Studies Of Both Quantum Size Distribution And Temperature Effects On Quantum Dot Semiconductor Optical Amplifier

Considering both the inhomogeneous broadening of the carrier energies caused by quantum dot size distribution and homogeneous broadening caused by carrier-phonon scattering,a general optical gain expression with both quantum dot size distribution?QDSD?and temperature effects are given for a quantum dot semiconductor optical amplifier?QD-SOA?.Furthermore,using this expression associated with a group of carrier rate equations the amplified spontaneous emission?ASE?and the saturation gain of an InAs/GaAs QD-SOA related to both QDSD and temperature,the carrier recovery time due to light pumping are numerically investigated by using 4^th order Runge-Kutta method.The results are proved as fellows1.The ASEs of both ground and excited states strongly depend on the temperature of QD-SOA.The higher the temperature is,the larger the ASE is for a given QDSD.However,the change becomes slow when the temperature is in excess of 400 K.Contrast to this,the QDSD larger,the smaller the ASE is for a given temperature.2.There are two peaks in the ASE emitted by both ground and excited states and the ASE peak generated by excited state is higher than ground one.The ASE exhibits a Gaussian at low temperature but a Lorentzian when the temperature is up to 400 K.In general,it is a combined profile.The total spectral width is in excess of 120 nm and is much larger than those in bulk and quantum well semiconductor optical amplifiers,which is very beneficial to amplifying the optical signal in the WDM system of fiber web.3.The gain in the ground state is drastically decreased when,owing to an amount of carriers depleted by stimulated emission,a pumping light excites resonantly with the ground one.Meanwhile,the gain in the excited state also is decreased because the carriers are relaxed to the ground state caused by LO-phonon assistance.The smaller the excited state effected by temperature,the larger the QDSD is at room temperature.In this case,the saturated gain in the ground state strongly depends on the temperature and the gain is easier saturated at lower temperature.4.The gain in the excited state is not only drastically decreased but also the one in ground state is pumping resonantly the excited state by using an external laser.The gain in the ground state becomes a negative gain?absorption?changed from a positive one in this case and is almost independence on the QDSD.Thus a large detuning all-optical wavelength conversion may be realized and the inverse codes in XGM are eliminated based on the optical behavior to some extent.And this effect is closely related to both QDSD and temperature.The lower the temperature,the fast the gain is decreased for a given QDSD.The smaller the QDSD,the easier the gain is saturated at room temperature.5.The gains in both the ground and excited states based on the pump-probe technique are numerically investigated for the InAs/GaAs QD-SOA.The results show that the recovery time of the carriers is ranging from 0.15⁰.175 ps and is almost unchanged under the same condition.And only a litter change can be made for this recovery time in the range of QDSD 2%⁵%.Compared to both bulk and quantum-well semiconductor optical amplifiers,it has faster nonlinear response.