Noise Figure of Watt-Class Ultralow-Confinement Semiconductor Optical Amplifiers

Abstract

We investigate the noise figure (NF) of high-power semiconductor InGaAsP optical amplifiers (SOAs) based on the slab-coupled optical waveguide (SCOW) concept having both ultralow optical confinement (Γ ~ 0.5%) and low optical loss (α <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> ~ 0.5 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ). At 1550 nm and 5-A current bias, the NF of SCOW amplifier (SCOWA) is 5.5 dB, and the small-signal gain and saturation output power are 13 dB and 0.8 W, respectively. A minimum NF of 4.5 dB is achieved at 2-A bias. These NF results represent the lowest reported for a packaged SOA. Using the measured NF, the population inversion factor ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sp</sub> ) of the SCOWA was also estimated. The derived <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sp</sub> values indicate that intervalence band absorption loss, carrier heating, and quasi-bound higher order modes may ultimately limit the noise performance of InGaAsP SOAs.