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Direct electronic compensation of the inherent amplification nonlinearity of semiconductor laser amplifiers is investigated. It is found that operating the active layer junction from a voltage source, which in theory would hold the carrier density at a constant value, does not remove the amplification nonlinearity because of the intraband carrier dynamics. However, compensation of the nonlinearity is shown to be possible by driving the laser amplifier from a negative output impedance source. Using this at 80 mA drive current compensation of the amplification nonlinearity is demonstrated for a 1310 nm polarization insensitive multiple quantum well laser amplifier showing 18 dB gain (13 dB fiber to fiber) and a nonlinearity of 0.36 dB/mW. It is further shown that the intraband carrier dynamics, mainly the carrier heating, cause limitations to both the driving conditions for which the nonlinearity can be compensated, and to the use of laser amplifiers as an amplifying detector.

A polarization insensitive (less than 1 dB gain difference over the 3 dB gain bandwidth) multiple quantum well laser amplifier for the 1300 nm window is reported for the first time. The amplifiers employ a single active layer containing three tensile strained and four compressively strained quantum wells and show a fiber to fiber gain of 16 dB at 1310 nm and 200 mA driving current. Furthermore at the same wavelength these devices have a record low fiber coupled noise figure of 6.5 dB and a conveniently high fiber coupled saturation output power of 13 dBm for both polarizations.

1.5 μm wavelength InxGa1−xAs‐InGaAsP (x=0.7, resulting in 1.2% compressive strain and x=0.53, resulting in zero strain) multiple quantum well (MQW) structures were grown on (311)B, (511)A, (511)B, and (001)InP substrates by low‐pressure organometallic vapor phase epitaxy (LP‐OMVPE). Intense and narrow linewidth room‐temperature photoluminescence spectra indicate the device quality of the MQW structures. Strained MQW lasers grown on InP substrates misoriented towards (111)B show about 25% lower threshold current densities than the unstrained MQW lasers. The high quality of the strained MQW structures grown on (311)B InP substrates is demonstrated by the realization of 0.9 mA threshold current buried heterostructure lasers employing semi‐insulating current blocking layers, and entirely grown by LP‐OMVPE.

In this letter the linewidth enhancement factor measured from a tensile strained, a compressively strained, and a lattice matched InGaAs/InP multiple quantum well laser is analyzed taking free‐ carrier effects into account. We find that the free carriers in the wells of compressively strained and lattice matched structures degrade the linewidth enhancement factor by about 40% due to the plasma effect. In tensile strained TM polarized lasers however, carrier movement parallel to the E vector is inhibited due to the quantum confinement, allowing a linewidth enhancement factor as low as 1.6 at the peak wavelength. Heterobarrier carrier leakage must be prevented using sufficiently large band‐gap barrier and separate confinement layers, otherwise the free carriers in these layers result in an additional degradation of the linewidth enhancement factor.

Transparency current densities of 250 and 160 A/cm2 per well at the bandgap wavelength are reported for compressively and tensile strained multi quantum‐well laser amplifiers. A strong wavelength dependence of the transparency current is found, due to level broadening, which shows that the threshold current of a quantum‐well laser is inherently loss limited, rather than transparency limited. The spectral and polarizational dependence of the gain is measured and analyzed. From this it is concluded that the compressively (1.8%) and tensile (1.6%) strained quantum‐well laser amplifiers exhibit valence band effective masses of 0.07 m0 and 0.1 m0, respectively, which shows that they both have a nearly symmetric band structure.