High Spatial Resolution Measurement of Volume Holographic Gratings

The conventional approach for measuring volume holographic gratings typically requires measuring the transmitted and diffracted beams simultaneously while varying the angle of incidence. To obtain the spectral response a tunable laser is used with a fixed angle of incidence. In the former case, the motion of the diffracted beam from reflection gratings requires the detector to move with it, or otherwise the range of angles must be limited. Furthermore it is often difficult to separate the diffraction from the specular surface reflections, increasing the error of the measurement. In the latter case, a high cost tunable laser is required.