AbstractFor a highly information‐oriented society, further enhancement of the capacity and speed of communications and information systems is necessary. For this purpose, all‐optical logic elements are expected as a promising solution. In this paper, structures of new all‐optical logic elements using a nonlinear medium with its index of refraction varying with the optical intensity are proposed and their properties are analyzed. Most of the all‐optical logic elements based on nonlinear materials proposed to date either make use of more than two wavelengths or require a specific phase condition (such as 0° or 180°) for combined lightwaves with identical wavelengths. It is extremely difficult to fix the phase difference between the two lightwaves to be combined. This is a significant problem in practical fabrication. In this paper, all‐optical logic elements are proposed in which only one wavelength is used and no specific phase relationship is required. For the numerical analysis, the FD‐BPM (Finite Difference Beam Propagation Method) based on the Padé) (1, 1) approximation is used. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 85(9): 1–12, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10048