Impact of Non-Central Input in $N \times M$ Mid-IR Arrayed Waveguide Gratings Integrated on Si

This letter presents a 9 × 35 arrayed waveguide grating (AWG) operating at 1265-1365 cm
^-1
designed for gas sensing applications. The phenomenon of channel spacing variation depending on the position of the input light is demonstrated experimentally. First, the theoretical background is presented. Then, simulations are compared with experimental measurements on 1315-cm
^-1
(7.6 μm) central wavelength AWG. Experimental data are in good agreement with simulation results. Overall scatter of channel spacing variation is 5 cm
^-1
. Input channels inclined from the central position lead either to an increase or a decrease of the spectral channel spacing depending on the specific design of the multiplexer.