CN104536146B - Polarization control method used in fiber point-diffraction interferometer wave surface reference source - Google Patents

Abstract

The invention relates to a polarization control method used in a fiber point-diffraction interferometer wave surface reference source. The polarization control method includes the steps that optical fiber diffraction spherical wave is collimated through a high-quality collimator lens, and then passes through a rotatable polarizing film placed on a single-axis displacement platform, a double-layer density disk located in a through hole, a pentaprism, and an optical power meter, wherein the pentaprism and the optical power meter are placed on the single-axis displacement platform, and the polarization state of an initial light beam can be determined by theoretical calculation through the rotatable polarizing film; the rotatable polarizing film is then moved out of the light path through the single-axis displacement platform, the double-layer density disk is turned to be in the circularly polarized light detection state, namely, a 1/4 wave plate and a polarizing film, the control voltages of two control channels of a polarization controller are calculated through the polarization state of the initial light beam, which is obtained in the previous step, and then the circular polarization state is obtained through fine adjustment and observation of the optical power meter reading till extinction. The system has the advantages of being capable of achieving quick adjustment of the circular polarization state under the premise that extra error is not introduced to the wave surface reference source and effectively improving contrast ratio and detection precision of interference fringe.

Description

Using the polarization control method in the reference source of optical fiber point-diffraction interferometer corrugated

Technical field

The invention belongs to point-diffraction interferometer corrugated reference source Polarization Control field is and in particular to a kind of use in fiber optic point Polarization control method in the reference source of diffraction interferometer corrugated.

Background technology

Extreme ultraviolet photolithographic (euvl) technology is considered as one of most potential Next Generation Lithography, and it is to use The extreme ultraviolet of 13.5nm by the pattern imaging on mask on the silicon chip being coated with photoresist, in order to realize projection optical system The resolution of diffraction limit, according to marachel criterion it is desirable to system wave aberration is less than λ/14, i.e. 1nm rms, therefore projection system System wave aberration detection means will reach the precision of Subnano-class, and traditional interference detection method has not enabled extreme ultraviolet photolithographic The high precision test of system objective wave aberration.Since raymond n.smart and j.strong in 1972 is by the thought of a diffraction Since generation for interferometer Plays spherical wave, micropore point diffraction, optical fiber point-diffraction and optical fiber cone point diffraction has successively been had to think The proposition thought, optical fiber point-diffraction has the advantages that manufacturing technology is ripe, aperture be aligned is easy, light path is foldable, but optical fiber diffraction ball The na of face ripple is less than 0.2 it is impossible to realize the detection to large-numerical aperture extreme ultraviolet projection objective wave aberration, therefore often optical fiber spreads out Penetrate spherical wave collimation, focus on after again through micropore diffraction produce big na spherical wave, that is, be configured to corrugated reference source.In order to improve interference Pattern contrast and the astigmatism error reducing diffractive spherical ripple, the light polarization of corrugated reference source should be circular polarization state.

Content of the invention

The invention solves the problems that technical problem of the prior art, the point diffraction meeting extreme ultraviolet photolithographic optical detection use is done Interferometer, for the demand of circular polarization state before diffracted wave, quickly realizes circular polarization state in the case of can not introducing extra error Regulation and control, provide a kind of polarization control method in the reference source of optical fiber point-diffraction interferometer corrugated for use.

In order to solve above-mentioned technical problem, technical scheme is specific as follows:

Using the polarization control method in the reference source of optical fiber point-diffraction interferometer corrugated, comprise the following steps:

Rotatory polarization piece is put in light path, dual-layer density disk goes to through hole；Pentaprism is put in light path to realize light Bundle deviation；Surveyed after the polarization state of initial light with rotatory polarization piece method, remove rotatory polarization piece with single shaft displacement platform；

Obtain when only adjustment ch1, ch2 voltage is calculated according to initial polarization state right-circularly polarized light Phase delay and Magnitude of voltage；

Ch1, ch2 control voltage is transferred to the magnitude of voltage of Theoretical Calculation, and dual-layer density disk is gone to right-circularly polarized light The position of detection, observes energy meter registration；

Until complete extinction, then optical fiber diffraction light beam is right-hand circular polarization state to fine setting ch3, ch4 control voltage, removes five ribs Mirror simultaneously recovers dual-layer density disk to through hole state.

In technique scheme, the magnitude of voltage of the Theoretical Calculation of described ch1, ch2 control voltage is according to formula:

$\begin{array}{c}\left(\begin{array}{c}{s}_{0\mathrm{out}}\\ s_{1\mathrm{out}}\\ s_{2\mathrm{out}}\\ s_{3\mathrm{out}}\end{array}\right)=j_{45}\left({\mathrm{\δ}}_2\right)j_0\left({\mathrm{\δ}}_1\right)\left(\begin{array}{c}{s}_{0\mathrm{in}}\\ s_{1\mathrm{in}}\\ s_{2\mathrm{in}}\\ s_{3\mathrm{in}}\end{array}\right)\\ =\left(\begin{array}{c}{s}_{0\mathrm{in}}\\ s_{1\mathrm{in}}\cos {\mathrm{\δ}}_2-s_{2\mathrm{in}}\sin {\mathrm{\δ}}_1\sin {\mathrm{\δ}}_2-s_{3\mathrm{in}}\cos {\mathrm{\δ}}_1\sin {\mathrm{\δ}}_2\\ s_{2\mathrm{in}}\cos {\mathrm{\δ}}_1-s_{3\mathrm{in}}\sin {\mathrm{\δ}}_1\\ s_{1\mathrm{in}}\sin {\mathrm{\δ}}_2+s_{2\mathrm{in}}\sin {\mathrm{\δ}}_1\cos {\mathrm{\δ}}_2+s_{3\mathrm{in}}\cos {\mathrm{\δ}}_1\cos {\mathrm{\δ}}_2\end{array}\right)\end{array}$

Obtain.

The present invention has a following beneficial effect:

The present invention passes through to analyze Polarization Controller operation principle effectively by the control passage degree of freedom reduction of Polarization Controller To 2, improve regulation and control speed；

Obtain the control voltage of two control passages by Theoretical Calculation, it is to avoid the blindness of regulation and control；

After the completion of circular polarization state regulation and control, control system can be removed light path, light beam can continue to focus on microwell plate The spherical wave that upper diffraction goes out big na is used for detecting, it is to avoid the introducing of extra error.

Brief description

With reference to the accompanying drawings and detailed description the present invention is described in further detail.

Fig. 1 is polarization control system schematic diagram.

Fig. 2 is Polarization Controller schematic diagram.

Fig. 3 is wave plate orientation diagram on dual-layer density disk.

Fig. 4 be when only controlling ch1, ch2 voltage controllable to expression schematic diagram in poincare sphere for the polarization state, input is partially Polarization state is (1,0.831,0.4941,0.2557).

Fig. 5 be when only controlling ch1, ch2 voltage controllable to expression schematic diagram in poincare sphere for the polarization state, input is partially Polarization state is (1,0.309,0.9511,0).

In figure reference is expressed as:

1. Polarization Controller；2. optical fiber；3. collimate camera lens；4. rotatable polaroid；5. dual-layer density disk；6. pentaprism； 7. light power meter.

Specific embodiment

The invention thought of the present invention is: the technical though of the present invention is to change optical fiber diffraction light beam by Polarization Controller Polarization state, then with circularly polarized light detecting system, light polarization is detected, except that the polarization of incipient beam of light State is calculated with rotatory polarization piece law theory, then calculates control two passages of Polarization Controller and reaches the electricity needed for circular polarization state Pressure, on the basis of Theoretical Calculation accurate adjustment, the other two-way control voltage of fine setting, finally give circular polarization state, then can be by partially Isolation control system easily removes light path, thus not introducing extra error.

Theoretical calculation method:

Polarization Controller control passage degree of freedom is reduced to 2 theory analysis: if the stoke in polarization state poincare sphere Ch1, ch2 passage Muller matrix of Polarization Controller can be represented its regulation and control (δ table to light polarization by this vector representation Show phase-delay quantity), obtain formula (1) and (2):

$j_0\left(\mathrm{\δ}\right)=\left(\begin{array}{cccc}1& 0& 0& 0\\ 0& 1& 0& 0\\ 0& 0& \cos \mathrm{\δ}& -\sin \\ 0& 0& \sin \mathrm{\δ}& \cos \mathrm{\δ}\end{array}\right){,j}_{45}\left(\mathrm{\δ}\right)=\left(\begin{array}{cccc}1& 0& 0& 0\\ 0& \cos \mathrm{\δ}& 0& -\sin \\ 0& 0& 1& 0\\ 0& \sin \mathrm{\δ}& 0& \cos \mathrm{\δ}\end{array}\right)---\left(1\right)$

$\begin{array}{c}\left(\begin{array}{c}{s}_{0\mathrm{out}}\\ s_{1\mathrm{out}}\\ s_{2\mathrm{out}}\\ s_{3\mathrm{out}}\end{array}\right)=j_{45}\left({\mathrm{\δ}}_2\right)j_0\left({\mathrm{\δ}}_1\right)\left(\begin{array}{c}{s}_{0\mathrm{in}}\\ s_{1\mathrm{in}}\\ s_{2\mathrm{in}}\\ s_{3\mathrm{in}}\end{array}\right)\\ =\left(\begin{array}{c}{s}_{0\mathrm{in}}\\ s_{1\mathrm{in}}\cos {\mathrm{\δ}}_2-s_{2\mathrm{in}}\sin {\mathrm{\δ}}_1\sin {\mathrm{\δ}}_2-s_{3\mathrm{in}}\cos {\mathrm{\δ}}_1\sin {\mathrm{\δ}}_2\\ s_{2\mathrm{in}}\cos {\mathrm{\δ}}_1-s_{3\mathrm{in}}\sin {\mathrm{\δ}}_1\\ s_{1\mathrm{in}}\sin {\mathrm{\δ}}_2+s_{2\mathrm{in}}\sin {\mathrm{\δ}}_1\cos {\mathrm{\δ}}_2+s_{3\mathrm{in}}\cos {\mathrm{\δ}}_1\cos {\mathrm{\δ}}_2\end{array}\right)\end{array}---\left(2\right)$

Arbitrary ellipse polarized light or line polarized light are done with numerical simulation such as Figure 4 and 5 show, when phase-shift phase changes at (0,2 π) When, it is circular polarization state that polarization state regulation scope can cover north and south two limit.

Rotatory polarization piece method determines incipient beam of light polarization state: a branch of complete polarized light bundle is through a rotatable polaroid When, the minimum position of light intensity is the minor axis location of polarization ellipse, and light intensity is maximum to be transverse position, and therefore we are permissible Determine the long and short axle orientation of polarization ellipse according to the size of light power meter registration, the relatively large I of major and minor axis is by corresponding light The square root of performance number, and then can be in the hope of the Jones matrix of incipient beam of light characterizing.

Ch1, ch2 voltage determines method: four control passages of Polarization Controller can be seen as having added four respectively on optical fiber Individual quick shaft direction is fixed, the wave plate of phase-delay quantity change.So after polarization control system, the luminous power of light beam can be by The Jones matrix of wave plate is calculated, and taking the regulation and control of right-circularly polarized light as a example (left-hand polarization light can be obtained by same method Arrive):

$\begin{array}{c}{e}_{\mathrm{out}}=\left(\begin{array}{cc}1& 0\\ 0& 0\end{array}\right)\left(\begin{array}{cc}1& i\\ i& 1\end{array}\right)\left(\begin{array}{cc}\cos {\mathrm{\δ}}_2/2& i\sin {\mathrm{\δ}}_2/2\\ i\sin {\mathrm{\δ}}_2/2& \cos {\mathrm{\δ}}_2/2\end{array}\right)\left(\begin{array}{cc}1& 0\\ 0& e^{-i}{\mathrm{\δ}}_1\end{array}\right)e_{\mathrm{in}}\\ =\left(\begin{array}{cc}\cos {\mathrm{\δ}}_2/2-\sin {\mathrm{\δ}}_2/2& i{e}^{-i}{\mathrm{\δ}}_1(\cos {\mathrm{\δ}}_2/2+\sin {\mathrm{\δ}}_2/2)\\ 0& 0\end{array}\right)e_{\mathrm{in}}\end{array}---\left(3\right)$

(3) formula δ₁And δ₂Respectively represent ch1 and ch2 delay phase place, the matrix on the right of equal sign represent respectively polarization direction with Polaroid, fast axle and x-axis quarter wave plate at 45 °, the Jones matrix of ch2, ch1 that x-axis overlaps, the e being obtained by previous step_inI.e. Can get e_out, and then delay phase place during delustring can be obtained, can be obtained by the relation postponing phase place and control voltage right The control voltage value answered.

Below in conjunction with the accompanying drawings the present invention is described in detail.

As Figure 1-3, the constitutive characteristic of polarization control system is as follows: optical fiber, Polarization Controller (have four control passages Ch1, ch2, ch3, ch4), collimate camera lens, the rotatable polaroid being placed on single shaft displacement platform, dual-layer density disk (by two Relatively rotating between layer wave plate position can form through hole, inspection left circularly polarized light, inspection three kinds of states of right-circularly polarized light), solid It is scheduled on pentaprism, light power meter on single shaft displacement platform.

Concrete methods of realizing (taking realize dextrorotation circle and be inclined as a example, left-handed method is the same) is:

Rotatory polarization piece is put in light path, dual-layer density disk goes to through hole, pentaprism is also in the optical path to realize light beam Deviation, is surveyed after the polarization state of initial light with rotatory polarization piece method, removes rotatory polarization piece with single shaft displacement platform；

Obtain when only adjustment ch1, ch2 voltage is calculated according to initial polarization state right-circularly polarized light Phase delay and Magnitude of voltage；

Ch1, ch2 control voltage is transferred to the magnitude of voltage that formula (2) calculates, and dual-layer density disk is gone to right-hand circular polarization The position of light detection, observes energy meter registration；

Until complete extinction, then optical fiber diffraction light beam is right-hand circular polarization state to fine setting ch3, ch4 control voltage, removes five ribs Mirror simultaneously recovers dual-layer density disk to through hole state.

Obviously, above-described embodiment is only intended to clearly illustrate example, and the not restriction to embodiment.Right For those of ordinary skill in the art, can also make on the basis of the above description other multi-forms change or Change.There is no need to be exhaustive to all of embodiment.And the obvious change thus extended out or Change among still in the protection domain of the invention.

Claims (1)

1. use in the polarization control method in the reference source of optical fiber point-diffraction interferometer corrugated it is characterised in that walking below including Rapid:

Polarization Controller adjusts polarized light, and then collimation camera lens is collimated；

Rotatory polarization piece is put in light path, dual-layer density disk goes to through hole；Pentaprism is put into inclined to realize light beam in light path Folding；Surveyed after the polarization state of initial light with rotatory polarization piece method, remove rotatory polarization piece with single shaft displacement platform；

Phase delay and the voltage of right-circularly polarized light is obtained when calculating and only adjust ch1, ch2 voltage according to initial polarization state Value；

Ch1, ch2 control voltage is transferred to the magnitude of voltage of Theoretical Calculation, and dual-layer density disk is gone to right-circularly polarized light detection Position, observe energy meter registration；

Until complete extinction, then optical fiber diffraction light beam is right-hand circular polarization state to fine setting ch3, ch4 control voltage, and removal pentaprism is simultaneously Dual-layer density disk is recovered to through hole state；

The magnitude of voltage of the Theoretical Calculation of described ch1, ch2 control voltage is according to formula:

$\begin{array}{c}\left(\begin{array}{c}{s}_{0out}\\ s_{1out}\\ s_{2out}\\ s_{3out}\end{array}\right)=j_{45}\left({\mathrm{\δ}}_2\right)j_0\left({\mathrm{\δ}}_1\right)\left(\begin{array}{c}{s}_{0in}\\ s_{1in}\\ s_{2in}\\ s_{3in}\end{array}\right)\\ =\left(\begin{array}{c}{s}_{0in}\\ s_{1in}{\mathrm{cos\δ}}_2-s_{2in}{\mathrm{sin\δ}}_1{\mathrm{sin\δ}}_2-s_{3in}{\mathrm{cos\δ}}_1{\mathrm{sin\δ}}_2\\ s_{2in}{\mathrm{cos\δ}}_1-s_{3in}{\mathrm{sin\δ}}_1\\ s_{1in}{\mathrm{sin\δ}}_2+s_{2in}{\mathrm{sin\δ}}_1{\mathrm{cos\δ}}_2+s_{3in}{\mathrm{cos\δ}}_1{\mathrm{cos\δ}}_2\end{array}\right)\end{array}$

Obtain.