All optical switching and tunable wavelength filtering in grating assisted directional coupler

In this paper we propose a simple approach to optically tune/switch the wavelength selectivity of a grating assisted directional coupler (GADC) using a strong tuning beam launched into one of the two GADC subwaveguides which is nonlinear. In the absence of the tuning beam, the structure supports a particular wavelength (of weak signal) that exchanges power between the two subwaveguides. In the presence of the tuning beam, refractive index of the nonlinear subwaveguide changes and the modified structure supports the exchange of energy for a different wavelength (of weak signal). We show that desired wavelength could be either gradually or instantly tuned from one wavelength to another to provide power exchange for an appropriate length of the device. © 2007 Old City Publishing, Inc.