Steady-state model for the electron beam pumped KrF laser

In this paper the kinetics of excitation, quenching, and absorption in an e-beam pumped KrF laser is discussed. It is argued that under usual experimental conditions the steady-state approximation can be applied. For that case a comprehensive kinetic model can be treated analytically. The model simulates quite well the experimental results obtained so far. It predicts the maximum performance conditions, limiting behaviour, and scaling properties of e-beam pumped KrF lasers

Pulse-forming and line-broadening in AM mode locking of the TEA-CO2laser

The present paper describes AM mode locking for homogeneously broadened systems, a procedure for measuring linewidths under laser conditions, and finally, experimental results for a 1-atm CO2laser. Working in the frequency domain, analytic solutions are given for the pulse bandwidth and pulse shape as a function of frequency detuning. We arrive at a simple expression for the maximum positional shift of the mirror distance. It turns out that the linewidth is inversely proportional to the maximum frequency shift and can be obtained independent of the modulation parameters and time constant of the pulse-signal detector. Applying this analysis to an amplitude-modulated CO2laser the pulsewidth and linewidth have been measured as a function of gas composition and modulation depth. In contrast to predictions deduced from absorption measurements under neutral conditions we find the striking result that under laser-discharge conditions the linewidth increases and the pulsewidth decreases with increasing helium percentage

Gain induced stability of active plane-parallel resonators

It has been observed for a plane-parallel resonator with a saturated medium that under certain conditions confined beams mainly concentrated near the axis are present. The experiments have been done with a sealed-off plane-parallel CO2 laser of one meter length and with an internal diameter of 20 mm. Without gain variations such a system is unstable because of thermal defocussing by the heated gas. But due to sufficiently high gain variations the beam converges nevertheless. Since the gain variation increases with decreasing reflectivity confined beams near the optical axis are only observed at sufficiently low reflectivity. The experiments were done with a totally reflecting mirror and an outcoupling mirror having a reflectivity of, respectively, 90%, 80%, 50%, and 36%. For the high reflectivities the outcoupled beam is mainly concentrated near the edge with irregular density distributions. For the low reflectivity the beam is more or less radially symmetric, concentrated near the axis having decreasing intensity with the distance from the axis.\ud \ud The behaviour can be understood by an analysis in which the constant and quadratic term of the complex propagation constant near the optical axis due to gain variations, dispersion and heat effects are taken into account

High energy extraction of electron beam pumped KrF lasers at multi atmospheres

The construction is described of a simple and compact KrF laser with electron beam excitation. The electron beam is generated in a coaxial vacuum diode, driven directly by a ten-stage coaxial Marx generator. A flat MgF2 outcoupler and a suprasil roof prism, protected by an MgF2 window, proved to be resistant against optically and chemically induced damage. A gas mixture of 4.5 bar Ar, 150 mbar Kr and 10 mbar F2 gives an energy output of 0.46 J from a 16 cm3 volume in 40 ns pulses or 0.72 MW/cm3

On the saturation effects and start jump of Gaussian modes in oscillators

The present paper deals with the interaction of a Gaussian mode with a homogeneous and an inhomogeneous laser transition. The interaction of the beam with the medium in a laser is treated by taking into account the spatial distribution of both radiation and gain. The intensity characteristics are very different from those obtained for a one-dimensional interaction of a plane wave with a saturating medium. In the presence of a small-signal gain profile the threshold condition requires much higher inversion densities along the optic axis than by ignoring this profile. For gas lasers, for instance, having a small-signal gain profile that is approximately described by a zero-order Bessel function, the threshold inversion density can be about 50 percent higher. For high-power systems the saturation of the medium by the Gaussian intensity distribution results in a considerable amount of radial radiation transport. For homogeneous transitions this amount is about equal to the stimulated emission and for inhomogeneous transitions it is about half of it, independent of the beamwidth. Further, it is found that if one slowly passes the threshold condition for laser action, the intensity jumps from zero to a certain value and vice versa. This effect has also been verified experimentally

Psychologists’ Diagnostic Processes during a Diagnostic Interview

In mental health care, psychologists assess clients’ complaints, analyze underlying problems, and identify causes for these problems, to make treatment decisions. We present a study on psychologists’ diagnostic processes, in which a mixed-method approach was employed. We aimed to identify a common structure in the diagnostic processes of different psychologists. We engaged an actor to simulate a client. Participants were asked to perform a diagnostic interview with this “client”. This interview was videotaped. Afterwards participants first wrote a report and then were asked to review their considerations during the interview. We found that psychologists were comprehensive in their diagnostic interviews. They addressed the client’s complaints, possible classifications, explanations, and treatments. They agreed about the classifications, more than about causal factors and treatment options. The content of the considerations differed between the interviews and the reports written afterwards. We conclude that psychologists continuously shifted between diagnostic activities and revised their decisions in line with the dynamics of the interview situatio

Saturation studies of the E-beam sustained discharge atomic xenon laser

In an electron beam sustained discharge xenon laser the discharge energy deposition has been varied in order to investigate the saturation effect on the xenon laser. The current density of the electron beam is varied separately in the range of 0.1-2.7 A/cm2 to obtain optimized discharge excitation conditions as a function of electron beam current density and gas pressure. An optimal fractional ionization f=3.5-4×10-5 is found, independent of the electron beam parameters. The synergy of electron beam and discharge excitation has resulted in a maximum specific energy of 15 J/l at a total gas pressure of 9 ba

Tunable sealed-off CW CO laser at room temperature

Starting from a sealed-off CO laser with a long-life output of 29 W/m in multiline operation, we developed a tunable version of this device. The system described has a discharge length of 97 cm. It was made transition-selective by using a three-mirror configuration. In this way we were able to tune the laser to more than 70 oscillating vibrational-rotational transitions of the CO molecule

Construction and operation of high power gas lasers

In the present paper some typical gas laser construction and their performances will be described. Aspects of transition selective systems and high pressure operation will be treated

An independently adjustable multiline AM mode-locked TEA CO2laser

A new method is described for constructing an AM mode-locked, multiline TEA CO2laser oscillator generating nanosecond pulses. The multiline behavior is achieved by spatial separation of the rotational transitions at the amplifying medium. The setup generates 1.15 ns pulses with an energy of 3.7 mJ per pulse and containing simultaneously six rotational transitions in the 10.6 µmP-branch