Laser absorption spectroscopy with a blue diode laser in an aluminum hollow cathode discharge

Abstract

A GaN-based blue diode laser is employed for laser absorption spectroscopy in an aluminum hollow cathode glow discharge plasma. A Littrow grating stabilized external resonator is used for tuning the wavelength of laser emission. Scanning the wavelength of the laser probes the absorption profile of aluminum transitions yielding ground state aluminum densities. Hyperfine structure has to be taken into account in order to obtain correct temperatures. The diode laser is used to investigate both the temperature and the density of aluminum atoms sputtered from a cathode surface by ion bombardment from the cathode fall region. The blue diode laser allows quick and easy access to aluminum ground state atoms at low costs.

Time resolved metal line profile by near-ultraviolet tunable diode laser absorption spectroscopy

“…The Fabry-Pérot works like a wavelength etalon to transform the abscise time-scale of the oscilloscope into wavelength variation. The measuring beam is reflected by another mirror (5), passes through the plasma volume (parallel to the target of a planar circular magnetron discharge) by two quartz windows facing each other (6,7), and is finally reflected by the last mirror (8) into the photodiode detector (9). The absorption signal is then recorded on the oscilloscope (Fig.…”

“…5,6 Note that near-UV and blue laser diodes are suitable for most of the metals (medium and heavy atoms) spectroscopy, involving directly their ground state. For instance, absorption measurements at 394.40 and 396.15 nm have been reported to determine the temperature and density of thermalized aluminum atoms in: the hollow cathode discharge, 7 the DC (direct current) magnetron discharge, 8 and the time averaged density and temperature of aluminum atoms for high pulsed plasma magnetron sputtering (HPPMS) system. 9 Most of the previous works using diode lasers present the diagnostic of steady state or time averaged measurements of plasma species, [10][11][12] and only few of them deal with time evolution of probed species.…”

Measurement of Aluminum Erosion Rate by Cavity Ring-Down Spectroscopy

“…At 0 mm, the spectrum has two peaks 14) , due to the Doppler shift of the sputtered aluminum atoms. The whole spectrum is fitted as six Gaussian functions due to the aluminum hyper fine structure of aluminum 15) and symmetric Doppler shift. The frequency-integrated spectrum is calculated as � �������� and substituted into Eq.…”

Blue Diode Laser Absorption Spectroscopy of Pulsed Magnetron Discharge

“…In addition, hyperfine interaction needs to be taken into account, giving rise to a splitting of the 396.15 nm transition into six components. 11) 2. Experiment Figure 1 shows the experimental set-up used for our measurement.…”

“…0 is the central frequency, taken as a free fit parameter, i and Á i are the relative intensity and the frequency shift of the ith component of the hyperfine-split transitions with respect to 0 as given by ref. 11. Fitting algorithm 14) was used for selecting the best fit function.…”