The capabilities of the optoacoustic principle as a means of temperature measurement have been explored by means of experiments. In the experiments, a tissue test specimen, biological muscle sample, was positioned in a precisely temperature-controlled environment and irradiated with 532-nm laser light. The absorbed radiation gave rise to thermal expansion whose induced stresses created a sound field which was detected by a piezoelectric sensor. During the course of the experiments, the temperature of the water bath was systematically varied, with ample time being allowed to enable the test specimen to achieve thermal equilibrium. The temperature variation encompassed both increasing and decreasing protocols. Replicate samples were tested to ensure accuracy. It was found that temperature increases gave rise to decreasing acoustic amplitudes. An opposite trend was observed when the temperature was decreased. This outcome, when compared with the published literature, suggested that accurate use of the photoacoustic effect as a means of temperature measurement requires great care in the setup and execution of the experiment.
Experimental investigation of the photoacoustic effect in liquids and solids
