Mr. Jianhui Li Profile

Jianhui Li

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Proceedings Article | 16 February 2018 Paper

Longitudinally excited CO2 laser with short laser pulse and high quality beam

Jianhui Li, Hayato Goto, Takahisa Jitsuno, Kazuyuki Uno

Proceedings Volume 10518, 105181Y (2018) https://doi.org/10.1117/12.2288071

KEYWORDS: Carbon monoxide, Electrodes, Mirrors, Capacitance

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We developed a longitudinally excited CO₂ laser with a tail-free short pulse and a high quality beam. The laser system had a longitudinal discharge tube, a long optical cavity and a simple driver circuit. The discharge tube was made of an alumina ceramic pipe with an inner diameter of 16 mm and a length of 45 cm, two metallic electrodes and two windows. Gas medium was a 20:1 mixture of CO₂/N₂at a pressure of 2.6 kPa. The optical cavity with the length of 180 cm was formed by an output coupler with a reflectivity of 70% and a high-reflection mirror. The optical cavity had an aperture or did not. The driver circuit consisted of −600 V pulse power supply and a primary capacitance of 9.6 μF, a step-up transformer, a storage capacitance of 700 pF, a spark gap and the discharge tube. The CO₂ laser produced a tail-free short pulse with the width of 281 ns. The CO₂ laser beam was a ununifomly distributed circular beam with the M² factor of 22.8 in the laser system without an aperture, a top-hat shape of circular beam with the M² factor of 9.61 in the laser system with a φ11-mm aperture, 5.40 in the laser system with a φ9-mm aperture, or a Gaussian shape of circular beam with the M² factor of 3.01 in the laser system with a φ7-mm aperture.

Proceedings Article | 9 November 2016 Paper

Longitudinally excited CO2 laser with short laser pulse operating at high repetition rate

Jianhui Li, Kazuyuki Uno, Tetsuya Akitsu, Takahisa Jitsuno

Proceedings Volume 10016, 100161G (2016) https://doi.org/10.1117/12.2245529

KEYWORDS: Carbon dioxide lasers, Pulsed laser operation, Laser development, Optical resonators, Output couplers, Gas lasers, Carbon monoxide, Laser energy, Laser applications, Electrodes

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A short-pulse longitudinally excited CO₂ laser operating at a high repetition rate was developed. The discharge tube was made of a 45 cm-long or 60 cm-long dielectric tube with an inner diameter of 16 mm and two metallic electrodes at the ends of the tube. The optical cavity was formed by a ZnSe output coupler with a reflectivity of 85% and a high-reflection mirror. Mixed gas (CO₂:N₂:He = 1:1:2) was flowed into the discharge tube. A high voltage of about 33 kV with a rise time of about 200 ns was applied to the discharge tube. At a repetition rate of 300 Hz and a gas pressure of 3.4 kPa, the 45 cm-long discharge tube produced a short laser pulse with a laser pulse energy of 17.5 mJ, a spike pulse energy of 0.2 mJ, a spike width of 153 ns, and a pulse tail length of 90 μs. The output power was 5.3 W. The laser pulse waveform did not depend on the repetition rate, but the laser beam profile did. At a low repetition rate of less than 50 Hz, the laser beam had a doughnut-like shape. However, at a high repetition rate of more than 150 Hz, the discharge concentrated at the center of the discharge tube, and the intensity at the center of the laser beam was higher. The laser beam profile depended on the distribution of the discharge. An output power of 7.0 W was achieved by using the 60 cm-long tube.

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