Abstract

We have designed, fabricated, and characterized a micro-optical beam-shaping device that is intended to optimize the coupling of an incoherent, linearly extended high-power diode laser into a multimode fiber. The device uses two aligned diffractive optical elements (DOEs) in combination with conventional optics. With a first prototype, we achieved an overall efficiency of 28%. Straightforward improvements, such as antireflective coatings and the use of gray-tone elements, are expected to lead to an efficiency of approximately 50%. The device is compact, and its fabrication is suited for mass production at low cost. This micro-optical device, used in a range-finder measurement system, will extend the measurement range. In addition to the direct laser writing technique, which was used for fabrication of the DOEs of the prototype, we applied two other technologies for the fabrication of the micro-optical elements and compared their performance. The technologies were multiple-projection photolithography in combination with reactive-ion etching in fused silica and high-energy beam-sensitive glass gray-tone lithography in photoresist. We found that refractive-type elements (gray tone) yield better efficiency for large deflection angles, whereas diffractive elements (multilevel or laser written) give intrinsically accurate deflection angles.

© 2001 Optical Society of America

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References

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  1. B. Gächter, A. Schilling, L. Stauffer, U. Vokinger, “Optischer Entfernungsmesser,” European patent application00108836.8 (20June2000); patent pending.
  2. J. R. Leger, W. C. Goltsos, “Geometrical transformation of linear diode-laser arrays for longitudinal pumping of solid state lasers,” IEEE J. Quantum Electron. 28, 1088–1100 (1992).
    [CrossRef]
  3. J. N. Mait, “Understanding diffractive optic design in the scalar domain,” J. Opt. Soc. Am. A 12, 2145–2158 (1995).
    [CrossRef]
  4. C. Kopp, L. Ravel, P. Meyrueis, “Efficient beamshaper homogenizer design combining diffractive optical elements, microlens array and random phase plate,” J. Opt. A 1, 398–403 (1999).
    [CrossRef]
  5. P. Ehbets, H. P. Herzig, R. Dändliker, P. Regnault, I. Kjelberg, “Beam shaping of high-power laser diode arrays by continuous surface-relief elements,” J. Mod. Opt. 40, 637–645 (1993).
    [CrossRef]
  6. J. W. Goodmann, Introduction to Fourier Optics (McGraw-Hill, New York, 1996).
  7. U. Vokinger, “Propagation, modification and analysis of partial coherent light fields,” Ph.D. dissertation (Université de Neuchâtel, Neuchâtel, Switzerland, 1999).
  8. M. T. Gale, M. Rossi, “Continuous-relief diffractive lenses and microlens arrays,” in Diffractive Optics for Industrial and Commercial Applications, J. Turunen, F. Wyrowski, eds. (Akademie-Verlag, Berlin, 1997), Chap. 4.
  9. M. T. Gale, Th. Hessler, R. E. Kunz, H. Teichmann, “Fabrication of continuous-relief micro-optics: progress in laser writing and replication technology,” in Diffractive Optics and Microoptics, Vol. 5 of 1996 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1996), p. 335.
  10. M. B. Stern, “Binary optics fabrication” in Micro-Optics: Elements, Systems, and Applications, H. P. Herzig, ed. (Taylor & Francis, London, 1997), Chap. 3.
  11. C. Wu, “Method of making high energy beam sensitive glass,” U.S. patent5,078,771 (7January1992).
  12. W. Däschner, C. Wu, S. H. Lee, “General aspheric refractive micro-optics fabricated by optical lithography using a high energy beam sensitive glass gray-level mask,” J. Vac. Sci. Technol. B 14, 135–138 (1996).
    [CrossRef]
  13. Ch. Gimkiewicz, D. Hagedorn, J. Jahns, E.-B. Kley, F. Thoma, “Fabrication of microprisms for planar optical interconnections by use of analog gray-scale lithography with high-energy-beam-sensitive glass,” Appl. Opt. 38, 2986–2990 (1999).
    [CrossRef]

1999

C. Kopp, L. Ravel, P. Meyrueis, “Efficient beamshaper homogenizer design combining diffractive optical elements, microlens array and random phase plate,” J. Opt. A 1, 398–403 (1999).
[CrossRef]

Ch. Gimkiewicz, D. Hagedorn, J. Jahns, E.-B. Kley, F. Thoma, “Fabrication of microprisms for planar optical interconnections by use of analog gray-scale lithography with high-energy-beam-sensitive glass,” Appl. Opt. 38, 2986–2990 (1999).
[CrossRef]

1996

W. Däschner, C. Wu, S. H. Lee, “General aspheric refractive micro-optics fabricated by optical lithography using a high energy beam sensitive glass gray-level mask,” J. Vac. Sci. Technol. B 14, 135–138 (1996).
[CrossRef]

1995

1993

P. Ehbets, H. P. Herzig, R. Dändliker, P. Regnault, I. Kjelberg, “Beam shaping of high-power laser diode arrays by continuous surface-relief elements,” J. Mod. Opt. 40, 637–645 (1993).
[CrossRef]

1992

J. R. Leger, W. C. Goltsos, “Geometrical transformation of linear diode-laser arrays for longitudinal pumping of solid state lasers,” IEEE J. Quantum Electron. 28, 1088–1100 (1992).
[CrossRef]

Dändliker, R.

P. Ehbets, H. P. Herzig, R. Dändliker, P. Regnault, I. Kjelberg, “Beam shaping of high-power laser diode arrays by continuous surface-relief elements,” J. Mod. Opt. 40, 637–645 (1993).
[CrossRef]

Däschner, W.

W. Däschner, C. Wu, S. H. Lee, “General aspheric refractive micro-optics fabricated by optical lithography using a high energy beam sensitive glass gray-level mask,” J. Vac. Sci. Technol. B 14, 135–138 (1996).
[CrossRef]

Ehbets, P.

P. Ehbets, H. P. Herzig, R. Dändliker, P. Regnault, I. Kjelberg, “Beam shaping of high-power laser diode arrays by continuous surface-relief elements,” J. Mod. Opt. 40, 637–645 (1993).
[CrossRef]

Gächter, B.

B. Gächter, A. Schilling, L. Stauffer, U. Vokinger, “Optischer Entfernungsmesser,” European patent application00108836.8 (20June2000); patent pending.

Gale, M. T.

M. T. Gale, Th. Hessler, R. E. Kunz, H. Teichmann, “Fabrication of continuous-relief micro-optics: progress in laser writing and replication technology,” in Diffractive Optics and Microoptics, Vol. 5 of 1996 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1996), p. 335.

M. T. Gale, M. Rossi, “Continuous-relief diffractive lenses and microlens arrays,” in Diffractive Optics for Industrial and Commercial Applications, J. Turunen, F. Wyrowski, eds. (Akademie-Verlag, Berlin, 1997), Chap. 4.

Gimkiewicz, Ch.

Goltsos, W. C.

J. R. Leger, W. C. Goltsos, “Geometrical transformation of linear diode-laser arrays for longitudinal pumping of solid state lasers,” IEEE J. Quantum Electron. 28, 1088–1100 (1992).
[CrossRef]

Goodmann, J. W.

J. W. Goodmann, Introduction to Fourier Optics (McGraw-Hill, New York, 1996).

Hagedorn, D.

Herzig, H. P.

P. Ehbets, H. P. Herzig, R. Dändliker, P. Regnault, I. Kjelberg, “Beam shaping of high-power laser diode arrays by continuous surface-relief elements,” J. Mod. Opt. 40, 637–645 (1993).
[CrossRef]

Hessler, Th.

M. T. Gale, Th. Hessler, R. E. Kunz, H. Teichmann, “Fabrication of continuous-relief micro-optics: progress in laser writing and replication technology,” in Diffractive Optics and Microoptics, Vol. 5 of 1996 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1996), p. 335.

Jahns, J.

Kjelberg, I.

P. Ehbets, H. P. Herzig, R. Dändliker, P. Regnault, I. Kjelberg, “Beam shaping of high-power laser diode arrays by continuous surface-relief elements,” J. Mod. Opt. 40, 637–645 (1993).
[CrossRef]

Kley, E.-B.

Kopp, C.

C. Kopp, L. Ravel, P. Meyrueis, “Efficient beamshaper homogenizer design combining diffractive optical elements, microlens array and random phase plate,” J. Opt. A 1, 398–403 (1999).
[CrossRef]

Kunz, R. E.

M. T. Gale, Th. Hessler, R. E. Kunz, H. Teichmann, “Fabrication of continuous-relief micro-optics: progress in laser writing and replication technology,” in Diffractive Optics and Microoptics, Vol. 5 of 1996 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1996), p. 335.

Lee, S. H.

W. Däschner, C. Wu, S. H. Lee, “General aspheric refractive micro-optics fabricated by optical lithography using a high energy beam sensitive glass gray-level mask,” J. Vac. Sci. Technol. B 14, 135–138 (1996).
[CrossRef]

Leger, J. R.

J. R. Leger, W. C. Goltsos, “Geometrical transformation of linear diode-laser arrays for longitudinal pumping of solid state lasers,” IEEE J. Quantum Electron. 28, 1088–1100 (1992).
[CrossRef]

Mait, J. N.

Meyrueis, P.

C. Kopp, L. Ravel, P. Meyrueis, “Efficient beamshaper homogenizer design combining diffractive optical elements, microlens array and random phase plate,” J. Opt. A 1, 398–403 (1999).
[CrossRef]

Ravel, L.

C. Kopp, L. Ravel, P. Meyrueis, “Efficient beamshaper homogenizer design combining diffractive optical elements, microlens array and random phase plate,” J. Opt. A 1, 398–403 (1999).
[CrossRef]

Regnault, P.

P. Ehbets, H. P. Herzig, R. Dändliker, P. Regnault, I. Kjelberg, “Beam shaping of high-power laser diode arrays by continuous surface-relief elements,” J. Mod. Opt. 40, 637–645 (1993).
[CrossRef]

Rossi, M.

M. T. Gale, M. Rossi, “Continuous-relief diffractive lenses and microlens arrays,” in Diffractive Optics for Industrial and Commercial Applications, J. Turunen, F. Wyrowski, eds. (Akademie-Verlag, Berlin, 1997), Chap. 4.

Schilling, A.

B. Gächter, A. Schilling, L. Stauffer, U. Vokinger, “Optischer Entfernungsmesser,” European patent application00108836.8 (20June2000); patent pending.

Stauffer, L.

B. Gächter, A. Schilling, L. Stauffer, U. Vokinger, “Optischer Entfernungsmesser,” European patent application00108836.8 (20June2000); patent pending.

Stern, M. B.

M. B. Stern, “Binary optics fabrication” in Micro-Optics: Elements, Systems, and Applications, H. P. Herzig, ed. (Taylor & Francis, London, 1997), Chap. 3.

Teichmann, H.

M. T. Gale, Th. Hessler, R. E. Kunz, H. Teichmann, “Fabrication of continuous-relief micro-optics: progress in laser writing and replication technology,” in Diffractive Optics and Microoptics, Vol. 5 of 1996 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1996), p. 335.

Thoma, F.

Vokinger, U.

B. Gächter, A. Schilling, L. Stauffer, U. Vokinger, “Optischer Entfernungsmesser,” European patent application00108836.8 (20June2000); patent pending.

U. Vokinger, “Propagation, modification and analysis of partial coherent light fields,” Ph.D. dissertation (Université de Neuchâtel, Neuchâtel, Switzerland, 1999).

Wu, C.

W. Däschner, C. Wu, S. H. Lee, “General aspheric refractive micro-optics fabricated by optical lithography using a high energy beam sensitive glass gray-level mask,” J. Vac. Sci. Technol. B 14, 135–138 (1996).
[CrossRef]

C. Wu, “Method of making high energy beam sensitive glass,” U.S. patent5,078,771 (7January1992).

Appl. Opt.

IEEE J. Quantum Electron.

J. R. Leger, W. C. Goltsos, “Geometrical transformation of linear diode-laser arrays for longitudinal pumping of solid state lasers,” IEEE J. Quantum Electron. 28, 1088–1100 (1992).
[CrossRef]

J. Mod. Opt.

P. Ehbets, H. P. Herzig, R. Dändliker, P. Regnault, I. Kjelberg, “Beam shaping of high-power laser diode arrays by continuous surface-relief elements,” J. Mod. Opt. 40, 637–645 (1993).
[CrossRef]

J. Opt. A

C. Kopp, L. Ravel, P. Meyrueis, “Efficient beamshaper homogenizer design combining diffractive optical elements, microlens array and random phase plate,” J. Opt. A 1, 398–403 (1999).
[CrossRef]

J. Opt. Soc. Am. A

J. Vac. Sci. Technol. B

W. Däschner, C. Wu, S. H. Lee, “General aspheric refractive micro-optics fabricated by optical lithography using a high energy beam sensitive glass gray-level mask,” J. Vac. Sci. Technol. B 14, 135–138 (1996).
[CrossRef]

Other

B. Gächter, A. Schilling, L. Stauffer, U. Vokinger, “Optischer Entfernungsmesser,” European patent application00108836.8 (20June2000); patent pending.

J. W. Goodmann, Introduction to Fourier Optics (McGraw-Hill, New York, 1996).

U. Vokinger, “Propagation, modification and analysis of partial coherent light fields,” Ph.D. dissertation (Université de Neuchâtel, Neuchâtel, Switzerland, 1999).

M. T. Gale, M. Rossi, “Continuous-relief diffractive lenses and microlens arrays,” in Diffractive Optics for Industrial and Commercial Applications, J. Turunen, F. Wyrowski, eds. (Akademie-Verlag, Berlin, 1997), Chap. 4.

M. T. Gale, Th. Hessler, R. E. Kunz, H. Teichmann, “Fabrication of continuous-relief micro-optics: progress in laser writing and replication technology,” in Diffractive Optics and Microoptics, Vol. 5 of 1996 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1996), p. 335.

M. B. Stern, “Binary optics fabrication” in Micro-Optics: Elements, Systems, and Applications, H. P. Herzig, ed. (Taylor & Francis, London, 1997), Chap. 3.

C. Wu, “Method of making high energy beam sensitive glass,” U.S. patent5,078,771 (7January1992).

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Figures (9)

Fig. 1
Fig. 1

Schematic of the optical setup: laser-diode chip (active region, 1 µm × 350 µm), combined DOE, additional poly(methyl methacrylate) (PMMA) imaging lens, and optical multimode fiber (ϕ = 100 µm; NA = 0.2).

Fig. 2
Fig. 2

Schematic working principle of the beam-shaping device (the Doric and the PMMA lenses are omitted for clarity). The parts of the source are denoted 1–3. The arrows mark the prism functions in the planes of the two DOEs.

Fig. 3
Fig. 3

Typical measured two-dimensional intensity distributions in the plane of the second DOE.

Fig. 4
Fig. 4

Microscope pictures of the two DOEs: (a) the first element, close to the diode laser, (b) the second element. The elements were fabricated by direct laser writing in a photoresist.

Fig. 5
Fig. 5

Calculated and measured intensity distributions in the plane of the second DOE: (a) cross section parallel to the slow axis of the diode laser, (b) cross section parallel to the fast axis of the diode laser. Solid curves, theory; dashed curves, experiment.

Fig. 6
Fig. 6

Calculated and measured intensity distributions in the plane of the fiber: (a) cross section parallel to the slow axis of the diode laser, (b) cross section parallel to the fast axis of the diode laser. Solid curves, theory; dashed curves, experiment.

Fig. 7
Fig. 7

Scanning-electron microscope image of the first element fabricated by HEBS glass gray-tone lithography in photoresist: (a) overview, (b) enlarged detail.

Fig. 8
Fig. 8

Scanning-electron microscope image of the second element fabricated by HEBS glass gray-tone lithography in photoresist: (a) overview, (b) enlarged detail.

Fig. 9
Fig. 9

Scanning-electron microscope image of the first element fabricated as a multilevel structure (eight levels) in fused silica: (a) overview, (b) enlarged detail.

Tables (4)

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Table 1 Experimental Efficiencies of the Single Diffractive Elementsa

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Table 2 Experimental Efficiencies of the Laser-Written Elements and Estimated Optimization Potential Considering Antireflection Coatings and Micro-Optical Elements Fabricated by Gray-Tone Technology

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Table 3 Measured Diffraction Efficiencies Normalized with Respect to Transmitted Intensity through an Unstructured Substrate

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Table 4 Comparison of Measured and Designed Deflection Angles for the Two DOEs

Equations (2)

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SBP=d2λNA,
SBP=1/π.

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