An electron‐beam‐controlled discharge has been used to pump a variety of CO2 laser gas mixtures at atmospheric pressure in substantial volumes. Electrical and laser properties of the pumped medium have been measured. Small‐signal‐gain coefficients up to 0.045 cm−1 were achieved at field strengths of 3 kV/cm.

Electron-beam-controlled electrical discharge as a method of pumping large volumes of CO2 laser media at high pressure

The propagation of phase-locked and non-phase-locked laser array beams of radial and rectangular symmetries in a turbulent atmosphere are investigated based on the extended Huygens–Fresnel integral. The beamlet used in our paper for constructing the laser array beams is of elliptical Gaussian mode. Analytical formulae for the average irradiance of phase-locked and non-phase-locked radial and rectangular laser array beams are derived through vector integration and tensor operation. The irradiance properties of these laser array beams in a turbulent atmosphere are studied numerically. It is found that both phase-locked and non-phase-locked radial and rectangular laser array beams eventually become circular Gaussian beams in a turbulent atmosphere, which is much different from their propagation properties in free space. The propagation properties are closely related to the parameters of laser array beams and the structure constant of the turbulent atmosphere.

Propagation of laser array beams in a turbulent atmosphere

A review of studies of the properties of radiation from optically coupled lasers is presented. The methods for phase locking the fields in optically coupled lasers of different types are considered and the methods for supermode selection and correction of the radiation pattern are discussed.

http://iopscience.iop.org/article/10.1070/QE2003v033n04ABEH002415/pdf

Phase locking of optically coupled lasers

A three-stage magnetic modulator utilizing magnetic pulse compression designed to provide a 60 kV pulse to a copper vapor laser at a 4.5 kHz repetition rate is disclosed. This modulator operates at 34 kW input power. The circuit includes a step up auto transformer and utilizes a rod and plate stack construction technique to achieve a high packing factor.

High average power magnetic modulator for metal vapor lasers

The gases and cathode of a TEA CO2 laser are irradiated with uv radiation. The resulting photoionization and photoemission initiate and assist in sustaining a high‐energy low‐field‐strength discharge. Output energy of 50 J/liter at an efficiency of 15% has been obtained in an initial demonstration.

Photoinitiated and photosustained laser

An investigation of phase-locking phenomena in a multichannel, slab-type electrode, CO2 laser array is presented. External and self-phase-locking percentages of 90% and 60%, respectively, have been demonstrated. Azimuthally distributed radial injection within the central region of this gain geometry has been identified as the principal phase-locking mechanism. Fundamental optical modes are initiated simultaneously within each individual discharge slot via injection from this central core-oscillator region.

Phase-locking phenomena in a radial multislot CO 2 laser array

The dynamics of a rotating plasma in a transverse electrode geometry appropriate to high power CO2 laser discharge pumping is examined. The magneto‐gas‐dynamic fluid model used reveals that the spatially nonuniform electric and magnetic fields within the discharge cause the plasma and neutral gas rotational velocities to be strongly sheared within the cathode fall and the positive column regions. This sheared rotation serves to both stabilize the discharge against glow to arc transitions and to drive a centrifugal neutral gas flow within the volume. The concomitant bulk gas cooling effect so produced is particularly beneficial in a high powered CO2 electrical discharge laser as it inhibits thermal bottle necking. An order of magnitude increase in discharge power loading has been achieved utilizing a simple ’’magnetic electrode’’ discharge configuration.

Dynamics of magnetically stabilized laser discharge

An excitation and optical extraction geometry suitable for compact high power gas lasers is described. Multiple slab discharges are established in a diffusion-cooled radial electrode array. Each gain channel is independently driven from a common RF source via a resonant-cavity power distribution system. Radial excitation augmented with multi-channel self-injection phase locking provides stable optical power extraction at good efficiency. The concept is easily scalable to very high powers while dramatically reducing unit size and cost.

Power scaling of diffusion-cooled lasers

The beam quality of a diffusion-cooled RF-excited radial-geometry CO/sub 2/-slab-laser array is investigated. The system is shown to negate many of the disadvantages inherent with slab lasers, namely, asymmetric beams, multiple focal spots, and linear polarization. In addition, the effective spot size is reduced as a result of radial stacking of the individual asymmetric but azimuthally distributed, incoherent, output beamlets. A performance demonstration with sheet-metal cutting has produced excellent results in terms of kerf width, depth of penetration, and cut directionality. >

Symmetry enhancement and spot-size reduction through radial beam stacking in a multichannel CO/sub 2/ laser array

Details of an experimental investigation of the small signal gain and saturation parameter of a 10 kW CW photoinitiated, impulse-enhanced, electrically excited (PIE) CO2 laser are presented. Measurements were made as a function of several device operational conditions, such as gas pressure, input electrical power, pulser ionisation and flow velocity. Gain profiles were also obtained, both from anode to cathode, and in the direction of gas flow. The results document the effectiveness of the PIE excitation technique, while providing detailed information on the gain medium. Such data are essential to the design of an efficient optical extraction system.

H. J. J. Seguin

Papers

Phase-locking phenomena in a radial multislot CO 2 laser array

Dynamics of magnetically stabilized laser discharge

Power scaling of diffusion-cooled lasers

Symmetry enhancement and spot-size reduction through radial beam stacking in a multichannel CO/sub 2/ laser array

Gain and saturation parameters of a multikilowatt PIE CO2 laser