Optimal Characteristics of a Long-pulse $CO_2$Laser by Controlling SCR Firing Angle in AC Power Line

  • Noh, Ki-Kyung (Dept. of Electrical Engineering, Pusan University) ;
  • Kim, Geun-Yong (Dept. of Electrical Engineering, Pusan University) ;
  • Chung, Hyun-Ju (Dept. of Electrical Engineering, Pusan University) ;
  • Min, Byoung-Dae (Dept. of Electrical Engineering, Pusan University) ;
  • Song, Keun-Ju (Dept. of Electrical Engineering, Pusan University) ;
  • Kim, Hee-Je (Dept. of Electrical Engineering, Pusan University)
  • 발행 : 2002.06.01

초록

We demonstrate a simple pulsed $CO_2$ laser with millisecond long pulse duration in a tube at a low pressure of less than 30 Torr. The novel power supply for our laser system switches the voltage of the AC power line (60Hz) directly. The power supply doesn't need elements such as a rectifier bridge, energy-storage capacitors, or a current-limiting resistor in the discharge circuit. To control the laser output power, the pulse repetition rate is adjusted up to 60Hz and the firing angle of SCR(Silicon Controlled Rectifier) gate is varied from 30。 to 150。. A ZCS (Zero Crossing Switch) circuit and a PIC one-chip microprocessor are used to control precisely the gate signal of the SCR. The maximum laser output of 35 W is obtained at a total pressure of 18 Torr, a pulse repetition rate of 60 Hz, and a SCR gate firing angle of 90。 . In addition, the resulting laser pulse width is approximately 3㎳(FWHM). This is a relatively long pulse width, compared with other repetitively pulsed $CO_2$ lasers.

키워드

참고문헌

  1. Dhruba J. et al', 'Single switch as a driver of two high-repetition-rate lasers,' Opt. Eng. 36, pp. 588-592, 1997
  2. J, J. Lowke, 'Predicted transport coefficients and operating characteristics of $CO_2-N_2-He$ laser mixtures,' J.Appl. Phys., Vol.44, No. 10, pp. 4754-4761, 1973
  3. Hirokazu Hokazono and Minoru Obara, 'Improvement of self-regeneration of gas mixtures in a convection- cooled 1.2kW $CO_2$ laser', J. Appl. Phys. 30, pp.1103-1110, 1997
  4. N. Menyuk and P. F. Moulton, 'Development of a high-repetition-rate mini-TEA $CO_2$ laser,' Rev. Sci. lnstrum., vol.51,No.2, pp.216-220, 1980
  5. K. R. Rickwood and J. Mcinnes, 'High repetition rate mini TEA $CO_2$ laser using a semiconductor preionizer,' Rev. Sci. lnstrum. vol.53,No.ll, pp.1667-1669, 1982
  6. M. M. T. Loy and P. A. Roland, 'Simple longitudinally pulsed $CO_2$ laser and its application in singlemode operation of TEA lasers,' Rev. Sci. Instrum., vol.48,No.5, pp. 554/556, 1977
  7. E. V. Ross, Y. Domankevitz, M. Skrobal, and R. R. Anderson, 'Effects of $CO_2$laser pulse duration in ablation and residual thermal damage: Implications for skin resurfacing:, Lasers in Surgery and Medicine, vol.19, pp. 123/129, 1996
  8. P. Wilder-Smith, G. M. Peavy, D. Nielsen, and A. M. Arrastia-Jitosho, '$CO_2$ laser treatment of traumatic pulpal exposures in dogs,' Lasers in Surgery and Medicine, 21, pp.432/437, 1997
  9. T. Wildi, 'Electrical Machines, Drives, and Power Systems,' Prenctice Hall, 1997
  10. Dong-Hoon Lee, Hyun-Ju Chung, and Hee-Je Kim, 'Comparison of DC and AC excitation of a sealed $CO_2$ laser,' Rev Sci. Instrum, 71, pp577/578, 2000
  11. E. Wasserstrom, Y. Crispin, J. Rom, and J. Shwartz, 'The interaction between electrical discharges and gas flow,' J. Appl. Phys. vol.49,No.1, pp81/86, 1978
  12. Koechner W., Solid-State Laser Engineering, New York Springer Verlag, 1996