In 1880, by studying light passing through Earth's atmosphere, Lord Rayleigh mathematically demonstrated that graded-refractive-index layers have broadband antireflection characteristics1. Graded-index coatings with different index profiles have been investigated for broadband antireflection properties, particularly with air as the ambient medium2,3,4. However, because of the unavailability of optical materials with very low refractive indices that closely match the refractive index of air, such broadband antireflection coatings have not been realizable. Here we report the fabrication of TiO2 and SiO2 graded-index films deposited by oblique-angle deposition, and, for the first time, we demonstrate their potential for antireflection coatings by virtually eliminating Fresnel reflection from an AlN–air interface over a broad range of wavelengths. This is achieved by controlling the refractive index of the TiO2 and SiO2 nanorod layers, down to a minimum value of n = 1.05 in the case of the latter, the lowest value so far reported.
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Rayleigh, J. S. On reflection of vibrations at the confines of two media between which the transition is gradual. Proc. London Math. Soc. 11, 51–56 (1880).
Southwell, W. H. Gradient-index antireflection coatings. Opt. Lett. 8, 584–586 (1983).
Dobrowolski, J. A., Poitras, D., Ma, P., Vakil, H. & Acree, M. Toward perfect antireflection coatings: numerical investigation. Appl. Opt. 41, 3075–3083 (2002).
Poitras, D. & Dobrowolski, J. A. Toward perfect antireflection coatings. 2. Theory. Appl. Opt. 43, 1286–1295 (2004).
Vollgraff, J. A. Snellius' notes on the reflection and refraction of rays. Osiris 1, 718–725 (1936).
Boutry, G. A. Augustin Fresnel: His time, life and work 1788–1827. Science Progress 36, 587–604 (1948).
Xi, J.-Q. et al. Internal high reflectivity omni-directional reflectors. Appl. Phys. Lett. 87, 031111 (2005).
Xi, J.-Q. et al. Omnidirectional reflector using nanoporous SiO2 as a low-refractive-index material. Opt. Lett. 30, 1518–1520 (2005).
Sharma, R., Haberer, E. D., Meier, C., Hu, E. L. & Nakamura, S. Vertically oriented GaN-based air-gap distributed Bragg reflector structure fabricated using band-gap-selective photoelectrochemical etching. Appl. Phys. Lett. 87, 051107 (2005).
Ho, S.-T. et al. High index contrast mirrors for optical microcavities. Appl. Phys. Lett. 57, 1387–1389 (1990).
Xu, Q., Almeida, V. R., Panepucci, R. R. & Lipson, M. Experimental demonstration of guiding and confining light in nanometer-size low-refractive-index material. Opt. Lett. 29, 1626–1628 (2004).
Kim, J. K. et al. GaInN light-emitting diode with conductive omnidirectional reflector having a low-refractive-index indium-tin oxide layer. Appl. Phys. Lett. 88, 013501 (2006).
Jain, A. et al. Porous silica materials as low-k dielectrics for electronic and optical interconnects. Solid Thin Films 398–399, 513–522 (2001).
Xi, J.-Q., Kim, J. K. & Schubert, E. F., Silica nanorod-array films with very low refractive indices. Nano Lett. 5, 1385–1387 (2005).
Xi, J.-Q. et al. Very low-refractive-index optical thin films consisting of an array of SiO2 nanorods. Opt. Lett. 31, 601–603 (2006).
Hodgkinson, I. J., Horowitz, F., Macleod, H. A., Sikkens, M. & Wharton, J. J. Measurement of the principal refractive indices of thin films deposited at oblique incidence. J. Opt. Soc. Am. A 2, 1693–1697 (1985).
Southwell, W. H. Pyramid-array surface-relief structures producing antireflection index matching on optical surfaces. J. Opt. Soc. Am. A 8, 549–553 (1991).
Minot, M. J. Single-layer, gradient refractive index antireflection films effective from 0.35 µm to 2.5 µm. J. Opt. Soc. Am. 66, 515–519 (1976).
Asahara, Y. & Izumitani, T. The properties of gradient index antireflection layer on the phase separable glass. J. Non-Crys. Solids 42, 269–279 (1980).
Yoldas, B. E. & Partlow, D. P. Wide spectrum antireflective coating for fused silica and other glasses. Appl. Opt. 23, 1418–1424 (1984).
Maffitt, K. N., Brueckner, H. U. & Lowrey, D. R. Polymeric optical element having antireflecting surface. US Patent 4,153,654, 8 May 1979.
Wilson, S. J. & Hutley, M. C. The optical properties of “moth eye” antireflection surfaces. Opt. Acta 7, 993–1009 (1982).
Wu, G. et al. Preparation and properties of scratch-resistant nano porous broadband AR silica films derived by a two-step catalytic sol-gel process. Proc. SPIE 4086, 807–810 (2000).
Robbie, K. & Brett, M. J. Sculptured thin films and glancing angle deposition: Growth mechanics and applications. J. Vac. Sci. Technol. A 15, 1460–1465 (1997).
Robbie, K. et al. Ultrahigh vacuum glancing angle deposition system for thin films with controlled three-dimensional nanoscale structure. Rev. Sci. Instrum. 75, 1089–1097 (2004).
Kennedy, S. R. & Brett, M. J. Porous broadband antireflection coating by glancing angle deposition. Appl. Opt. 42, 4573–4579 (2003).
Robbie, K., Sit, J. C. & Brett, M. J. Advanced techniques for glancing angle deposition. J. Vac. Sci. Technol. B 16, 1115–1122 (1998).
Abelmann, L. & Lodder, C. Oblique evaporation and surface diffusion. Thin Solid Films 305, 1–21 (1997).
Harris, K. D., Westra, K. L. & Brett, M. J. Fabrication of perforated thin films with helical and chevron pore shapes. Electrochem. Solid-State Lett. 4, C39–C42 (2001).
Pulker, H. K., Paesold, G. & Ritter, E. Refractive indices of TiO2 films produced by reactive evaporation of various titanium-oxygen phases. Appl. Opt. 15, 2986–2991 (1976).
The authors gratefully acknowledge support from Sandia National Laboratories (USA), Crystal IS Corporation (USA), Samsung Advanced Institute of Technology (Korea), the Army Research Office (USA), the New York State Office of Science, Technology and Academic Research (USA), the National Science Foundation (USA) and the Department of Energy (USA).
The authors declare no competing financial interests.
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Xi, JQ., Schubert, M., Kim, J. et al. Optical thin-film materials with low refractive index for broadband elimination of Fresnel reflection. Nature Photon 1, 176–179 (2007). https://doi.org/10.1038/nphoton.2007.26
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