CN101430427A - Super-resolution photon screen - Google Patents

Abstract

The invention discloses a super resolution photon sieve. In the super resolution photon sieve, super resolution topological rings with equal apertures are integrated and etched on a common photon sieve, thus forming the topological board of a topological diffraction unit which is provided with a plurality of concentric ring belts and is combined by the common photon sieve and super resolution topological plates with equal apertures. In the invention, the circular hole diffraction mathematical processing tool of the super resolution technology is combined with the common photon sieve, thus realizing the repressed light intensity distribution of a main spot focused and diffracted by the photon sieve, namely realizing to repress the size of the main spot of the far field diffraction spot of a laser beam.

Description

Super-resolution photon screen

Technical field

The present invention relates to shaping technique field, laser beam corrugated, particularly a kind of super-resolution photon screen (superresolutionPhoton sieve (SPS)) that is used to realize laser beam in the compression of far field construction hot spot master spot.

Background technology

Development along with optical storage and three-dimensional imaging technology, the resolution, the so-called super-resolution of realization that improve traditional spherical lens imaging are the problems that people were concerned about always, therefore, compress for laser diffraction spot master spot by all means, and the energy of the other spot of inhibition is practical problem.Need energy focusing in the various instruments of center spot, all to need minimum main spot width and high main spot energy at beam shaping, microelectronics non-mask etching, light laser concentration of energy and other.

Thereby position phase modulation technique is to distribute mutually by the position that changes diffracted ray propagation cross section to realize the technology of expection diffraction intensity distribution.Be used to carry out the position mutually the method for modulation have multiple, the phase board that has fixed bit to distribute mutually, also the modulation sheet that can distribute mutually by the Control of Voltage position made of using light electric crystal.Because the utilization ratio of diffraction phase board luminous energy is the highest, so the most frequently used.

So-called photon screen is a kind of novel focal imaging diffraction optical device, utilizes it to focus on and imaging X-ray, and this is that the image optics device of general prism and glass material can't be realized.Photon screen is compared with traditional optical element Fresnel zone plate, has advantages such as high resolving power and inhibition second-order diffraction principal maximum, can improve the contrast of imaging.And, as novel diffraction element, advantages such as volume is little, in light weight, transreplication that it has.

Photon screen can be applied to high resolution microscope, astronomical telescope, photoetching of future generation, the controlled nuclear fusion of laser (ICF) research etc.

In calendar year 2001, Kipper et al. has proposed a kind of novel diffraction optical device first: photon screen, come grenz ray and EUV radiating light source are focused on and imaging [Kipp with it, L., Skibowski, M., Johnson, R.L., Berndt, R., Adelung, R., Harm, S., andSeemann, R.Sharper images by focusing soft X-ray with photonsieves.Nature[J], 2001.414,184-188.].

Gil and Menon in 2003 is reported in " beam flying photoetching " and (ZPAL) substitutes zone plate [Menon with photon screen in the system, R., Gil, D.Barbastathis, G., and Smith, H.I.Photon-sieve lithography[J] .Opt.Soc.Am.A, 2005.22 (2), 342-345.].

After this, because the superior performance that photon screen itself has, people are more and more interested in it, and it is applied to various new research fields, as EUV telescope around solar satellite, [S.Wang and X.Zhang.Terahertz tomographic imagingwith a Fresnel lens[J] .Opt.Photon.2002.News 13,59 such as THZ ripple holography].

Photon screen (Photon Sieve, PS) be the diffraction optical elements of on the Fresnel zone ring, making a large amount of transparent micropores that suitably distribute with different radii (Diffraction OpticalElement, DOE).

Photon screen has good application in the focusing of grenz ray, extreme ultraviolet line and imaging, can be applicable to fields such as high resolving power microscopy, spectroscopy, photoetching of future generation.Replace fresnel's zone plate Fresnel zone plate (FZP) that grenz ray is focused on and imaging with photon screen (PS), can obtain higher resolution, reduce requirement the photoetching technique manufacture craft.But the hot spot that photon screen focuses on can be done further compression.

Super resolution technology is a technology of being furtherd investigate.The core of super resolution technology is to realize the central diffraction disk less than Airy disk by the aperture transmittance function that changes entrance pupil (modulation mutually of amplitude or position).[referring to Opt.Lett, T.R.M.Sales and G.M.Morris, 22, pp.582-584,1997].

What super resolution technology was concerned about is the size of center zero level spectrum point, and energy distributions ratio situation between non-zero spectrum point is not considered.But the circular aperture often that super-resolution is handled, therefore, super resolution technology provides the mathematics manipulation instrument of relevant aperture and annulus aperture light diffraction.Super resolution technology provides the instrument of describing central main spot compression to us.They are these tal fibres than (Strehl ratio) and the first zero than (first zero).

This tal fibre is than being defined as the ratio that main spot energy accounts for the diffractional field gross energy, the first zero than be defined as the main spot and the diffraction first order big between ratio between the minimum of diffractional field energy.

Summary of the invention

(1) technical matters that will solve

In view of this, fundamental purpose of the present invention is to provide a kind of super-resolution photon screen, with the recompression of the main spot size that realizes laser beam far field construction spot.

(2) technical scheme

For achieving the above object, the invention provides a kind of super-resolution photon screen, this super-resolution photon screen is the super-resolution position photo of integrated etching equal aperture on common photon screen sheet, thereby forms by the synthetic position that a plurality of concentric endless belt are arranged of common photon screen and the equal aperture super-resolution position photo phase board of diffraction element mutually.

In the such scheme, the size of described super-resolution position photo is identical with corresponding photon screen outermost annular aperture, the position of endless belt be distributed in mutually in the same annulus the position mutually value be identical.

In the such scheme, the super-resolution position photo of equal aperture is two rings or three ring super-resolution position photos, and wherein the design parameter of earrings two-value position photo is: a=0.34, φ ₁=0, φ ₂=π, the design parameter of three ring two-value position photos is: a=0.09, b=0.36, φ ₁=0.9 π, φ ₂=0, φ ₃=0.9 π, the design parameter of the many-valued position photo of three rings is a=0.09, b=0.36, φ ₁=0, φ ₂=0.06 π, φ ₃=0.86 π; A, b are the normalization radius of each ring, φ ₁, φ ₂, φ ₃Radius for each endless belt.Two rings and three encircle the design constraint that encircles mutually the super-resolution positions: the first zero than the situation of G≤0.8 under this tal fibre maximize than S.

(3) beneficial effect

Super-resolution photon screen provided by the invention, exactly by being combined into same position photo with common photon screen with the super-resolution two ring three ring position photos in aperture, make that to form center master's spot in the far field by its collimation parallel laser littler than center master's spot of common Fresnel zone plate diffraction, but the optical field distribution that energy does not significantly reduce.The present invention combines the circular hole diffraction mathematics manipulation instrument of super resolution technology and common photon screen, realized that photon screen focuses on the light distribution of the main spot recompression of diffraction, promptly realized the recompression of the main spot size of laser beam far field construction spot, this be traditional photon screen can't realize.This also is the content that traditional super resolution technology is not studied.

Description of drawings

Fig. 1 (a) is 50 common ring photon screen synoptic diagram;

Fig. 1 (b) expression 2 ring two-value super-resolution photon screen synoptic diagram;

Fig. 1 (c) expression 3 ring two-value super-resolution photon screen synoptic diagram;

The many-valued super-resolution photon screen synoptic diagram of Fig. 1 (d) expression 3 rings;

Fig. 2 (a) is common circular aperture synoptic diagram;

Fig. 2 (b) expression 2 ring two-value super-resolution position photo synoptic diagram;

Fig. 2 (c) expression 3 ring two-value super-resolution position photo synoptic diagram;

The many-valued super-resolution position photo synoptic diagram of Fig. 2 (d) expression 3 rings;

Fig. 3 represents the normalized intensity function synoptic diagram of the super-resolution light distribution that three kinds of super-resolution position photos and circular aperture form in far diffraction field;

Fig. 4 represents the distribution plan of the spot intensity that common photon screen and three kinds of super-resolution photon screens form in far diffraction field;

Fig. 5 represents the experiment pick-up unit synoptic diagram of super-resolution photon screen of the present invention.

Embodiment

For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.

Super-resolution photon screen is a kind of novel diffraction optics phase part, i.e. phase board.This phase board is positioned over before or after the diffraction limit lens, and laser beam far field construction hot spot spectrum light intensities at different levels are revised, and realizes the diffraction center diffraction spot littler than the diffraction center spot of common photon screen.Super-resolution photon screen of the present invention is a kind of on transparent medium, make common photon screen earlier, the super-resolution position of integrated etching equal aperture is encircled mutually on photon screen then, the parameter that the super-resolution position is encircled is mutually provided by design, and the super-resolution position of final photon screen and equal aperture is encircled the phase board of the position phase diffraction element that is integrated into a plurality of concentric endless belt mutually.So-called endless belt is meant that it is donut that the position of phase board distributes mutually, and the position that equal aperture the is represented described super-resolution position photo radius of the outer shroud of outer shroud radius and photon screen of ring mutually is identical.

The present invention has provided the project organization and the parameters optimization of three kinds of super-resolution photon screens in the following embodiments, and has carried out relevant simulated experiment.Experimental verification adopt super-resolution photon screen can realize the further compression of laser beam far field main spot.The technology of the present invention can be used for beam shaping, microelectronics non-mask etching, light laser concentration of energy and other needs energy focusing in the various instruments of center spot.

This super-resolution photon screen provided by the invention, be a kind of on transparent medium, make common photon screen earlier, the super-resolution position of integrated etching equal aperture is encircled mutually on photon screen then, the parameter that the super-resolution position is encircled is mutually provided by design, and the super-resolution position of final photon screen and equal aperture is encircled the phase board of the position phase diffraction element that is integrated into a plurality of concentric endless belt mutually.Wherein the design parameter of two ring two-value super-resolution position photos is: a=0.34, φ ₁=0, φ ₂=π, the design parameter of three ring two-value super-resolution position photos is: a=0.09, b=0.36, φ ₁=0.9 π, φ ₂=0, φ ₃=0.9 π, the design parameter of the many-valued super-resolution position photo of three rings is a=0.09, b=0.36, φ ₁=0, φ ₂=0.06 π, φ ₃=0.86 π.In the above-mentioned parameter, a, b are the normalization radius of each ring, φ ₁φ ₂φ ₃Radius for each endless belt.

Fig. 1 is the synoptic diagram of the 50 ring super-resolution photon screens of one of super-resolution photon screen embodiment of the present invention.Fig. 1 (a) is 50 common ring photon screen synoptic diagram; (b) be 2 ring two-value super-resolution photon screen synoptic diagram; (c) be 3 ring two-value super-resolution photon screen synoptic diagram; (d) be the many-valued super-resolution photon screen synoptic diagram of 3 rings.As seen from the figure, super-resolution photon screen of the present invention is a kind of on the basis of the common photon screen of elder generation's making on the transparent medium, and three of the etching equal aperture kinds of super-resolution position photos form three kinds of super-resolution photon screens again.

The super-resolution photon screen characterising parameter has:

1) this tal fibre ratio of super-resolution photon screen: the coherent light of expression collimation passes through circular ring type photon screen, in the diffractional field that is produced, and the energy ratio of main spot and total diffractional field.Ratio is high more, illustrates that the energy of main spot gathering is many more.

2) first zero of super-resolution photon screen ratio: the first zero is minimizing position between the main spot and first diffraction maximum, and the first zero is than the ratio of the first zero that is defined as super-resolution photon screen and the common photon screen first zero.Ratio is 1, illustrates that two diffraction master spot chassis sizes are the same.Ratio is greater than 1, and main spot size expands, and ratio is less than 1, and main spot size is compressed.

In a preferred embodiment of the present invention, above-mentioned two rings and three encircle the design constraint that encircles mutually the super-resolution positions and are: the first zero than the situation of G≤0.8 under this tal fibre maximize than S.

By the conclusion of diffraction optics angular spectrum as can be known:

Be located at and introduce an infinitely-great opaque screen that includes the photon screen structure on the z=0 plane, desirable plane wave impinges upon on the photon screen.The transmittance function of photon screen is:

$E(x,y,0)=\left\{\begin{array}{cc}1& {(x-x_{\mathrm{ij}})}^2+{(y-y_{\mathrm{ij}})}^2\≤{r_i}^2\\ 0& \mathrm{other}\end{array}\right.---\left(1\right)$

In (1), xij, yij represent micropore central coordinate of circle on the wavestrip, i=1, and 2......n, (n is the zone plate number of rings) j=1,2 ... m (m is the number cells on the respective rings).Discrete Fourier transformation obtains the angular spectrum F0 (fx, fy, 0) of incident light on diffraction screen to E (x, y, 0) through two-dimensional space.

$E(f_x,f_Y,0)=\underset{-\∞}{\overset{\∞}{\∫}}\underset{-\∞}{\overset{\∞}{\∫}}E(x,y,0)\exp [-j2\mathrm{\π}(f_{X}x+f_{Y}y)]\mathrm{dxdy}---\left(2\right)$

In (2), f _X, f _YBe spatial frequency, $f_X=\frac{\mathrm{\α}}{\mathrm{\λ}},$ $f_Y=\frac{\mathrm{\β}}{\mathrm{\λ}}$ (α, β are wave vectors

With X-axis, the angle between the Y-axis).Incident light is propagated along the Z direction through behind the photon screen.At the Z=z place, the frequency spectrum E. of spatial frequency (fx, fy z) are:

$E(f_X,f_Y,z)=E(f_X,f_Y,0)\exp (j2\mathrm{\π}\sqrt{\frac{1}{{\mathrm{\λ}}^2}-f_X^2-f_Y^2}\·z)---\left(3\right)$

In (3), f _X, f _YMust satisfy condition $f_X^2+f_Y^2\≤1/{\mathrm{\λ}}^2,$ This formula shows that the effect of propagating the z of a segment distance has just changed the relative phase of each angular spectrum component.But work as $f_X^2+f_Y^2>1/{\mathrm{\λ}}^2$ The time, the frequency spectrum E (f of spatial frequency _X, f _Y, z) be

E(f _X，f _Y，z)＝E(f _X，f _Y，0)exp(-μz) (4)

In (4), $\mathrm{\μ}=\frac{2\mathrm{\π}}{\mathrm{\λ}}\sqrt{{\left(\frac{x}{z}\right)}^2+{\left(\frac{y}{z}\right)}^2-1}$

Because μ is an arithmetic number, these wave components increase decay rapidly because of propagation distance.(4) formula is done inverse Fourier transform, obtain light wave amplitude E (x, y, z)

$E(x,y,z)={\∫}_{-\∞}^{\∞}{\∫}_{-\∞}^{\∞}E(f_X,f_Y,0)\exp (j2\mathrm{\π}\sqrt{\frac{1}{{\mathrm{\λ}}^2}-f_X^2-f_Y^2}\·z)\exp \left[j2\mathrm{\π}(f_{X}x+f_{Y}y)\right]d{f}_{X}d{f}_Y---\left(5\right)$

More than be the diffraction theory of common photon screen, at super-resolution photon screen, what need modification is exactly each transmittance function, is become the transmittance function of super-resolution position photo by the circular aperture of complete printing opacity.

The present invention has provided the design parameter embodiment of aforementioned three kinds of super-resolution photon screens, and the synoptic diagram of corresponding super-resolution position photo as shown in Figure 2.Fig. 2 (a) is common circular aperture synoptic diagram; Fig. 2 (b) is 2 ring two-value super-resolution position photo synoptic diagram; Fig. 2 (c) is 3 ring two-value super-resolution position photo synoptic diagram; Fig. 2 (d) is the many-valued super-resolution position photo synoptic diagram of 3 rings.(a) among Fig. 2 (b) (c) (d) four position photos combine the common photon screen (a) that produces respectively among Fig. 1 and three super-resolution photon screens (b), (c), (d) with (a) among Fig. 1.Wherein Fig. 2 (a) is a common circular aperture, after common photon screen combines, or common photon screen itself.

Fig. 3 represents the normalized intensity function of the super-resolution light distribution that three kinds of super-resolution position photos and circular aperture form in far diffraction field, what this figure demonstrated is the super-resolution effect of these three kinds of super-resolution position photos, and their first zero all is 0.8 place in the Airy disk first zero.Also this just super-resolution effect makes our designed super-resolution photon screen can produce the diffraction spot littler than common zone plate.

Fig. 4 represents the distribution plan of the spot intensity that common photon screen and three kinds of super-resolution photon screens form in far diffraction field.From this figure we as can be seen, three kinds of designed super-resolution photon screens can produce littler, more sharp-pointed far field construction spot than common photon screen really, the ratio of compression of diffraction master spot is greatly about about 0.8.

Super-resolution photon screen of the present invention experiment pick-up unit in actual applications as shown in Figure 5, the 1st, collimation laser device, the 2nd, condenser lens, the 3rd, super-resolution photon screen of the present invention, the 4th, CCD photodetector.Light process condenser lens 2 and super-resolution photon screen 3 from collimation laser 1 sends produce the main spot diffractogram of compression on the focal plane of condenser lens 2.Such diffraction master spot intensity distributions can be detected and be confirmed by the ccd detector on the focal plane that is placed on condenser lens 24.

Experimental results show that add designed super-resolution photon screen after, realized the further compression of main spot of the common photon screen of ratio of far field construction hot spot main lobe really.This explanation the present invention can be used for beam shaping, microelectronics non-mask etching, light laser concentration of energy and other needs energy focusing in the various instruments of center spot.

This super-resolution photon screen provided by the invention can utilize lsi technology technology and plane photoetching process technology to make, and making step is as follows:

Step 1, utilize the electron-beam direct writing legal system to make mother matrix;

Step 2, master pattern is transferred on the optical glass that scribbles photoresist by the contact photolithography method;

Step 3, utilize the inductive couple plasma lithographic technique, will move on to pattern etch on the optical glass photoresist in optical glass.

Wherein, the photoresist that is adopted is Shipley s1818, and thickness is 1.8 μ m.The error of repelication of contact exposure is less than 0.5 μ m.Each parameter of super-resolution photon screen provides in preamble.At last, utilize the inductive couple plasma lithographic technique, in optical glass, the etching gas that is adopted is fluoroform (CHF with pattern etch ₃), flow is 30SCCM, and RF power is 500W, and bias power is 200W, is 0.077 μ m/min to the etch rate of quartz substrate.Corresponding to 0.6328 mum wavelength, the refractive index of optical glass is 1.521, thereby the corresponding degree of depth in π position is 0.607 μ m, and the etching depth of corresponding 0.9 π is 0.547 μ m, the etching depth of corresponding 0.86 π is 0.522 μ m, and the etching depth of corresponding 0.06 π is 0.036 μ m.Light path synoptic diagram according to Fig. 5 arranges the measurement light path. and the laser works wavelength is 632.8nm.Expand bundle, collimation then.In experiment, super-resolution Fresnel zone plate focal length is 100 millimeters and places super ight soil Fresnel zone plate, places ccd detector, the considerable thus size of measuring diffraction pattern then at the focal beam spot place.Measured data has proved the correctness of Theoretical Calculation.

Super-resolution photon screen with one 50 ring is an example below, describes its method for making:

1, determines optical maser wavelength and photon screen focal length, number of rings;

2, according to the definite common photon screen that will make of need of work;

3, determine the parameter of super-resolution photon screen according to method as herein described;

4, make super-resolution photon screen.

The data that the super-resolution position photo provides all are normalization datas.Should converse concrete data as required in the reality.Suppose that optical maser wavelength is 632.8 nanometers, focal length is 100 millimeters, and number of rings is 50 rings.Common photon screen based on 50 ring Fresnel zone plate radiuses be from small to large: 251.6,355.8,435.7,503.1,562.5,616.2,665.6,711.5,754.7,795.5,834.3,871.4,907.0,941.2,974.3,1006.2,1037.2,1067.3,1096.5,1125.0,1152.8,1179.9,1206.4,1232.4,1257.8,1282.7,1307.1,1331.1,1354.7,1377.8,1400.6,1423.0,1445.1,1466.8,1488.2,1509.3,1530.2,1550.7,1571.0,1591.0,1610.7,1630.3,1649.6,1668.6,1687.5,1706.1,1724.6,1742.8,1760.9,1778.8 microns.

The design parameter of two corresponding ring two-value super-resolution position photos is: a=0.34, φ ₁=0, φ ₂=π, then the actual value of a is the 0.34*1778.8=604.8 micron; The design parameter of three ring two-value super-resolution position photos is: a=0.09, b=0.36, φ ₁=0.9 π, φ ₂=0, φ ₃=0.9 π,, Shi Ji a=0.09*1778.8=160.1 micron then, b=0.36*1778.8=640.4 micron; Three the ring many-valued oversubscription, distinguish that the design parameter of position photo is a=0.09, b=0.36, φ ₁=0, φ ₂=0.06 π, φ ₃=0.86 π.Actual a=160.1 micron, the b=640.4 micron.In different endless belt etching corresponding thickness, the corresponding degree of depth in π position is 0.607 μ m, and the etching depth of corresponding 0.9 π is 0.547 μ m, and the etching depth of corresponding 0.86 π is 0.522 μ m, and the etching depth of corresponding 0.06 π is 0.036 μ m.Just can make super-resolution photon screen.

Above-described concrete embodiment has carried out further detailed explanation to purpose of the present invention, technical scheme and beneficial effect.Institute it should be understood that the above only for concrete embodiment of the present invention, is not limited to the present invention.All any modifications of being made within the spirit and principles in the present invention, be equal to and replace or improvement etc., all should be included within protection scope of the present invention.

Claims (8)

1, a kind of super-resolution photon screen, it is characterized in that, this super-resolution photon screen is the super-resolution position photo of integrated etching equal aperture on common photon screen sheet, thereby forms by the synthetic position that a plurality of concentric endless belt are arranged of common photon screen and the equal aperture super-resolution position photo phase board of diffraction element mutually.

2, super-resolution photon screen according to claim 1 is characterized in that, the size of described super-resolution position photo is identical with corresponding photon screen outermost annular aperture, the position of endless belt be distributed in mutually in the same annulus the position mutually value be identical.

3, super-resolution photon screen according to claim 1 is characterized in that, the super-resolution position photo of described equal aperture is two rings or three ring super-resolution position photos.

4, super-resolution photon screen according to claim 3 is characterized in that, described two ring super-resolution position photos are two ring two-value position photos, and its design parameter is: a=0.34, φ ₁=0, φ ₂=π, wherein a is the normalization radius of ring, φ ₁, φ ₂Radius for each endless belt.

5, super-resolution photon screen according to claim 3 is characterized in that, described three ring super-resolution position photos are three ring two-value position photos, and its design parameter is: a=0.09, b=0.36, φ ₁=0.9 π, φ ₂=0, φ ₃=0.9 π, a wherein, b is the normalization radius of each ring, φ ₁, φ ₂, φ ₃Radius for each endless belt.

6, super-resolution photon screen according to claim 3 is characterized in that, described three ring super-resolution position photos are the many-valued position photos of three rings, and its design parameter is a=0.09, b=0.36, φ ₁=0, φ ₂=0.06 π, φ ₃=0.86 π, a wherein, b is the normalization radius of each ring, φ ₁φ ₂φ ₃Radius for each endless belt.

7, super-resolution photon screen according to claim 3 is characterized in that, the design constraints that the position of described two rings and three ring super-resolution position photos is encircled mutually are: the first zero than the situation of G≤0.8 under this tal fibre maximize than S.

8, super-resolution photon screen according to claim 1 is characterized in that, described common photon screen is the amplitude type photon screen.

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