Fig. 1 (a) X-Y cross section of a single SOI shallow ridge waveguide and plan view of the structure showing TM to TE mode coupling at the side wall of the ridge, (b) X-Y cross section of two identical and parallel SOI shallow ridge waveguides and plan view of the structure showing the mechanism of the summation of the radiation of the two waveguides in both sides of the structure. Waveguide dimensions are shown.

Fig. 2 Electric field components of the guided mode of the waveguide of Fig. 1 with width 1µm to maximize TE radiation at λ = 1.55μm. (a) real component; (b) imaginary component.

Fig. 3 The magnitude of the y-component of the electric fields of the TM-like modes of (a) the original SOI waveguide; (b) the additional identical SOI waveguides with a 4.58µm lateral translation and a π/2 phase shift and (c) the coherent superposition of these two modes; (d) the magnitude (in Log scale) of the super-imposed radiation fields of identical modes at two symmetric fixed points (y1 = + 8µm and y2 = −8µm, x1 = x2 = midpoint of the Si film) on right & left hand sides of both waveguides versus the gap (S) between the waveguides and the magnitude of the summation of the TE radiation waves as obtained from Eq. (1) and (2) which account for the phase difference between the two TE waves.

Fig. 4 .Real (a) and imaginary (b) parts of the effective refractive indices of the even and odd supermodes of the structure versus the waveguide separation, respectively. The magnitude of the y-component of the electric fields of the TM-like supermodes of the structure with 4.54µm waveguide separation respectively: (c) even mode (d) odd mode.

Fig. 5 (a) Magnitude of the y-component of the electric field of the superimposed TM-like even and odd supermodes of the structure with a phase difference of π/2 and 4.54µm waveguide separation; (b) magnitude (Log scale) of the radiation field from the superposition of the supermodes for two symmetric fixed points (y1 = + 8µm and y2 = −8µm, x1 = x2 = middle point of the Si film) to the right and left of the structure as a function of waveguide separation.

Fig. 6 Poynting vector magnitude of Y-Z cross section of the structure for waveguide separations of, (a) 4.36μm, (b) 4.54μm and (c) 4.45μm; Poynting vector magnitude at two symmetric fixed points to the right and left of the structure (y1 = + 8µm and y2 = −8µm, x1 = x2 = midpoint of the Si-film) as a function of propagation distance in the z-direction for (d) 4.36μm, (e) 4.54μm and (f) 4.45μm.