Photodetection in the LHC experiments

The challenging requirements on photodetection in the LHC experiments have motivated large-scale R\&D efforts on various detector technologies, which started already in the 1990s. The state-of-the-art of the LEP era would not have allowed satisfying the demanding needs, particularly from calorimetry and particle identification. After almost two decades of intense development, construction and integration efforts, the LHC and its four major experiments are performing in a just exemplary manner, in many respects exceeding the expectations. Hundreds of thousands of photodetectors with millions of readout channels contribute to this success story. This article aims at reviewing the main activities in photodetection, the initial achieved performance as well as some consolidation and first upgrade efforts.