Abstract

A design approach is described to achieve spectral blocking filters of any spectral width and optical density for narrow blocking bands. The ratio of the thickness of the high-index material to the low-index material in the layer pairs is adjusted to obtain the desired bandwidth in the first-harmonic reflection band. The number of layer pairs is adjusted to provide the required optical density. Equations are provided for estimating the ratios and number of layer pairs needed to achieve a given bandwidth and optical density. This approach can be useful for laser line blocking filters, night vision filters, and other general applications.

© 2007 Optical Society of America

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References

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  1. A. Thelen, Design of Optical Interference Coatings (McGraw-Hill, 1988), Chap. 7.
  2. R. R. Willey, Practical Design and Production of Optical Thin Films (Dekker, 2002), pp. 106-111.

Thelen, A.

A. Thelen, Design of Optical Interference Coatings (McGraw-Hill, 1988), Chap. 7.

Willey, R. R.

R. R. Willey, Practical Design and Production of Optical Thin Films (Dekker, 2002), pp. 106-111.

Other

A. Thelen, Design of Optical Interference Coatings (McGraw-Hill, 1988), Chap. 7.

R. R. Willey, Practical Design and Production of Optical Thin Films (Dekker, 2002), pp. 106-111.

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Figures (7)

Fig. 1
Fig. 1

Blocking bands with low-index layers of index 1.46 and high layers of 2.35, 1.65, and 1.38 to achieve progressively narrower bands.

Fig. 2
Fig. 2

Same designs seen in Fig. 1 on a transmittance scale. (The out-of-band ripples can be reduced by further design work.)

Fig. 3
Fig. 3

Higher-order harmonic bands at three, five, seven, and nine times the basic (1H 1L)20 design at 1.000 wavenumbers on a frequency scale.

Fig. 4
Fig. 4

Blocking filter at 550nm using the seventh-harmonic-order band but showing the intrusion of the fifth- and ninth-order bands.

Fig. 5
Fig. 5

Higher-order harmonic bands from two to nine times the basic (0.2H 1.8L)20 design (10:1) at 1.000 wavenumbers on a frequency scale.

Fig. 6
Fig. 6

Peak OD versus BW and number of layers for a high index of 2.1. Dark is between OD 3.0 and 6.0.

Fig. 7
Fig. 7

Ratio required as a function of high index and BW for 90 layers. This will vary somewhat with the number of layers.

Equations (4)

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L=(OD+1.757280.32558*H)/(0.79501*BW).
R=0.493912.8864/BW+0.01908/(BW*BW)+5.54919*(H1.46)/((H+1.46)*BW)+6.5233/(L0.25*BW).
BW=0.01391.0257/(R+1)+0.42241*H/L+0.75582*H/(R+1),
OD=0.535890.03003*L+0.01878*H*L+0.3804*H*L/R0.5111*L/R.

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