Optimum excitation wavelength and photon energy threshold for spintronic terahertz emission from Fe/Pt bilayer.

Terahertz emission from ferromagnetic/non-magnetic spintronic heterostructures had been demonstrated as pump wavelength-independent. We report, however, the pump wavelength dependence of terahertz emission from an optimized Fe/Pt spintronic bilayer on MgO substrate. Maximum terahertz generation per total pump power was observed in the 1200- to 1800-nm pump wavelength range, and a marked decrease in the terahertz emission efficiency beyond 2500 nm (pump photon energies <0.

Effect of heteroepitaxial growth on LT-GaAs: ultrafast optical properties.

Epitaxial low temperature grown GaAs (LT-GaAs) on silicon (LT-GaAs/Si) has the potential for terahertz (THz) photoconductive antenna applications. However, crystalline, optical and electrical properties of heteroepitaxial grown LT-GaAs/Si can be very different from those grown on semi-insulating GaAs substrates ('reference'). In this study, we investigate optical properties of an epitaxial grown LT-GaAs/Si sample, compared to a reference grown under the same substrate temperature, and with the same layer thickness.

A modulation-doped heterostructure-based terahertz photoconductive antenna emitter with recessed metal contacts.

We present the implementation of an efficient terahertz (THz) photoconductive antenna (PCA) emitter design that utilizes high mobility carriers in the two-dimensional electron gas (2DEG) of a modulation-doped heterostructure (MDH). The PCA design is fabricated with recessed metal electrodes in direct contact with the 2DEG region of the MDH. We compare the performance of the MDH PCA having recessed contacts with a PCA fabricated on bulk semi-insulating GaAs, on low temperature-grown GaAs, and a MDH PCA with the contacts fabricated on the surface.

Dynamics of Optically-Generated Carriers in Si (100) and Si (111) Substrate-Grown GaAs/AlGaAs Core-Shell Nanowires.

GaAs/Al0.1Ga0.9As core-shell nanowires (CSNWs), with average lateral size of 125 nm, were grown on gold nanoparticle-activated Si (100) and Si (111) substrates via molecular beam epitaxy.

Confined photocarrier transport in InAs pyramidal quantum dots via terahertz time-domain spectroscopy.

We present experimental demonstration of photocarrier dynamics in InAs quantum dots (QDs) via terahertz (THz) time-domain spectroscopy (TDS) using two excitation wavelengths and observing the magnetic field polarity characteristics of the THz signal. The InAs QDs was grown using standard Stranski-Krastanow technique on semi-insulating GaAs substrate. Excitation pump at 800 nm- and 910 nm-wavelength were used to distinguish THz emission from the InAs/GaAs matrix and InAs respectively.

Terahertz emission from Indium Oxide films grown on MgO substrates using sub-bandgap photon energy excitation.

Indium oxide (In2O3) films grown by thermal oxidation on MgO substrates were optically excited by femtosecond laser pulses having photon energy lower than the In2O3 bandgap. Terahertz (THz) pulse emission was observed using time domain spectroscopy. Results show that THz emission saturates at an excitation fluence of ~400 nJ/cm2.