W. Sarjeant

Electrical and gain characteristics of a multiatmosphere UV-preionized CO 2 laser

The scaling parameters of a UV-preionized TE CO 2 laser which permit the direct comparison of small-signal gains as a function of laser pressure have been investigated in the pressure range of 4-19 atm. Careful measurements of the gain as a function of laser pressure in both the 9.4 and 10.4 μm vibrational bands were made under the appropriate scaling conditions. A theoretical model for the gain incorporating regular, hot band, and sequence band rotational lines, with proper account taken of non-Lorentzian line overlap effects, predicts the observed pressure dependence of the small-signal gain.

Picosecond XeF amplified laser pulses

Picosecond third harmonic (353 nm) Nd : glass laser pulses have been amplified by factors of ≳6 000 in a high‐pressure XeF discharge. Peak powers ∼50 kW have been observed.

Parametric study of a constant E/N pumped high-power KrF* laser

The application of a novel constant voltage excitation technique has led to the production of volume glow discharges in a scalable multiatmosphere rare gas halide laser. Such discharges are obtained using a high-voltage discharge circuit which optimizes energy transfer from the power conditioning system into the load, up to the voltage limit of the system components. A detailed parametric study has been carried out for KrF* at pressures up to 6 atm and output energies in excess of 0.6 J were obtained from an active volume of 0.18 l.

A scalable multiatmosphere high‐power XeF laser

A scalable uv‐preionized transverse discharge XeF laser has been operated at pressures up to 5 atm. uv output energies in excess of 250 mJ with a minimum pulse duration of less than 20 ns have been obtained from an active volume of 0.18 liter.

Some characteristics of efficient dye laser emission obtained by pumping at 248 nm with a high power KrF∗ discharge laser

Abstract Characteristics of dye laser emission under high intensity uv pumping, at 248 nm wavelength have been investigated with peak pump powers of ∼ 10 MW at a pulse duration of ∼ 30 ns, provided by a multi-atmosphere KrF ∗ discharge laser. Energy conversion efficiencies, spectral features and temporal behaviour of several dyes were parametrically studied. Significant pump intensity dependent conversion efficiency and pulse shape variations were observed for the most efficient uv dye, p-terphenyl.

Glow-discharge characteristics of a 0.8 J multi-atmosphere rare gas halide laser

Abstract The temporal behaviour of the discharge in a transversely excited high-power KrF laser has been investigated using streak photography as a diagnostic technique. The experimental results demonstrate that uniform glow discharges occur over a broad range of laser pressures and dc charging voltages, up to the nominal operating limits of 6 atm and 100 kV.

Picosecond gain and saturation measurements of the 353‐nm XeF laser line

The spectral characteristics, temporal gain profile, and saturation energy have been measured for the 353‐nm XeF laser line using a picosecond probe pulse of the third harmonic of a Nd : glass laser.

Tunable, narrow bandwidth, 2 MW dye laser pumped by a KrF∗ discharge laser

Abstract Characteristics of p-terphenyl and PBD, the most efficient uv dyes, have been investigated under high intensity pumping by a multi-atmosphere KrF∗ discharge laser at 248 nm wavelength. Energy conversion efficiencies, spectral features and temporal behaviour of the dyes were studied parametrically. A maximum powerof 2 MW uv emission with a bandwidth of ∼2×10-2 nm was obtained for PBD. It was found that a mixture of both dyes provided higher (by a factor of 1.3) output in the range 348–366 nm than either of the dyes alone. Significant pump intensity dependent conversion efficiency and pulse shape variations were observed for the most efficient uv dye, p-terphenyl and were related to triplet-triplet adsorption processes in the dye.

Amplification of UV picosecond pulses in high pressure XeF discharges

At present, C 0 2 and atomic iodine are the only two lasers with demonstrated properties that make them candidates for a repetitivelypulsed laser fusion system. However, there are uncertainties for each of these lasers which must be evaluated to project large system performance. At Sandia, we are conducting experiments to evaluate properties oftheatomiciodine laser pertinent to its possible use in a laser fusion system. The results presented below were obtained from the SAIL-1 facility, which consists of an actively modelocked oscillator, a 1-cm diameter x 1Wcm long preamplifier and a 7.5cm diameter x 3 5 k m long final amplifier.’ The subnanosecond atomic iodine oscillator developed by Jones et al.’ has been modified to produce pulses with more reliable beam quality. This is accomplished by pumping faster and allowing the oscillator to gain-switch 6 psec after flash initiation. Therefore lasing occurs before the onset of the gas dynamic disturbance which occurs in the lasing volume at 10 psec after flash initiation. The beam profile was photographed 20 m from the oscillator and is nearly Gaussian with no hot spots. Also, data from a shearing plate interferometer indicate that here is no detectable phase distortion across the wave front and that the oscillator output is nominally diffraction limited. The reproducibility of the SAIL-I oscillator (an important consideration for laser fusion) is good, approximately & 10% in amplitude and pulse width. Temporal pulse distortion can occur in an iodine laser amplifier because of gain saturation and/or insufficient bandwidth for short pulse amplification. Data were obtained which demonstrate the range of pulse distortion versus bandwidth in an unsaturated amplifier. Working with sufficient bandwidth to give true pulse amplification, the pulse distortion due to gain saturation was characterized. In both cases, the data were used to check a computer code which models pulse propagation in an iodine amplifier. Good beam quality and focusability are essential for laser fasion. In an iodine amplifier. the beam quality can be affected by gas dynamic disturbances or anomalous dispersion in a saturated amplifier. Using a shear plate interferometer amplified pulses from the preamplifier were found to have < 1/2 wave phase distortion. Calculations indicate that this amount of phase distortion will not affect the focusability. In addition, data were obtained with the shearing plate interferometer for a saturated beam in the large amplifier. Also, the beam profile of the output from the large amplifier was photographed at various degrees of focus.