Nanosecond pulsed lasers with high single-pulse energy show significant advantages in industrial fields such as material processing and laser cleaning. However, the traditional free-space or waveguide transmission methods are often limited by high energy loss, transmission distance, and difficulty in realizing flexible transmission in practical applications. This research is dedicated to exploring the realization of efficient, stable and flexible transmission of nanosecond pulsed lasers with high single-pulse energy. By combining the simulation of the effect of the decenter and tilt of the optical fiber on the coupling efficiency with the ZEMAX software, we have solved the problem of the spot defocusing in the horizontal and vertical directions caused by the thermal effect of the slab laser by precisely adjusting and optimizing the spatial positions of the lenses in the focusing system and the beam shaping system. This reduces the energy loss of the laser during the optical fiber transmission process and improves the transmission efficiency and stability. Finally, a 178mJ laser is coupled into an optical fiber with a core diameter of 800μm. The coupling efficiency is as high as 96% with a flexible transmission distance of 15m. Our research provides strong support for the development and application of laser technology.
With the advantages of safety, non-contact operation, high precision and real-time feedback, laser cleaning technology plays an important role in the field of intelligent manufacturing. In this study, a nanosecond pulsed laser with a wavelength of 1064 nm, a repetition frequency of 20 kHz, a pulse width of 70 ns, an average power of 3000 W, and a spot size of 40 mm*0.5 mm was used as the laser cleaning light source. Additionally, a laser cleaning prototype was constructed with a three-dimensional gantry displacement platform. With a scanning speed of 160 mm/s, a spot interval of 25 mm, and a laser energy density of 750 mJ/cm2 , the oxide film on the surface of marine steel was completely removed, achieving a good cleaning effect and a cleaning efficiency of up to 20 m2 /h. The entire cleaning process was achieved without dust emission. Our high-repetition-frequency, high-power nanosecond laser cleaning prototype is highly effective in removing rust from marine corrosion class B steel.
We adopt a flat-concave resonant cavity structure, and the laser propagates along the Zigzag optical path in the slab. In order to effectively reduce the thermal lens effect in the thickness direction of the slab crystal and reduce the local thermal effect at the pump region, we propose a module structure under the mixed cooling mode. The large surface under the slab is welded in the microchannel cooling heat sink, and the large surface on the module is cooled by strong convection, so that the crystal surface is evenly cooled, and the thermal distortion in the thickness direction of the slab crystal is suppressed. On the other hand, We use the fast axis collimated semiconductor laser stack as the pump source, and the pump light is coupled to the slab to achieve a uniform distribution of the pump intensity, which is through the optical waveguide and the aspheric lens. When the pump power is 9500W, the average output power is 4.352kW, and the corresponding optical-to-optical conversion efficiency is 45.8%. The repetition rate is 400Hz, the laser pulse width is 180μs, and the single pulse energy is 10.88J. The laser beam βx is 3.4 times of the diffraction limit, and βy is 1.5 times of the diffraction limit.
We propose a high-power, high-repetition-rate nanosecond slab laser amplifier that can operate at room temperature. The laser seed source uses a self-developed nanosecond laser with 500 W and 1064 nm. Based on the principle of multi-angle amplification of Nd:YAG slab structure, the seed source is injected into the Nd:YAG slab crystal at an incident angle of 10.2° and 20.6° after passing through the isolation system, the collimation system and the beam shaping system in turn. The rectangular output spot greatly improves the cleaning efficiency. The seed source operates in pulse mode, and the pump source of the amplifier operates in quasi-continuous mode. The pump uses a single side pump source with a wavelength of 808 nm and a bar number of 60 × 8. When the pulse width, repetition frequency and current of the pump are set to 200 μs, 400 Hz and 120 A, respectively, the output power of the seed source through the amplifier is 521 W and the magnification is 6 times. The output power of the seed source secondary through the amplifier is 872 W, and the magnification is as high as 19 times. When the pump pulse width, repetition rate and current are 400 μs, 400 Hz and 120 A, respectively, the output power of the seed source passing through the slab crystal twice is as high as 1747 W. The nanosecond slab laser amplifier with rectangular output spot designed by us can be applied to the field of high-efficiency laser cleaning.
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