Adaptive Holographic Interferometry Using Photorefractive Crystals

A modified technique of dynamic holographic interferometry is described which allows high-frequency vibrations of real objects with amplitudes as low as 1 Å to be measured. In the technique, a low-frequency phase modulation of a relatively large amplitude was imposed on one of the beams. The modulation was used to both actively stabilize the setup and enhance the measured high-frequency signal. Active stabilization of the setup ensures a high accuracy and reliability of measurements of low vibration amplitudes. Dynamic holograms were recorded in a photo-refractive Bi12TiO20 crystal at the HeNe laser wavelength (6328 Å). © 1989.7028286Huignard, Herriau, Valentin, Time average holographic interferometry with photoconductive electrooptic Bi_12SiO_20 crystals (1976) Applied Optics, 16, p. 2796Kamshilin, Mokrushina, (1986) Soc. Techn. Phys. Lett., 12, p. 149Kamshilin, Frejlich, Cescato, Photorefractive crystals for the stabilization of the holographic setup (1986) Applied Optics, 25, p. 2375Frejlich, Cescato, Mendes, Analysis of an active stabilization system for a holographic setup (1988) Applied Optics, 27, p. 753Huignard, Micheron, (1976) Appl. Phys. Lett., 29, p. 591Kamshilin, Petrov, (1985) Optics Comm., 53, p. 2

Growth And Characterization Of Photorefractive Bi12tio20 Single Crystals

Photorefractive Bi12TiO20 single crystals of high optical quality were grown in a resistive heating furnace from high temperature nonstoichiometric (10:1) solutions of Bi2O3 and TiO2 at pulling rates 0.3-0.8 mm/h at rotation 20-30 rpm along the 〈001〉 and 〈011〉 axis. Powder X-ray analysis, Laue method, and electron-probe microanalysis were used for characterization. BTO crystals have the bcc structure of sillenite type with a0 = 10.178(8) angstrom. The chemical composition of the crystals can be written down as Bi12.1±0.2Ti0.96±0.09O20.1. Natural optical activity q of BTO crystals is 6.3 ± 0.2 deg/mm at λ = 0.633 μm and 11.9 ± 0.2 deg/mm at λ = 0.5145 μm, optical absorption coefficient α = 0.42 ± 0.04 cm-1 at λ = 0.633 μm and linear electro-optic coefficient r41 = r52 = r63 = 5.3pm/V. Fanning effect in the 'fiber-like' BTO sample was studied and double phase conjugation with conversion efficiency up to 8% was observed in a wide range of incidence angles of the pump at λ = 0.633 μm for 2 × 3 mW input light power.30217117