Single-mode operation over a wide temperature range in 1.3 μm InGaAsP/InP distributed feedback lasers

An approach for single mode operation of 1.3 μm distributed feedback (DFB) lasers with a large side mode suppression ratio over a wide temperature range of -40°C to 100°C, is reported. The lasers utilize an optimized strained-layer multiquantum well (MQW) active region in combination with index/gain-coupling and detuning effect. A high characteristic temperature T₀ (90-100 K) was obtained in 1.3 μm InGaAsP/InP strained-layer MQW Fabry-Perot lasers when the number of QWs exceeded 10. In gain-coupled DFB lasers, a very low temperature dependence of the threshold current has been obtained when there is no detuning or positive detuning of the lasing wavelength at room temperature with respect to the material gain peak. An infinite T₀ can be realized over certain temperature ranges, in which the threshold current exhibits a minimum, depending on the amount of detuning. The physical mechanism responsible for the appearance of this minimum, as well as the high side mode suppression ratio, are explained theoretically