Waveguide crossings,
QUEP simulations of configurations with the following specification: background refractive index nb = 1.45, refractive index of the guiding regions ng = 3.4, width of the horizontal core h = 0.2 µm, vacuum wavelength 1.55 µm. All calculations are meant for TE polarization, i.e. Ey is the single nonvanishing component of the electrical field.  

Dependence of the transmission on the width of the vertical core:
The device is excited at the left by the guided mode of the horizontal core. PR, PT, PU, and PD are the relative guided power fractions that are reflected, transmitted straight ahead, or scattered upwards and downwards. Note that due to the symmetry the curves related to PU and PD are superimposed. The links at the positions indicated by the the blue tick marks lead to illustrations of the time dependent electric field.

v = 0.218 µm v = 0.374 µm v = 0.591 µm v = 0.823 µm