The presence of trace materials in a sample is detected using both macroscopic and microscopic properties. A detector includes a light source and an optical resonator. The light source may be located either inside the resonance cavity of the resonator or outside the cavity, in which case it may be a...http://www.google.com/patents/US5538850?utm_source=gb-gplus-sharePatent US5538850 - Apparatus and method for intracavity sensing of microscopic properties of chemicals
