We present a simple experimental approach to generating and detecting surface-propagating magneto-elastic waves. Using the ultrafast optical transient grating geometry, we drive in-plane propagating surface acoustic waves which couple to, and resonantly drive, magnetization precession in thin magnetic films. The optical approach provides for the real-time detection of both elastic wave transients as well as the tightly coupled magnetization precession in independent detection channels and thus reveals the tight coupling between the two when an appropriate magnetic field is applied. We discuss the experimental geometry and resulting linear magneto-elastic responses. We briefly touch upon nonlinear magnetoelastic properties, which is the focus of our current work.
In order to investigate the ultrafast dynamics of free carriers generated in bulk dielectrics by intense femtosecond laser pulses we have designed a setup for ultrafast time-resolved imaging Mach-Zehnder interferometry. The application of the 2D-Fourier-transform technique allows us to accurately reconstruct the actual laser-induced phase shifts and transmission changes for the probe pulses, which provide the properties of free carriers. Interferometric measurements in high-purity fused silica clearly demonstrate that the dominant ionization mechanism for intensities below 10 TW/cm<sup>2</sup> is multiphoton ionization.
The formation of well-defined craters is a general feature of laser ablation with ultrashort laser pulses, indicative of a sharp ablation threshold. Results of a microscopic characterization of ablation craters on semiconductors after irradiation with single intense ultrashort laser pulses are presented.
Ultrafast time resolved microscopy of femtosecond laser irradiated surfaces reveals a universal feature of the ablating surface on nanosecond time scale. All investigated materials show rings in the ablation zone, which were identified as an interference pattern (Newton fringes). Optically sharp surfaces occur during expansion of the heated material as a result of anomalous hydrodynamic expansion effects. Experimentally, the rings are observed within a certain fluence range which strongly depends on material parameters. The lower limit of this fluence range is the ablation threshold. We predict a fluence ratio between the upper and the lower fluence limit approximately equal to the ratio of critical temperature to boiling temperature at normal pressure. This estimate is experimentally confirmed on different materials (Si, graphite, Au, Al).
Ultrafast time resolved microscopy of femtosecond laser irradiated surfaces reveals a universal feature of the ablating surface on nanosecond time scale. All investigated materials show rings in the ablation zone, which were identified as an interference pattern. Optically sharp surface occur during expansion of the heated material as a result of anomalous hydrodynamic expansion effects. Experimentally, the rings are observed within a certain fluence range which strongly depends on material parameters. The lower limit of this fluence range is the ablation threshold. We predict a fluence ratio between the upper and the lower fluence limit approximately equal to the ratio of critical temperature to boiling temperature at normal pressure. This estimate is experimentally confirmed on different materials.
Conference Committee Involvement (5)
Spintronics XIII
23 August 2020 | San Diego, California, United States
Spintronics XII
11 August 2019 | San Diego, California, United States
Spintronics XI
19 August 2018 | San Diego, California, United States
Spintronics X
6 August 2017 | San Diego, California, United States
Spintronics IX
28 August 2016 | San Diego, California, United States
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