Intersublevel Spectroscopy on Single InAs-Quantum Dots by Terahertz Near-Field Microscopy

Abstract

Using scattering-type near-field infrared microscopy in combination with a free-electron laser, intersublevel transitions in buried single InAs quantum dots are investigated. The experiments are performed at room temperature on doped self-assembled quantum dots capped with a 70 nm GaAs layer. Clear near-field contrast of single dots is observed when the photon energy of the incident beam matches intersublevel transition energies, namely the p-d and s-d transition of conduction band electrons confined in the dots. The observed room-temperature line width of 5-8 meV of these resonances in the mid-infrared range is significantly below the inhomogeneously broadened spectral lines of quantum dot ensembles. The experiment highlights the strength of near-field microspectroscopy by demonstrating signals from bound-to-bound transitions of single electrons in a probe volume of the order of (100 nm)(3).

Ultrafast multi-terahertz nano-spectroscopy with sub-cycle temporal resolution

“…To isolate the near-field response from background scattering, the tip is operated in tapping mode and the scattered electric-field waveform E 3 (t) or the scattered intensity I 3 is measured at the third demodulation order of the tapping frequency [18][19][20][21][23][24][25][26] . We map out E 3 (t) by electro-optic sampling and detect I 3 using a time-integrating mercury cadmium telluride (MCT) photodiode, which can also be used to perform standard Fourier transform infrared spectroscopy (FTIR) 26 .…”

Optimum Operating Conditions for Terahertz Scattering-Type Near-Field Microscopes

“…In a THz s-NFM system, we can extract the nth-order harmonic component, d (n) , by suppressing the large background signal using a lock-in demodulation technique [1][2][3][4][5][6].…”

Preparation of a nonlinear coherent state of the mechanical resonator in an optomechanical microcavity

“…(19) are established in the subspace of the reduced QD-cavity subsystem, which involves the strong driving field ω L . Moreover, the resonant frequency of the cavity ω c is at least a factor of 10 3 with the frequency of ω m [8][9][10]50,[62][63][64][65][66]. In this situation, the energy interval between the subspaces of the reduced QD-cavity system is much larger than the energy interval of the MR Fock space.…”