Kinetics of optically pumped Ar metastables

Abstract

Optically pumped lasers that use metastable excited states of Ar have been demonstrated using both pulsed and CW excitation. In terms of Paschen labeling of the states of Ar, the laser system uses excitation of the 2p9-1s5 transition, and lases on the 2p10-1s5 line. Collisional transfer of population from 2p9 to 2p10 is achieved using He as the buffer gas. For the purpose of modeling and developing this laser, rate constants for state-to-state transfer in Ar(2p(i))+Ar/He mixtures are needed. As the 2p10 level can radiate down to 1s4, this lower level also plays a significant role in the laser kinetics. Consequently, rate constants for the relaxation of 1s4 by Ar and He are also required. In the present study we have used pulsed laser excitation techniques to measure rate constants of relevance to the optically pumped metastable Ar laser.

Characterization of an RF-driven argon plasma at atmospheric pressure using broadband absorption and optical emission spectroscopy

“…Plasmas operating at atmospheric pressure in argon have witnessed a tremendous growth in last few decades. The nonequilibrium feature of such discharges allows production of highly excited and reactive species initiated by energetic electrons, which have enabled a plethora of applications, including gas discharge laser systems such as optically pumped rare gas lasers (OPRGLs) operated in Ar/He mixtures, [1][2][3][4][5] gas discharge lamps, plasma medicine, [6][7][8] surface modification, [9][10][11] and surface decontamination. [12][13][14] In highly repetitive discharges, such as radio frequency (RF) driven plasmas, the long-lived charged and energetic species from the previous discharge cycle enable to sustain stable discharges at lower voltage requirements.…”

“…Most of the argon metastable species measurements are performed using tunable diode laser absorption spectroscopy 4,5,[21][22][23][24][25] or time-resolved laser induced fluorescence measurements. 1 In addition, the resonant states of argon could also be important energy reservoirs, but they have only been studied in low pressure argon plasmas. [26][27][28] At atmospheric pressure, the effective lifetimes of the metastable states of Ar, 1s 5 and 1s 3 (Paschen's notation, details provided further in Table II), are governed by three-body collisions with two ground state Ar atoms, producing Ar * 2 excimers, and by collisional transfer to the resonant states, 1s 2 and 1s 4 via both electron-impact and heavy particle collisions.…”

Energy-Transfer Kinetics for Xe (6p[1/2]0) Atoms in Kr, Ar, Ne, and He

“…This new system has many advantages such as mild working conditions, an inert chemical property, and abundant states. Therefore, many groups have investigated this system. − High Ar (5s­[3/2] 2 ) concentrations and optical efficiency (55%) have been obtained. , Heaven and co-workers have demonstrated a CW diode-pumped Ar* laser providing 4 W . However, abundant states can result in complex kinetics between the excited states.…”

On the possibility of developing quasi-CW high-power high-pressure laser on 4p–4s transition of ArI with electron beam—optical pumping: quenching of 4s (3P2) lower laser level

“…Applying an electric field to the ionized gain medium with such new properties made it possible to efficiently pump 5d-6p laser transitions via a four-level excitation scheme not from the ground state, but from the 6s states already produced by the electron beam, which brought Ar-Xe lasers to a qualitatively new level setting them on a par with the most powerful of the known lasers [5][6][7][8]. In the present paper, we also propose to form a gain medium with new properties by means of fast electron beam, which makes it possible to perform a quasi-cw (in contrast to [2][3][4]) optical pumping of ArI 4p[1/2] 1 -4s[3/2] 2 transition through a three-level scheme of figure 1 from metastable 4s[3/2] 2 state. Implication of such a quasi-cw "electron beam-optical" procedure has to highly increase both geometric dimension of the gain medium and laser pulse width and, consequently, substantially elevate the laser output.…”

“…Optical pumping was accomplished with a laser diode via allowed optical transition 4p[5/2] 3 -4s[3/2] 2 with a large oscillator strength and the wavelength of 811.5 nm that is relatively close to the laser wavelength. In [1][2][3][4], pumping of high-pressure gain medium by an electric discharge imposed fundamental limitations on the maximum values of excited volume and pump pulse width. Indeed, their increase over tens of cubic centimeters and tens of nanoseconds, respectively, lead to the development in rare gas mixtures of various, primarily ionization, instabilities because of particular structure of rare gas atomic levels (small energy gap between the lowest excited states and ionization potential), which results in rapid discharge contraction.…”