We report the demonstration of distributed-feedback terahertz quantum-cascade lasers based on a first-order grating fabricated via a lateral corrugation in a double-sided metal ridge waveguide. The phase of the facet reflection was precisely set by lithographically defined facets by dry etching. Single-mode emission was observed at low to moderate injection currents, although multimode emission...

We present a numerical study of the effects of optical feedback on the static and dynamic characteristics of verticalcavity surface-emitting lasers (VCSEL’s) under both single-mode and two-mode operations. Our model includes transverse effects such as carrier diffusion and spatial hole burning (SHB) and is therefore capable of including gain-saturation-induced coupling among transverse modes. F...

The beam-quality factor of an amplified spontaneous emission source based on a Yb-doped, large-mode-area (LMA), multimode fiber was found to be optimized when the gain became saturated. A model using spatially resolved gain and transverse-mode decomposition of the optical field showed that transverse spatial-hole burning (TSHB) was responsible for the observed behavior. A simplified model witho...

We theoretically discuss the impact of the cavity configuration on the possible longitudinal mode multistability in homogeneously broadened lasers. We present a general method allowing to perform a direct bifurcation diagram and to determine the stability of the solutions of a Travelling wave model. We find, in agreement with recent experimental reports, that multistability is more easily reach...

The physical phenomena that dominate the power characteristics of a laser depend on the detailed nature of the amplifying medium and the resonator structure. In predicting the power characteristics, numerous approximations are always required. The most important approximations are considered here in detail, and error estimates are presented so that a designer can select the appropriate model fo...