Laser assisted catalytic chemical vapor deposition has recently emerged as an attractive method for locally growing carbon nanotubes (CNTs) in a cold wall reactor. So far, reported laser assisted CNT growth has been carried out without in situ process monitoring. This has made it difficult to control the growth process and limits the applicability of the method. Using a set of photodetectors with different spectral responses, we show that one can identify characteristic regimes of laser assisted CNT growth. More specifically, key process steps like catalyst activation, growth of CNTs, and amorphous carbon deposition are identified. Furthermore, the method allows optimization of growth conditions with respect to the quality of the growth products.