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We numerically studied the saturated absorption spectrum of an argon arcjet plasma with the aim of developing a method for diagnosing the collision parameters of the plasma. In a plasma with strong velocity-changing collisions with a buffer gas, the saturated absorption spectrum was partially or fully broadened to a Gaussian shape whose width is on the same order as that of the Doppler broadening. In an argon arcjet plasma—a plasma that exhibits an intermediate pressure region, a variety of saturated absorption spectra have been experimentally observed by tuning the pressure in the discharge section. We performed a numerical analysis to validate the shape of the experimentally observed spectrum by numerically solving the two-state rate equation system with the assumption of strong velocity-changing collisions. In particular, we numerically reproduced the spectrum with an inverted pedestal, which has not been previously reported, by assuming that the collisional frequency is significantly different for each electronic state. The conditions for the emergence of the inverted pedestal were numerically determined by regression.

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An absolute wavelength standard broader than the Doppler width of the atomic absorption signal was developed by using a method called dichroic atomic vapor spectroscopy (DAVS). DAVS is known as a method to obtain an error signal for stabilization of laser wavelength, called dichroic atomic vapor laser locking (DAVLL). In the DAVS, a magnetic field is applied to the atomic vapor cell and a stretched signal is obtained by the Zeeman effect. The DAVS experiment was performed by using ring-type permanent magnets and a cesium vapor cell at room temperature, and the placement and number of magnets were optimized. By measuring the height of the DAVS signal calibrated in advance, continuous monitoring of the absolute laser wavelength become possible. The developed system is suitable to be used as a stretched wavelength standard in the experiment of the light-induced drift.