Abstract

A new technique based on laser vitrification of cordierite ceramic powders is used to fabricate arbitrarily shaped microlens arrays on a glass substrate. Crack-free semispherical and quasi-spherical lenses with good optical and surface quality are demonstrated.

© 2009 Optical Society of America

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References

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  1. R. Guo, S. Xiao, X. Zhai, J. Li, A. Xia, and W. Huang, “Micro lens fabrication by means of femtosecond two photon photopolymerization,” Opt. Express 14, 810-816 (2006).
    [CrossRef] [PubMed]
  2. K. Naessens, H. Ottevaere, P. Van Daele, and R. Baets, “Flexible fabrication of microlenses in polymer layers with excimer laser ablation,” Appl. Surf. Sci. 208-209, 159-154 (2003).
    [CrossRef]
  3. S.-K. Lee, K.-C. Lee, and S. S. Lee, “A simple method for microlens fabrication by the modified LIGA process,” J. Micromech. Microeng. 12, 334-340 (2002).
    [CrossRef]
  4. S.-D. Moon, S. Kang, and J.-U. Bu, “Fabrication of polymeric microlens of hemispherical shape using micromolding,” Opt. Eng. 41, 2267-2270 (September 2002).
    [CrossRef]
  5. M. R. Wang and H. Su, “Multilevel diffractive microlens fabrication by one-step laser-assisted chemical etching upon high-energy beam sensitive glass,” Opt. Lett. 23, 876-878(1998).
    [CrossRef]
  6. V. J. Pilletteri, E. E. Case, and T. Negas, “Laser surface melting and cutting of cordierite substrates,” J. Mater. Sci. Lett. 9, 133-136 (1990).
    [CrossRef]
  7. F. G. Razavy, D. C. Van Aken, and J. D. Smith, “Effect of laser surface melting upon the devitrification of plasma sprayed cordierite,” Mater. Sci. Eng. A 362, 213-222(2003).
    [CrossRef]

2006 (1)

2003 (2)

K. Naessens, H. Ottevaere, P. Van Daele, and R. Baets, “Flexible fabrication of microlenses in polymer layers with excimer laser ablation,” Appl. Surf. Sci. 208-209, 159-154 (2003).
[CrossRef]

F. G. Razavy, D. C. Van Aken, and J. D. Smith, “Effect of laser surface melting upon the devitrification of plasma sprayed cordierite,” Mater. Sci. Eng. A 362, 213-222(2003).
[CrossRef]

2002 (1)

S.-K. Lee, K.-C. Lee, and S. S. Lee, “A simple method for microlens fabrication by the modified LIGA process,” J. Micromech. Microeng. 12, 334-340 (2002).
[CrossRef]

1998 (1)

1990 (1)

V. J. Pilletteri, E. E. Case, and T. Negas, “Laser surface melting and cutting of cordierite substrates,” J. Mater. Sci. Lett. 9, 133-136 (1990).
[CrossRef]

Baets, R.

K. Naessens, H. Ottevaere, P. Van Daele, and R. Baets, “Flexible fabrication of microlenses in polymer layers with excimer laser ablation,” Appl. Surf. Sci. 208-209, 159-154 (2003).
[CrossRef]

Bu, J.-U.

S.-D. Moon, S. Kang, and J.-U. Bu, “Fabrication of polymeric microlens of hemispherical shape using micromolding,” Opt. Eng. 41, 2267-2270 (September 2002).
[CrossRef]

Case, E. E.

V. J. Pilletteri, E. E. Case, and T. Negas, “Laser surface melting and cutting of cordierite substrates,” J. Mater. Sci. Lett. 9, 133-136 (1990).
[CrossRef]

Guo, R.

Huang, W.

Kang, S.

S.-D. Moon, S. Kang, and J.-U. Bu, “Fabrication of polymeric microlens of hemispherical shape using micromolding,” Opt. Eng. 41, 2267-2270 (September 2002).
[CrossRef]

Lee, K.-C.

S.-K. Lee, K.-C. Lee, and S. S. Lee, “A simple method for microlens fabrication by the modified LIGA process,” J. Micromech. Microeng. 12, 334-340 (2002).
[CrossRef]

Lee, S. S.

S.-K. Lee, K.-C. Lee, and S. S. Lee, “A simple method for microlens fabrication by the modified LIGA process,” J. Micromech. Microeng. 12, 334-340 (2002).
[CrossRef]

Lee, S.-K.

S.-K. Lee, K.-C. Lee, and S. S. Lee, “A simple method for microlens fabrication by the modified LIGA process,” J. Micromech. Microeng. 12, 334-340 (2002).
[CrossRef]

Li, J.

Moon, S.-D.

S.-D. Moon, S. Kang, and J.-U. Bu, “Fabrication of polymeric microlens of hemispherical shape using micromolding,” Opt. Eng. 41, 2267-2270 (September 2002).
[CrossRef]

Naessens, K.

K. Naessens, H. Ottevaere, P. Van Daele, and R. Baets, “Flexible fabrication of microlenses in polymer layers with excimer laser ablation,” Appl. Surf. Sci. 208-209, 159-154 (2003).
[CrossRef]

Negas, T.

V. J. Pilletteri, E. E. Case, and T. Negas, “Laser surface melting and cutting of cordierite substrates,” J. Mater. Sci. Lett. 9, 133-136 (1990).
[CrossRef]

Ottevaere, H.

K. Naessens, H. Ottevaere, P. Van Daele, and R. Baets, “Flexible fabrication of microlenses in polymer layers with excimer laser ablation,” Appl. Surf. Sci. 208-209, 159-154 (2003).
[CrossRef]

Pilletteri, V. J.

V. J. Pilletteri, E. E. Case, and T. Negas, “Laser surface melting and cutting of cordierite substrates,” J. Mater. Sci. Lett. 9, 133-136 (1990).
[CrossRef]

Razavy, F. G.

F. G. Razavy, D. C. Van Aken, and J. D. Smith, “Effect of laser surface melting upon the devitrification of plasma sprayed cordierite,” Mater. Sci. Eng. A 362, 213-222(2003).
[CrossRef]

Smith, J. D.

F. G. Razavy, D. C. Van Aken, and J. D. Smith, “Effect of laser surface melting upon the devitrification of plasma sprayed cordierite,” Mater. Sci. Eng. A 362, 213-222(2003).
[CrossRef]

Su, H.

Van Aken, D. C.

F. G. Razavy, D. C. Van Aken, and J. D. Smith, “Effect of laser surface melting upon the devitrification of plasma sprayed cordierite,” Mater. Sci. Eng. A 362, 213-222(2003).
[CrossRef]

Van Daele, P.

K. Naessens, H. Ottevaere, P. Van Daele, and R. Baets, “Flexible fabrication of microlenses in polymer layers with excimer laser ablation,” Appl. Surf. Sci. 208-209, 159-154 (2003).
[CrossRef]

Wang, M. R.

Xia, A.

Xiao, S.

Zhai, X.

Appl. Surf. Sci. (1)

K. Naessens, H. Ottevaere, P. Van Daele, and R. Baets, “Flexible fabrication of microlenses in polymer layers with excimer laser ablation,” Appl. Surf. Sci. 208-209, 159-154 (2003).
[CrossRef]

J. Mater. Sci. Lett. (1)

V. J. Pilletteri, E. E. Case, and T. Negas, “Laser surface melting and cutting of cordierite substrates,” J. Mater. Sci. Lett. 9, 133-136 (1990).
[CrossRef]

J. Micromech. Microeng. (1)

S.-K. Lee, K.-C. Lee, and S. S. Lee, “A simple method for microlens fabrication by the modified LIGA process,” J. Micromech. Microeng. 12, 334-340 (2002).
[CrossRef]

Mater. Sci. Eng. A (1)

F. G. Razavy, D. C. Van Aken, and J. D. Smith, “Effect of laser surface melting upon the devitrification of plasma sprayed cordierite,” Mater. Sci. Eng. A 362, 213-222(2003).
[CrossRef]

Opt. Eng. (1)

S.-D. Moon, S. Kang, and J.-U. Bu, “Fabrication of polymeric microlens of hemispherical shape using micromolding,” Opt. Eng. 41, 2267-2270 (September 2002).
[CrossRef]

Opt. Express (1)

Opt. Lett. (1)

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Figures (7)

Fig. 1
Fig. 1

Schematic of the process when the laser beam is modified by a lens arrangement to melt cordierite powder leading to its vitrification. Here, the laser light is absorbed by the cordierite generating heat that changes its properties leading not only to vitrification but also reflow of the molten glass resulting in a spherical droplet lens shape formed by surface tension (least energy shape/state). The bottom glass that forms the substrate is common 1737 display glass or other common glass such as soda-lime glass. The inset shows a SEM micrograph of a 2-D microlens array formed using the technique described for 1737 display glass.

Fig. 2
Fig. 2

Diagram of a generic laser cycle for the manufacture of a single microlens. The substrate is initially preheated on a hot plate to a specific temperature, e.g., 400 ° C . The cordierite powder is then irradiated by the laser for a duration of T warm with a power up-slope to premelt the powder. Subsequently, the powder is melted and surface tension forms the microlens by irradiation of the laser for a duration of T melt with power P melt . Finally the formed lens is irradiated by the laser for a duration of T cool with a power down-slope to reduce the thermal stress during cooling and to avoid cracking the sample. The inset shows a 2-D array of microlenses manufactured on 1.2 mm thick soda-lime glass slides (VWR scientific glass slides).

Fig. 3
Fig. 3

XRD patterns of samples after laser vitrification of cordierite powder. One can also observe the presence of residual peaks of the cordierite powder as well as the WC residue from the mill that was used to crush the glass.

Fig. 4
Fig. 4

Transmission loss spectral measurement of a microlens built on 1737 glass. Here one observes total transmission losses (including absorption, coupling, and reflection) typically around 1.5 dB in the visible spectral range of 400 880 nm . Measurements were taken at intervals of 1 nm with a setup based on an Ocean Optics spectrometer. The inset shows details of a defective mi crolens with a crack near its base due to stress during the cooling process.

Fig. 5
Fig. 5

Diagram describing the geometry of the reflow process. (a) Equivalent irradiation cylinder formed by a laser beam with width w and height of the cordierite powder h 1 . (b) Lens after vitrification and reflow of cordierite powder leading to a microlens with the underpinned base w and a customized lens with inner angle 2 θ , radius r, and final height h 2 . The dimensions are based on the equivalence of volume taking into account the compaction factor of the cordierite powder.

Fig. 6
Fig. 6

SEM pictures of microlens arrays manufactured with different defocus (or beam diameters of the laser) and different powder thicknesses. As expected, smaller beam widths and thicker powder (small w / h 1 ) lead to more spherical lenses. The opposite also occurs because larger beam widths and thinner powder (high w / h 1 ) lead to less spherical lenses.

Fig. 7
Fig. 7

Diagram describing the geometric features achieved with the manufactured microlenses. The solid curves represent the theoretical prediction for normalized height h 2 / h 1 and θ as a function of normalized width of base w / h 1 . Here a family of curves (solid and dotted) are plotted with compaction ratios η compaction (0 to 1) at 25%, 50%, 75%, and 100%. The filled and open data points represent the measurements taken with the microlenses by a SEM and optical confocal microscope. One can see good agreement for w / h 1 < 3 with a compaction factor of 25%. For w / h 1 < 3 the compaction appears to be up to 75% because of imperfection at the deposition of very thin films and the grain size of the powder.

Equations (2)

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η compaction π w 2 h 1 4 = π r 3 ( 2 3 cos ( θ ) + cos 3 ( θ 3 ) ) .
h 2 = r ( 1 cos ( θ ) ) ,

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