A Novel Compact and Selective Gas Sensing System Based on Microspherical   Lasers
  We propose the use of wavelength-dependent spectroscopic absorption in the evanescent field of ultra-compact whispering gallery mode microspherical lasers as selective gas sensors and estimate few ppm detection sensitivity using a simple model. We also propose a sensor configuration based on integrated multi-channel microspherical laser arrays capable of selective gas detection at low concentration, and demonstrate that a compact 14channel device could generate a unique and distinguishable power distribution over channel outputs upon exposure to three different gases. 
Behsan Behzadi, Ravinder K. Jain, Mani Hossein-Zadeh
physics.ins-det physics.optics