Abstract

Second-order nonlinear optical effects require non-centrosymmetric materials. The development of new second-order materials therefore traditionally relies on the growth of single crystals, which is tedious and expensive. Recently, however, it has been found that relatively simple film-growth techniques can also lead spontaneously to non-centrosymmetric structures, as observed for CVD-grown silicon nitride [1,2] and silicon-oxide [3]. Chalcogenides (ChG) are another interesting material platform, particularly for infrared applications. They are mainly known for their high third-order nonlinearity, although crystalline chalcogenides have been studied also for their second-order response [4]. In this paper, we show that thermally-evaporated indium selenide (InSe) thin films have appreciable second-order response that grows with the films thickness, suggesting that this material also possesses an inherent order.

© 2015 IEEE