Photoacoustic Optical and Infrared Detector

In recent years there has been a rapid rise of interest in the photoacoustic (PA) effect and its applications in the investigation of gases, liquids, and solids1-17). The basic principles and the theory of the PA effect are now well established18–21). The primary source of the acoustic signal is the periodic heat flow from the sample to the surrounding gas, as the sample enclosed within a gas cell is cyclically heated by the absorption of chopped light. The periodic flow of this heat into the gas cell produces pressure fluctuations which are detected by a sensitive condenser microphone as an acoustic signal. The present research applies the technique of PA spectroscopy to the detection of the optical and infrared(IR) radiation itself. In PA energy conversion process, the thermal properties of the sample play an important role. Therefore this PA optical and IR detector can be classified as the thermal detector. The operation principle of this detector is different from those of presently available optical and IR detectors22-24). The sketch of PA optical and IR detector is shown in Fig. 1.