Automated pressure scanning of tunable dye lasers

Tunable laser spectroscopy has recently been used in diagnosing the chemistry and physics of plasma, combustion, and chemical vapor deposition reactors. However, the impact of these spectroscopic techniques on real-time process monitoring has been limited to date. One of the reasons for this is the difficulty in tuning the laser frequency to a specific transition and having it remain there for more than a few minutes. I describe a simple method by which these difficulties can be circumvented and frequency tuning can be controlled remotely. A microprocessor is used to regulate the gas flow of a pressure tuned oscillator so that constant pressure (and, indirectly, freqency) is maintained (for excitation of a particular transition) or swept (to record an excitation or absorption spectrum). As a natural extension the pressure can be slaved to a wavemeter so that direct frequency control can be achieved.