective again, thus obtain the focal beam spot of array.By rotating the second half-wave plate, the rotational speed of the spot array after focusing on can be controlled easily.The inventive method easily realizes, and apparatus structure is simple, is easy to adjustment, low cost of manufacture; Device stability is good, does not need the optical element that other are special.

Description

The production method of the tight focal beam spot of a kind of post polarization vector light beam and device

Technical field

The present invention relates to production method and the device of the tight focal beam spot array of post polarization vector light beam that can rotate arbitrarily of the production method of the tight focal beam spot array of post polarization vector light beam, particularly a kind of dynamic realtime.

Background technology

Laser optical tweezer, be that utilization laser is captured as technological means, a technology of maneuvering and control molecule, being an emerging front subject, is the cross discipline in conjunction with physics, biology, medical science equally.Light tweezer because of its vital movement to biological particle interference minimum, the cells survival environment that whole manipulation system relates to almost is equal to " natural " environment, the vital movement of biological particle complete reservation be can be changed and aseptic, not damaged, in real time dynamically manipulation realized, optical tweezer technology makes the life process of biomedical molecule or cell become artificially controlled simultaneously, arbitrary link in its vital movement artificially can be regulated, its individual behavior is studied.

China just explicitly points out the frontier science and technology of operation as country of gene and protein at " National Program for Medium-to Long-term Scientific and Technological Development (2006-2020) ", some cross disciplines and new branch of science is also listed in the important directions in fundamental research field simultaneously.

The principle of work of laser optical tweezer is that the gradient force utilizing distribution of light intensity spatial variations to be formed stably is captured in light intensity most strength, the i.e. focal position of light beam particulate, particulate just can be driven to move together, realize manipulating the precision of particulate when laser beam moves.If utilize the transmission of the orbital angular momentum of photon and spin angular momentum and captured particulate, the rotation to particulate can also be realized.For single beam Gauss light tweezer, when the Gauss light field action of a branch of high concentration is in a transparent particulate, when the refractive index of particulate is greater than the refractive index of surrounding medium, it is no matter the direction of propagation at light, or perpendicular in the plane of the direction of propagation, the gradient force that distribution of light intensity change is formed, to particle being pushed to place with a tight waist, forms three-dimensional optical potential well.So want to be strapped in light field potential well by particle-stabilised, laser beam height must be converged thus produce enough strong gradient force.This needs the microcobjective using high-NA usually, and hot spot light beam being tightly focused into wavelength magnitude realizes.

In recent years, post polarization vector light beam causes people and more and more pays close attention to.The optical field distribution of this light beam and polarization state distribution are all column symmetry about optical axis.Wherein, two the most special classes are exactly radial polarisation light and angle polarized light, the polarization state of this two classes light beam on xsect respectively radially with deflection directional spreding.Due to the polarization characteristic of post polarization vector light beam uniqueness, this kind of light beam is by having very unique tight focus characteristics after high numerical aperture lens.Such as, after radial polarisation light is tightly focused on by high-NA, the transverse electric field component that a hollow circle is symmetrical can be produced, and the Gaussian longitudinal component along optical axis direction that much better than and more much smaller than cross stream component, thus obtain a very little tight focal beam spot.After angle polarized light is tightly focused on by high numerical aperture lens, then the pure cross stream component that the circle that only generation one is hollow is symmetrical.The tight focus characteristics of these uniquenesses has very important using value in laser optical tweezer.Such as, radial polarisation light ratio linearly polarized light after assembling has larger gradient force, and there is not scattering force in the direction of the optical axis; And the angle polarized light after assembling can catch the little particulate of refractive index ratio surrounding medium.

The document tightly focused on by high numerical aperture lens for research post polarization vector light beam is very many.Researchers are by regulating and controlling the post polarization vector light beam of incidence thus reaching the tight object focusing on rear hot spot of regulation and control.Regulate and control the regulation and control of main amplitude, position regulates and controls mutually and coherence regulates and controls three kinds.Main employing inserts optical element to realize before high numerical aperture lens.Concrete optical element mainly contains the frosted glass plate etc. of annular pupil, amplitude filter, Binary photograph and rotation.By these control methods, shaping regulation and control can be carried out to the light spot shape after tight focusing, thus reach different application demands, such as, be focused into less hot spot to provide larger gradient force, thus more stable catch particulate; Produce the focal beam spot of special shape, thus catch dissimilar particulate.Further, researchers also utilize vortex position photo, make incident post polarization vector light beam with orbital angular momentum, thus reach the hot spot after focusing can the object of stably rotating particle.But it should be noted that profit is rotating particle in this way, when needs adjustment rotational speed, larger adjustment must be made to light path.

Summary of the invention

The object of the invention is production method and the device of the tight focal beam spot array of post polarization vector light beam that can rotate arbitrarily designing a kind of dynamic realtime.

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

The production method of the tight focal beam spot of a kind of post polarization vector light beam, the post polarization vector light beam produced is passed through the first half-wave plate, the second half-wave plate and microcobjective successively, obtain focal beam spot, rotate the rotational speed that the second half-wave plate controls described focal beam spot, definition polar coordinate system, the expression formula of described post polarization vector light beam is:

${\stackrel{r}{E}}_1(r,\mathrm{\φ},0)=\exp (-\frac{r^2}{w_0^2}){\left(\frac{2r^2}{w_0^2}\right)}^{(n+1)/2}{L}_p^{n+1}\left(\frac{2r^2}{w_0^2}\right)\[cos\left(n\mathrm{\φ}\right){\stackrel{r}{e}}_{\mathrm{\φ}}-\sin \left(n\mathrm{\φ}\right){\stackrel{r}{e}}_r\]$

Wherein, r and φ is radial direction under polar coordinate system and angle coordinate respectively, w ₀be the waist radius of post polarization vector light beam, be generally a millimeter magnitude, p and n+1 is the exponent number of Laguerre polynomials, is integer.Incident light beam wavelength generally selects visible-range, and objective focal length is generally at centimetres, and numerical aperture is close to 1.

Preferably, in the production method of the tight focal beam spot of above-mentioned post polarization vector light beam, described first half-wave plate and the second half-wave plate are identical half-wave plate and coaxial, and described first half-wave plate and the second half-wave plate are close to described microcobjective and are placed

Correspondingly, the invention also discloses the generation device of the tight focal beam spot of a kind of post polarization vector light beam, it is characterized in that, comprising:

Post polarization vector optical beam generating device, definition polar coordinate system, the expression formula of described post polarization vector light beam is:

${\stackrel{r}{E}}_1(r,\mathrm{\φ},0)=\exp (-\frac{r^2}{w_0^2}){\left(\frac{2r^2}{w_0^2}\right)}^{(n+1)/2}{L}_p^{n+1}\left(\frac{2r^2}{w_0^2}\right)\[cos\left(n\mathrm{\φ}\right){\stackrel{r}{e}}_{\mathrm{\φ}}-\sin \left(n\mathrm{\φ}\right){\stackrel{r}{e}}_r\]$

Wherein, r and φ is radial direction under polar coordinate system and angle coordinate respectively, w ₀be the waist radius of post polarization vector light beam, p and n+1 is the exponent number of Laguerre polynomials, is integer;

Along the first half-wave plate, the second half-wave plate and microcobjective that the radiation direction of described post polarization vector light beam sets gradually.

Preferably, in the generation device of the tight focal beam spot of above-mentioned post polarization vector light beam, described first half-wave plate and the second half-wave plate are identical half-wave plate and coaxial, and described first half-wave plate and the second half-wave plate are close to described microcobjective and are placed; The waist radius of described post polarization vector light beam is millimeter magnitude; The focal length of described microcobjective is at centimetres.

Compared with prior art, the present invention on the basis producing post polarization vector light beam, comes the polarization direction of column spinner polarization vector light beam by allowing light beam by the method for two half-wave plates according to prior art.Finally allow this light beam tightly be focused on by high-NA microcobjective again, thus obtain the focal beam spot of array.By rotating second half-wave plate, the rotational speed of the spot array after focusing on can be controlled easily.The inventive method easily realizes, and apparatus structure is simple, is easy to adjustment, low cost of manufacture; Device stability is good, does not need the optical element that other are special.

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.

It is the structural representation of the generation device of the tight focal beam spot of specific embodiment of the invention center pillar polarization vector light beam described in Fig. 1;

Fig. 2 produces the tight launching spot figure focusing on four spot arrays in the embodiment of the present invention 1;

Fig. 3 is that tight focusing four spot array of generation in the embodiment of the present invention 1 is with the second half-wave plate anglec of rotation hot spot rotation diagram;

Fig. 4 produces the tight launching spot figure focusing on six spot arrays in the embodiment of the present invention 2;

Fig. 5 is that tight focusing six spot array of generation in the embodiment of the present invention 2 is with the second half-wave plate anglec of rotation hot spot rotation diagram

Embodiment

The embodiment of the invention discloses a kind of production method and device of the tight focal beam spot array of post polarization vector light beam that can rotate arbitrarily of dynamic realtime, specific as follows:

(1) expression formula of the post polarization vector light beam in primary face is:

${\stackrel{r}{E}}_1(r,\mathrm{\φ},0)=\exp (-\frac{r^2}{w_0^2}){\left(\frac{2r^2}{w_0^2}\right)}^{(n+1)/2}{L}_p^{n+1}\left(\frac{2r^2}{w_0^2}\right)\[cos\left(n\mathrm{\φ}\right){\stackrel{r}{e}}_{\mathrm{\φ}}-\sin \left(n\mathrm{\φ}\right){\stackrel{r}{e}}_r\],$

Wherein, w ₀be the waist radius of light beam, p and n+1 is the exponent number of Laguerre polynomials.The high-order post polarization vector light beam of this complexity can be by the patent No.: the patent way of 200710191085.6 produces.

(2) vector formula is utilized with the expression formula of this incident beam can be expressed as:

$\stackrel{r}{E}(r,\mathrm{\φ},0)=\exp (-\frac{r^2}{w_0^2}){\left(\frac{2r^2}{w_0^2}\right)}^{(n+1)/2}{L}_p^{n+1}\left(\frac{2r^2}{w_0^2}\right)\{-\sin \[\left(n\mathrm{+1}\right)\mathrm{\φ}\]{\stackrel{r}{e}}_x+\cos \[\left(n\mathrm{+1}\right)\mathrm{\φ}\]{\stackrel{r}{e}}_y\},$

Therefore its polarization vector can be expressed as under rectangular coordinate system $\left[\begin{array}{c}-sin\[(n+1)\mathrm{\φ}\]\\ cos\[(n+1)\mathrm{\φ}\]\end{array}\right].$

(3) on the radiation direction of the light source along generation post polarization vector light, set gradually the first half-wave plate 10, its fast axle overlaps with y-axis, and its Jones matrix can be expressed as $\left[\begin{array}{cc}i& 0\\ 0& -i\end{array}\right],$ So, the polarization vector of light beam becomes

$\left[\begin{array}{cc}i& 0\\ 0& -i\end{array}\right]\left[\begin{array}{c}-sin\[(n+1)\mathrm{\φ}\]\\ cos\[(n+1)\mathrm{\φ}\]\end{array}\right]=\left[\begin{array}{c}-isin\[(n+1)\mathrm{\φ}\]\\ -icos\[(n+1)\mathrm{\φ}\]\end{array}\right].$

(4) allow light beam by the second half-wave plate 20 again, its fast axle becomes angle with x-axis direction the Jones matrix of this half-wave plate is:

Can obtain after abbreviation

So, the polarization vector of light beam becomes

As can be seen from the above equation, after two half-wave plates, the polarization direction of incident post polarization vector light beam have rotated angle.

(5) recycle vector formula, light beam expression formula represented under cylindrical coordinates:

(6) most relief light beam is tightly focused on by high-NA microcobjective 30, obtains tight focal beam spot array.According to the tight sine condition r=fsin θ focused on, substitute into above-mentioned light field expression formula, the apodizing function on focusing surface can be obtained:

According to tightly focusing on formula, in conjunction with integral formula

The light field expression formula after focusing on can be obtained:

Wherein, A is constant, and its size does not affect the Relative distribution of each point light intensity.α=arcsin (NA) is the maximum convergent angle of high-NA microcobjective.R _s, φ _s, z _sit is the cylindrical coordinates of observation point.The light distribution of focal beam spot is:

$\begin{array}{c}I(r_s,{\mathrm{\φ}}_s,z_s)=I_r(r_s,{\mathrm{\φ}}_s,z_s)+I_{\mathrm{\φ}}(r_s,{\mathrm{\φ}}_s,z_s)+I_z(r_s,{\mathrm{\φ}}_s,z_s)\\ =|E_r^{\left(s\right)}(r_s,{\mathrm{\φ}}_s,z_s){|}^2+|E_{\mathrm{\φ}}^{\left(s\right)}(r_s,{\mathrm{\φ}}_s,z_s){|}^2+|E_z^{\left(s\right)}(r_s,{\mathrm{\φ}}_s,z_s){|}^2\end{array}.$

As can be seen from the above equation, focal beam spot along with change and rotate.When the second half-wave plate 20 rotates during angle, focal beam spot rotates angle, namely the rotational speed of focal beam spot is second half-wave plate 20 rotational speed doubly.By controlling the rotational speed of the second half-wave plate 20, we can rotary-focusing hot spot arbitrarily.

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.

Embodiment one: the production method of can rotate arbitrarily four tight focal beam spot arrays

(1) expression formula of incident post polarization vector light beam is:

${\stackrel{r}{E}}_1(r,\mathrm{\φ},0)=\exp (-\frac{r^2}{w_0^2}){\left(\frac{2r^2}{w_0^2}\right)}^{(n+1)/2}{L}_p^{n+1}\left(\frac{2r^2}{w_0^2}\right)\[cos\left(n\mathrm{\φ}\right){\stackrel{r}{e}}_{\mathrm{\φ}}-\sin \left(n\mathrm{\φ}\right){\stackrel{r}{e}}_r\]$

Wherein, waist radius elects w as ₀=2mm, light beam exponent number elects p=0 as, n=2.The wavelength of incident beam elects λ=632.8nm as.

As shown in Figure 2, in figure, arrow represents the polarization direction of this light beam aloft each point to the surface of intensity distribution of incident beam.As can be seen from the figure, the light distribution of the post polarization vector light beam of this incidence is that open circles is symmetrical.

(2) each optical device placement location as shown in Figure 1.The first half-wave plate 10, second half-wave plate 20 and high-NA microcobjective 30 is placed successively along incident ray direction.The quick shaft direction of the first half-wave plate 10 overlaps with y-axis, and the quick shaft direction of the second half-wave plate 20 and the angle of x-axis are the focal length parameter of high-NA microcobjective 30 is 1cm, and its numerical aperture is in free space 0.95.

After the post polarization vector light beam of incidence passes through the first half-wave plate 10 and the second half-wave plate 20 successively, its light field expression formula becomes:

This shows, the light distribution of this light beam does not change, but the polarization direction of spatial points have rotated angle.

(3) most relief is tightly focused on by high numerical value microcobjective by the post polarization vector light beam of two half-wave plates.Light field expression formula after focusing is:

Wherein, A is constant, and its size does not affect the Relative distribution of each point light intensity.α=arcsin (NA) is the maximum convergent angle of high-NA microcobjective.R _s, φ _s, z _sit is the cylindrical coordinates of observation point.The light distribution of focal beam spot is:

$\begin{array}{c}I(r_s,{\mathrm{\φ}}_s,z_s)=I_r(r_s,{\mathrm{\φ}}_s,z_s)+I_{\mathrm{\φ}}(r_s,{\mathrm{\φ}}_s,z_s)+I_z(r_s,{\mathrm{\φ}}_s,z_s)\\ =|E_r^{\left(s\right)}(r_s,{\mathrm{\φ}}_s,z_s){|}^2+|E_{\mathrm{\φ}}^{\left(s\right)}(r_s,{\mathrm{\φ}}_s,z_s){|}^2+|E_z^{\left(s\right)}(r_s,{\mathrm{\φ}}_s,z_s){|}^2\end{array}.$

After tight focusing, the light distribution on focal plane as shown in Figure 3.As can see from Figure 3, focal beam spot becomes 4 spot array distributions, and spot array can rotate along with the rotation of the second half-wave plate 20.The rotational speed of focal beam spot is identical with the rotational speed of half-wave plate.

Embodiment two: the production method of can rotate arbitrarily six tight focal beam spot arrays

(1) expression formula of incident post polarization vector light beam is:

${\stackrel{r}{E}}_1(r,\mathrm{\φ},0)=\exp (-\frac{r^2}{w_0^2}){\left(\frac{2r^2}{w_0^2}\right)}^{(n+1)/2}{L}_p^{n+1}\left(\frac{2r^2}{w_0^2}\right)\[cos\left(n\mathrm{\φ}\right){\stackrel{r}{e}}_{\mathrm{\φ}}-\sin \left(n\mathrm{\φ}\right){\stackrel{r}{e}}_r\]$

Wherein, waist radius elects w as ₀=2mm, light beam exponent number elects p=0 as, n=3.The wavelength of incident beam elects λ=632.8nm as.

As shown in Figure 4, in figure, arrow represents the polarization direction of this light beam aloft each point to the surface of intensity distribution of incident beam.As can be seen from Figure 4, light distribution and Fig. 2 of the post polarization vector light beam of this incidence are similar, but the polarisation distribution of spatial points is different.

(2) each optical device placement location as shown in Figure 1.The first half-wave plate 10, second half-wave plate 20 and high-NA microcobjective 30 is placed successively along incident ray direction.The quick shaft direction of the first half-wave plate 10 overlaps with y-axis, and the quick shaft direction of the second half-wave plate 20 and the angle of x-axis are the focal length parameter of high-NA microcobjective is 1cm, and its numerical aperture is in free space 0.95.

After the post polarization vector light beam of incidence passes through the first half-wave plate 10 and the second half-wave plate 20 successively, its light field expression formula becomes:

This shows, the light distribution of this light beam does not change, but the polarization direction of spatial points have rotated angle.

(3) most relief is tightly focused on by high numerical value microcobjective by the post polarization vector light beam of two half-wave plates.Light field expression formula after focusing is:

$L_p^{n+1}\left(\frac{2f^2{\sin }^2\mathrm{\θ}}{w_0^2}\right)J_n\left({\mathrm{kr}}_{s}sin\mathrm{\θ}\right)\exp \left({\mathrm{ikz}}_{s}cos\mathrm{\θ}\right)d\mathrm{\θ}$

Wherein, A is constant, and its size does not affect the Relative distribution of each point light intensity.α=arcsin (NA) is the maximum convergent angle of high-NA microcobjective.R _s, φ _s, z _sit is the cylindrical coordinates of observation point.The light distribution of focal beam spot is:

$\begin{array}{c}I(r_s,{\mathrm{\φ}}_s,z_s)=I_r(r_s,{\mathrm{\φ}}_s,z_s)+I_{\mathrm{\φ}}(r_s,{\mathrm{\φ}}_s,z_s)+I_z(r_s,{\mathrm{\φ}}_s,z_s)\\ =|E_r^{\left(s\right)}(r_s,{\mathrm{\φ}}_s,z_s){|}^2+|E_{\mathrm{\φ}}^{\left(s\right)}(r_s,{\mathrm{\φ}}_s,z_s){|}^2+|E_z^{\left(s\right)}(r_s,{\mathrm{\φ}}_s,z_s){|}^2\end{array}.$

After tight focusing, the light distribution on focal plane as shown in Figure 5.As can see from Figure 5, focal beam spot becomes 6 spot array distributions, and spot array can rotate along with the rotation of the second half-wave plate 20.The rotational speed of focal beam spot is 2/3 of the rotational speed of half-wave plate.

In sum, the present invention on the basis producing post polarization vector light beam, comes the polarization direction of column spinner polarization vector light beam by allowing light beam by the method for two half-wave plates according to prior art.Finally allow this light beam tightly be focused on by high-NA microcobjective again, thus obtain the focal beam spot of array.By rotating second half-wave plate, the rotational speed of the spot array after focusing on can be controlled easily.The inventive method easily realizes, and apparatus structure is simple, is easy to adjustment, low cost of manufacture; Device stability is good, does not need the optical element that other are special.

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 (4)

1. a production method for the tight focal beam spot of post polarization vector light beam, is characterized in that:

The post polarization vector light beam produced is passed through the first half-wave plate, the second half-wave plate and microcobjective successively, and obtain focal beam spot, wherein the quick shaft direction of the first half-wave plate overlaps with y-axis, and the quick shaft direction of the second half-wave plate and the angle of x-axis are

Rotate the rotational speed that the second half-wave plate controls described focal beam spot, definition polar coordinate system, the expression formula of described post polarization vector light beam is:

${\stackrel{r}{E}}_1(r,\mathrm{\φ},0)=\exp (-\frac{r^2}{w_0^2}){\left(\frac{2r^2}{w_0^2}\right)}^{(n+1)/2}{L}_p^{n+1}\left(\frac{2r^2}{w_0^2}\right)\[cos\left(n\mathrm{\φ}\right){\stackrel{r}{e}}_{\mathrm{\φ}}-\sin \left(n\mathrm{\φ}\right){\stackrel{r}{e}}_r\]$

Wherein, r and φ is radial direction under polar coordinate system and angle coordinate respectively, w ₀be the waist radius of post polarization vector light beam, p and n+1 is the exponent number of Laguerre polynomials, is integer; Waist radius elects w as ₀=2mm, light beam exponent number elects p=0 as, n=2 or n=3, and the wavelength of incident beam elects λ=632.8nm as;

The focal length parameter of described microcobjective is 1cm, and its numerical aperture is in free space 0.95;

The light distribution of described focal beam spot is:

$\begin{array}{c}I(r_s,{\mathrm{\φ}}_s,z_s)=I_r(r_s,{\mathrm{\φ}}_s,z_s)+I_{\mathrm{\φ}}(r_s,{\mathrm{\φ}}_s,z_s)+I_z(r_s,{\mathrm{\φ}}_s,z_s)\\ =|E_r^{\left(s\right)}\left(r_s,{\mathrm{\φ}}_s,z_s\right){|}^2+|E_{\mathrm{\φ}}^{\left(s\right)}\left(r_s,{\mathrm{\φ}}_s,z_s\right){|}^2+|E_z^{\left(s\right)}\left(r_s,{\mathrm{\φ}}_s,z_s\right){|}^2\end{array},$

Wherein, described r _s, φ _s, z _sthe cylindrical coordinates of observation point, described in it is the light field expression formula after focusing on;

Described focal beam spot along with change and rotate, when second half-wave plate rotate during angle, focal beam spot rotates angle, namely the rotational speed of focal beam spot is the second half-wave plate rotational speed doubly.

2. the production method of the tight focal beam spot of post polarization vector light beam according to claim 1, it is characterized in that: described first half-wave plate and the second half-wave plate are identical half-wave plate and coaxial, described first half-wave plate and the second half-wave plate are close to described microcobjective and are placed.

3. a generation device for the tight focal beam spot of post polarization vector light beam, is characterized in that, comprising:

Post polarization vector optical beam generating device, definition polar coordinate system, the expression formula of described post polarization vector light beam is:

${\stackrel{r}{E}}_1(r,\mathrm{\φ},0)=\exp (-\frac{r^2}{w_0^2}){\left(\frac{2r^2}{w_0^2}\right)}^{(n+1)/2}{L}_p^{n+1}\left(\frac{2r^2}{w_0^2}\right)\[cos\left(n\mathrm{\φ}\right){\stackrel{r}{e}}_{\mathrm{\φ}}-\sin \left(n\mathrm{\φ}\right){\stackrel{r}{e}}_r\]$

Wherein, r and φ is radial direction under polar coordinate system and angle coordinate respectively, w ₀be the waist radius of post polarization vector light beam, p and n+1 is the exponent number of Laguerre polynomials, is integer;

Along the first half-wave plate, the second half-wave plate and microcobjective that the radiation direction of described post polarization vector light beam sets gradually, wherein the quick shaft direction of the first half-wave plate overlaps with y-axis, and the quick shaft direction of the second half-wave plate and the angle of x-axis are

Waist radius elects w as ₀=2mm, light beam exponent number elects p=0 as, n=2 or n=3, and the wavelength of incident beam elects λ=632.8nm as;

The focal length parameter of described microcobjective is 1cm, and its numerical aperture is in free space 0.95;

The light distribution of described focal beam spot is:

$\begin{array}{c}I(r_s,{\mathrm{\φ}}_s,z_s)=I_r(r_s,{\mathrm{\φ}}_s,z_s)+I_{\mathrm{\φ}}(r_s,{\mathrm{\φ}}_s,z_s)+I_z(r_s,{\mathrm{\φ}}_s,z_s)\\ =|E_r^{\left(s\right)}\left(r_s,{\mathrm{\φ}}_s,z_s\right){|}^2+|E_{\mathrm{\φ}}^{\left(s\right)}\left(r_s,{\mathrm{\φ}}_s,z_s\right){|}^2+|E_z^{\left(s\right)}\left(r_s,{\mathrm{\φ}}_s,z_s\right){|}^2\end{array},$

Wherein, described r _s, φ _s, z _sthe cylindrical coordinates of observation point, described in it is the light field expression formula after focusing on;

Described focal beam spot along with change and rotate, when second half-wave plate rotate during angle, focal beam spot rotates angle, namely the rotational speed of focal beam spot is the second half-wave plate rotational speed doubly.

4. the generation device of the tight focal beam spot of post polarization vector light beam according to claim 3, it is characterized in that: described first half-wave plate and the second half-wave plate are identical half-wave plate and coaxial, described first half-wave plate and the second half-wave plate are close to described microcobjective and are placed.