Simple Optoacoustic Energy Meter for Pulsed Lasers

When a pulsed laser is utilized for spectroscopic or engineering applications, it often becomes necessary to measure the optical pulse energy (as opposed to instantaneous or peak power). This report details the design and performance of a unique energy meter for pulsed sources based on the optoacoustic (OA) phenomenon and a Helmholtz resonator (HR) cell (1,2). This new instrument accomplishes a time domain change, converting short optical pulses of varying duration into a slower acoustic pulse that can be measured with simple detection electronics. An inexpensive sample-and-hold amplifier was employed. The OA energy meter accurately produces a dc voltage corresponding to the energy/pulse of a single laser pulse or the average value for a train of pulses over a wide input pulse energy range.