Large third-order optical nonlinearities in transition-metal oxides

Abstract

ADVANCES in the field of optical computing^1–3 will require the development of materials that combine a large nonlinear optical response with a fast response time. For many applications, this translates into a third-order nonlinear optical susceptibility, χ⁽³⁾, in excess of 10⁻⁸ e.s.u., and a response time faster than lO ps (ref. 4). Although a wide range of inorganic^5–18 and organic^19–21 materials have been found to exhibit a large χ⁽³⁾, either the response times tend to be far too slow or the materials are not sufficiently stable for device applications. Recently, the transition-metal oxide Fe₂O₃ was found to have a large χ⁽³⁾ (ref. 22). Here we show that oxides of several other 3d transition metals show a similarly large nonlinear optical response; moreover, we find that a significant contribution to the overall χ⁽³⁾ (∼10⁻⁸ e.s.u. in the case of V₂O⁵) has a response time of the order of 35 ps.