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Evaluation of fluences and surface characteristics in laser polishing SKD 11 tool steel
摘要： In this paper, a continuous-wave laser beam from a multimode fiber laser was applied to study the polishing effect. Three kinds of surface morphologies were acquired by fast-speed (FS) & lower-speed (LS) wire electrical discharge machining (EDM), milling processing methods on SKD11 tool steel. Then influence of laser fluence on the polished surface characteristics was analyzed. The results showed that surface roughness parameters (Ra, Rz, Rt, and Sa) can be significantly affected by this effect. With laser fluence increasing, the polished surface underwent a comprehensive topographical evolution from superficial surface melting to surface over-melting. The improvements by FS-EDM, LS-EDM, and milling in roughness were 86.83%, 90.70% and 86.07%, respectively. The corresponding laser fluences were 14.26 J/mm2, 12.73 J/mm2 and 13.55 J/mm2, indicating that LS-EDM tool steel surface has the best polishing effect. The comparative statistical results of the bearing area curve, bidirectional reflectance distribution function, and power spectral density from the LS-EDM surfaces showed the best polishing results. In addition, all the pre-prepared surfaces could be polished to Ra < 0.5 μm using high polishing velocities. These findings also signified that laser beam with top-hat distribution has a great potential for high-efficiency polishing of tool steel surfaces.
关键词： Power spectral density,Surface morphology,Bearing area curve,Fluence,Laser polishing,Tool steel
更新于2025-11-28 14:24:20
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Roughness of surface decorated with randomly distributed pillars
摘要： We have presented a quantitative analysis of roughness of planar surfaces decorated with randomly distributed, cylindrical pillars, disks, or cavities. We have described the roughness in terms of the surface power spectral density (PSD). First, we have derived a general equation for the PSD of such surfaces. Then, we have found the PSD for the special case of statistically isotropic, circular areas. We have demonstrated that the PSD provides quantitative information on the radius of the circular area, dimensions of the pillar, and surface coverage. We have also discussed the numerical method of extracting the parameters from experimental PSD data obtained from discrete Fourier transform of surface scanning measurements.
关键词： Fourier transform,cylindrical pillars,surface roughness,random distribution,power spectral density
更新于2025-09-23 15:21:01
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Simulational and experimental investigation on the wavefront sensing method based on near-field profile acquisition in high power lasers
摘要： This paper presents a novel wavefront sensing method based on near-field profile acquisition (NIA) to acquire the wavefront information. This method uses a cross mark at the focal plane of the spatial filter to directly obtain wavefront slope from the power spectral density (PSD) distribution of the output near-field profile. Principles of this method are introduced and the numerical simulation model is built. The influence of primary parameters on the measurement precision are analyzed and discussed. Based on the designed cross mark structure, an experiment is carried out in a multi-pass amplification high power laser and the wavefront of the pre-amplifier is reconstructed. Experimental results show that the difference between the reconstructed wavefronts by using the traditional Shack–Hartmann (SH) and the NIA wavefront sensing method is as small as 0.09 μm (peak-to-valley value).
关键词： Power spectral density,Near-field profile,Wavefront sensing,Wavefront
更新于2025-09-23 15:21:01
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Phase Noise Characterization and EEPN of a Full C-band Tunable Laser in Coherent Optical Systems
摘要： We perform phase noise characterization of a tunable laser source that is capable of tuning to 103 channels between 1527.6-1568.36 nm with 50 GHz grid spacing between the channels. The measured frequency modulation (FM) noise power spectral density (PSD) is reproduced by simulations in order to investigate the impact of equalization-enhanced phase noise (EEPN) in a coherent transmission system. The simulations are performed on a 30 Gbaud channel with 16 quadrature amplitude modulation (16QAM) and using pilot-based carrier phase estimation with 3% overhead. By performing extensive system simulations, we show the impact of different accumulated dispersion. Furthermore, we show the possibility to overcome EEPN related penalties by using a local oscillator (LO) with reduced low frequency phase noise or flat FM-noise PSD profiles with lower linewidths.
关键词： Equalization-Enhanced Phase Noise,coherent systems,Laser Phase Noise,FM-noise power spectral density,Tunable Laser Source
更新于2025-09-11 14:15:04
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Dynamics of surface evolution of rutile TiO <sub/>2</sub> (110) after ion irradiation
摘要： The dynamics of TiO2 surfaces evolving under 60 keV Ar+ ions have been explored here. Dynamic scaling ansatz, height–height correlation (HHC) model and power spectral density (PSD) model have been applied to investigate the growth mechanisms. The surfaces are growing under non-equilibrium growth processes and three separate domains of evolution have been noticed. Early time growth of the surfaces can be characterized by roughness exponent, α ～ 0.72–0.74, and growth exponent, β ～ 0.3. Dominance of diffusion is also noticed with Edward Wilkinson (EW) growth scaling. In the next time regime, non-local instabilities get incorporated, due to sputter-induced nanostructuring of the surfaces, resulting in a rapid surface roughening with a high value of β. The surface roughness saturates in late time regime.
关键词： height–height correlations,TiO2,power spectral density,AFM
更新于2025-09-10 09:29:36