Abstract

Wide band-gap semiconductors recently have attracted substantial interest for their applications in solid-state electronics and optics [1]. In particular, zinc oxide (ZnO) is a II-VI semiconductor with a wide band-gap of 3.37-eV, and a direct gap structure at room temperature. It is especially attractive because of the recent demonstrations of its applicability as a perspective material for near-UV emitters [2-3] and ultrafast UV light modulators [4]. On the other hand, there is a significant demand for thin-film nonlinear optical materials, which can be easily integrated into an opto-electronic device. It has been recently pointed out that ZnO films have a strong nonlinear second-order optical susceptibility χ⁽²⁾ and the efficient coherent second harmonic has been generated in thin films of ZnO [5-6]. In this report we demonstrate that nanocrystalline ZnO leads to a very high χ⁽³⁾ nonlinearity as well, leading to a very efficient non-resonant third harmonic generation from an unamplified near-IR radiation of femtosecond Cr⁴⁺:forsterite laser (1200-1300 nm) [7].

© 2003 Optical Society of America