my grating image attached. i have a waveguide. wveguide core:PMMA_DR1 & waveguide clad:PVA i have 3 mod in waveguide. my RI diffrent is about of 0.005 to 0.02 i writing grating and my grating period : 20 , 25 , 30, 35, 40, 45, 50 , 60 , 70 , 80, 90,100, 150,200,250 micron but but but :-( answer is same and i do not see dipes my light source is helium-dotriom and my spectrometr is ocean optic please help me [IMG]
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