V. A. Seguin

Annular-coupled concave–convex stable resonator for large-volume high-quality energy extraction

A theoretical investigation of a stable concave-convex resonator configuration, which appears suitable for single-mode high-power energy extraction from large volume gain media, is presented. The design features annular output coupling with a surprisingly uniform near-field intensity distribution. The computer-based analysis, supported by preliminary experimental results, suggests that acceptable alignment tolerances are provided along with an unusually small beam divergence. With proper design, a far-field divergence of 0.5 mrad, encompassing near 80% of the total laser energy, appears feasible. Operational data, recently obtained with this optical extraction approach, have revealed a further important practical advantage over an unstable resonator, being far less prone to mode degradation and hot spot formation on optical component misalignment.

Gain characteristics of a MAGPIE coaxial CO 2 laser system

Gain coefficient measurements of a MAGPIE (magnetically stabilized, photoinitiated, impulse-enhanced, electrically excited) coaxial CO 2 laser discharge are presented. The effects of gas composition, input power, pulser ionization, and magnetic field on gain are examined. Measurements of the radial gain profile and saturation intensity are also discussed. A maximum small-signal gain of 0.30 m-1is observed, along with a saturation intensity of 190 W/cm2.

Multiple pass unstable resonator for an annular gain CO2 laser.

The design, construction, and operational characteristics of an optical resonator for an annular gain media are described. The system, developed for laser power extraction investigations in a new type of coaxial discharge geometry, features a folded multipass unstable resonator concept, fabricated from lightweight uncoated diamond-turned aluminum substrates. The resulting cw CO2 device incorporates excitation aspects of the nonself-sustained PIE excitation process in addition to a new magnetic discharge stabilization technique. Laser performance and output beam characteristics are presented.

High-average power-pulsed performance of a multikilowatt PIE laser

The application of a burst-mode pulsed discharge technique to a large-volume, multikilowatt, PIE (photo-initiated, impulse-enhanced, electrically excited) carbon dioxide laser is described. A factor of two enhancement in average output power, up to the 10 kW level, was obtained using a burst duration of 1.2 ms and a repetition rate of 500 burst/s. The small signal-gain increased to essentially double that of the normal continuous-wave value. Gain profile information, together with details of the lasers power performance, as a function of various discharge parameters, is illustrated. These data clearly document the versatility of this unique and cost-effective burst-mode laser excitation process. >

Operational characteristics of a MAGPIE coaxial CO2 discharge system

The operational characteristics of a convectively cooled Magnetically stabilized, Photo-initiated, Impulse-enhanced, Electrically-excited (MAGPIE) coaxial discharge system are described. terminal behavior is examined as a function of several parameters, such as gas flow, pulser ionization, and magnetic field strength. In-situ plasma potential measurements are also presented, which indicate that CO2 attachment effects have considerable influence on the spatial electrical characteristics of the gas discharge.

High repetition rate operation of a photoinitiated impulse‐enhanced electrically excited CO2 laser discharge using a burst‐mode technique

The incorporation of a gating signal into the trigger circuit of a photoinitiated, impulse‐enhanced, electrically excited (PIE) laser system has permitted high‐power, pulsed operation of a normally cw CO2 discharge. The 40 liter gain medium has been run at repetition rates approaching 1 kHz utilizing this approach. Plasma uniformity and stability have been significantly enhanced, such that a factor of two increase in electrical power deposition into the excited volume has been achieved. Results suggest that pulsed performance considerably in excess of that achievable under cw operating conditions can be realized through the adoption of this simple modification to the PIE ionization process.

Burst-mode gain switched technique for high peak and average optical energy extraction

The optical performance of a cw PIE CO(2) laser has been substantially improved through the adoption of a burst-mode gain switching technique. The approach has provided a doubling of the average beam power extractable from the device. With appropriate optimization, the process could possibly permit the attainment of pulsed energy extraction in the kilohertz range, and with average optical powers within the several tens of kilowatt category.

Compact axial flow gas transport system for a coaxial CO2 discharge laser

The design and construction of an axial flow gas transport system for a coaxial CO2 laser discharge is described. The system features a novel annular flow geometry, which yields a compact, cylindrical package. Flow velocities of up to 50 m/s have been obtained in the device. Measurements of active medium working temperature and gain profiles are also presented.

Numerical simulation of gas flow in a magnetically stabilized coaxial laser discharge

The neutral gas flow profile within a magnetically stabilized coaxial laser gas discharge is analyzed by using a single fluid magnetogasdynamic model. Equations describing the rotational, radial and axial gas transport are solved by using an iterative alternating direction implicit method. Steady state rotational velocities of the order of 20 m/s are found.

Electron density measurements in a photoinitiated, impulse‐enhanced, electrically excited laser gas discharge

Measurements of the electron density within a photo‐initiated, impulse‐enhanced, electrically excited (PIE) laser gas discharge are presented. Ion current measurements were made using a single Langmuir electrostatic probe positioned within the laser discharge volume. Calculations of the electron density were made utilizing a thick‐sheath analysis. The results indicate that the electron density increases by two orders of magnitude as the pulser power level is increased. In addition, the electron density was observed to decrease markedly as the dc discharge current was increased.