Measuring Temporal Photon Bunching in Blackbody Radiation

Light from thermal black body radiators such as stars exhibits photon bunching behaviour at sufficiently short timescales. However, with available detector bandwidths, this bunching signal is difficult to be directly used for intensity interferometry with sufficient statistics in astronomy. Here we present an experimental technique to increase the photon bunching signal in blackbody radiation via spectral filtering of the light source. Our measurements reveal strong temporal photon bunching in light from blackbody radiation, including the Sun. Such filtering techniques may revive the interest in intensity interferometry as a tool in astronomy.