Maria Bayard Dühring - Solid Mechanics

42 Chapter 6 Design of acousto-optical interaction [P3]-[P7]
Δn eff,ν [W −1/2 ]
(a)
1.5
1
0.5
x 10−5
2
mode 1
mode 2
0
0.1 0.15 0.2 0.25 0.3 0.35 0.4
height, h [μm]
normalized index, n eff,ν /n org [−]
1
0.9
0.8
0.7
left waveguide
right waveguide
mode 1
mode 2
0.6
0.1 0.15 0.2 0.25 0.3 0.35 0.4
(b)
height, h [μm]
Figure 6.6 Influence of the waveguide height h on the acousto-optical interaction with
(- - -) indicating results for the original waveguide geometry. (a): ∆neff,ν for the two first
order modes as function of h. (b): Normalized index neff,ν/norg as functions of h.
Figure 6.7 Study of acousto-optical interaction in an optical waveguide in the SOI sample.
The color bars show ∆n11/ √ P and the time averaged power flow in the x3-direction of the
fundamental mode is indicated by the contour lines with an arbitrary scale. (a): For the
optimal height h = 0.19 µm. (b): For the height h = 0.19 µm and the width w = 2.30 µm.
to the normal stresses have opposite sign compared to Si. So, if a big part of the
optical wave propagates in the air and the SiO2 the difference between the effective
refractive indices in the two waveguides will decrease. The optimal value of h is
therefore found as a compromise between how close the center of the optical mode
can come to the surface and how confined it is to the waveguide. Figure 6.6(b) shows
the effective refractive index as function of h for the two first order modes normalized
to the value neff,org of the fundamental mode in the left waveguide with a wave crest
for the original height. neff,ν are in both cases decreasing for decreasing height as
less Si, with high refractive index, is used. The waveguide with the original height