7.1 INTRODUCTION

This chapter deals with infrared (ir) gas lasers and their applications. These lasers were the first ones to make significant inroads in industry, and CO ₂ lasers, in particular, account for about two-thirds of all industrial laser sales,1 which comprise the largest share of the laser market. IR gas lasers, which are exclusively molecular lasers, ^{[ ]} are unique in that they combine high electric to photonic energy conversion efficiency with high average power. This makes them the easiest lasers to fabricate, and because the active medium is a gas, it is also much easier to scale them to higher power. Indeed, CO ₂ lasers in the 2- to 5-kW range are now commonplace in the automobile manufacturing industry.2

Recently, CO ₂ lasers with average powers of 50 kW have been constructed,3 and powers of 100 kW appear attainable. No commercial lasers of this size have been constructed to date, however, because a market for them does not yet exist. By contrast, Nd:YAG lasers are not expected to exceed a few kilowatts of average power, although they have advantages in fiber-optic beam delivery. Excimer lasers have much higher efficiencies than Nd:YAG lasers and may some day rival CO ₂ lasers in terms of average power; but none have been built that exceed 1 kW.

IR gas lasers are, simply, lasers in which the active medium is a molecular gas, and which lase on vibrational-rotational transitions within the same...