(a) near field profile for a “shallow” (Al0.23Ga0.77As/Al0.20Ga0.80As/Al0.60As0.40As) waveguide structure for the n-OCL thickness of la = 1.8 μm (curve 1); 0.85 μm (2); 0.57 μm (3); (b) far field profiles (curves 1′,2′,3′) and the vertical angle (aperture) dependences of the input efficiency (curves 1,2,3) for the same structures. The horizontal line in Figure 1(b) corresponds to the input efficiency of 0.95; the total waveguide thickness is h = la + da ′ + 0.05 μm, da ′ = da + da being the total active layer thickness including the thickness da of the barrier(s) separating the quantum wells. The inset shows schematically the waveguide profile and the definitions of the geometric parameters of the waveguide.
As Figure 1 , but for a “deep” (Al0.30Ga0.70As/Al0.20Ga0.80As/Al0.60As0.40As) waveguide structure and the values of la = 0.9 μm (curve 1); 0.45 μm (2); 0.17 μm (3).
The 95% input angle and the active layer confinement factor as function of the thickness la of the n-side of the waveguide (active layer position) for the shallow (a) and deep (b) asymmetric waveguide structures. Total waveguide thickness h = la + da ′ + 0.05 μm as in Fig. 1 . The vertical dashed line corresponds to the boundary between the narrow and broad waveguide as defined in the text. The values of la used in Figures 1 and 2 are shown by filled circles on the curves.
Illustration of the correlation between the vertical input angle and the active layer confinement factor (and the corresponding equivalent spot size) for shallow and deep asymmetric waveguide structures. The point of transition from narrow to broad waveguide is marked on both curves. The active layer width assumed for calculation of the confinement factor is da = 16 nm (two Quantum Wells).
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