Minoru Uehara

Experimental study on operation at room temperature of transverse flow carbon monoxide laser excited by radio frequency discharge

A high output and high conversion efficiency transverse flow carbon monoxide laser has been developed for operation at room temperature. The adoption of radio frequency discharge for excitation has permitted obtaining at room temperature (289 K), without xenon addition to the gas, a maximum output of 665 W at a conversion efficiency of the 10.7%. The output characteristics observed from the experiment are discussed, and the factors that effect laser output are considered.

Characteristics of a transverse-flow CO laser excited by RF-Discharge

We have developed a compact, efficient kW-class CO laser excited by transverse radio frequency (RF) discharge. The discharge and output characteristics of the RF-excited CO laser were investigated and were compared with those of the DC-excited one. The RF discharge power at 13.56 MHz was supplied to a discharge volume of 40H/spl times/35W/spl times/280L (mm/sup 3/). Utilization of the RF excitation instead of the DC excitation enhanced the maximum input power, the electrical conversion efficiency and the beam quality. Six gas conditions (pressure, temperature, flow speed, and the concentrations of CO, N/sub 2/, and O/sub 2/) were chosen as the experimental parameters. The optimum values of the gas parameters to maximize the output power were 50 torr, 200 K, 17 m/s, 5%, 12% and 0.4% respectively. The maximum output power obtained was 1.32 kW, with an electrical conversion efficiency of 27% and a slope efficiency of 39%. The specific laser power, which characterizes the scaling law of a transverse-flow laser, was 4.6 kW/m for the length, and 3.3 W/cm/sup 3/ for the volume. >

Recent studies of high-power CO laser under room temperature operation

Application of radio frequency excitation to transverse flow CO laser has led to the successful realization of high output-high-power high-conversion-efficiency oscillation at room temperature. The operating performance of the laser system thus developed has been examined in such aspects as the effects brought by changes in the laser operating parameters on the discharge and laser output characteristics, and on the beam profile. In experiments performed to date, an output power of 992 W at a conversion efficiency of 15% has been achieved with a gas temperature of 286 K, using gas made up of He, N2, CO and O2, without Xe addition. Compared with operation at cryogenic temperature, room temperature operation has proved to ensure more stable and more uniform excitation over the entire discharge space, and to permit extraction a beam of distinctly higher quality, thus demonstrating the superiority of room temperature operation.

Development of CO laser excited by transverse rf discharge

We have developed a compact kW-class CO laser excited by transverse-rf-discharge. The discharge and output characteristics of the rf-excited CO laser were investigated experimentally. Six gas conditions (pressure, temperature, flow speed, CO-, N2-, and O2-concentration) are chosen as the experimental parameters. The optimum values of them to maximize the output power are 50 Torr, 200 K, 17 m/s, 5%, 12%, and 0.4%, respectively. The maximum output power obtained is 1.3 kW with the electrical conversion efficiency of 27% and the slope efficiency of 39%.

5-kW lamp-pumped Nd:YAG lasers and their applications

Design and performance details of a 5-kW cw arc-lamp-pumped Nd:YAG laser are given. Two types of 5-kW Nd:YAG lasers have been developed, which have enough laser power and beam intensity necessary to realize deep penetration and high speed welding of metals. Experiments of welding and thick plate cutting were performed in order to investigate the ability of 5-kW Nd:YAG lasers. Maximum penetration of 15 mm is achieved with stainless steel and that of 6 mm with aluminum alloys. Moreover high speed welding up to 8 m/min is realized.

High-average-power YAG lasers and applications

A novel multi-rod cw Nd:YAG laser with 4 kW output power through an optical fiber has been developed. We adopted a unique YAG rod arrangement which minimizes the distance between adjacent rods. By using such a resonator, the laser output power of 4.8 kW was extracted from the laser resonator at an oscillation efficiency of 3.9%. The fiber power transmission with a fused silica fiber of 1.0 mm diameter is possible for the delivered laser power of 4.4 kW with transmission efficiency of about 92%, which is the same as a theoretical reflection loss at end surfaces. Welding experiments using the developed 4 kW YAG laser with a fiber- connected multi-joint robots showed excellent performance of 10 mm penetration for stainless steel welding and of more than 4 mm penetration for aluminum alloys.

Room temperature operating pulse rf-discharge-excited CO laser

A high power pulse CO laser operating at room temperature has been developed using the modulated pulse rf discharge excitation technique. The fast pulse response and the good reproducibility of laser pulse were obtained for pulse frequency up to 1 kHz with a stable and homogeneous discharge. A maximum peak power of 920 W with a pulse width of 1.0 ms FWHM has been attained by the optimizing N2 and CO concentration.