Directionally-coupled semiconductor optical amplifier for all-optical digital wavelength conversion

The all-optical wavelength conversion gives flexibilities to the optical fiber communication networks, especially to the wavelength-division-multiplexed (WDM)-based ones, because it allows them to reuse wavelengths and to avoid wavelength channel contentions. Recently, we proposed a novel cross-phase modulation (XPM) wavelength converter that had a directionally-coupled semiconductor optical amplifier (DCSOA) structure, and reported its preliminary results of simulation, in which several unique wavelength conversion characteristics, such as improved extinction ratio, digital-like input-output response, and possibility of polarity-non-inverted wavelength conversion, were predicted. We then fabricated the devices and characterized their static wavelength conversion, where we confirmed the digital response and the extinction ratio enhancement in practice. We present an extremely large nonlinear gain found in the DC SOA, that can potentially be utilized for non-inverted wavelength conversion and digital optical processing. Devices were fabricated by using 1.55 /spl mu/m InGaAsP/lnP multiple quantum wells grown by metal-organic vapor phase epitaxy and by using an optimized self-aligned processes.