The high frequency characteristics of laser reflection and visible light during solid state disk laser welding

Abstract

Optical properties are related to weld quality during laser welding. Visible light radiation generated from optical-induced plasma and laser reflection is considered a key element reflecting weld quality. An in-depth analysis of the high-frequency component of optical signals is conducted. A combination of a photoelectric sensor and an optical filter helped to obtain visible light reflection and laser reflection in the welding process. Two groups of optical signals were sampled at a high sampling rate (250 kHz) using an oscilloscope. Frequencies in the ranges 1-10 kHz and 10-125 kHz were investigated respectively. Experimental results showed that there was an obvious correlation between the high-frequency signal and the laser power, while the high-frequency signal was not sensitive to changes in welding speed. In particular, when the defocus position was changed, only a high frequency of the visible light signal was observed, while the high frequency of the laser reflection signal remained unchanged. The basic correlation between optical features and welding status during the laser welding process is specified, which helps to provide a new research focus for investigating the stability of welding status.

Sub-kHz-linewidth VECSELs for cold atom experiments

“…Stable, high power, narrow linewidth, and tunable laser sources are crucial for a wide range of applications in several scientific [1][2][3] and industrial fields [4][5][6]. In particular, they are required for the development of quantum technologies based on cold atoms with transitions at optical frequencies [7].…”

Progress and perspectives of in-situ optical monitoring in laser beam welding: Sensing, characterization and modeling

“…From these optical sensors, the acquired signals were first applied as benchmarks to correlate with the weld quality and defects. By using photodiodes responsive to either visible or near-infrared emissions, a low-cost optical-based monitoring system was developed to relate the photodiode signals to various weld features, imperfections and process anomalies, in order to in-situ detect the high-power laser welding quality [35]- [36].…”

Multi-sensor measurement and data fusion technology for manufacturing process monitoring: a literature review

“…The welding width and molten pool size can be directly monitored by the radiation intensity received [82,83]. In [84], the effects of welding velocity on high frequency signals and the relationship with the high frequency were studied using an optical filter and photodiode, acquiring laser reflection and visible light radiation in the process of welding. In [85], a spectrometer was used to acquire the spectral distribution; and the high-speed camera was utilized to capture the keyhole image.…”