D. McKen

Ultraviolet photoionization in TEA lasers

Measurements of UV photoionization parameters for TEA CO 2 gas lasers are presented. Electron density and ionization decay times are given as a function of pressure for several gases and gas mixtures. Penetration depth of ionizing radiation in the gases is determined. The effect of selected additives on photoionization is demonstrated. The results show that a significant enhancement in electron density can be achieved. The X -band microwave interferometer data provide additional insight into the mechanisms involved and further substantiate the effectiveness of the technique in high-powered CO 2 laser design.

Photoionization parameters in the carbon dioxide laser gases

The data and results of an extended investigation of the more salient parameters associated with the application of ultraviolet (UV) photoionization processes in TEA CO 2 lasers are presented. The study encompasses emission spectra, wavelength dependence, and influence of circuit parameters for a typical UV spark source. This investigation and a companion study utilizing a specialized charge collection apparatus on a monochromator provides further insight into the primary mechanisms involved in these photoinitiated laser devices and has, in addition, provided design criteria for the development of more efficient photoionization sources.

uv photoionization density measurements in TEA lasers

Diagnostic measurements on uv photogenerated laser plasmas are presented. Ionization data obtained with an X‐band microwave interferometer show plasma density to be a function of both the gas mix and the irradiation source parameters. Electron density as a function of pressure is given for selected gases and mixtures. At atmospheric pressure the photoplasma density in the standard CO2 laser mix is found to be surprisingly low.

High-efficiency stimulated Brillouin scattering of KrF laser radiation in SF 6

Stimulated Brillouin scattering of KrF laser radiation focused in SF(6) gas at pressures of 1.4 to 9.8 atm has been studied experimentally. For an input linewidth of 0.08 cm(-1) and focal lengths of 1 and 2 m, reflectivities of 80% have been measured. Pulse compression up to peak intensities of two times the pump intensity has been achieved in a pulse that is partially phase conjugate to the pump pulse. At high pressures a short backward Raman spike was observed preceding the Brillouin backscattered signal.

Stimulated Brillouin scattering of KrF laser radiation in dichlorodifluoromethane

Experimental measurements have been made of the stimulated Brillouin backscatter from CCl 2 F 2 gas in the range of pressures from 1 to 5.75 atm. Using narrow-linewidth KrF laser radiation as the pump backscatter efficiencies of up to 35 percent have been achieved, while at low backscatter efficiencies pulses as short as 1.5 ns in width were obtained.

Enhancement of photoelectron density in TEA lasers using additives

The photoplasma produced in laser gases by a spark uv source is measured using a microwave bridge. The results show that an increase in plasma density of four orders of magnitude is obtained using trace amounts of low‐ionization‐threshold additives in the gas mix. The technique has been shown to enhance laser performance. An output energy density of 60 J/liter has been obtained from such a photoionized TEA laser.

Experimental study of an SF6 Brillouin amplifier pumped by KrF laser radiation

Experimental measurements are presented of the gain for a backward Brillouin amplifier using SF6 gas, in the pressure range of 3–10 atm, pumped by KrF laser radiation. A small signal gain of 6×10−4 cm MW−1, pump depletion of 20%, and an intensity gain of 2.5 have been demonstrated.

Photoabsorption and ionization cross sections in a seeded CO 2 laser mixture

Photon absorption and photoionization spectra in a CO(2) laser mixture seeded with selected low ionization threshold additives are presented. Such data are used to determine total absorption and ionization cross sections for some gases and vapors of interest. The results identify tripropylamine as an interesting seedent material, as it exhibits a longer wavelength photoionization effect essentially independent of the primary host laser gases.

Photon emission and photoionization measurements in the CO2 laser environment

Recent monochromator measurements of the photon emission and volume photoionization produced by a simple spark source within the laser gas environment are presented. Nitrogen gas is seen to dominate the ultraviolet radiation generated while carbon dioxide is shown to control the photon transmittance in the laser volume. The data clearly identify two narrow photon bands as the only useful portions, of the spark emission spectrum, in the production of volume ionization.

Source emission and photoelectron production in a seeded CO2 laser mixture

Measurements of spark source emission, transmission, and photoionization spectra in a CO2 laser mixture seeded with a low‐ionization‐threshold additive are presented. The results show a photoelectron density enhancement in excess of 3 orders of magnitude contained within a narrow transmission band at 1200 A. Enhancement is also observed at wavelengths between 1700 and 2100 A. The long‐wavelength effect, characterized by an increased photon mean free path, may identify a two‐step photoionization process.