The wavelength which exits the grating at an angle equal and opposite to the angle of incidence with respect to the grating surface normal, this is also known as the Bragg condition.
$\lambda_g = 2 \frac{\sin\left( \alpha \right)} {m\nu}$
Where:
- $\lambda_g$ [m]: the undeviated wavelength.
- $\alpha$ [°]: the angle of incidence.
- $m$: the diffraction order.
- $\nu$ [lines/m]: the fringe frequency.
Volume‐Phase Holographic Gratings and the Efficiency of Three Simple Volume‐Phase Holographic Gratings on JSTOR