Lecture
This lecture discusses various examples of noise in optical detectors, focusing on the implications of noise in different types of detectors. The instructor begins with avalanche photodiodes, explaining how internal gain can amplify both signal and noise, leading to a degradation of the signal-to-noise ratio. The importance of optimizing gain is highlighted, as it can enhance detectivity. The second example covers noise in photoconductors, detailing how impurities and traps contribute to different noise types, including 1/f noise and thermal noise. The instructor emphasizes the significance of working at the correct frequency to minimize noise impact. The final example introduces fluorescence correlation spectroscopy, illustrating how the movement of fluorescent molecules through a small illuminated volume affects noise and correlation times. The relationship between autocorrelation and spectral noise density is also discussed, demonstrating how different molecule sizes influence transit times and noise characteristics. Overall, the lecture provides a comprehensive overview of noise considerations in optical detection systems.