Nonlinear magneto-plasmonics (NMP) describes systems where nonlinear optics, magnetics and plasmonics are all involved. NMP can be referred to as interdisciplinary studies at the intersection of Nonlinear Plasmonics (NP), Magneto- Plasmonics (MP), and nanoscience. In NMP systems, nanostructures are the bases, Surface Plasmons (SPs) work as catalyst due to strong field enhancement effects, and the nonlinear magneto-optical Kerr effect (nonlinear MOKE) plays an important role as a characterization method. Many new effects were discovered recently, which include enhanced magnetization-induced harmonic generation, controlled and enhanced magnetic contrast, magneto-chiral effect, correlation between giant magnetroresistance (GMR) and nonlinear MOKE, etc. We review the structures, experiments, findings, and the applications of NMP.
We studied the spatial beam profile of a high peak power, ultra-short laser pulse passing through a diffractive beam shaping system. In theoretical simulation, we considered the effects of both group velocity dispersion and nonlinear self-phase modulation on the reshaped beam profile. The output spatial and temporal intensity profile of a 100-fs laser pulse at different energy levels is calculated. We also present the experimental result of the fluence profile at the beam shaping system's target plane for a 1-mJ, 100-fs near infrared laser pulse which is generated from a multi-pass laser amplification system.
Femtosecond optical reflectivity measurements of La<sub>2-x</sub>Sr<sub>x</sub>CuO<sub>4</sub>, La<sub>2</sub>CuO<sub>4+y</sub>, Bi<sub>2</sub>Sr<sub>2</sub>CuO<sub>6+z</sub> and Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>O<sub>8+δ</sub> thin films and single crystal samples indicate qualitative changes with fluence. At the lowest fluencies, there is a power law divergence in the relaxation time. The divergence has an onset temperature of 55±15K, independent of whether the sample is in the superconducting or normal states. At slightly higher fluencies, still perturbative, the additional response does not exhibit this power law divergence. At quite high fluencies- no longer perturbative- the metallic samples exhibit oscillations in the reflectivity amplitude. The period of these oscillations varies with the probe wavelength but not with the pump wavelength. The oscillations exhibit a decay time as long as 10 nsec.
We extended the study of a diffractive laser beam shaping system which is originally designed for continuous waves (SPIE vol. 2863, pp 237-45, 1996). The beam profile of an ultra-short laser pulse passing through this optical system is calculated. Two different numerical methods, Monte Carlo and Gaussian method, are applied to this problem. We find that the Gaussian method yields better results because the step size algorithms used in this method are well suited for this specific problem. The Gaussian numerical simulation shows that the fluence still yields a top-hat radial distribution. Beam shaping of ultra-short laser pulses using this optical scheme is feasible.
We report first IR free-electron laser experiments to compare and elucidate the effects of surface-localized vibrational excitation versus bulk vibrational excitation on the ablation of polycrystalline diamond. The measured ablation yield values as a function of laser intensity indicate the existence of two separate thresholds. The lower intensity thresholds is identified as the ablation threshold, and the higher intensity threshold is associated with the formation of a plasma plume. The wavelength dependences of both thresholds indicate that eh C-H absorption occurring at surfaces and grain boundaries does not play a significant role in the ablation process. However, both thresholds are lower when the laser is resonant with the two-phonon bulk absorption band. These findings are consistent with the model that a rapid laser- induced phase transition to graphite is responsible for the low-intensity ablation of diamond at and above the first threshold.
Conference Committee Involvement (6)
Laser Beam Shaping XII
21 August 2011 | San Diego, California, United States
Laser Beam Shaping XI
2 August 2010 | San Diego, California, United States
Laser Beam Shaping X
3 August 2009 | San Diego, California, United States
Laser Beam Shaping IX
11 August 2008 | San Diego, California, United States
Laser Beam Shaping VIII
28 August 2007 | San Diego, California, United States
Laser Beam Shaping VII
13 August 2006 | San Diego, California, United States