Optical damage limit of efficient spintronic THz emitters
Sandeep Kumar,
Anand Nivedan,
Arvind Singh,
Yogesh Kumar,
Purnima Malhotra,
Marc Tondusson,
Eric Freysz,
Sunil Kumar
Affiliations
Sandeep Kumar
Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
Anand Nivedan
Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
Arvind Singh
Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
Yogesh Kumar
Laser Science and Technology Center, Metcalfe House, Civil Lines, New Delhi 110054, India
Purnima Malhotra
Laser Science and Technology Center, Metcalfe House, Civil Lines, New Delhi 110054, India
Marc Tondusson
Univ. Bordeaux, CNRS, LOMA, UMR 5798, 33405 Talence, France
Eric Freysz
Univ. Bordeaux, CNRS, LOMA, UMR 5798, 33405 Talence, France
Sunil Kumar
Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India; Corresponding author
Summary: THz pulses are generated from femtosecond pulse-excited ferromagnetic/nonmagnetic spintronic heterostructures via inverse spin Hall effect. The highest possible THz signal strength from spintronic THz emitters is limited by the optical damage threshold of the corresponding heterostructures at the excitation wavelength. For the thickness-optimized spintronic heterostructure, the THz generation efficiency does not saturate with the excitation fluence even up till the damage threshold. Bilayer (Fe, CoFeB)/(Pt, Ta)-based ferromagnetic/nonmagnetic (FM/NM) spintronic heterostructures have been studied for an optimized performance for THz generation when pumped by sub-50 fs amplified laser pulses at 800 nm. Among them, CoFeB/Pt is the best combination for an efficient THz source. The optimized FM/NM spintronic heterostructure having α-phase Ta as the nonmagnetic layer shows the highest damage threshold as compared to those with Pt, irrespective of their generation efficiency. The damage threshold of the Fe/Ta heterostructure on a quartz substrate is ∼85 GW/cm2.
