A lot of books explain the first order and second order coherence correlations for light. They explain the difference between these using interferometers (Michelson and Hanbury-Brown and Twiss (HBT) interferometer). However, it is odd none of the books mention the essential difference between the two interferometers. I just want to be sure that the difference between the two techniques is that, Michelson has one detector and HBT has two detectors?
Michelson interferes the light and then detects while HBT detects light at different detectors and then checks the correlation.