Terahertz magnetospectroscopy of transient plasmas in semiconductors

Abstract

A comparison of impurity-free and ion-implantation-induced intermixing of InGaAs/InP quantum wellsUsing synchronized near-infrared ͑NIR͒ and terahertz ͑THz͒ lasers, we have performed picosecond time-resolved THz spectroscopy of transient carriers in semiconductors. Specifically, we measured the temporal evolution of THz transmission and reflectivity after NIR excitation. We systematically investigated transient carrier relaxation in GaAs and InSb with varying NIR intensities and magnetic fields. Using this information, we were able to determine the evolution of the THz absorption to study the dynamics of photocreated carriers. We developed a theory based on a Drude conductivity with time-dependent density and density-dependent scattering lifetime, which reproduced the observed plasma dynamics. Detailed comparison between experimental and theoretical results revealed a linear dependence of the scattering frequency on density, which suggests that electronelectron scattering is the dominant scattering mechanism for determining the scattering time. In InSb, plasma dynamics was dramatically modified by the application of a magnetic field, showing rich magnetoreflection spectra, while GaAs did not show any significant magnetic field dependence. We attribute this to the small effective masses of the carriers in InSb compared to GaAs, which made the plasma, cyclotron, and photon energies all comparable in the density, magnetic field, and wavelength ranges of the current study.

Cyclotron Resonance in High Magnetic Fields

“…Time-resolved THz/FIR spectroscopies have been used recently for studying carrier dynamics in magnetic fields. These include FIR single-color pump-probe spectroscopy 15 , opticalpump/FIR-probe spectroscopy 14,16,91 , and time-domain THz spectroscopy (TDTS) 92,93,20 . TDTS techniques allow one to measure the amplitude and phase of the coherent THz radiation emitted by or transmitted through the sample.…”

Nonperturbative terahertz electro-optics of semiconductor quantum wells in strong magnetic fields

“…In the last decade, the need for broad-band communication systems has heightened interest in terahertz electro-optics. Nonlinear optical phenomena, such as THz sideband generation [1][2][3][4][5][6][7][8] and the Franz-Keldysh effect [9][10][11][12][13][14], both discovered recently, are expected to play key roles in the realization of such systems. In a previous publication, I have proposed a perturbation theory for resonant THz sideband generation (i.e., sum and difference frequency generation involving one near-infrared photon and multiple THz photons) in undoped semiconductor quantum wells in strong magnetic fields [15,16].…”

A table-top, repetitive pulsed magnet for nonlinear and ultrafast spectroscopy in high magnetic fields up to 30 T

“…Combining access to applied magnetic fields with ultrafast spectroscopy techniques and/or intense, pulsed laser sources can provide a wealth of information in condensed matter physics, including many-body interactions and Coulomb correlations in semiconductors in the quantum Hall regime, 1-3 optical properties of exotic materials and/or semiconductor magneto-plasmas in the terahertz frequency range, [4][5][6][7][8][9][10][11][12][13][14][15] and ultrafast spectroscopy and control of magnetization in magnetic semiconductors and ferromagnets. [16][17][18] Typically, experimental access to magnetic fields up to 30 T are limited to special facilities in the form of national laboratories.…”