Fig. 1. Illustration of a single-groove grating for five-port beam splitting.

Fig. 2. Unified profiles of all of the propagating modes of a grating under a normal incidence with five transmitted orders. The shaded region is meant to be the ridge of the grating region. The parameters of the grating are f=0.5, Λ=3800nm, wavelength of incidence is λ=1550nm, the refractive indices of the groove and ridge are ng=1, nc=1.5007. Modes 0, 1, 4 are odd symmetric, while modes 2, 3, 5 are even symmetric.

Fig. 3. Contour plot of uniformity (%) calculated by SMM. The grating material is BK-7 glass, and its duty cycle is f=0.5.

Fig. 4. (a) Total transmitted diffraction efficiency and (b) uniformity of 1×5 beam splitting gratings with some fabrication errors.

Table 1. Coupling Coefficients and Effective Indices

Table 2. Diffraction Efficiency and Uniformity Before and After Optimization