Plasma and gaseous diagnostics with a tuned GaAs laser diode

This paper demonstrates that the classical gaseous diagnostic techniques of resonant absorption, anomalous dispersion interferometry, and resonant scattering can be performed with considerable ease utilizing a tunable GaAs diode laser. Absorption measurements of Cs133 in the ground state have been performed by matching the GaAs laser emission to the 8521 Å transition (62S1/2→62P3/2). The measured number density of Cs in the ground state is in general agreement with the value obtained from the known vapor pressure of cesium. The same type of measurements have also been made for the 1s2 and 1s4 resonant states in an argon plasma by tuning the laser to the 8408 Å and 8424 Å lines, respectively. In addition, interferometry studies using the swept GaAs laser are also reported here for the first time. These studies have been carried out simultaneously with the absorption measurement for the same 1s2 and 1s4 states in the argon discharge. The number densities of argon atoms in these states as obtained by both methods are in reasonable agreement.