Abstract

High-numerical-aperture zone plates have important applications in high-resolution optical maskless lithography as well as scanning confocal microscopy. We describe two methods to experimentally characterize the focusing properties, i.e., the point-spread function, of such diffractive lenses. The first method uses spot exposures in photoresist and the second uses a conventional knife-edge scan. The experimental results agree well with rigorous theoretical calculations.

© 2006 Optical Society of America

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References

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  1. R. Menon, A. A. Patel, D. Gil and H. I. Smith, 'Maskless lithography,' Mater. Today , February 2005, pp. 26-33.
    [CrossRef]
  2. L. Kipp, M. Skibowski, R. L. Johnson, R. Berndt, R. Adelung, S. Harm, and R. Seemann, 'Sharper images by focusing soft X-rays with photon sieves,' Nature 414, 184-188 (2001).
    [CrossRef] [PubMed]
  3. R. Menon, D. Gil, G. Barbastathis, and H. I. Smith, 'Photon sieve lithography,' J. Opt. Soc. Am. A 22, 342-345 (2005).
    [CrossRef]
  4. D. Gil, R. Menon, and H. I. Smith, 'Fabrication of high-numerical-aperture phase zone plates with a single lithography exposure and no etching,' J. Vac. Sci. Technol. B 21, 2956-2960 (2003).
    [CrossRef]
  5. D. W. Prather and S. Shi, 'Formulation and application of the finite-difference time-domain method for the analysis of axially symmetric diffractive optical elements,' J. Opt. Soc. Am. A 16, 1131-1142 (1999).
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  6. D. Gil, R. Menon, D. J. D. Carter, and H. I. Smith,' Lithographic patterning and confocal imaging with zone plates,' J. Vac. Sci. Technol. B 18, 2881-2885 (2000).
    [CrossRef]
  7. H. J. Tiziani, R. Achi, R. N. Kramer, and L. Wiegers, 'Theoretical analysis of confocal microscopy with microlenses,' Appl. Opt. 35, 120-125 (1996).
    [CrossRef] [PubMed]
  8. W. J. Dallas, H. H. Barrett, R. E. Wagner, H. Roehrig, and C. N. West, 'Finite-length line-spread function,' J. Opt. Soc. Am. A 4, 2039-2044 (1987).
    [CrossRef] [PubMed]
  9. T. Wilson and C. J. R. Sheppard, Theory and Practice of Scanning Optical Microscopy (Academic, 1984), Chap. 3.

2005 (2)

R. Menon, A. A. Patel, D. Gil and H. I. Smith, 'Maskless lithography,' Mater. Today , February 2005, pp. 26-33.
[CrossRef]

R. Menon, D. Gil, G. Barbastathis, and H. I. Smith, 'Photon sieve lithography,' J. Opt. Soc. Am. A 22, 342-345 (2005).
[CrossRef]

2003 (1)

D. Gil, R. Menon, and H. I. Smith, 'Fabrication of high-numerical-aperture phase zone plates with a single lithography exposure and no etching,' J. Vac. Sci. Technol. B 21, 2956-2960 (2003).
[CrossRef]

2001 (1)

L. Kipp, M. Skibowski, R. L. Johnson, R. Berndt, R. Adelung, S. Harm, and R. Seemann, 'Sharper images by focusing soft X-rays with photon sieves,' Nature 414, 184-188 (2001).
[CrossRef] [PubMed]

2000 (1)

D. Gil, R. Menon, D. J. D. Carter, and H. I. Smith,' Lithographic patterning and confocal imaging with zone plates,' J. Vac. Sci. Technol. B 18, 2881-2885 (2000).
[CrossRef]

1999 (1)

1996 (1)

1987 (1)

Achi, R.

Adelung, R.

L. Kipp, M. Skibowski, R. L. Johnson, R. Berndt, R. Adelung, S. Harm, and R. Seemann, 'Sharper images by focusing soft X-rays with photon sieves,' Nature 414, 184-188 (2001).
[CrossRef] [PubMed]

Barbastathis, G.

Barrett, H. H.

Berndt, R.

L. Kipp, M. Skibowski, R. L. Johnson, R. Berndt, R. Adelung, S. Harm, and R. Seemann, 'Sharper images by focusing soft X-rays with photon sieves,' Nature 414, 184-188 (2001).
[CrossRef] [PubMed]

Carter, D. J.

D. Gil, R. Menon, D. J. D. Carter, and H. I. Smith,' Lithographic patterning and confocal imaging with zone plates,' J. Vac. Sci. Technol. B 18, 2881-2885 (2000).
[CrossRef]

Dallas, W. J.

Gil, D.

R. Menon, D. Gil, G. Barbastathis, and H. I. Smith, 'Photon sieve lithography,' J. Opt. Soc. Am. A 22, 342-345 (2005).
[CrossRef]

R. Menon, A. A. Patel, D. Gil and H. I. Smith, 'Maskless lithography,' Mater. Today , February 2005, pp. 26-33.
[CrossRef]

D. Gil, R. Menon, and H. I. Smith, 'Fabrication of high-numerical-aperture phase zone plates with a single lithography exposure and no etching,' J. Vac. Sci. Technol. B 21, 2956-2960 (2003).
[CrossRef]

D. Gil, R. Menon, D. J. D. Carter, and H. I. Smith,' Lithographic patterning and confocal imaging with zone plates,' J. Vac. Sci. Technol. B 18, 2881-2885 (2000).
[CrossRef]

Harm, S.

L. Kipp, M. Skibowski, R. L. Johnson, R. Berndt, R. Adelung, S. Harm, and R. Seemann, 'Sharper images by focusing soft X-rays with photon sieves,' Nature 414, 184-188 (2001).
[CrossRef] [PubMed]

Johnson, R. L.

L. Kipp, M. Skibowski, R. L. Johnson, R. Berndt, R. Adelung, S. Harm, and R. Seemann, 'Sharper images by focusing soft X-rays with photon sieves,' Nature 414, 184-188 (2001).
[CrossRef] [PubMed]

Kipp, L.

L. Kipp, M. Skibowski, R. L. Johnson, R. Berndt, R. Adelung, S. Harm, and R. Seemann, 'Sharper images by focusing soft X-rays with photon sieves,' Nature 414, 184-188 (2001).
[CrossRef] [PubMed]

Kramer, R. N.

Menon, R.

R. Menon, A. A. Patel, D. Gil and H. I. Smith, 'Maskless lithography,' Mater. Today , February 2005, pp. 26-33.
[CrossRef]

R. Menon, D. Gil, G. Barbastathis, and H. I. Smith, 'Photon sieve lithography,' J. Opt. Soc. Am. A 22, 342-345 (2005).
[CrossRef]

D. Gil, R. Menon, and H. I. Smith, 'Fabrication of high-numerical-aperture phase zone plates with a single lithography exposure and no etching,' J. Vac. Sci. Technol. B 21, 2956-2960 (2003).
[CrossRef]

D. Gil, R. Menon, D. J. D. Carter, and H. I. Smith,' Lithographic patterning and confocal imaging with zone plates,' J. Vac. Sci. Technol. B 18, 2881-2885 (2000).
[CrossRef]

Patel, A. A.

R. Menon, A. A. Patel, D. Gil and H. I. Smith, 'Maskless lithography,' Mater. Today , February 2005, pp. 26-33.
[CrossRef]

Prather, D. W.

Roehrig, H.

Seemann, R.

L. Kipp, M. Skibowski, R. L. Johnson, R. Berndt, R. Adelung, S. Harm, and R. Seemann, 'Sharper images by focusing soft X-rays with photon sieves,' Nature 414, 184-188 (2001).
[CrossRef] [PubMed]

Sheppard, C. J.

T. Wilson and C. J. R. Sheppard, Theory and Practice of Scanning Optical Microscopy (Academic, 1984), Chap. 3.

Shi, S.

Skibowski, M.

L. Kipp, M. Skibowski, R. L. Johnson, R. Berndt, R. Adelung, S. Harm, and R. Seemann, 'Sharper images by focusing soft X-rays with photon sieves,' Nature 414, 184-188 (2001).
[CrossRef] [PubMed]

Smith, H. I.

R. Menon, A. A. Patel, D. Gil and H. I. Smith, 'Maskless lithography,' Mater. Today , February 2005, pp. 26-33.
[CrossRef]

R. Menon, D. Gil, G. Barbastathis, and H. I. Smith, 'Photon sieve lithography,' J. Opt. Soc. Am. A 22, 342-345 (2005).
[CrossRef]

D. Gil, R. Menon, and H. I. Smith, 'Fabrication of high-numerical-aperture phase zone plates with a single lithography exposure and no etching,' J. Vac. Sci. Technol. B 21, 2956-2960 (2003).
[CrossRef]

D. Gil, R. Menon, D. J. D. Carter, and H. I. Smith,' Lithographic patterning and confocal imaging with zone plates,' J. Vac. Sci. Technol. B 18, 2881-2885 (2000).
[CrossRef]

Tiziani, H. J.

Wagner, R. E.

West, C. N.

Wiegers, L.

Wilson, T.

T. Wilson and C. J. R. Sheppard, Theory and Practice of Scanning Optical Microscopy (Academic, 1984), Chap. 3.

Appl. Opt. (1)

J. Opt. Soc. Am. A (3)

J. Vac. Sci. Technol. B (2)

D. Gil, R. Menon, and H. I. Smith, 'Fabrication of high-numerical-aperture phase zone plates with a single lithography exposure and no etching,' J. Vac. Sci. Technol. B 21, 2956-2960 (2003).
[CrossRef]

D. Gil, R. Menon, D. J. D. Carter, and H. I. Smith,' Lithographic patterning and confocal imaging with zone plates,' J. Vac. Sci. Technol. B 18, 2881-2885 (2000).
[CrossRef]

Mater. Today (1)

R. Menon, A. A. Patel, D. Gil and H. I. Smith, 'Maskless lithography,' Mater. Today , February 2005, pp. 26-33.
[CrossRef]

Nature (1)

L. Kipp, M. Skibowski, R. L. Johnson, R. Berndt, R. Adelung, S. Harm, and R. Seemann, 'Sharper images by focusing soft X-rays with photon sieves,' Nature 414, 184-188 (2001).
[CrossRef] [PubMed]

Other (1)

T. Wilson and C. J. R. Sheppard, Theory and Practice of Scanning Optical Microscopy (Academic, 1984), Chap. 3.

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Figures (10)

Fig. 1
Fig. 1

(Color online) Schematic of ZPAL. An array of high-numerical-aperture diffractive lenses (for example, zone plates) is used to create an array of tightly focused spots on the photoresist-coated substrate. By scanning the substrate while modulating the intensity of each spot, patterns of complex geometries can be printed in a dot matrix fashion. Inset: Images of an array of phase zone plates of NA = 0.7 . These zone plates were fabricated in fused silica and were designed to focus λ = 400 nm at a focal length of 40 μ m (the printing of the digitized image creates moiré artifacts).

Fig. 2
Fig. 2

(Color online) (a) Schematic illustrating the nonlinear response of the photoresist. Single-spot exposure at a given dose samples the PSF for an ideal resist response of thresholding. (b) Exposure doses. The samples were chosen such that they are closely spaced near the center of the spot and are more widely spaced away from the center. This provides high resolution near the center and minimizes the total number of samples.

Fig. 3
Fig. 3

(Color online) Comparison of experimentally determined PSF with theory for phase zone plates with NAs of 0.85, 0.8, and 0.7. The simulation data are plotted by the dashed curves.

Fig. 4
Fig. 4

(Color online) Same data as in Fig. 3, but the intensity is plotted in log scale to emphasize the correlation between the theoretical and experimental values even for points far from the center of the spot. The simulation data are plotted by the dashed curves.

Fig. 5
Fig. 5

(Color online) Focusing efficiency of the phase zone plate as a function of NA. Note the excellent agreement between the experimental and theoretical data.

Fig. 6
Fig. 6

(Color online) Technique to experimentally determine the image contrast. Measurement of the doses corresponding to equal lines and spaces ( t 2 ) , overexposure (i.e., mostly spaces) ( t 1 ) , and underexposure (i.e., mostly lines) t 3 provides enough information to determine the image contrast for the corresponding grating pattern.

Fig. 7
Fig. 7

(Color online) Measured image contrast as a function of grating period. Single-pixel lines refer to lines formed by a single pass of the focused spot, while double-pixel lines refer to the case in which each line is formed by two overlapping passes.

Fig. 8
Fig. 8

(Color online) Schematic of a ZPAM. Each zone plate in the array provides a separate confocal signal on the CCD detector. Thus the system behaves as a massively parallel confocal microscope.

Fig. 9
Fig. 9

(Color online) Knife-edge scans for zone plates of three NAs. Detector signal is plotted as a function of scan coordinates in X and Y for zone plates with NAs of 0.7, 0.8, and 0.85. The transition from bright to dark in the signal is sharper for higher NA as expected.

Fig. 10
Fig. 10

(Color online) Reconstructed PSF from knife-edge scan data. (a) Two-dimensional PSF. (b) Cross section through the center compared with the simulated PSF.

Equations (4)

Equations on this page are rendered with MathJax. Learn more.

PSF ( r n ) × t n = T h PSF ( r n ) = T h t n ,
η = 0 r FWHM PSF ( r ) r d r 0 PSF ( r ) r d r ,
E 2 = I max + I min 2 .
C = I max I min I max + I min = 1 t 2 t 1 = t 2 t 3 1 .

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