Analysis of titanium concentration and refractive index profiles of Ti:LiNbO3 channel waveguide

Abstract

An analytical approach has been used to derive Ti-concentration profiles of a titanium indiffused lithium niobate (Ti:LiNbO 3 ) waveguide. Computed results are in good agreement with published experimental data. The work is also extended to compute the Ti-induced refractive index changes of Ti:LiNbO 3 waveguides.

Nonlinear Cherenkov radiations modulated by mode dispersion in a Ti in-diffused LiNbO_3 planar waveguide

“…Subsequently, the effective refractive index was characterized through a prism coupler at 632.8 nm. With the inverse WKB analysis [12], the diffusion depth was fitted to be 4.03 μm, thus we could obtain the refractive index profiles at different wavelengths according to [13][14][15]. We calculated the mode dispersion by the WKB analysis [16], finding four guided modes (TM0, TM1, TE0 and TE1) were supported at 1064 nm, while three modes (TM0, TM1 and TE0) were supported at the longer wavelength of 1342nm in this waveguide.…”

Polarization separation in titanium-diffused waveguides on lithium niobate substrates

“…The depth of titanium diffusion is determined by the process temperature and duration, while being independent of the state of light polarization. Since the refractive index change is greater for the extraordinary polarization, especially at a high concentration of titanium [6], the cutoff wavelength in this case will also be greater. Therefore, by setting the wavelength of propagating light, it is possible to select technological conditions such that the concentration of titanium in the waveguide will ensure that the desired cutoff wavelength for the extraordinary polarization would be greater, and that for the ordinary polarization would be smaller than the given light wavelength.…”

“…The dependence of the local change in refractive index for the ordinary and extraordinary polarization modes is described by the following empirical formula [6]:…”

“…Calculations were performed for a fixed diffusion temperature of T = 1050°C, which provides for the formation of high-quality waveguides with low optical losses for two values of the strip thickness (τ = 80 and 100 nm). Parameters D x = D z = 6 × 10 -17 m 2 s -1 , C e = 7 × 10 29 m -3 , C o = 2.5 × 10 31 m -3 , η e = 0.9, and η o = 0.6 were selected based on an analysis of published data [6].…”