Abstract

We present a new approach of beam homogenizing elements based on a statistical array of concave cylindrical microlens arrays. Those elements are used to diffuse light in only one direction and can be employed together with fly’s eye condensers to generate a uniform flat top line for high power coherent light sources. Conception, fabrication and characterization for such 1D diffusers are presented in this paper.

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References

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  1. M. Miyasaka and J. Stoemenos, “Excimer laser annealing of amorphous and solid-phase-crystallized silicon films,” J. Appl. Phys. 86(10), 5556–5565 (1999).
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  3. R. Bitterli, M. Kim, T. Scharf, H. P. Herzig, A. Bich, C. Dumouchel, S. Roth, R. Voelkel, and K. J. Weible, “Refractive statistical concave 1D diffusers for laser beam shaping,” Proc. SPIE 7062, 70620P (2008).
    [CrossRef]
  4. I. Steingoetter and H. Fouckhardt, “Deep fused silica wet etching using an Au-free and stress-reduced sputter-deposited Cr hard mask,” J. Micromech. Microeng. 15(11), 2130–2135 (2005).
    [CrossRef]
  5. H. Zhu, M. Holl, T. Ray, S. Bhushan, and D. R. Meldrum, “Characterization of deep wet etching of fused silica glass for single cell and optical sensor deposition,” J. Micromech. Microeng. 19, 065013 (2009).
    [CrossRef]
  6. F. Wippermann, U.-D. Zeitner, P. Dannberg, A. Bräuer, and S. Sinzinger, “Beam homogenizers based on chirped microlens arrays,” Opt. Express 15(10), 6218–6231 (2007).
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  7. T. A. Leskova, A. A. Maradudin, E. R. Méndez, and A. V. Shchegrov, “The design and fabrication of one-dimensional random surfaces with specified scattering properties,” Phys. Solid State 41 (5), 835–841 (1999).
    [CrossRef]
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    [CrossRef]
  10. N. M. Ganzherli, “Microlens rasters and holographic diffusers based on PFG-01 silver halide photographic material,” J. Opt. Technol. 76, 384–387 (2009).
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2009 (3)

2008 (1)

R. Bitterli, M. Kim, T. Scharf, H. P. Herzig, A. Bich, C. Dumouchel, S. Roth, R. Voelkel, and K. J. Weible, “Refractive statistical concave 1D diffusers for laser beam shaping,” Proc. SPIE 7062, 70620P (2008).
[CrossRef]

2007 (1)

2005 (1)

I. Steingoetter and H. Fouckhardt, “Deep fused silica wet etching using an Au-free and stress-reduced sputter-deposited Cr hard mask,” J. Micromech. Microeng. 15(11), 2130–2135 (2005).
[CrossRef]

2001 (1)

1999 (2)

M. Miyasaka and J. Stoemenos, “Excimer laser annealing of amorphous and solid-phase-crystallized silicon films,” J. Appl. Phys. 86(10), 5556–5565 (1999).
[CrossRef]

T. A. Leskova, A. A. Maradudin, E. R. Méndez, and A. V. Shchegrov, “The design and fabrication of one-dimensional random surfaces with specified scattering properties,” Phys. Solid State 41 (5), 835–841 (1999).
[CrossRef]

1972 (1)

Albero, J.

Berry, D. H.

Bhushan, S.

H. Zhu, M. Holl, T. Ray, S. Bhushan, and D. R. Meldrum, “Characterization of deep wet etching of fused silica glass for single cell and optical sensor deposition,” J. Micromech. Microeng. 19, 065013 (2009).
[CrossRef]

Bich, A.

R. Bitterli, M. Kim, T. Scharf, H. P. Herzig, A. Bich, C. Dumouchel, S. Roth, R. Voelkel, and K. J. Weible, “Refractive statistical concave 1D diffusers for laser beam shaping,” Proc. SPIE 7062, 70620P (2008).
[CrossRef]

Bitterli, R.

R. Bitterli, M. Kim, T. Scharf, H. P. Herzig, A. Bich, C. Dumouchel, S. Roth, R. Voelkel, and K. J. Weible, “Refractive statistical concave 1D diffusers for laser beam shaping,” Proc. SPIE 7062, 70620P (2008).
[CrossRef]

Bräuer, A.

Dannberg, P.

Dumouchel, C.

R. Bitterli, M. Kim, T. Scharf, H. P. Herzig, A. Bich, C. Dumouchel, S. Roth, R. Voelkel, and K. J. Weible, “Refractive statistical concave 1D diffusers for laser beam shaping,” Proc. SPIE 7062, 70620P (2008).
[CrossRef]

Escamilla, H. M.

Fouckhardt, H.

I. Steingoetter and H. Fouckhardt, “Deep fused silica wet etching using an Au-free and stress-reduced sputter-deposited Cr hard mask,” J. Micromech. Microeng. 15(11), 2130–2135 (2005).
[CrossRef]

Ganzherli, N. M.

García-Guerrero, E. E.

Gomez, V.

Gorecki, C.

Herzig, H. P.

R. Bitterli, M. Kim, T. Scharf, H. P. Herzig, A. Bich, C. Dumouchel, S. Roth, R. Voelkel, and K. J. Weible, “Refractive statistical concave 1D diffusers for laser beam shaping,” Proc. SPIE 7062, 70620P (2008).
[CrossRef]

Holl, M.

H. Zhu, M. Holl, T. Ray, S. Bhushan, and D. R. Meldrum, “Characterization of deep wet etching of fused silica glass for single cell and optical sensor deposition,” J. Micromech. Microeng. 19, 065013 (2009).
[CrossRef]

Kim, M.

R. Bitterli, M. Kim, T. Scharf, H. P. Herzig, A. Bich, C. Dumouchel, S. Roth, R. Voelkel, and K. J. Weible, “Refractive statistical concave 1D diffusers for laser beam shaping,” Proc. SPIE 7062, 70620P (2008).
[CrossRef]

King, M. C.

Leskova, T. A.

E. R. Méndez, E. E. García-Guerrero, H. M. Escamilla, A. A. Maradudin, T. A. Leskova, and A. V. Shchegrov, “Photofabrication of random achromatic optical diffusers for uniform illumination,” Appl. Opt. 40(7), 1098–1108 (2001).
[CrossRef]

T. A. Leskova, A. A. Maradudin, E. R. Méndez, and A. V. Shchegrov, “The design and fabrication of one-dimensional random surfaces with specified scattering properties,” Phys. Solid State 41 (5), 835–841 (1999).
[CrossRef]

Maradudin, A. A.

E. R. Méndez, E. E. García-Guerrero, H. M. Escamilla, A. A. Maradudin, T. A. Leskova, and A. V. Shchegrov, “Photofabrication of random achromatic optical diffusers for uniform illumination,” Appl. Opt. 40(7), 1098–1108 (2001).
[CrossRef]

T. A. Leskova, A. A. Maradudin, E. R. Méndez, and A. V. Shchegrov, “The design and fabrication of one-dimensional random surfaces with specified scattering properties,” Phys. Solid State 41 (5), 835–841 (1999).
[CrossRef]

Meldrum, D. R.

H. Zhu, M. Holl, T. Ray, S. Bhushan, and D. R. Meldrum, “Characterization of deep wet etching of fused silica glass for single cell and optical sensor deposition,” J. Micromech. Microeng. 19, 065013 (2009).
[CrossRef]

Méndez, E. R.

E. R. Méndez, E. E. García-Guerrero, H. M. Escamilla, A. A. Maradudin, T. A. Leskova, and A. V. Shchegrov, “Photofabrication of random achromatic optical diffusers for uniform illumination,” Appl. Opt. 40(7), 1098–1108 (2001).
[CrossRef]

T. A. Leskova, A. A. Maradudin, E. R. Méndez, and A. V. Shchegrov, “The design and fabrication of one-dimensional random surfaces with specified scattering properties,” Phys. Solid State 41 (5), 835–841 (1999).
[CrossRef]

Miyasaka, M.

M. Miyasaka and J. Stoemenos, “Excimer laser annealing of amorphous and solid-phase-crystallized silicon films,” J. Appl. Phys. 86(10), 5556–5565 (1999).
[CrossRef]

Nieradko, L.

Ottevaere, H.

Päivänranta, B.

Passilly, N.

Pietarinen, J.

Ray, T.

H. Zhu, M. Holl, T. Ray, S. Bhushan, and D. R. Meldrum, “Characterization of deep wet etching of fused silica glass for single cell and optical sensor deposition,” J. Micromech. Microeng. 19, 065013 (2009).
[CrossRef]

Roth, S.

R. Bitterli, M. Kim, T. Scharf, H. P. Herzig, A. Bich, C. Dumouchel, S. Roth, R. Voelkel, and K. J. Weible, “Refractive statistical concave 1D diffusers for laser beam shaping,” Proc. SPIE 7062, 70620P (2008).
[CrossRef]

Scharf, T.

R. Bitterli, M. Kim, T. Scharf, H. P. Herzig, A. Bich, C. Dumouchel, S. Roth, R. Voelkel, and K. J. Weible, “Refractive statistical concave 1D diffusers for laser beam shaping,” Proc. SPIE 7062, 70620P (2008).
[CrossRef]

Shchegrov, A. V.

E. R. Méndez, E. E. García-Guerrero, H. M. Escamilla, A. A. Maradudin, T. A. Leskova, and A. V. Shchegrov, “Photofabrication of random achromatic optical diffusers for uniform illumination,” Appl. Opt. 40(7), 1098–1108 (2001).
[CrossRef]

T. A. Leskova, A. A. Maradudin, E. R. Méndez, and A. V. Shchegrov, “The design and fabrication of one-dimensional random surfaces with specified scattering properties,” Phys. Solid State 41 (5), 835–841 (1999).
[CrossRef]

Sinzinger, S.

Steingoetter, I.

I. Steingoetter and H. Fouckhardt, “Deep fused silica wet etching using an Au-free and stress-reduced sputter-deposited Cr hard mask,” J. Micromech. Microeng. 15(11), 2130–2135 (2005).
[CrossRef]

Stoemenos, J.

M. Miyasaka and J. Stoemenos, “Excimer laser annealing of amorphous and solid-phase-crystallized silicon films,” J. Appl. Phys. 86(10), 5556–5565 (1999).
[CrossRef]

Thienpont, H.

Voelkel, R.

R. Bitterli, M. Kim, T. Scharf, H. P. Herzig, A. Bich, C. Dumouchel, S. Roth, R. Voelkel, and K. J. Weible, “Refractive statistical concave 1D diffusers for laser beam shaping,” Proc. SPIE 7062, 70620P (2008).
[CrossRef]

Weible, K. J.

R. Bitterli, M. Kim, T. Scharf, H. P. Herzig, A. Bich, C. Dumouchel, S. Roth, R. Voelkel, and K. J. Weible, “Refractive statistical concave 1D diffusers for laser beam shaping,” Proc. SPIE 7062, 70620P (2008).
[CrossRef]

Wippermann, F.

Zeitner, U.-D.

Zhu, H.

H. Zhu, M. Holl, T. Ray, S. Bhushan, and D. R. Meldrum, “Characterization of deep wet etching of fused silica glass for single cell and optical sensor deposition,” J. Micromech. Microeng. 19, 065013 (2009).
[CrossRef]

Appl. Opt. (2)

J. Appl. Phys. (1)

M. Miyasaka and J. Stoemenos, “Excimer laser annealing of amorphous and solid-phase-crystallized silicon films,” J. Appl. Phys. 86(10), 5556–5565 (1999).
[CrossRef]

J. Micromech. Microeng. (2)

I. Steingoetter and H. Fouckhardt, “Deep fused silica wet etching using an Au-free and stress-reduced sputter-deposited Cr hard mask,” J. Micromech. Microeng. 15(11), 2130–2135 (2005).
[CrossRef]

H. Zhu, M. Holl, T. Ray, S. Bhushan, and D. R. Meldrum, “Characterization of deep wet etching of fused silica glass for single cell and optical sensor deposition,” J. Micromech. Microeng. 19, 065013 (2009).
[CrossRef]

J. Opt. Technol. (1)

Opt. Express (2)

Phys. Solid State (1)

T. A. Leskova, A. A. Maradudin, E. R. Méndez, and A. V. Shchegrov, “The design and fabrication of one-dimensional random surfaces with specified scattering properties,” Phys. Solid State 41 (5), 835–841 (1999).
[CrossRef]

Proc. SPIE (1)

R. Bitterli, M. Kim, T. Scharf, H. P. Herzig, A. Bich, C. Dumouchel, S. Roth, R. Voelkel, and K. J. Weible, “Refractive statistical concave 1D diffusers for laser beam shaping,” Proc. SPIE 7062, 70620P (2008).
[CrossRef]

Other (1)

G. Schröder, Technische Optik, Grundlagen und Anwendungen, (Vogel Verlag und Druck, 2002).

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Figures (18)

Fig. 1
Fig. 1

SEM micrograph of a linear diffuser showing the 100% fill factor of the concave cylindrical lenses and the smooth surface.

Fig. 2
Fig. 2

Schematic representation of the HF etch process. A) Fused silica substrate with a patterned poly-Si etch stop mask. B) Start of the etch process. C) The etch stop mask is completely under etched resulting in 100% fill-factor. D) Continued mask-less etching to adjust the lens’ ROC to the desired value. The dotted circles with their respective center at the edges of the mask openings illustrate how the etched surfaces propagate into the substrate.

Fig. 3
Fig. 3

SEM micrographs of a random 2D diffuser (left) and a regular square lens array (right, seen from a slight angle). The fill factor for both arrangements of concave microlenses is close to 100%.

Fig. 4
Fig. 4

Photo of a section of the intensity distribution for a 1D diffuser showing the non periodic intensity variations.

Fig. 5
Fig. 5

Simulated intensity distribution for a 1D diffuser. The simulation was done by Gaussian ray tracing (FRED).

Fig. 6
Fig. 6

Cross section of the simulated intensity distribution as seen in Fig. 5. The parameters for the diffuser are 200μm mean lens width, 40μm lens variation and 1.5mm ROC. The predicted diffusion angle is about 3° FWHM.

Fig. 7
Fig. 7

Expected diffusion angle based on the lens array’s average numerical aperture as a function of lens ROC and average lens width.

Fig. 8
Fig. 8

Surface profiles of 1D diffusers with a mean lens width of 100μm. The left profile is for a device with standard deviation of 20μm and the right profile is for a standard deviation of 40μm. The right profile shows a clear increase in irregularity compared to the left one.

Fig. 9
Fig. 9

Unwrapped phase obtained by Mach-Zehnder interferometry showing the surface topography of a linear diffuser.

Fig. 10
Fig. 10

Baseline corrected measured profile and the simulated profile. The two curves are nearly identical.

Fig. 11
Fig. 11

Schematics of the photogoniometer setup. The Laser source together with a beam expander (A) and the sample (B) is mounted on a rotating table. The photodetector with a pinhole (C) is mounted fix at a distance of 2m.

Fig. 12
Fig. 12

Intensity distribution for a diffuser with a mean lens width of 100μm and a variation of 20μm. The lens ROC is 1500μm. The measured FWHM diffusion angle is about 1° and the simulated angle is slightly larger.

Fig. 15
Fig. 15

Intensity distribution for a diffuser with a mean lens width of 200μm and a variation of 80μm. The lens ROC is 300μm. The measured FWHM diffusion angle is about 20°. The diffusion angle is close to maximum

Fig. 13
Fig. 13

Intensity distribution for a diffuser with the same parameters as in Fig. 10 but with a ROC of 300μm. The measured FWHM diffusion angle is about 10°.

Fig. 14
Fig. 14

Intensity distribution for a diffuser with a mean lens width of 200μm and a variation of 40μm. The lens ROC is 1500μm. The measured FWHM diffusion angle is about 3° which is slightly smaller than the simulated value of about 3.5°.

Fig. 16
Fig. 16

Schematics of test the setup with an Excimer laser source. From left to right: raw beam, fly’s eye condenser flat top element, random linear diffuser, field lens and PMMA target slide at the focus of the field lens.

Fig. 17
Fig. 17

Trace in a PMMA sample left by an Excimer laser after passing through a flat top element from SUSS MicroOptics. The periodic intensity peaks are clearly visible.

Fig. 18
Fig. 18

Trace left in a PMMA sample slide for a fly’s eye condenser flat top element combined with a linear diffuser with a diffusion angle of 1° FWHM. Compared to Fig. 17 the intensity is very smooth without any periodic intensity peaks.

Equations (2)

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ϕ a = e 2 π i ( n 1 ) y λ .
Θ diff = 2 arctan ( D ( n 1 ) 2 R O C ) .

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