A 35-mm-long periodically poled device was fabricated from a near-stoichiometric lithium tantalate, and optical parametric oscillation was demonstrated with a low oscillation threshold (106 mW). The emitted signal and idler wavelengths were 1.53–1.63 and 3.06–3.49 μm, respectively, and the highest slope conversion efficiency was 65% with a maximum output power of 628 mW at 1.1 W pumping. The influence of Curie temperature inhomogeneity on fabrication of the device was investigated to improve poling quality in long devices.
We have demonstrated a novel optical interferometric technique for a highly scattering environment, using photorefractive coherence gating. A two-wave mixing process in a photorefractive barium titanate crystal effectively reduces scattering noise, and we have successfully detected interferometric signals through scattering media of up to 17 mfp, with a high visibility. We have also demonstrated a two-dimensional thickness measurement of an optically scattering thin film using our new interferometry.
A new configuration holographic memory with a one-beam geometry in a photorefractive crystal has been proposed, and recording of ten angle-multiplexed holograms in a Fe:LiNbO3 crystal has been experimentally demonstrated. A maximum page number of 1728 pages in the LiNbO3 crystal was theoretically estimated by the angular multiplexing method at an incident beam diameter of 5.10 mm and the laser wavelength of 514.5 nm. In this new configuration, one incident beam can simultaneously play two roles as an object beam and a reference beam, therefore, an optical setup becomes simpler than conventional setups, which leads to compact and robust holographic recording system.
A novel high-resolution surface sensing device is developed and demonstrated, which utilizes Bragg diffraction from the volume holograms in the photorefractive BaTiO 3 crystal. In this device, the angular information of a surface is obtained as a diffraction pattern from the multiplexed holograms stored in the crystal. The resolution of this device is as high as submilliradian due to the Bragg selectivity. Additionally, a new method of surface structure comparison between two samples is also demonstrated using this device, which is applicable to the nondestructive surface inspection of optical components.
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