Codeposition of continuous composition rugate filters

Abstract

Rugate filters are optical thin film interference structures with sinusoidal refractive index profiles. Two-wavelength reflection filters have been fabricated by codeposition of SiO(2) and TiO(2). Composition modulation was monitored and controlled using quartz crystal rate controllers. The resulting filters exhibited two well-defined stopbands. Microscopic examination revealed that the structure is glasslike without pronounced thin film microstructure.

Porous silicon-based rugate filters

“…These structures have been investigated for 20 years, because a smooth index profile can improve many features of optical devices with respect to dielectric multilayers. The main difficulty is their experimental achievement, which requires the gradual mixing of two different materials; rugate filters obtained by evaporation, 13,14 reactive sputtering, 15 plasma-enhanced chemical-vapor deposition, 16 and glancing angle deposition 17 were reported in the past. Birefringent rugate filters have been reported too.…”

Physicochemical, structural, and mechanical properties of Si3N4 films annealed in O2

“…14,31 Moreover, the possibility to obtain Si 3 N 4 films at substrate temperatures as low as 100°C, allows the deposition of silicon nitride in different kinds of substrates. GAXRD results are shown in Fig.…”

Optics of subwavelength gradient nanofilms

“…Side by side with these artificial interfaces, the successes in nanotechnology has favored other applications of subwavelength dielectric films, such as, e.g., the gradient-index filters [22], photonic heterostructures (contiguous stacks) [52] and metal-dielectric structures [53]. The rugate optical filter, characterized by continuous sinusoidal index variations along the direction of substrate normal [54], exhibit a range of wavelengths in which the transmittance is nearly zero.…”

“…However, addressing this review to the physical problems of gradient media, we will refer the reader to the original papers, describing the technique of manufacturing of technologically managed profiles ( ) z ε , such as, e.g., etching and photolitography [18], controlled regimes of doping [19], molecular beam epitaxy [20], ion implantation [21], nanoscale porosity variations [22], fabrication of graded metallo-dielectric composites [23], physical vapor deposition of multiple materials [24], production of sculptured thin films [25]. A special attention was given to thin periodical graded-index filters and coatings, characterized by continuous sinusoidal index variation [26]- [28].…”

“…This artificial dispersion of gradient layer, arising due to technological treatment [18][19][20][21][22][23][24][25][26][27][28] of the host dielectric, is determined by the shape and spatial scales of refractive index profile across the layer. We restrict ourselves to layers, whose thickness d is much greater than the spatial dimension in which the refractive index is formed (d > few nm).…”