Lecture
This lecture discusses the principles of single photon detection using Electron Multiplying Charge-Coupled Devices (EM-CCDs). It begins with an overview of avalanche photodiodes, explaining how primary electrons are accelerated by an electric field, leading to impact ionization and the generation of electron-hole pairs. The instructor highlights the self-sustaining nature of the avalanche process and the critical importance of the breakdown voltage, which is temperature-dependent. The lecture then introduces hybrid photodetectors that combine electron bombardment gain with avalanche gain. The discussion transitions to frame transfer CCDs, detailing the process of recording images and transferring them to a storage matrix. The instructor explains the concept of a gain register that enhances the voltage between CCD cells, facilitating avalanche amplification through impact ionization. The lecture concludes with an explanation of the unidirectional avalanche effect and the potential for significant total gain through multiple stages, emphasizing the capabilities of EM-CCDs in low-light imaging applications.