Measurement of temporal coherence loss in laser light scattered from simulated coastal waters

Different techniques of measuring the coherence length of a scattered laser signal propagating through water are reviewed. A Michelson interferometer experiment was used to measure the coherence length of an argon-ion laser both in air and scattered in water. It was shown in this experiment that light scattered through water experiences a definite, measurable loss in coherence of ~10 cm. The Michelson experiment measured the total coherence loss due to all spectral broadening mechanisms present. A heterodyne experiment was used to measure the coherence loss due to Doppler broadening of an HeNe laser scattered in water. A decrease in the coherence length was observed as more light was scattered. The coherence length of the HeNe laser in air was measured with a Michelson interferometer