Abstract-Efficient Terahertz Generation Using Fe/Pt Spintronic Emitters Pumped at Different Wavelengths

Evangelos Th. Papaioannou, Garik Torosyan, Sascha Keller, Laura Scheuer, Marco Battiato, Valynn Katrine Mag-usara, Johannes L'huillier, Masahiko Tani, René Beigang

https://128.84.21.199/abs/1803.08838

Recent studies in spintronics have highlighted ultrathin magnetic metallic multilayers as a novel and very promising class of broadband terahertz radiation sources. Such spintronic multilayers consist of ferromagnetic (FM) and non-magnetic (NM) thin films. When triggered by ultrafast laser pulses, they generate pulsed THz radiation due to the inverse spin-Hall effect, a mechanism that converts optically driven spin currents from the magnetized FM layer into transient transverse charge currents in the NM layer, resulting in THz emission. As THz emitters, FM/NM multilayers have been intensively investigated so far only at 800-nm excitation wavelength using femtosecond Ti:sapphire lasers. In this work, we demonstrate that an optimized spintronic bilayer structure of 2-nm Fe and 3-nm Pt grown on 500 {\mu}m MgO substrate is just as effective as a THz radiation source when excited either at {\lambda} = 800 nm or at {\lambda} = 1550 nm by ultrafast laser pulses from a fs fiber laser (pulse width close to 100 fs, repetition rate around 100 MHz). Even with low incident power levels, the Fe/Pt spintronic emitter exhibits efficient generation of THz radiation at both excitation wavelengths. The efficient THz emitter operation at 1550 nm facilitates the integration of such spintronic emitters in THz systems driven by relatively low cost and compact fs fiber lasers without the need for frequency conversion.

Abstract-Epitaxial growth of p-InAs on GaSb with intense terahertz emission under 1.55-μm femtosecond laser excitation

Cyril P. Sadia, Lorenzo P. Lopez Jr., Ramon M.delos Santos, Joselito E. Muldera, Alexander E.De Los Reyes, Mae Agatha C.Tumanguil, Christopher T.Que, Valynn Katrine Mag-usara, Masahiko Tani, Armando S.Somintac,  Elmer S.Estacio, Arnel A.Salvador,

https://www.sciencedirect.com/science/article/pii/S0040609017309276

We report the molecular beam epitaxy growth of high-quality p-InAs thin films evaluated in the context of 1.55 μm femtosecond laser-excited THz emission efficiency. The presence of p-InAs is confirmed via scanning electron microscopy and X-ray diffraction. Using a GaAs buffer layer, the epitaxial growth of p-InAs layers was successfully achieved. Initiating GaAs deposition by growth interruption, we find that GaAs adheres to the GaSb substrate and provides a quasi-planar surface for the subsequent layers. We also find a significant enhancement in the THz radiation intensity of p-InAs films that is approximately twice compared to that of bulk p-InAs for 1.55 μm wavelength.

Abstract-Low temperature-grown GaAs carrier lifetime evaluation by double optical pump terahertz time-domain emission spectroscopy

Valynn Katrine Mag-usara, Stefan Funkner, Gudrun Niehues, Elizabeth Ann Prieto, Maria Herminia Balgos, Armando Somintac, Elmer Estacio, Arnel Salvador, Kohji Yamamoto, Muneaki Hase, and Masahiko Tani

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-23-26175

We present the use of a “double optical pump” technique in terahertz time-domain emission spectroscopy as an alternative method to investigate the lifetime of photo-excited carriers in semiconductors. Compared to the commonly employed optical pump-probe transient photo-reflectance, this non-contact and room temperature characterization technique allows relative ease in achieving optical alignment. The technique was implemented to evaluate the carrier lifetime in low temperature-grown gallium arsenide (LT-GaAs). The carrier lifetime values deduced from “double optical pump” THz emission decay curves show good agreement with data obtained from standard transient photo-reflectance measurements on the same LT-GaAs samples grown at 250 °C and 310 °C.

© 2016 Optical Society of America

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