The fundamental limit for optical detection is . In many real-world scenarios, the noise from the environment (the 300K background radiating onto your detector) is higher than the noise from your amplifier or the signal itself.
Robert W. Boyd’s 1983 textbook, "Radiometry and the Detection of Optical Radiation," serves as a foundational graduate-level text on the generation, transfer, and measurement of optical and infrared radiation. It covers essential topics including electromagnetic propagation, the radiance theorem, and the principles of various detector types while addressing fundamental noise limitations. For a detailed overview of the text's contents, see the NASA ADS abstract at NASA ADS . radiometry and the detection of optical radiation boyd pdf