One way to write bragg holographic grating is to use the phase mask. if the period of phase mask is 1 micron and the refractive index of recording materail n =1.5
(a) find the period of trecorded bragg grating
(b) what is the resonant wavelength of this bragg grating.
(c) if the number of grating period is 1000, and the refreactive index modulation is △n= 0.0001， estimate the spectral width of reflection spectrum at the resonant wavelength.

increases it

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