It can be seen that the TE mode transmittance always remains below -30dB with the change of the period number of the gradient grating, while the transmittance of the TM mode varies greatly with the period number of the gradient grating.
It can be seen that the transmittance of TE mode always remains below -30dB as the number of gradient grating cycles changes, while the transmittance of TM mode varies significantly with the number of gradient grating cycles,
It can be seen that the transmittance of TE mode is always below -30dB with the change of the period number of graded grating, while the transmittance of TM mode changes greatly with the period number of graded grating.