Discharge medium uniformity influence on XeCl excimer laser beam quality (original) (raw)
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Small volume coaxial discharge as precision testbed for 0D-models of XeCl lasers
Applied Physics B Photophysics and Laser Chemistry, 1992
In order to check the predictions of 0D-models experimentally, a small coaxial discharge configuration for the generation of homogeneous high pressure glow discharges (diameter 11 mm, length 20 mm) in rare gas halogen excimer laser gas mixtures under accurately controlled conditions has been developed. It uses X-ray preionization and a special pulse-forming network (PFN) delivering fast rising (8ns) single square pulses (U0 = 25kV; I = 300A; ~-= lOOns). Discharge current and voltage are measured precisely by a capacitive voltage divider and a shunt integrated into the discharge chamber. All circuit data needed for the model calculations have been evaluated. Interferometric and spectroscopic diagnostics of the bulk of the discharge and of the cathode sheath have been performed. First results for Ne/Xe/HC1 mixtures are compared with model calculations.
Repetition-rate influence on the beam quality of a XeCl excimer laser
Optics Communications vol. 167, pp. 291-298 (1999), 1999
The results of beam quality measurements of a XeCl (λ=0.308 μm) laser, equipped with a generalised self-filtering unstable resonator (GSFUR), while operating in the burst mode at repetition rates of up to 50 Hz are presented. In particular, the behaviour of the laser-energy distribution (both in the near- and far-field) and of the beam-angular stability vs. the repetition rate was measured. The time evolution of the divergence within the single laser pulse was also measured. The GSFUR showed its remarkable ability to achieve a nearly diffraction-limited divergence since the beginning of the laser pulse, and, most importantly, to maintain the values of the times diffraction-limit (TDL) number, of the M2 parameter and of the beam angular stability (BAS) independent of the repetition rate. The BAS resulted in fluctuations smaller than one third of the beam divergence.
Features of plasma produced by excimer laser at low intensities
Physica Scripta 55, 483-490 (1997), 1997
A plasma, created at interaction of short-wavelength excimer laser radiation with flat targets was investigated (T = 12 ns, λ = 0.308 μm, I = (4 – 8) × 10^12 W/cm2) with the help of various x-ray spectroscopic methods. The comparison of shapes and intensities of some observable spectral lines of H-, He and Li-like ions of Na, Mg and Al with results of model calculations has allowed to determine space distributions of laser plasma parameters up to distances of 0.4 mm from the target surface. Comparison of obtained results with theoretical models of absorption of short-wavelength radiation in a plasma shows, that the absorption of short-wavelength laser radiation in a plasma (at considered values of laser flux density) is executed due to inverse bremsstrahlung process in the areas with Ne < Ne, crit..
This paper investigates the dependence of discharge uniformity of a high pulse repetition frequency (PRF) long-pulse XeCl laser on cathode roughness in single-shot regime and in burst mode (10th shot) as a function of PRF ( f ≤ 500 Hz). The cathode roughness governing local disturbances of the electric field acts on the stability of discharge processes in excimer lasers. Space and time discharge stability evolution is experimentally analysed from discharge photographs obtained with a CCD video camera and pressure perturbation measurements achieved with a piezoelectric pressure probe set close to the discharge volume. The results clearly show that the cathode roughness plays an important role in discharge stability. The spatial and dynamic development of microarcs in the discharge is discussed in relation to the cathode roughness. Finally we show that certain values of cathode roughness may efficiently prevent an arc from forming during the laser emission. These cathode surface states are then suitable to achieve high and reproducible laser performances at high PRF.
Investigation of the characteristics of an excimer laser with a narrow emission line
Soviet Journal of Quantum Electronics, 1990
An investigation was made of the spatial coherence of excimer lasers in different resonator geometries. Lasing with a spectral width of 5 nm was obtained in a scheme using a grating in the autocollimation regime and a four-prism telescope. A discussion is given of the questions involved in employing excimer lasers having a narrow laser emission line in photolithographic projection systems.
XeCl laser pumped by an electron beam and X-ray assisted discharge
Journal de Physique Lettres, 1981
2014 Une émission laser de longue durée (200 ns) et de rendement élevé a été obtenue à 3 080 Å à partir de l'excimère XeCl* à la suite de l'excitation de mélanges Ne/Xe/HCl à température ambiante et à très basse température par une décharge en régime d'avalanche assistée par un faisceau d'électrons et de rayons X. L'énergie apportée au milieu actif par la décharge était de plusieurs ordres de grandeur supérieure à celle apportée par le faisceau de préionisation. L'énergie spécifique laser maximale obtenue était de 3 J/1 à température ambiante pour une longueur de gain de 16 cm et une énergie apportée au milieu actif par la décharge égale à 150 J/l. Abstract. 2014 Long pulse (200 ns) XeCl excimer laser emission (03BB = 3 080 Å), has been obtained when Ne/Xe/HCl mixtures are excited by an electron beam and X-rays assisted discharge either at room temperature or at very low temperature. Absorbed discharge energy is several orders of magnitude higher than the absorbed beam energy. Maximum specific laser energy is 3 J/l at room temperature for a 16 cm gain length and an absorbed discharge energy of 150 J/1.
Space and time resolved discharge evolution of a large volume X-ray triggered XeCl laser system
Applied Physics B Photophysics and Laser Chemistry, 1992
The spatial distribution and the temporal development of the net gain have been measured in a ten liter active volume switchless discharge XeC1 laser. The experimental results are compared with both zero-dimensional and two-dimensional kinetic code predictions. The comparison between the results of the kinetic codes and of some measurements relevant to the time-dependent discharge homogeneity allows a deeper insight into the influence of the streamer evolution on the discharge characteristics.
Excimer laser gain by pulse shape analysis
IEEE Journal of Quantum Electronics, 1981
An analysis of the temporal emission of broadband tunable excimer lasers such as XezCl shows that the laser pulse can be described in terms of a Q-switch model rather than by steady-state considerations. For eiectron-beam (e-beam) pumped rare gas halide mixtures, transient absorption of the majority gas-usually argon-acts as a chemical Q-switch. The ring-up time of the delayed laser pulse may be conveniently used for optimization of the laser gas mixture.