Abstract

We propose a method for designing a self-aligned microlens. We have improved its fabrication by employing metallization on a 45° angled surface of the optical fiber. We designed the focal length of the microlens to be 14.0 µm, considering the dimensions of a scanning near-field optical microscopy (SNOM) probe, and we calculated possible dimensions of diameter and height by the ray-tracing method. The modeling of lens formation was also carried out with two assumptions: no volume change and no movement of peripheral parts of the photoresist (PR) on the substrate during reflow. To fabricate a microlens of diameter 16.0 µm and height 5.0 µm we exposed a coated PR to UV light guided into the optical fiber, followed by optimized reflow of 150 °C for 2 min. For this microlens the focal length and the beam waist were 14.0 and 1.4 µm, respectively. This lens can be used for compact optical data storage.

© 2005 Optical Society of America

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References

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  1. E. Betzig, J. K. Trautman, R. Wolfe, E. M. Gyorgy, P. L. Finn, “Near-field magneto-optics and high density data storage,” Appl. Phys. Lett. 61, 142–144 (1992).
    [Crossref]
  2. T. D. Milster, “Near-field optics: a new tool for data storage,” Proc. IEEE 88, 1480–1490 (2000).
    [Crossref]
  3. K.-B. Song, J. Y. Kim, K. H. Park, “Minimization of cut-off effect by use of self-focusing effect to enhance throughput on near-field aperture,” Jpn. J. Appl. Phys. 41(3B), 1724–1727 (2002).
    [Crossref]
  4. T. Hirota, T. Ohkubo, K. Itao, H. Yoshikawa, Y. Ando, “Air-bearing design and flying characteristics of flexible optical head slider combined with visible laser light guide,” Microsyst. Technol. 8, 155–160 (2002).
    [Crossref]
  5. W. H. Kim, J. H. Lee, “A novel illumination technique using 45° angled fiber for nanoapertured NSOM tips fabricated by bulk and surface micromachining,” presented at the Sixth International Symposium on Contemporary Photonics Technology, Tokyo, Japan, 15–17 January 2003.
  6. C.-H. Tien, Y.-C. Lai, T. D. Milster, H.-P. D. Shieh, “Design and fabrication of fiber lenses for optical recording applications,” Jpn. J. Appl. Phys. 41(3B), 1834–1837 (2002).
    [Crossref]
  7. M. Sasaki, T. Ando, S. Nogawa, K. Hane, “Direct photolithography on optical fiber end,” Jpn. J. Appl. Phys. 41(6B), 4350–4355 (2002).
    [Crossref]
  8. L. G. Cohen, M. V. Schneider, “Microlens for coupling junction lasers to optical fibers,” Appl. Opt. 13, 89–94 (1974).
    [Crossref] [PubMed]
  9. M. S. Kim, K. W. Jo, J.-H. Lee, “Self-aligned microlens fabricated on the sidewall of 45°-angled optical fiber for NSOM illumination system,” in Conference on Optical Microelectromechanical Systems (Institute of Electrical and Electronics Engineers, 2003), pp. 18–19.
  10. R. van Woudenberg, “Short wavelength phase-change recording,” Jpn. J. Appl. Phys. 37(4B), 2159–2162 (1998).
    [Crossref]
  11. B. E. A. Saleh, Fundamentals of Photonics, 1st ed. (Wiley-Interscience, 1991), p. 86.

2002 (4)

K.-B. Song, J. Y. Kim, K. H. Park, “Minimization of cut-off effect by use of self-focusing effect to enhance throughput on near-field aperture,” Jpn. J. Appl. Phys. 41(3B), 1724–1727 (2002).
[Crossref]

T. Hirota, T. Ohkubo, K. Itao, H. Yoshikawa, Y. Ando, “Air-bearing design and flying characteristics of flexible optical head slider combined with visible laser light guide,” Microsyst. Technol. 8, 155–160 (2002).
[Crossref]

C.-H. Tien, Y.-C. Lai, T. D. Milster, H.-P. D. Shieh, “Design and fabrication of fiber lenses for optical recording applications,” Jpn. J. Appl. Phys. 41(3B), 1834–1837 (2002).
[Crossref]

M. Sasaki, T. Ando, S. Nogawa, K. Hane, “Direct photolithography on optical fiber end,” Jpn. J. Appl. Phys. 41(6B), 4350–4355 (2002).
[Crossref]

2000 (1)

T. D. Milster, “Near-field optics: a new tool for data storage,” Proc. IEEE 88, 1480–1490 (2000).
[Crossref]

1998 (1)

R. van Woudenberg, “Short wavelength phase-change recording,” Jpn. J. Appl. Phys. 37(4B), 2159–2162 (1998).
[Crossref]

1992 (1)

E. Betzig, J. K. Trautman, R. Wolfe, E. M. Gyorgy, P. L. Finn, “Near-field magneto-optics and high density data storage,” Appl. Phys. Lett. 61, 142–144 (1992).
[Crossref]

1974 (1)

Ando, T.

M. Sasaki, T. Ando, S. Nogawa, K. Hane, “Direct photolithography on optical fiber end,” Jpn. J. Appl. Phys. 41(6B), 4350–4355 (2002).
[Crossref]

Ando, Y.

T. Hirota, T. Ohkubo, K. Itao, H. Yoshikawa, Y. Ando, “Air-bearing design and flying characteristics of flexible optical head slider combined with visible laser light guide,” Microsyst. Technol. 8, 155–160 (2002).
[Crossref]

Betzig, E.

E. Betzig, J. K. Trautman, R. Wolfe, E. M. Gyorgy, P. L. Finn, “Near-field magneto-optics and high density data storage,” Appl. Phys. Lett. 61, 142–144 (1992).
[Crossref]

Cohen, L. G.

Finn, P. L.

E. Betzig, J. K. Trautman, R. Wolfe, E. M. Gyorgy, P. L. Finn, “Near-field magneto-optics and high density data storage,” Appl. Phys. Lett. 61, 142–144 (1992).
[Crossref]

Gyorgy, E. M.

E. Betzig, J. K. Trautman, R. Wolfe, E. M. Gyorgy, P. L. Finn, “Near-field magneto-optics and high density data storage,” Appl. Phys. Lett. 61, 142–144 (1992).
[Crossref]

Hane, K.

M. Sasaki, T. Ando, S. Nogawa, K. Hane, “Direct photolithography on optical fiber end,” Jpn. J. Appl. Phys. 41(6B), 4350–4355 (2002).
[Crossref]

Hirota, T.

T. Hirota, T. Ohkubo, K. Itao, H. Yoshikawa, Y. Ando, “Air-bearing design and flying characteristics of flexible optical head slider combined with visible laser light guide,” Microsyst. Technol. 8, 155–160 (2002).
[Crossref]

Itao, K.

T. Hirota, T. Ohkubo, K. Itao, H. Yoshikawa, Y. Ando, “Air-bearing design and flying characteristics of flexible optical head slider combined with visible laser light guide,” Microsyst. Technol. 8, 155–160 (2002).
[Crossref]

Jo, K. W.

M. S. Kim, K. W. Jo, J.-H. Lee, “Self-aligned microlens fabricated on the sidewall of 45°-angled optical fiber for NSOM illumination system,” in Conference on Optical Microelectromechanical Systems (Institute of Electrical and Electronics Engineers, 2003), pp. 18–19.

Kim, J. Y.

K.-B. Song, J. Y. Kim, K. H. Park, “Minimization of cut-off effect by use of self-focusing effect to enhance throughput on near-field aperture,” Jpn. J. Appl. Phys. 41(3B), 1724–1727 (2002).
[Crossref]

Kim, M. S.

M. S. Kim, K. W. Jo, J.-H. Lee, “Self-aligned microlens fabricated on the sidewall of 45°-angled optical fiber for NSOM illumination system,” in Conference on Optical Microelectromechanical Systems (Institute of Electrical and Electronics Engineers, 2003), pp. 18–19.

Kim, W. H.

W. H. Kim, J. H. Lee, “A novel illumination technique using 45° angled fiber for nanoapertured NSOM tips fabricated by bulk and surface micromachining,” presented at the Sixth International Symposium on Contemporary Photonics Technology, Tokyo, Japan, 15–17 January 2003.

Lai, Y.-C.

C.-H. Tien, Y.-C. Lai, T. D. Milster, H.-P. D. Shieh, “Design and fabrication of fiber lenses for optical recording applications,” Jpn. J. Appl. Phys. 41(3B), 1834–1837 (2002).
[Crossref]

Lee, J. H.

W. H. Kim, J. H. Lee, “A novel illumination technique using 45° angled fiber for nanoapertured NSOM tips fabricated by bulk and surface micromachining,” presented at the Sixth International Symposium on Contemporary Photonics Technology, Tokyo, Japan, 15–17 January 2003.

Lee, J.-H.

M. S. Kim, K. W. Jo, J.-H. Lee, “Self-aligned microlens fabricated on the sidewall of 45°-angled optical fiber for NSOM illumination system,” in Conference on Optical Microelectromechanical Systems (Institute of Electrical and Electronics Engineers, 2003), pp. 18–19.

Milster, T. D.

C.-H. Tien, Y.-C. Lai, T. D. Milster, H.-P. D. Shieh, “Design and fabrication of fiber lenses for optical recording applications,” Jpn. J. Appl. Phys. 41(3B), 1834–1837 (2002).
[Crossref]

T. D. Milster, “Near-field optics: a new tool for data storage,” Proc. IEEE 88, 1480–1490 (2000).
[Crossref]

Nogawa, S.

M. Sasaki, T. Ando, S. Nogawa, K. Hane, “Direct photolithography on optical fiber end,” Jpn. J. Appl. Phys. 41(6B), 4350–4355 (2002).
[Crossref]

Ohkubo, T.

T. Hirota, T. Ohkubo, K. Itao, H. Yoshikawa, Y. Ando, “Air-bearing design and flying characteristics of flexible optical head slider combined with visible laser light guide,” Microsyst. Technol. 8, 155–160 (2002).
[Crossref]

Park, K. H.

K.-B. Song, J. Y. Kim, K. H. Park, “Minimization of cut-off effect by use of self-focusing effect to enhance throughput on near-field aperture,” Jpn. J. Appl. Phys. 41(3B), 1724–1727 (2002).
[Crossref]

Saleh, B. E. A.

B. E. A. Saleh, Fundamentals of Photonics, 1st ed. (Wiley-Interscience, 1991), p. 86.

Sasaki, M.

M. Sasaki, T. Ando, S. Nogawa, K. Hane, “Direct photolithography on optical fiber end,” Jpn. J. Appl. Phys. 41(6B), 4350–4355 (2002).
[Crossref]

Schneider, M. V.

Shieh, H.-P. D.

C.-H. Tien, Y.-C. Lai, T. D. Milster, H.-P. D. Shieh, “Design and fabrication of fiber lenses for optical recording applications,” Jpn. J. Appl. Phys. 41(3B), 1834–1837 (2002).
[Crossref]

Song, K.-B.

K.-B. Song, J. Y. Kim, K. H. Park, “Minimization of cut-off effect by use of self-focusing effect to enhance throughput on near-field aperture,” Jpn. J. Appl. Phys. 41(3B), 1724–1727 (2002).
[Crossref]

Tien, C.-H.

C.-H. Tien, Y.-C. Lai, T. D. Milster, H.-P. D. Shieh, “Design and fabrication of fiber lenses for optical recording applications,” Jpn. J. Appl. Phys. 41(3B), 1834–1837 (2002).
[Crossref]

Trautman, J. K.

E. Betzig, J. K. Trautman, R. Wolfe, E. M. Gyorgy, P. L. Finn, “Near-field magneto-optics and high density data storage,” Appl. Phys. Lett. 61, 142–144 (1992).
[Crossref]

van Woudenberg, R.

R. van Woudenberg, “Short wavelength phase-change recording,” Jpn. J. Appl. Phys. 37(4B), 2159–2162 (1998).
[Crossref]

Wolfe, R.

E. Betzig, J. K. Trautman, R. Wolfe, E. M. Gyorgy, P. L. Finn, “Near-field magneto-optics and high density data storage,” Appl. Phys. Lett. 61, 142–144 (1992).
[Crossref]

Yoshikawa, H.

T. Hirota, T. Ohkubo, K. Itao, H. Yoshikawa, Y. Ando, “Air-bearing design and flying characteristics of flexible optical head slider combined with visible laser light guide,” Microsyst. Technol. 8, 155–160 (2002).
[Crossref]

Appl. Opt. (1)

Appl. Phys. Lett. (1)

E. Betzig, J. K. Trautman, R. Wolfe, E. M. Gyorgy, P. L. Finn, “Near-field magneto-optics and high density data storage,” Appl. Phys. Lett. 61, 142–144 (1992).
[Crossref]

Jpn. J. Appl. Phys. (1)

C.-H. Tien, Y.-C. Lai, T. D. Milster, H.-P. D. Shieh, “Design and fabrication of fiber lenses for optical recording applications,” Jpn. J. Appl. Phys. 41(3B), 1834–1837 (2002).
[Crossref]

Jpn. J. Appl. Phys. (3)

M. Sasaki, T. Ando, S. Nogawa, K. Hane, “Direct photolithography on optical fiber end,” Jpn. J. Appl. Phys. 41(6B), 4350–4355 (2002).
[Crossref]

K.-B. Song, J. Y. Kim, K. H. Park, “Minimization of cut-off effect by use of self-focusing effect to enhance throughput on near-field aperture,” Jpn. J. Appl. Phys. 41(3B), 1724–1727 (2002).
[Crossref]

R. van Woudenberg, “Short wavelength phase-change recording,” Jpn. J. Appl. Phys. 37(4B), 2159–2162 (1998).
[Crossref]

Microsyst. Technol. (1)

T. Hirota, T. Ohkubo, K. Itao, H. Yoshikawa, Y. Ando, “Air-bearing design and flying characteristics of flexible optical head slider combined with visible laser light guide,” Microsyst. Technol. 8, 155–160 (2002).
[Crossref]

Proc. IEEE (1)

T. D. Milster, “Near-field optics: a new tool for data storage,” Proc. IEEE 88, 1480–1490 (2000).
[Crossref]

Other (3)

W. H. Kim, J. H. Lee, “A novel illumination technique using 45° angled fiber for nanoapertured NSOM tips fabricated by bulk and surface micromachining,” presented at the Sixth International Symposium on Contemporary Photonics Technology, Tokyo, Japan, 15–17 January 2003.

M. S. Kim, K. W. Jo, J.-H. Lee, “Self-aligned microlens fabricated on the sidewall of 45°-angled optical fiber for NSOM illumination system,” in Conference on Optical Microelectromechanical Systems (Institute of Electrical and Electronics Engineers, 2003), pp. 18–19.

B. E. A. Saleh, Fundamentals of Photonics, 1st ed. (Wiley-Interscience, 1991), p. 86.

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Figures (13)

Fig. 1
Fig. 1

Schematic of SNOM data storage with a nanoapertured probe, a microlens, and a 45° angled optical fiber: (a) whole system; (b) details of the SNOM pyramid and microlens (d, diameter; h, height; r, radius of curvature).

Fig. 2
Fig. 2

Lens-forming mechanism using thermal reflow: (a) cylindrical PR pattern after development; (b) spherical microlens after reflow (t, thickness of the cylindrical PR pattern; h, height of the microlens).

Fig. 3
Fig. 3

Design window of the microlens with respect to its diameter and height for a given focal length of the microlens and thickness of the developed PR pattern.

Fig. 4
Fig. 4

Reflection and leakage characteristics of the 45° angled surface of the optical fiber: (a) partial reflection and refracted leak without a metal coating; (b) perfect reflection with a metal coating.

Fig. 5
Fig. 5

Flow of the process for fabrication of a self-aligned microlens on the sidewall of 45° angled optical fiber: (a) 45° angle polishing, (b) Al coating, (c) PR coating, (d) UV exposure, (e) development, (f) thermal reflow for lens formation.

Fig. 6
Fig. 6

Experimental diameters of the PR pattern with respect to exposure power and time for lithography.

Fig. 7
Fig. 7

PR profile after reflow at 150 °C: (a) before reflow and for (b) 150 °C at 30 s, (c) 150 °C at 60 s, (d) 150 °C at 2 min, (e) 150 °C at 5 min, and (f) 150 °C at 10 min. Deep valleys in the profiles denote the regions that could not be measured because of their highly inclined surfaces.

Fig. 8
Fig. 8

Experimental diameter, height, and estimated radius of curvature versus reflow time at 150 °C.

Fig. 9
Fig. 9

Profiles of the cylindrical PR (solid line) overlapped with a microlens after reflow (dotted line). The dashed circle indicates the fitted lens shape passing the two edge points at which the cylindrical PR shares its bottom.

Fig. 10
Fig. 10

Microscopic photograph of the fabricated microlens: (a) top view, (b) side view.

Fig. 11
Fig. 11

Schematic of the experimental setup for measuring the focal length and the beam waist of the microlens.

Fig. 12
Fig. 12

Intensity distribution of the microlens at the focal point and its profiles on the x and y axes. The beam waist of experimental intensity data was 1.4 µm for a Gaussian curve fit (dotted curves).

Fig. 13
Fig. 13

Experimental and theoretical (focal length, 14 µm) comparison of the beam radii along the z axis for a self-aligned microlens fabricated on the sidewall of a 45° angled optical fiber.

Equations (3)

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V c = π ( d 2 ) 2 t ,
V l = π h 24 ( 3 d 2 + 4 h 2 ) .
sin φ = NA / n 1 ,

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