REDUCTION OF NOISE-FIGURE IN SEMICONDUCTOR-LASER AMPLIFIERS WITH GA1-XINXAS/GAINASP/INP STRAINED-QUANTUM-WELL STRUCTURES

The noise characteristics of semiconductor laser amplifiers (SLAs) in the Ga1-xInxAs/GaInAsP/InP strained quantum well system were theoretically calculated and analyzed using density-matrix theory taking into account the effects of band-mixing on both the valence subbands and the transition dipole moments. The numerical results showed that a reduced noise figure can be obtained in both tensile and compressively strained quantum well structures due to the increase in differential gain and the decrease in transparent carrier density. From a comparison among compressively strained (x = 0.70), unstrained (x = 0.53), and tensile strained (x = 0.40) QW SLAs at a fixed carrier density and optical confinement factor, it was found that the noise figure of the tensile strained QW becomes the lowest value of 3.4 dB at average input optical power of -20 dB.