Computer models developed so far on electron‐beam‐excited KrF(B–X, 248 nm) lasers that include the vibrational relaxation process in the upper lasing B level at the finite rate could not predict the high intrinsic laser efficiency which was experimentally reported. This is attributed to the reduction of the laser extraction efficiency. We have developed a four‐level KrF laser model that includes the vibrational relaxation process and also the collisional mixing of the KrF*(B) and the KrF*(C) levels. The collisional quenching rates for KrF*(B,C) that we used and the vibrational relaxation rate were carefully estimated by using the effective spontaneous lifetimes for KrF*(B,C). As a result, the model prediction was in quite good agreement with many experimental results for a saturation behavior of KrF*(B–X) fluorescence, for small‐signal gains, for small‐signal absorptions, and for intrinsic efficiencies. Estimated rate constants in this model for the vibrational relaxation and the KrF*(B,C) mixing are 4×10...

An advanced kinetic model of electron‐beam‐excited KrF lasers including the vibrational relaxation in KrF*(B) and collisional mixing of KrF*(B,C)

A laser cell with 21 of excitation volume was used to study the electron-beam pumped KrF laser system at excitation rates of 1.8- 7.0 MW/cm3. The system was optimized as an oscillator for various mixtures of Ar, Kr, and F 2 at total pressures of 1000 and 2500 torr. The resulting optimum conditions gave an intrinsic efficiency (laser energy out/electron-beam energy deposited) of 12 percent for the 1000 torr total pressure mixture with an output energy of 11 J/1. An efficiency of 10 percent with an output of 40 J/1 was obtained for the 2500 torr mixture. The system was then used as an amplifier to measure the extracted power as a function of input power for the two mixtures. The small-signal gain go, the nonsaturable absorption α, and the saturation intensity I s were determined for the two mixtures. Analysis of the data gave g 0 = 16-18 percent/cm, \alpha = 0.75-1.25 percent/cm, and I s = 2 MW/cm2for the 1000 torr mixture and g 0 = 17-19 percent/cm, \alpha = 1.0-1.5 percent/cm, and I_{s} = 9 MW/cm2for the 2500 torr mix.

Oscillator performance and energy extraction from a KrF laser pumped by a high-intensity relativistic electron beam

Aurora is the Los Alamos National Laboratory short-pulse, high-power, KrF laser system. It serves as an end-to-end technology demonstration for large-scale ultraviolet laser systems of interest for...

Aurora Multikilojoule KrF Laser System Prototype for Inertial Confinement Fusion

We have measured the intrinsic efficiency of ArF, KrF, XeCl, and XeF lasers using 60‐ns e‐beam pumping at an excitation rate of 1.5 MW/cm3. Efficiencies between 3 and 11% have been obtained. These values are shown to be limited by the time required to build up oscillation in the laser cavity, and we have demonstrated a technique which can be used to overcome this problem. Peak power efficiencies of these lasers are calculated to be in the range 5–15%.

60‐ns E‐beam excitation of rare‐gas halide lasers

The gain and saturation intensity of a fast‐discharge KrF oscillator‐amplifier have been investigated. The small‐signal‐gain coefficient was found to be 0.145 cm−1 for a 2‐ns pulse and 0.160 cm−1 for a 10‐ns pulse, with the respective saturation intensities ∼1.6 and ∼2.0 MW/cm2. An energy of 250 mJ was extracted with a 10‐ns input pulse. It was possible to isolate by amplification a single 2‐ns pulse from a mode‐locked train (of 2 or 3 pulses) and to extract 35 mJ in the amplified beam.

Gain and saturation intensity measurements of a mode‐locked KrF oscillator‐amplifier

We have examined the performance of a 2‐liter KrF oscillator pumped by a high‐intensity electron beam. For input pump rates of 7 MW/cm3, up to 80 J of laser energy is extracted from the cavity in 50 ns with an efficiency (laser energy divided by deposited electron‐beam energy) of 11%. Values of the small‐signal‐gain length product g0L, the absorption length product αL, and the saturation intensity Is were determined to be 6–16, 0.3–0.6, and 1–10 MW/cm2, respectively.

Studies of an 80‐J KrF oscillator at excitation rates of 2–7 MW/cm3

A master oscillator power amplifier (MOPA) experiment using an electron‐beam‐excited KrF oscillator and amplifier is described. The amplifier gain as a function of input intensity is determined. A comparison of the measured gain with calculations using a steady‐state analysis yields a determination of the small‐signal gain coefficient and saturation intensity for the amplifier operating with two different gas mixtures. The small‐signal gain is found to be more than an order of magnitude larger than the nonsaturable loss, indicating that efficient energy extraction from the amplifier is possible under the high excitation conditions (1.5–6 MW/cm3) of this study.

A master oscillator power amplifier experiment for the determination of the gain coefficient and saturation intensity for an electron‐beam‐excited KrF amplifier

E. L. Patterson

Papers

Studies of an 80‐J KrF oscillator at excitation rates of 2–7 MW/cm3

A master oscillator power amplifier experiment for the determination of the gain coefficient and saturation intensity for an electron‐beam‐excited KrF amplifier