Reply To: Diffraction angle (-90~90 degree)

[Guilin Sun]

As you know, infinite period grating creates diffraction at isolated diffraction angles. So your result is correct.

As for the published result, please check the paper again. I suspect that its incidence is a cone beam, such as from a microscope objective. because of broad incident angles, it may induce continuous  angular distribution. From your grating analysis, the 1st diffraction has diffraciton angle of 30deg. therefore, I guess the incident beam would have about 30 deg cone. Please check.