Ultrafast lasers and Magnetodynamics Spectroscopies

For more details about this research see the webpage of IFIMUP or contact prof. Helder Crespo (hcrespo[AT]fc.up.pt)

Ultrafast Lasers

  • New techniques for ultrashort pulse characterization and control
    • Dispersion-scan technique (d-scan) for temporal pulse compression and measurement (patent pending)
    • Spatiotemporal and spatiospectral characterization of sub-two-cycle laser pulses
    • Direct carrier-envelope phase (CEP) measurement and stabilization
  • New light sources with unprecedented pulse durations and energies (via d-scan)
    • Generation, measurement and CEP stabilization of single-cycle pulses
    • Generation of CEP-stable terawatt-level 4-fs pulses
  • Ultrafast laser oscillators for direct few-cycle pulse generation
    • Design and construction of sub-two-cycle lasers
    • Detailed numerical simulation of intracavity laser dynamics
  • Ultrafast nonlinear optics
    • Broadband third-harmonic generation in Graphene
    • Generation and measurement of femtosecond deep-ultraviolet pulses
    • Ultrashort pulse synthesis by multicolor cascaded four-wave mixing (FWM)
    • Unique numerical code describing the intrinsically two-dimensional non-collinear cascaded FWM process
  • Ultrafast photonics in photonic crystal fibers
    • New sources of CEP-stable sub-two-cycle pulses based on soliton effect compression
    • Numerical modeling and proprietary code for nonlinear propagation in optical fibers

Representative Publications:
  • Simultaneous compression, characterization and phase stabilization of GW-level 1.4 cycle VIS-NIR femtosecond pulses using a single dispersion-scan setup, Opt. Express 22, 10181-10191 (2014)
  • Simultaneous compression and characterization of ultrashort laser pulses using chirped mirrors and glass wedges, Opt. Express 20, 688-697 (2012)
  • Cascaded nondegenerate four-wave-mixing technique for high-power single-cycle pulse synthesis in the visible and ultraviolet ranges, Physical Review A 79, 063838 (2009) - Paper selected for PRA Kaleidoscope Images, June 2009: |www|

Magnetodynamics spectroscopies

  • Spin dynamics (both continuous-wave and broadband Ferromagnetic resonance) in Ferromagnetic nanoparticles and discontinuous metal-insulator multilayers
    • Patterned magnetic nanostructures
    • Magnetic multilayered structures
    • Ultrafast demagnetisation studies in thin film and multilayer systems
    • Control and manipulation of magnetic nanoparticle assemblies

Representative Publications:
  • Introductory Solid State Physics: From the Material Properties of Solids to Nanotechnology, ISBN 978-0-9926368-6-9, The Pantaneto Press, UK (2014)
  • Tunable magnetic anisotropy in permalloy thin films grown on holographic relief gratings, Applied Physics Letters, 104, 082408 (2014)
  • Spin dynamics in exchange – spring nanosystems: a short review, (Invited review), Nanoscience and Nanotechnology Letters (Special edition), 3, 515, (2011)
  • Intensity inversion of vortex gyrotropic modes in thick ferromagnetic nanodots, Applied Physics Letters 104, 082408 (2014)
  • Dynamic exchange via spin currents in acoustic and optical modes of ferromagnetic resonance in spin-valve structures, Physical Review B 89, 144410 (2014)
  • Domain-wall structure in thin films with perpendicular anisotropy: Magnetic force microscopy and polarized neutron reflectometry stucdy, Physical Review B, 90, 054425 (2014)
  • Magnetization reversal and exchange bias effects in hard/soft ferromagnetic bilayers with orthogonal anisotropies, New Journal of Physics, 14, 113001 (2012)

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