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

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
_i
~ 0.5 cm
^-1
). 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 (
n
_sp
) of the SCOWA was also estimated. The derived
n
_sp
values indicate that intervalence band absorption loss, carrier heating, and quasi-bound higher order modes may ultimately limit the noise performance of InGaAsP SOAs.