Abstract

Practically all thin film systems for normal incidence can be realized using only two-layer materials. But for oblique incidence, polarization effects occur, designs may become complex, and polarization control is difficult or impossible to achieve. Here multi-index or gradient designs offer additional degrees of freedom, and can simplify or even enable challenging designs. Such gradient thin film stacks can be designed ab initio without any start or index profile approximations using a new design software developed by Carl Zeiss. With this software, a rugate omnidirectional AR coating was calculated and transferred to three different multi-index systems. All three examples were realized using ion beam sputter technology, and characterized at Laser Zentrum Hannover. Here we present comparative measurements of the optical performance together with femtosecond laser-induced damage threshold measurements.

© 2013 Optical Society of America

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References

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  1. S. W. Anzengruber, E. Klann, R. Ramlau, and D. Tonova, “Numerical methods for the design of gradient-index optical coatings,” Appl. Opt. 51, 8277–8295 (2012).
    [CrossRef]
  2. D. Ristau, “Ion beam sputtering—state of the art and industrial application,” in Proceedings of the 8th International Conference on Coatings on Glass and Plastics, 2010, pp. 203–208.
  3. M. Lappschies, B. Görtz, and D. Ristau, “Optical monitoring of rugate filters,” Proc. SPIE 5963, 59631Z (2005).
    [CrossRef]
  4. C. J. Stolz and D. Ristau, “Thin film femtosecond laser damage competition,” Proc. SPIE 7504, 75040S (2009).
    [CrossRef]

2012 (1)

2009 (1)

C. J. Stolz and D. Ristau, “Thin film femtosecond laser damage competition,” Proc. SPIE 7504, 75040S (2009).
[CrossRef]

2005 (1)

M. Lappschies, B. Görtz, and D. Ristau, “Optical monitoring of rugate filters,” Proc. SPIE 5963, 59631Z (2005).
[CrossRef]

Anzengruber, S. W.

Görtz, B.

M. Lappschies, B. Görtz, and D. Ristau, “Optical monitoring of rugate filters,” Proc. SPIE 5963, 59631Z (2005).
[CrossRef]

Klann, E.

Lappschies, M.

M. Lappschies, B. Görtz, and D. Ristau, “Optical monitoring of rugate filters,” Proc. SPIE 5963, 59631Z (2005).
[CrossRef]

Ramlau, R.

Ristau, D.

C. J. Stolz and D. Ristau, “Thin film femtosecond laser damage competition,” Proc. SPIE 7504, 75040S (2009).
[CrossRef]

M. Lappschies, B. Görtz, and D. Ristau, “Optical monitoring of rugate filters,” Proc. SPIE 5963, 59631Z (2005).
[CrossRef]

D. Ristau, “Ion beam sputtering—state of the art and industrial application,” in Proceedings of the 8th International Conference on Coatings on Glass and Plastics, 2010, pp. 203–208.

Stolz, C. J.

C. J. Stolz and D. Ristau, “Thin film femtosecond laser damage competition,” Proc. SPIE 7504, 75040S (2009).
[CrossRef]

Tonova, D.

Appl. Opt. (1)

Proc. SPIE (2)

M. Lappschies, B. Görtz, and D. Ristau, “Optical monitoring of rugate filters,” Proc. SPIE 5963, 59631Z (2005).
[CrossRef]

C. J. Stolz and D. Ristau, “Thin film femtosecond laser damage competition,” Proc. SPIE 7504, 75040S (2009).
[CrossRef]

Other (1)

D. Ristau, “Ion beam sputtering—state of the art and industrial application,” in Proceedings of the 8th International Conference on Coatings on Glass and Plastics, 2010, pp. 203–208.

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Figures (26)

Fig. 1.
Fig. 1.

Schematic diagram of (a) discrete versus (b) gradient designs.

Fig. 2.
Fig. 2.

Example for improved polarization control. Two cemented 45° beam splitter designs: (a) standard coating materials and (b) mixed layer.

Fig. 3.
Fig. 3.

Realization of mixed layers using Zeiss magnetron sputter tool.

Fig. 4.
Fig. 4.

Multi-index example 1: nonpolarizing edge filter.

Fig. 5.
Fig. 5.

Multi-index example 2: nonpolarizing beam splitter.

Fig. 6.
Fig. 6.

Schematic diagram of the rugate design problem.

Fig. 7.
Fig. 7.

Gradient-design examples. (a) Notch filter, (b) edge filter, and (c) band pass filter. Composition profile (left) and spectral performance (right).

Fig. 8.
Fig. 8.

Transformation to quasi-gradient designs.

Fig. 9.
Fig. 9.

Schematic sketch of an omnidirectional AR coating.

Fig. 10.
Fig. 10.

Calculated maximum AOI for R<1% as a function of the relative spectral bandwidth. Example design has Δλ=40nm.

Fig. 11.
Fig. 11.

Rugate AR design volume fraction profile.

Fig. 12.
Fig. 12.

Rugate AR design spectral performance.

Fig. 13.
Fig. 13.

Rugate AR design transferred to (a) 35-layer binary, (b) 44-layer multi-index, and (c) 159-layer best approximation.

Fig. 14.
Fig. 14.

IBS process with zone target for cosputtering.

Fig. 15.
Fig. 15.

Zone target: refractive index is a function of target position.

Fig. 16.
Fig. 16.

Measured and calculated transmittance spectra of the deposited design. Measured spectral performance is in good agreement with the design.

Fig. 17.
Fig. 17.

Measured reflectance at 800 nm versus AOI is in good agreement with the calculated one.

Fig. 18.
Fig. 18.

Calculated E-field distribution of the 35-layer binary at 800 nm.

Fig. 19.
Fig. 19.

Measured and calculated transmittance spectra of the 44-layer design. The spectral performance is in good agreement with the design.

Fig. 20.
Fig. 20.

Measured reflectance versus AOI is in good agreement with the calculated characteristic.

Fig. 21.
Fig. 21.

Calculated E-field distribution of the 44-layer multi-index design.

Fig. 22.
Fig. 22.

Measured and calculated transmittance spectra of the 159-layer design. The spectral performance is in good agreement with the design.

Fig. 23.
Fig. 23.

Measured reflectance versus AOI is in good agreement with the calculated characteristic.

Fig. 24.
Fig. 24.

Calculated E-field distribution of the 159-layer best approximation.

Fig. 25.
Fig. 25.

Error simulation: 100 tests, 95% probability corridor. Binary thickness error: 1% rms.

Fig. 26.
Fig. 26.

Error simulation: 100 tests, 95% probability corridor. Rugate thickness error, 0.5% rms; refractive index error, 1% rms.

Tables (1)

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Table 1. Femtosecond LIDT Values Determined at 800 nm

Equations (3)

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(q*,d*)=arg minJ(q,d)and0q1.
J(q*,d*)=F[q(z),d]F0(λi,φj)2
Jα(q*,d*)=F[q(z),d]F0(λi,φj)2+αP[q(z),d].

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