The refractive index contrast in dielectric multilayer structures, optical resonators and photonic crystals is an important figure of merit, which creates a strong demand for high quality thin films with a very low refractive index. SiO2 nano-rod layers with low refractive indicesn = 1.08, the lowest ever reported in thin-film materials, is grown by oblique-angle e-beam deposition of SiO2 with vapor incident angle 85 degree. Scanning electron micrographs reveal a highly porous columnar structure of the low-refractive-index (low-n) film. The gap between the SiO2 nano-rods is ≤50 nm, i.e. much smaller than the wavelength of visible light, and thus sufficiently small to make scattering very small. Optical micrographs of the low-n film deposited on a Si substrate reveal a uniform specular film with no apparent scattering. The unprecedented low index of the SiO2 nano-rod layer is confirmed by both ellipsometry measurements and thin film interference measurements. A single-pair distributed Bragg reflector (DBR) employing the SiO2 nano-rod layer is demonstrated to have enhanced reflectivity, showing the great potential of low-n films for applications in photonic structures and devices.
This is a preview of subscription content, access via your institution.
Buy single article
Instant access to the full article PDF.
Tax calculation will be finalised during checkout.
K. Streubel, S. Rapp, J. André, and N. Chitica, Elec. Lett. 32, 1369 (1996).
S.-T. Ho, S. L. McCall, R. E. Slusher, L. N. Pfeiffer, K. W. West, A. F. J. Levi, G. E. Blonder, and J. L. Jewell, Appl. Phys. Lett. 57, 1387 (1990).
B. Temelkuran, S. D. Hart, G. Benoit, J. D. Joannopoulos, and Y. Fink, Nature 420, 650 (2002).
J.-Q. Xi, M. Ojha, W. Cho, J. L. Plawsky, W. N. Gill, Th. Gessmann, and E. F. Schubert, Opt. Lett. 30, 1518 (2005).
J.-Q. Xi, M. Ojha, J. L. Plawsky, W. N. Gill, J. K. Kim, and E. F. Schubert, Appl. Phys. Lett. 87, 031111 (2005).
S. V. Nitta, V. Pisupatti, A. Jain, P. C. Wayner, Jr., W. N. Gill, and J. L. Plawsky, J. Vac. Sci. Technol. B 17, 205 (1999).
A. Jain, S. Rogojevic, S. Ponoth, N. Agarwal, I. Matthew, W. N. Gill, P. Persans, M. Tomozawa, J. L. Plawsky, and E. Simonyi, Thin Solid Films 398–399, 513 (2001).
J. G. W. van de Waterbeemd, and G. W. van Oosterhout, Philips Res. Repts. 22, 375 (1967).
A. Lakhtakia, R. Messier, Sculptured Thin Films: Nanoengineered Morphology and Optics, (SPIE, Washington, USA 2005).
K. Robbie, L. J. Friedrich, S. K. Dew, T. Smy, and M. J. Brett, J. Vac. Sci. Technol. A 13, 1032 (1995).
K. Robbie, and M. J. Brett, J. Vac. Sci. Technol. A 15, 1460 (1997).
D. Vick, L. J. Friedrich, S. K. Dew, M. J. Brett, K. Robbie, M. Seto, and T. Smy, Thin Solid Films 339, 88 (1999).
K. Kaminska, and K. Robbie, Appl. Opt. 43, 1570 (2004).
About this article
Cite this article
Xi, JQ., Kim, J.K., Ye, D. et al. Optical Thin Films with Very Low Refractive Index and Their Application in Photonics Devices. MRS Online Proceedings Library 901, 129 (2005). https://doi.org/10.1557/PROC-0901-Ra11-29-Rb11-29