Understanding the physical mechanism behind the laser-induced damage of multilayer dielectric interference coatings is essential for developing ultra-high intensity laser systems. The previous work reported high damage thresholds of MLD mirrors and blister formation near the threshold. Here, we present the cross-sectional study of the blisters using transmission electron microscopy and focused ion-beam processing. The measurement shows evidence of void formation and phase transformation under the surface, interdiffusion, and intermixing at the interfaces. These findings provide valuable insights into the mechanisms behind laser-induced damage, facilitating the development of more robust and reliable optics for high-power laser applications.
Glass drilling and cutting is crucial for optics, consumer electronics, and Micro-Electro-Mechanical System (MEMS) devices. Speed and reproducibility are issues common to traditional glass cutting methods. We use a femtosecond laser to efficiently and accurately cut interior shapes in glass. Unlike a traditional Gaussian beam, which has a shallow focal range and cannot penetrate deep into materials, Bessel beams have a much longer focal range, up to millimeters. With a Bessel beam, we can cut straight through without the need for mechanical cleaving or moving the sample through the focus, improving reproducibility and speed. The cut surfaces are analyzed with optical microscopy, atomic force microscopy, and scanning electron microscopy to observe any structural/morphological changes to the materials near the laser affected regions. Our 260fs laser operates at 10kHz, with 1030nm central wavelength, depositing 1.4W on target. An axicon generates the Bessel beam with a FWHM central spot size of 6±1µm and a fluence of up to 41Jcm-2. Our study has the potential to open new technological pathways for integrated electronic and photonic platforms.
We investigate the unique surface fractures of CaF2 found after single shot laser irradiation using 77 femtosecond, 1030 nm laser pulses. Optical microscopy and atomic force microscopy revealed elevated rectangular structures across laser-ablated craters. The underlying mechanism for this unique morphology may be related to anisotropic thermal conductivity and laser-induced defects. Our findings provide insights into the fundamental mechanisms of laser-induced damage in CaF2 and have implications for the design and optimization of high-power laser systems.
Cathodoluminescence and electrostatic techniques were used to study the nanoscale spatial evolution of native defects, crystallinity and work function in Ga2O3 across different morphological regions in laser induced periodic surface structures generated by an ultrafast laser. An emergent ~2.4 eV emission, likely related to oxygen interstitials or divacancy complexes, inversely correlates with the crystallinity of these regions. A contrast in work functions between the rims and troughs of the LIPSS, indicative of periodic differences in defect concentration, correlates with a reduction of crystallinity in the rim region relative to the trough region, suggesting an increased concentration of relatively shallow defects.
Understanding the physical process behind laser-induced damage of multilayer dielectric (MLD) interference coatings (IC) is of supreme importance for building ultrahigh-intensity laser systems. We experimentally studied the S-on-1 laser-induced damage threshold (LIDT) and damage characteristics of the SiO2/HfO2 high reflector quarter-wave stacks for three different femtosecond pulse durations operating at 1030nm wavelength. The S-on-1 LIDT for 1,10,100,1000 and 10000 pulses were recorded, and the values compare well with the state of the art. A strong correlation between single-shot damage morphology and laser focal intensity profiles was observed. Potential damage mechanisms of IC layers consistent with our observation will be discussed.
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