A single-photon detector for the measurement of optical activity in the deep sea

A module was constructed for the measurement of deep sea optical activity at a sensitivity level of a single photoelectron. We describe the features of the module and a method for calibrating it. The average sensitivity in the interval from 350 to 500 nm is 0.89 Hz/(photons cm(-2) s(-1)), where Hz is the rate detected by the module. (C) 2002 American Institute of Physics.