Chapter 12 - MOLECULAR GAS LASERS

Abstract

Molecular gas lasers are important because of their high efficiencies and high powers. This chapter reviews the nomenclature and fundamental ideas of molecular structure and spectra and discusses the molecular gas lasers. The pulsed molecular nitrogen laser is one of the first molecular lasers reported. The hydrogen laser system is very similar to the molecular nitrogen system. The carbon dioxide (CO2) lasers are of interest because of their high efficiencies, high powers, and the atmospheric window that exists for CO­2 laser signal propagation. The primary CO2 laser output wavelengths are around 9.4 μm and 10.4 μm and these are vibrational rotational transitions. The chapter describes the notation for the vibrational levels of CO2. CO2 is a linear triatomic molecule; therefore, three different modes of vibration are possible. A present, there are at least three processes that are considered to be important in exciting the upper laser level: (1) direct electron-impact excitation, (2) electron-impact pumping of nitrogen and resonant energy transfer, and (3) electron impact pumping of carbon monoxide and resonant energy transfer.