Rf-excited CO2 Waveguide Laser Research Articles

Mathematical modelling of gain-switched RF-excited CO 2 waveguide laser

The detailed mathematical models for the evolution of light pulses in RF-excited CO2 waveguide lasers are derived. Explicit expressions for the pulse characteristics in RF-excited CO2 waveguide lasers are obtained. The effects of losses and unsaturated gain on output power are calculated.

The stability of the active medium of RF-exited CO 2 lasers with gold as catalyst

Using mass-spectrometric investigations the gas composition of the active medium of sealed-off cw RF-excited CO2 waveguide lasers have been studied. It has been found that a low degree of CO2 dissociation and a laser power improvement can be achieved by means of a gold catalyst in the laser discharge volume. The conditions for long operational lifetimes of these lasers are described.

Influence of the electric field frequency on the performance of a RF excited CO2 waveguide laser

An analysis is presented of the effect of the RF frequency on the active media of CO2 waveguide lasers. It is found that the characteristics are improved with increasing RF frequency because the space charge sheath width decreases with increasing excitation frequency. We also found that the sheath width decreases with the discharge current; this fact was never discussed before. The higher the exciting frequency the higher is the maximum input power of the discharge in the stable low current mode. It is attractive to extend the input power while keeping the discharge in this mode. Finally, a stabilizing excitation technique is described for the inherent unstable region of the discharge.

Enhanced gain and output power of a sealed-off rf-excited CO2 waveguide laser with gold-plated electrodes

The small-signal gain and the laser output power have been measured in a cw sealed-off rf-excited CO2 waveguide laser for two different electrode materials, gold-plated copper and aluminum, at several excitation frequencies, gas pressures and mixture compositions. In the case of the gold-plated electrodes an enhancement of the gain up to a factor of 2 and the output power up to a factor of 1.4 with time at a frequency of 190 MHz and 60 Torr of 1:1:5+5% (CO2:N2:He+Xe) mixture is observed. This is believed to be the result of the gold catalytic activities which are favored by increased electrode temperatures and helium rich gas compositions.

Pulsed Q-switched CO2 waveguide laser

The performance of an rf-excited CO2 waveguide laser which was synchronously pulsed and electro-optically Q switched is described. Output power of up to 14 kW in 50 ns was achieved which was significantly higher than powers previously obtained from reported Q-switched CO2 waveguide lasers. Acoustical perturbations were created in the optical waveguide by the pulsed discharge. This resulted in discontinuous variation in the laser pulse energy as the pulse repetition frequency was varied. Extremely marked thermal effects on Q-switching performance were observed.

Chirp in pulsed, rf-excited CO2 waveguide lasers

An experimental investigation has been conducted to determine the frequency stability of a pulsed, rf-excited waveguide CO2 laser. Unlike transversely excited atmospheric CO2 lasers, for which the optical extraction of energy (laser-induced medium perturbation) is typically the dominant source of frequency instability, the driver in the long pulse (>30 μs) waveguide laser is the thermal heating of the gain medium due to the rf input energy. Modeling of the chirp in the pulsed waveguide laser is performed. Included are both finite V-T effects in the short term and heat conduction and particle migration out of the laser bore by the gaseous gain medium in the long term.

CO2 dissociation in sealed rf-excited CO2 waveguide lasers

A mass spectrometer has been used to study the gas composition in a sealed rf-excited CO2 waveguide laser during operation. CO2 dissociation levels, at 53% to 71%, are similar to those reported for dc-excited waveguide lasers and substantiate prior measurements on rf-excited discharges. The degree of dissociation decreases with increasing pressure and xenon content, but increases as the proportion of helium in the gas mixture is increased. Dissociation has been found to be insensitive to the rf input power per unit discharge length over the range of 2.7 to 4.7 W/cm. This is believed to be the result of increased rates of water vapor outgassing at higher input power levels.

The effect of C13O162 on the performance of a sealed-off pulsed CO2 laser

A sealed-off rf-excited CO2 waveguide laser was used to investigate the relative performance with C13O2 and C12O2 mixtures. By modulating the laser at various rates and pulse widths, we demonstrated effects due to both temperature and upper level relaxation rates. In addition, replacing N142 with N152 was shown to improve the performance of C13O2.

Parameters affecting the performance of a rf excited CO2 waveguide laser

This paper summarizes the results of a series of rf gas discharge experiments which were performed to assess the factors which influence the efficient operation of a transversely excited CO2 waveguide laser. Using multiple resonating inductors for impedance matching, the longitudinal voltage variations are shown to be affected by the rf operation frequency and the discharge geometry. The effect of the gas mixture and the rf input power density upon the discharge field to pressure ratio is also investigated.

Influence of xenon on sealed-off operation of rf-excited CO2 waveguide lasers

The addition of xenon to helium, nitrogen CO2 gas mixtures is shown to increase output power by 24% in sealed-off rf excited waveguide carbon dioxide lasers. Experiments with a range of laser output couplers indicate that this improvement is due to a corresponding increase in small signal gain, with the saturation intensity remaining fairly constant.

Ten-atmospheres high repetition rate rf-excited CO2 waveguide laser

The design and operating characteristics of a pulsed, rf-excited CO2 waveguide laser operated at gas pressures up to 10 atm are reported. The results of small signal gain and gain decay time-constant measurements are also given.

A transversely rf-excited CO2 waveguide laser

An electrodeless CO2 waveguide laser with transverse rf pumping is described. In the rf cw mode, the laser emits up to 0.6 W at 100 Torr. In the rf pulse mode, atmospheric operation has been achieved with pulse duration of 20 μs and peak power of a few watts at a repetition rate of 300 Hz.