This paper gives a comparative analysis of different techniques of continuous readout of volume holograms in photorefractive crystals. The techniques rely on self-diffraction of recording beams and can be used as a basis for developing adaptive holographic interferometers that ensure a high degree of reliability of interferogram formation. The use of adaptive interferometers for the analysis of vibrations and displacements of real objects is illustrated using the photorefractive Bi12Ti020 crystal. This crystal exhibits the highest holographic sensitivity among presently known photorefractive crystals for recording by cw lasers in the red region of the spectrum. The applicability of photorefractive crystals for conversion of phase variations of recording light beams into intensity variations is considered. This enhances the sensitivity of interferometers to vibrations to be measured. The experimental measurements of vibration amplitudes as low as 1 A using Bi12Ti020 and a 0.63 µm laser are reported.
Read full abstract