Abstract

Photothermal spectroscopic methods, notably photoacoustic, thermal lens and mirage detection, may be seen as alternatives to direct absorption spectroscopy for trace gas detection and offer many advantages, most notably high sensitivity and signal reference to a true zero. While direct absorption measures the typically weak signal difference between input and output energy, photothermal methods measure a signal either directly (thermal lens and mirage detection) or indirectly (photoacoustic) proportional to energy absorbed by the sample.

© 1996 Optical Society of America