The localized growth of carbon nanotube structures has potential in many applications such as interconnects, field emitters and sensors. Using a laser to locally heat the substrate offers a highly versatile process compatible with a broad range of substrates and devices. However, for laser-assisted CNT growth, detailed process information, such as temperature evolution and process monitoring over time are of ten unavailable. Here, we report on a miniaturized laser CVD reactor, where a precise control of the gas flow and composition on the laser-growth site is provided. The particular design of this miniaturized reactor results in a high reproducibility as well as faster growth time. A multi-parameter finite element method (FEM) model is implemented to link substrate temperature at the laser spot with emitted radiation, taking into account the gas flow, the process time and other temperature-dependent physical parameters such as forced convection, thermal-conductivity and heat capacity. The resulting growth is assessed using Scanning Electron Microscopy. Combined with results from the thermal model, process information is used to calculate activation energy for the nanotube nucleation. Finally, several demonstrations of possible applications are given, exploiting the potentials of the miniaturized reaction chamber.