A Method to Determine H⁺ Concentration in Dehydrated Iron Doped Lithium Niobate Using Photorefractive Beam Fanning Effect

Abstract

We investigated the thermal behavior of the photorefractive fanning effect in dehydrated lithium niobate doped with iron. Thermal dark decay of backward scattering did not follow the law determined for thermal fixing of two-wave mixing gratings. It can be explained by a combination of reflection and small-angle fanning. The concentration of hydrogen in the sample was determined by comparing the decay of 90° scattering with that of the small-angle one. A calibration factor of A/N _H = (2.5 ± 0.5) × 10⁻¹⁸ cm, and a cross section of (2.1 ± 0.4)× 10 ^{− 19} cm ² were also determined for the 3480 cm ^{− 1} IR absorption band of OH^– ions.

Keywords:

• Photorefractive effect
• beam fanning
• thermal dark decay
• lithium niobate

Acknowledgments

We express our gratitude to the Department of Crystal Technology for the samples, and to Dr. István Földvári and Dr. László Kovács for their advice on thermal treatments. Financial supports from the Hungarian Scientific Research Fund (Project Nos. OTKA T047265g and K60086), and from the Austrian Science Fund FWF (P-18988) are also gratefully acknowledged.

Notes

*Determined using Ref. 5.