An absolute method for measuring the energy output of a laser

Abstract

A laser output meter is described in which the detector element is a hollow sphere consisting of one piece of insulated, thin copper wire. Light coming through a small hole into the sphere is totally absorbed. The change in resistance caused by the change of temperature is measured by a d.c. Wheatstone bridge. This hollow `rat's nest' is simple to calibrate by heating with known current pulses. A practical hollow `rat's nest' calorimeter is described.