Demonstration of transverse-magnetic dominant gain in quantum dot semiconductor optical amplifiers

We demonstrated transverse-magnetic (TM)-mode dominated gain at the $1.5\mu \mathrm{m}$ wavelength in semiconductor optical amplifiers (SOAs) with columnar quantum dots (QDs). We show that we can control the polarization dependence of optical gain in QD-SOAs by changing the height and tensile-strained barrier of columnar QDs. The TM mode gain is $17.3\mathrm{dB}$ and a gain of over $10\mathrm{dB}$ was attained over a wide wavelength range of $200\mathrm{nm}$ . The saturation output power is $19.5\mathrm{dBm}$ at $1.55\mu \mathrm{m}$ .