C.B. Dane

Characterization of an ultrahigh peak power XeF(C to A) excimer laser system

The gain characteristics of an electron-beam pumped XeF(C to A) excimer amplifier operating in the blue-green spectral region were investigated for several laser pulse lengths. Saturation energy densities of 50 and 80 mJ/cm/sup 2/ were measured for injected laser pulse durations of 250 fs and approximately 100 ps, respectively. A gain bandwidth of 60 nm was observed with approximately 100-ps pulse injection. Using an optimized unstable resonator design, the laser amplifier has produced 275-mJ pulses with a pulse duration of 250 fs and a 2.5 times diffraction-limited beam quality, making the XeF(C to A) amplifier the first compact laser system in the visible spectral region to reach peak powers at the terawatt level. >

Scaling of an injection‐controlled XeF(C→A) laser pumped by a repetitively pulsed, high current density electron beam

This letter reports the design and performance of a scaled, injection‐controlled XeF(C→A) laser pumped by a repetitively pulsed, high current density electron beam with a temporal duration of 10 ns full width at half maximum. Injection of a 2 mJ pulse at 486.8 nm having a spectral width of <0.005 nm resulted in an amplified output of 0.7 J corresponding to energy density and efficiency values of 1.5 J/l and 1.2%.

Spectral characteristics of an injection‐controlled XeF(C→A) excimer laser

The spectral output characteristics of an injection‐controlled XeF(C→A) excimer laser pumped by a short pulse (10 ns), high current density (250 A/cm2) electron beam are reported. A tuning bandwidth of 50 nm full width half maximum, centered at 490 nm, with a peak specific energy density of 1.3 J/l was measured using an injection laser intensity of ∼2 MW/cm2. Continuously tuned output across the entire blue‐green region (450–530 nm) with an energy density exceeding 0.2 J/l was achieved. Injection beam spectral linewidths as narrow as 0.001 nm were shown to be preserved in the XeF(C→A) laser output.

Ultrashort-laser-pulse amplification in a XeF[C --> A] excimer amplifier.

Tunable blue-green subpicosecond laser pulses have been amplified in an electron-beam-pumped XeF(C --> A) excimer amplifier. Small-signal gains of 3.5% cm(-1) were measured using a 50-cm active gain length. At output energy densities as high as 170 mJ/cm(2), only a small degree of saturation occurred, resulting in a gain of 2.5% cm(-1).

Scaling characteristics of the XeF (C to A) excimer laser

The scaling characteristics and medium properties of an injection-controlled XeF(C to A) laser pumped by a 10-ns-high current density electron beam have been investigated. A five-component laser gas mixture, consisting of F/sub 2/, NF/sub 3/, Xe, Kr, and Ar was optimized for the scaled laser conditions, resulting in 0.8-J output pulses at 486.8 nm, corresponding to an energy density of small-signal-gain measurements combined with kinetic modeling permitted the characteristics of the dependence of net gain on the electron-beam energy deposition and gas mixture composition, resulting in an improved understanding of XeF(C to A) laser operation. >

Tunable, high-power, subpicosecond blue-green dye laser system with a two-stage dye amplifier

A two-stage dye amplifier design has been developed to amplify tunable, blue-green, subpicosecond dye laser pulses which are generated from a hybrid synchronously mode-locked dye oscillator directly (800 fs) or shorter to 200 fs by a fiber compressor stage. This system has achieved single pulse energies of 2 mJ, with an amplified spontaneous emission content of less than 0.1%. Using 40 mJ of the third-harmonic output of an Nd:YAG regenerative amplifier to pump the dye amplifier system, these pulse energies represent an energy extraction efficiency of approximately 5%. The tunability, stability, and spatial and temporal quality of the output pulses from the system have also been characterized. >

Repetitively pulsed operation of an injection-controlled high-power XeF(C to A) excimer laser

The operation at a 1-Hz repetition frequency of an injection-controlled electron-beam-pumped XeF(C to A) excimer laser system is reported. A compact, halogen-compatible, closed flow loop incorporating a transverse inline fan was used for gas circulation. In single-laser-shot operation, the timing between an electron beam and the injection dye laser was carefully adjusted to obtain an optimum laser pulse energy stability. An improved output-laser energy of 1.2 J per pulse with an intrinsic efficiency of 1.1% at 486.8 nm was achieved with a large-aperture unstable resonator. Interferograms taken during and after an electron-beam pump pulse to determine the minimum optical cavity recovery time of this device indicate that stable laser output energy performance at repetition rates of up to 25 Hz could be achieved with the present flow loop. >

Efficient XeF(C to A) laser excited by a coaxial electron beam at intermediate pumping rates

Experiments carried out with an electron-beam apparatus that produced pump pulses with an intermediate pulse length of about 174 ns (FWHM) and a power-deposition rate on the order of 1 MW/cm/sup 3/ are described. The authors present initial measurements with gas mixtures in which part of the Ar is replaced by Ne as a buffer gas. The lower stopping power of Ne can be compensated for by using a higher gas pressure because the system presented can be pressurized to a total gas pressure of 10 bar. It was found in earlier experiments with other excimers (ArF,KrF) that the variation of the buffer gas may have important effects on the optimum pressure regime total output energy, and kinetics. Useful information can be gained for discharge-excited systems, although the ionic channel dominates the electron-beam excitation kinetics. >

Wavelength‐agile operation of an injection‐controlled XeF(C→A) laser system

The performance of a pulsed laser system consisting of an electron beam pumped XeF(C→A) amplifier injection‐controlled by a wavelength‐agile dye laser is reported. Random sequence tuning over a 27 nm spectral region, centered at 478.5 nm, was demonstrated at a 1 Hz pulse repetition frequency. Laser output energies of 0.8 J with pulse durations of 10 ns were measured.

Optimization of an injection-controlled excimer laser guided by analytical modeling

The application of an analytical model describing the injection control of pulsed laser systems is successfully demonstrated for the design of a scaled XeF(C to A) excimer laser system. Enhancements to an earlier version o the model which improve the treatment of spatial beam overlap and saturation, unpumped volume, intracavity losses, and a noninteger number of roundtrips in the unstable resonator are described. These result in the accurate simulation of injection-controlled laser performance over a wide range of unstable resonator magnifications, mirror spacings, and intracavity optical losses. Excellent agreement between calculated and experimentally observed energies and temporal profiles of the injection-controlled laser output was obtained. >