APPLICATIONS  AND  PRACTICAL  UNITS

     Given their intense UV output and short pulse length, nitrogen lasers make excellent pump sources for pumping dye lasers  . The 337.1-nm UV emission is absorbed readily by many laser dyes, and in this application the wide spectral bandwidth and poor coherence of the laser beam are unimportant. In addition, the short pulse length does not allow triplet production in the dye, so the conversion efficiency of the laser-pumped dye laser is very high. Nitrogen lasers are also useful for exciting fluorescence in substances other than laser dyes, allowing studies of these molecules. As an excitation source, the molecules are commonly used to produce ions for time-of-flight spectroscopy. In the MALDI (matrix-assisted laser desorption/ionization) technique, the laser vaporizes and ionizes nonvolatile biological samples, which are then analyzed by a time-of-flight mass spectrometer and detected based on their mass-to-charge ratio. Nitrogen lasers may also be used for small microcutting procedures on individual biological cells or for trimming thin films for the semiconductor industry. With a typical pulse energy of less than 1 mJ and a repetition rate under 100 Hz, nitrogen lasers yield a low-cost source of intense UV light.

        A few commercial manufacturers of nitrogen lasers build both low-pressure and TEA variants. Many manufacturers of nitrogen lasers also offer matching dye lasers designed to be mated with the same brand of nitrogen pump laser to form a compact package. As well as a laser designed exclusively to operate as a nitrogen laser, many excimer lasers can also use nitrogen gas, although this is an expensive option for obtaining UV at 337.1 nm since excimer lasers are considerably more expensive. Since an excimer laser operating as a nitrogen laser operates in TEA mode with pressures averaging over 2 atm, measures must be taken to ensure that the discharge does not occur in localized hot spots along the long transverse electrodes. Aside from preionization employed in all excimers, the gas mixture also consists of a small amount of nitrogen diluted in helium. One popular manufacturer of excimer lasers specifies a gas mixture for use as a nitrogen laser (N₂ at 337.1 nm), consisting of 2% nitrogen and 98% helium. To lase the N⁺₂ species at 428 nm, the same manufacturer specifies a mixture consisting of only 0.2% nitrogen, with the balance helium.

     Owing to the simple mechanism of this laser, many are constructed in-house by both amateur laser constructors and commercial laboratories. Low-pressure lasers can be constructed easily using thin printed-circuit board for capacitors and a laser channel manufactured from acrylic plastic or glass. TEA types are constructed using lower-inductance materials (and hence faster discharge times), using capacitors fabricated from thin polyethylene or Mylar sheets and foil electrodes.