  Photonic integrated circuits are paving the way for novel on-chip
functionalities with diverse applications in communication, computing, and
beyond. The integration of on-chip light sources, especially single-mode
lasers, is crucial for advancing those photonic chips to their full potential.
Recently, novel concepts involving topological designs introduced a variety of
options for tuning device properties such as the desired single mode emission.
Here we introduce a novel cavity design that allows to amplify the topological
interface mode by deterministic placement of gain material within the
topological lattice. The proposed design is experimentally implemented by a
selective epitaxy process resulting in Si and InGaAs nanorods embedded within
the same topological lattice. This results in the first demonstration of a
single-mode laser in the telecom band using the concept of amplified
topological modes.
