Photon noise: Observation, squeezing, interpretation

A review of modern concepts of photon noise (PN), which is observed even in the case of an ideal laser, is presented. The methods of transformation, squeezing, and nondestructive observation of PN, are described. The optical nondestructive methods seem to be very important for the interpretation of PN. The experiments with PN suppression by negative electron feedback are analysed in detail with two alternative approaches, which could be called the a priori and aposteriori concepts. According to the first approach, PN exists in the laser beam from the beginning while according to the second one it appears only in the detectors. The theory based on the a priori concept predicts the squeezing of the in-loop field-in contrast to a posteriori concept. Several possible crucial experiments based on the nondestructive methods are discussed.