Abstract

Diffractive slanted gratings are manufactured onto plastic light guides using a high refractive index material and UV replication technology. We show that the manufacturing of such components is possible in large quantities. The applications of the slanted gratings are a high efficiency light in- and outcoupling with plastic light guides. We also show that it is possible to control which outcoupling diffraction order, reflective or transmissive, is dominating and hence to maximize the light power to one direction.

© 2007 Optical Society of America

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References

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    [CrossRef]
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    [CrossRef]
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2006

T. Levola, "Diffractive optics for virtual reality displays," J. Soc. Inf. Disp. 14, 467-475 (2006).
[CrossRef]

2005

R. Mercado et al., "Press patterned diffraction gratings on high refractive index polyimide films," Proc. SPIE 5728, 227-236 (2005).
[CrossRef]

2001

1999

J. P. Plumey et al., "Generalization of the coordinate transformation method with application to surface-relief gratings," J. Opt. Soc. Am A 16,508-516 (1999).
[CrossRef]

B-O. Cho et al., "Fabrication method for surface gratings using a Faraday cage in a conventional plasma etching apparatus," Electrochemical and Solid-State Letters 2, 129-130 (1999).
[CrossRef]

1997

1995

1993

Blomstedt, K.

Cho, B-O.

B-O. Cho et al., "Fabrication method for surface gratings using a Faraday cage in a conventional plasma etching apparatus," Electrochemical and Solid-State Letters 2, 129-130 (1999).
[CrossRef]

Fleming, M. B.

Jones, M. L.

Levola, T.

T. Levola, "Diffractive optics for virtual reality displays," J. Soc. Inf. Disp. 14, 467-475 (2006).
[CrossRef]

Mercado, R.

R. Mercado et al., "Press patterned diffraction gratings on high refractive index polyimide films," Proc. SPIE 5728, 227-236 (2005).
[CrossRef]

Miller, J. M.

Noponen, E.

Parikka, M.

Pascal, D.

Plumey, J. P.

J. P. Plumey et al., "Generalization of the coordinate transformation method with application to surface-relief gratings," J. Opt. Soc. Am A 16,508-516 (1999).
[CrossRef]

Appl. Opt.

Electrochemical and Solid-State Letters

B-O. Cho et al., "Fabrication method for surface gratings using a Faraday cage in a conventional plasma etching apparatus," Electrochemical and Solid-State Letters 2, 129-130 (1999).
[CrossRef]

J. Opt. Soc. Am A

J. P. Plumey et al., "Generalization of the coordinate transformation method with application to surface-relief gratings," J. Opt. Soc. Am A 16,508-516 (1999).
[CrossRef]

J. Opt. Soc. Am. A

J. Soc. Inf. Disp.

T. Levola, "Diffractive optics for virtual reality displays," J. Soc. Inf. Disp. 14, 467-475 (2006).
[CrossRef]

Proc. SPIE

R. Mercado et al., "Press patterned diffraction gratings on high refractive index polyimide films," Proc. SPIE 5728, 227-236 (2005).
[CrossRef]

Other

A. Amagai et al., "Resin for optical materials," US patent US6117923 (2000).

R. Petit, Electromagnetic theory of gratings (Springer-Verlag, Berlin, 1980).

G. Saxby, Practical holography (Institute of Physics Publications, Bristol, 2004).

P. Laakkonen et al., "A method of producing a diffraction grating," PCT patent application PCT/FI2005/050422 (2005).

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Figures (7)

Fig. 1.
Fig. 1.

Incoupling (ηT1 ) and back-coupling (2×ηT1 ) of the light in a wide grating area with a binary incoupling grating.

Fig. 2.
Fig. 2.

Definitions of the parameters of slanted binary grating. The width c of the groove is measured at the half height and the ratio c/d is called the filling ratio. The grating period is d and the grating vertical depth is h. The slanted angle is defined as φ=12)/2. Generally the angle φ1 must be bigger than the angle φ2 (i.e. causing a positive slope for the grating line).

Fig. 3.
Fig. 3.

The incoupling of the light in a splitted grating area.

Fig. 4.
Fig. 4.

Reflection (left) and transmission (right) type outcoupling of slanted gratings.

Fig. 5.
Fig. 5.

Calculated outcoupling efficiencies of slanted binary gratings as a function of grating vertical depth. The left graphs correspond to the reflection type outcoupling and right hand side the transmissive type outcoupling. The parametrers are λ=532 nm, d=405 nm, φ=35 °, and c/d=55% (episulfide material).

Fig. 6.
Fig. 6.

Left: A developed photoresist mask on 100 nm thick Cr layer (80 nm Cr+20 nm LRC). The grating period is d=405 nm. Right: An example of the 100 nm thick Cr mask profile after the chlorine dry etching process.

Fig. 7.
Fig. 7.

Left: A cross section of the manufactured SiO2 mould (grating period is d=405 nm and vertical depth is h=330 nm). Right: UV-replica number 520 showing almost an exact copy of the master mould. The corners are sharp that indicates a good replication degree. The grating lines have a small positive slope (few degrees) caused by the RIBE etching process which is one key factor for the replica separation.

Tables (1)

Tables Icon

Table 1. The measured and calculated efficiencies from a replicated slanted grating structure.

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