VPH Grating Physics (true holographic gratings)
Diffraction due to modulations in refractive index (Dn) of the grating material rather than by surface structure.
Light is diffracted at angles according to the classical diffraction equation:
The energy distribution is governed by the Bragg condition: e.g. for a Littrow grating configuration -
Grating depth (d) and index modulation (Dn) define Bragg performance.