Radiation Effects & Defects in Solids: Incorporating Plasma Science & Plasma Technology Vol. 165, No. 5, May 2010, 370–379 Swift ion beam irradiation on lithium niobate single crystals S. Gokul Raj a * and G. Ramesh Kumar b a Department of Physics, National Institute of Technology, Tiruchirappalli 620 015, India; b Department of Physics, University College of Engineering Arni, Anna University Chennai, Arni 632317, India (Received 3 October 2009; final version received 14 February 2010 ) Single crystals of lithium niobate were irradiated by 50 MeV Li 3+ ion irradiation at various ion fluences. The irradiated single crystals were subjected to various studies such as X-ray diffractometry, UV–VIS–NIR analysis and refractive index measurements. Atomic force microscopy patterns were recorded to study the surface changes after irradiation. Micro-Raman measurements were also recorded for irradiated specimens and the result of the measurements are discussed in detail. Keywords: lithium ion irradiation; X-ray diffraction; micro-Raman spectrum; UV–VIS–NIR spectra; AFM 1. Introduction Swift ions having energies in the range of greater than a mega electron volt generate amorphous tracks along the ion trajectories (1–3). Lithium niobate (LiNbO 3 ) is an important material for integrated and guided-wave optics because of its large pyroelectric, electro-optic and photoelastic coefficients. Several techniques have been employed to fabricate the waveguide on LiNbO 3 crystal such as Ti diffusion (4), proton exchange (5), ion implantation (6–8) and low-energy ion irradiation (e.g. helium, fluorine, oxygen) with some mega electron volt kinetic energy (9). Moreover, lithium niobate (LN) is a reference material for the development of photonic applications and electro- optic and nonlinear optical applications. The use of swift ions has started for exploring such applications. These high-energy ions have a range of 50–200 μm within the material before they stopped in a thin layer Bragg peak. Within this Bragg peak, most of the energy is deposited and thus large crystal damages yield substantial changes in the refractive index values. This layer acts as one waveguide wall, if it has reduced refractive index, and forms the resulting waveguide together with the unexposed part of the crystal surface. Kumar et al. (10) have recently reported on the influence of swift ion and proton implanted on the formation of waveguide in LN. But still, Li 3+ ion (50 MeV) irradiation on the single crystals of congruently grown LN has not been well studied in detail. In our earlier works (11), we have reported the 50 MeV Li 3+ ion irradiation effects on second-order nonlinear optical l-threonine single crystals. Following this, in the present work, *Corresponding author. Email: gokulrajs@yahoo.com ISSN 1042-0150 print/ISSN 1029-4953 online © 2010 Taylor & Francis DOI: 10.1080/10420151003716836 http://www.informaworld.com