Hydrogen gas detection by Raman Scattering using multiple laser reflection

It is the great interest for detecting hydrogen for safety in the hydrogen society. The sensitivity of detecting hydrogen by Raman scattering was improved about 35 times by using multiple reflections of excite laser beam compared to a single laser beam. 355 nm semiconductor laser beam was reflected about 30 to 40 times between the two concave mirrors. The detection limit of hydrogen was 0.1% and Raman intensity showed linear relation with the hydrogen concentration.