The “gain-lever" effect in InGaAsP/InP multiple quantum welllasers

The gain-lever-effect has been assessed in both multiple quantum well (MQW) and bulk active region lasers having a range of lengths and split ratios in the top contact. Compared with a conventional single-contact laser, a 500-μm MQW FP device with a top-contact split ratio of 8:1 exhibited >15-dB improvement in AM efficiency and a signal-to-noise ratio improvement of 7.5 dB. With proper impedance matching, these figures may be improved. A reduced noise figure is obtained at the expense of dynamic range with an additional nonlinearity seen experimentally due to thermal and carrier leakage when compared with simulations carried out using a harmonic balance model. Used carefully, these gain-lever lasers are useful components for future analogue fiber-optic systems