We have been studying the capabilities and limitations of using advanced tunable diode laser source for high sensitivity detection and precision measurements of atoms and atoms and molecules in the gas phase. Much of this work is done in collaboration with other institutions (particularly NOAA,  and the NOAA Aeronomy Lab and the Laser Science Group at Rice University). Applications include pollution monitoring, and atmospheric chemistry and monitoring related to ozone and global warming. Species we have studied in this work include: Pb, IO, NO₃, Ca, and CH₄.

Diode laser sources combined with PPLN crystals can provide a very convenient source of tunable IR. The figure below shows a typical experimental that uses PPLN to generate the 3.4 micron difference frequency between a 810 nm diode laser and a 1064 nm diode-pumped Nd-YAG laser.

We have been using this type of system for high precision, high sensitivity measurements of methane concentrations in air samples.

Spectrum of air taken with DFG system diagramed above shows water and methane absoprtion lines near 3 microns in IR. Normal air contains about 2 ppm methane which can be measured in this system with a precision of about 1 ppb.

A new collaborative project is also beginning with Paolo De Natale and coworkers at Istituto Nazionale di Ottica (INO), Firenze, Italy for measurements of CO_2.