Yahua Li | The University of Sydney (original) (raw)
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Papers by Yahua Li
Photonics Technology Letters, …, 2005
Dynamic Pulsing is demonstrated using a pulsed MOPA fiber laser at 1064nm. The output of the MOPA... more Dynamic Pulsing is demonstrated using a pulsed MOPA fiber laser at 1064nm. The output of the MOPA laser is a pulsed profile consisting of a burst of closely spaced pulses. Tests were performed under several materials with pulse bursts ranging from 10ns to 1μs and operating from 500kHz down to single shot. In particular, percussion drilling in stainless steel is demonstrated showing improvements in quality and speed of the process. These profiles allow high flexibility and optimization of the process addressing the specificity of the end application. Dynamic Pulsing allows the same MOPA fiber laser to be used in diverse materials as well as different processes such us marking, drilling, scribing and engraving. The pulsed fiber laser used in this study is a MOPA-DY by Multiwave Photonics. It is based on a modulated seed laser followed by a series of fiber amplifiers and ending with an optically isolated collimator. This pulsed laser model has an output in such a way that each trigger produces a fast burst of pulses, with a repetition frequency within the burst of the order of tens of MHz. Within the burst it is possible to change the number of pulses, the individual pulse profile, burst pulse period and even to generate non-periodic burst pulse separations. The laser allows full freedom for all these combinations. The study here reported compares the impact of pulse peak power, number of pulses within a burst and the pulse burst period, on process quality (heat affected zone, debris, hole uniformity) and drilling yield.
A new fiber coupled AOM for high power Q-switched fiber laser is proposed and experimentally pres... more A new fiber coupled AOM for high power Q-switched fiber laser is proposed and experimentally presented. Each end of the AOM has a fiber collimator. For its particular structure, amplified spontaneous emission (ASE) and other deleterious nonlinear processes such as stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) in high power pulsed fiber laser can be easily suppressed. Based on our proposed acoustic-optic modulator (AOM), the 3dB line width of the fiber laser can be narrowed to only 0.1nm, which made it suitable to be used as the seed in master-oscillator power amplifier (MOPA) configuration based all-fiber pulsed fiber laser. When the repetition rate is 20 kHz, 2W output from the fiber laser can be achieved. Full width at half maximum (FWHM) of the fiber laser's pulse is 56ns and the peak power of the fiber laser is nearly 1.8kW. When the fiber laser is used as the seed of a high power fiber laser, 20W with 20 kHz repetition rate pulsed fiber laser has been obtained. The pulse width is nearly 100ns and the peak power can reach as high as 10kW. Based on the proposed technique, mature product of the pulsed fiber laser with this configuration has been successfully implemented.
IEEE Photonics Technology Letters, 2004
An accurate experimental comparison of the pump absorption and the lasing features between Nd 3+ ... more An accurate experimental comparison of the pump absorption and the lasing features between Nd 3+ -doped fiber lasers using hexagonal-shaped and D-shaped fiber is reported. The measured slope efficiencies with respect to the absorbed pump power of 805 nm are nearly identical at 65.3% for both fibers. Taking advantage of the near symmetrical shape of the hexagonal fiber, the lowest reported splice loss of 0.05 dB is achieved between the double-clad fiber and standard 125-m fiber with the use of the fiber etching techniques. The pump absorption can be improved by bending the hexagonal fibers into a kidney shape.
Photonics Technology Letters, …, 2005
Dynamic Pulsing is demonstrated using a pulsed MOPA fiber laser at 1064nm. The output of the MOPA... more Dynamic Pulsing is demonstrated using a pulsed MOPA fiber laser at 1064nm. The output of the MOPA laser is a pulsed profile consisting of a burst of closely spaced pulses. Tests were performed under several materials with pulse bursts ranging from 10ns to 1μs and operating from 500kHz down to single shot. In particular, percussion drilling in stainless steel is demonstrated showing improvements in quality and speed of the process. These profiles allow high flexibility and optimization of the process addressing the specificity of the end application. Dynamic Pulsing allows the same MOPA fiber laser to be used in diverse materials as well as different processes such us marking, drilling, scribing and engraving. The pulsed fiber laser used in this study is a MOPA-DY by Multiwave Photonics. It is based on a modulated seed laser followed by a series of fiber amplifiers and ending with an optically isolated collimator. This pulsed laser model has an output in such a way that each trigger produces a fast burst of pulses, with a repetition frequency within the burst of the order of tens of MHz. Within the burst it is possible to change the number of pulses, the individual pulse profile, burst pulse period and even to generate non-periodic burst pulse separations. The laser allows full freedom for all these combinations. The study here reported compares the impact of pulse peak power, number of pulses within a burst and the pulse burst period, on process quality (heat affected zone, debris, hole uniformity) and drilling yield.
A new fiber coupled AOM for high power Q-switched fiber laser is proposed and experimentally pres... more A new fiber coupled AOM for high power Q-switched fiber laser is proposed and experimentally presented. Each end of the AOM has a fiber collimator. For its particular structure, amplified spontaneous emission (ASE) and other deleterious nonlinear processes such as stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) in high power pulsed fiber laser can be easily suppressed. Based on our proposed acoustic-optic modulator (AOM), the 3dB line width of the fiber laser can be narrowed to only 0.1nm, which made it suitable to be used as the seed in master-oscillator power amplifier (MOPA) configuration based all-fiber pulsed fiber laser. When the repetition rate is 20 kHz, 2W output from the fiber laser can be achieved. Full width at half maximum (FWHM) of the fiber laser's pulse is 56ns and the peak power of the fiber laser is nearly 1.8kW. When the fiber laser is used as the seed of a high power fiber laser, 20W with 20 kHz repetition rate pulsed fiber laser has been obtained. The pulse width is nearly 100ns and the peak power can reach as high as 10kW. Based on the proposed technique, mature product of the pulsed fiber laser with this configuration has been successfully implemented.
IEEE Photonics Technology Letters, 2004
An accurate experimental comparison of the pump absorption and the lasing features between Nd 3+ ... more An accurate experimental comparison of the pump absorption and the lasing features between Nd 3+ -doped fiber lasers using hexagonal-shaped and D-shaped fiber is reported. The measured slope efficiencies with respect to the absorbed pump power of 805 nm are nearly identical at 65.3% for both fibers. Taking advantage of the near symmetrical shape of the hexagonal fiber, the lowest reported splice loss of 0.05 dB is achieved between the double-clad fiber and standard 125-m fiber with the use of the fiber etching techniques. The pump absorption can be improved by bending the hexagonal fibers into a kidney shape.