G. Erez

Pulsed resonant optogalvanic effect in neon discharges

Pulsed resonant optogalvanic effect is investigated in a neon hollow cathode discharges utilizing a nitrogen pumped dye laser. We have studied by the pulsed technique transient effects in the discharge plasma such as fast relaxation of level population density and population inversion. The experimental results are correlated with a four states phenomenological model of the pulsed optogalvanic effect taking into account lumped relevant levels of the 3s and 3p manifolds of neon. The time integration of the pulsed optogalvanic siganls (OGS) yields the previously measured cw signals and explains their sign changes.

High-power, high-pressure, discharge-heated copper vapor laser

Abstract We have constructed a 40 mm diameter discharge-heated longitudinal copper vapor laser. The laser performs most efficiently at a neon buffer gas pressure of 200–600 Torr. The laser has produced over 20 W at 4 kHz as an oscillator and 30 W at 4 kHz and 20 W at 2 kHz (7.5 and 10 mJ/pulse) as an amplifier.

Temporal and spatial properties of an oscillator-amplifier copper vapor laser

Abstract Copper vapor laser operating parameters have been optimized for a MOPA chain configuration. Amplifier ASE is eliminated by relative lengthening of the oscillator pulse. The amplifier output beam diverges less than the input beam and its temporal shape is smooth while the oscillator beam contains three prominent peaks.

Structure of 510.6 and 578.2 nm copper laser lines

Abstract The structure of the 510.6 and 578.2 nm copper laser lines were calculated and measured as a function of cooper density and buffer gas pressure. The line shapes were consistent with the calculations only near the oscillation threshold. The buffer gas pressure data indicate that the pressure broadening coefficient is very small for our experimental conditions.

Inverted population observation using pulsed optogalvanic effect

Abstract We report on the use of pulsed optogalvanic effect in the detection of inverted population. An early positive part of the optogalvanic signal is shown to be characteristic of a population inversion and is measured using a high temporal resolution from the start of the laser pulse. Such inversion is obtained on a few of the neon 3p → 3s transitions in a standard DC hollow-cathode discharge tube with neon buffer gas. We observed inverted optogalvanic signal with exciting laser wavelengths at 659.9 nm, 585.2 nm and others. In fact, transient laser transitions on some of these wavelengths, in fast neon discharges have been reported. The optogalvanic effects, corresponding to neon levels 1s 5 and 1s 2 , and their dependent signals have opposite features and signs and are essentially mirror images of each other. The necessity of using pulsed optogalvanic mode and detection in the case of inverted population is discussed.

Cherenkov emission due to laser-induced moving polarisation in sodium

Red shifted conical emission induced by a laser blue shifted with respect to the D2 line of sodium is observed and interpreted in terms of Cherenkov emission. Measured cone angles and wavelength shifts agree well with model calculations taking into account saturation and dispersion effects.

Penning ionization spectroscopy using the optogalvanic effect

The optogalvanic effect is proposed and demonstrated as a new technique for quasiresonant Penning ionization spectroscopy in a discharge plasma of mixtures of rare gases and metal vapors. A calcium and neon mixture is used as a prototype. Neon’s lowest metastable level, 3P2 at 134 034 cm−1, is within kT from the excited state of 2D3/2,5/2 of Ca+. Thus Penning ionization occurs to an excited state of the ion. This process strongly alters the optogalvanic signal and has its own signature. In fact, other energy transfer processes should also change the time dependence of the optogalvanic signal.

Scaling of the discharge heated copper vapor laser

Abstract Optimum working temperature of 1650 ± 50°C was determined for the longitudinal copper vapor laser. Using neon in the pressure range 20–200 torr we were able to operate lasers of volumes up to 600 cm3 at optimum temperature. Power output was proportional to tube volume and efficiency to the square of tube radius. Average power of 19.5 W was obtained at 4 kHz with 0.7% efficiency.

On the optical characteristics of the conical emission

Abstract An intense laser beam blue detuned with respect to an atomic transition produces a forward conical emission. We demonstrate new experimental evidence that in sodium vapor this emission is generated at the surface of self-trapped filaments. This includes comparison of the polarization of the incident and emitted light as well as comparing the output pattern obtained by cylindrical and spherical focusing modes. As a surface phenomenon, the conical emission shares its characteristics with Cherenkov-type processes.

Observation of Penning ionization in Sr/Ne discharge by the optogalvanic effect

A study of the pulsed optogalvanic effect in a Sr/Ne hollow cathode tube for Penning ionization spectroscopy in this system is described. In the case of strontium this ionization is a multichannel process due to the quasi-resonance between the four excited 3s states of neon with the high density of Rydberg states close to a Sr+ ionization continuum. A detailed investigation of the signal as a function of tube current and its spatial dependence as well as a comparison with Ca/Ne Penning rate is also reported.