Comparing the Sensitivities of Intensity Interferometry and Michelson Interferometry

Intensity interferometry, in which intensity fluctuations at separate apertures are measured and then correlated, is an attractive technique for high angular resolution measurements because of its simplicity. There is no need to transport light beams from the telescopes of the interferometer array to a beam combiner, and the telescope optics need not be precise. Michelson interferometry, in which light beams are brought together and the interference pattern is measured, is significantly more difficult, requiring precision optics and precise pathlength control, but it has a great advantage in sensitivity, requiring milliseconds to make a detection that might require hours with an intensity interferometer. However, for interferometry with a large number of array elements, the sensitivity of Michelson interferometry suffers from the fact that the light beams must be shared among many correlations, thereby reducing the sensitivity of each measurement. We explore these and other influences on the relative sensitivities of these techniques to determine under what circumstances, if any, their sensitivities become comparable.