Detection of small anisotropies in holographic phase gratings

This paper shows the possibility to detect very small anisotropies in optically recorded phase gratings using a simple experimental apparatus. The method has been applied to characterize holographic polymer dispersed liquid crystals (HPDLCs). These materials are interesting for fabrication of novel devices to be used in telecom applications since they allow getting Electrically Switchable Bragg Gratings (ESBGs). The experimental technique is based on the spectral angular analysis made on the wavelengths selected and transmitted by the HPDLC grating.