Helical TEA-CO₂ Lasers

Abstract

A transversely excited atmospheric TEA-CO, laser having a helical electrode configuration is described and analyzed. This laser configuration possesses a radial gain profile which naturally favors the excitation of the lowest-order mode of the resonator. Pulses of 0.7 J, having a peak power close to 1 MW, have been obtained in the fundamental mode. However, a strong diverging lens effect caused by the transverse electric discharges in the laser cavity produces a far field beam divergence twice as small as that calculated from the geometry of the resonator. This lens effect has also been used to lase with some geometrically unstable cavities. Two independent types of measurements, performed to study this lens effect, are shown to agree with a proposed theoretical model.Un laser C0,-TEA, a pression atmosphtrique et a excitation transverse, posskdant une configuration helicoldale d'tlectrodes est decrit et analyse. Cette configuration donne au laser un profil de gain radial qui favorise naturellement I'excitation du mode de plus bas ordre du resonateur. Des impulsions de 0.7 J et d'une puissance pointe de pres de 1 MW ont ttC obtenues dans le mode fondamental. Cependant, un important effet de lentille divergente provenant des dkcharges Clectriques transverses dans la cavitC laser produit dans le champ eloignt une divergence du faisceau deux fois plus petite que celle calculte d'aprts la geomttrie du rksonateur. Cet effet lentille a aussi Cte utilist pour opkrer le laser dans des configurations de cavitt instables du point de vue geometrique. Deux types d'experiences independantes rkalisees pour mesurer cet effet lentille se conforment a un modele thiorique propost.

Parametric Study of a Helical TEA CO2 Laser

“…lo = peak current pulse 0, = current pulse width at half the peak value 0, = laser pulse width at half the peak value z = delay between the beginning of the laser pulse and the current pulse the diverging lens effect due to the influence of the localized discharges between pins in the laser (Fortin et al 1971). We have noted finally that the beam divergence is insensitive to a variation of the charging voltage and gas composition.…”

“…1705 (1973) TEA CO, lasers with helical configuration are has been used with each element in order to make simple to build and have a radial gain profile the discharge time short compared to the arc which naturally favors TEM,, mode excitation formation time (Laurie and Hale 1970). The low (Fortin et al 1971). They are of great interest as inductance capacitor and the spark gap are oscillators in double-discharge amplifier systems mounted in a copper cylinder to make a coaxial Girard and PCpin 1973).…”

“…The low (Fortin et al 1971). They are of great interest as inductance capacitor and the spark gap are oscillators in double-discharge amplifier systems mounted in a copper cylinder to make a coaxial Girard and PCpin 1973).…”

A simple self-triggered plasma shutter

“…This was important because the mode beating would then be suppressed and the laser pulse would have a smooth profile with very small amplitude fluctuation. The TEA section had pin resistor type electrodes in a helical geometry to restrict lasing in the lowest transverse mode [8]. The output was a smooth reproducibel 200 nsec CO, laser pulse with a peak power of about 0.7 MW.…”