Coherent control of excitonic excitations in II–VI quantum wells

Abstract

We present results of experimental work in which the coherent-control technique has been applied to study the coherent manipulation of excitonic polarization in ZnSe quantum-well samples. We will introduce the linear control of excitonic polarization in pulse-transmission experiments and afterwards focus on the question if and how the optical transition from the excitonic states to the bound-biexciton state can be subject to a directed coherent control. The experimental results will be compared to simulations based on a microscopic theory and will also be explained on the base of a phenomenological few-level model. The overall suitability of coherent control for the investigation of exciton systems in low-dimensional wide-gap materials will be discussed.

Selective Enhancements in 2D Fourier Transform Optical Spectroscopy with Tailored Pulse Shapes

“…Selection for different emission pathways can be accomplished using phase-controlled pulse pairs or longer sequences that induce constructively or destructively interfering coherent oscillations in the system, a technique that is ubiquitous in the coherent control literature. − In particular, using a DP for the final field interaction of a third-order optical spectroscopy measurement can enable selective enhancement and suppression of different emission pathways . A DP, as shown in Figure a, is defined as two Gaussian shaped pulses that are separated by a time difference, τ DP , and a relative phase difference between the two pulses, ϕ DP .…”

“…Optimal pulse shapes are designed using simple calculations based on perturbative coherent control techniques that have been previously developed in one-dimensional spectroscopy: double-pulse (DP) shapes that selectively enhance different resonance frequencies and pulses with a frequencydependent phase window (PW) that selectively enhance different two-quantum resonances. 9,10 The pulse shapes are incorporated in the laboratory using pulse-shaping-based 2D FT OPT, as already demonstrated. 5,11−14 The paper is organized as follows.…”

“…23−25 In particular, using a DP for the final field interaction of a third-order optical spectroscopy measurement can enable selective enhancement and suppression of different emission pathways. 9 A DP, as shown in Figure 2a, is defined as two Gaussian shaped pulses that are separated by a time difference, τ DP , and a relative phase difference between the two pulses, ϕ DP . In this case, the third-order density matrix of the system can be written as…”

“…Here, using only energy levels of the system as input parameters, tailored pulse sequences are designed to optimize specific peaks in the 2DS of gallium arsenide quantum wells (GaAs QWs). Optimal pulse shapes are designed using simple calculations based on perturbative coherent control techniques that have been previously developed in one-dimensional spectroscopy: double-pulse (DP) shapes that selectively enhance different resonance frequencies and pulses with a frequency-dependent phase window (PW) that selectively enhance different two-quantum resonances. , The pulse shapes are incorporated in the laboratory using pulse-shaping-based 2D FT OPT, as already demonstrated. ,− As has been extensively studied recently, ,− 2DS of GaAs QWs are dominated by many-body effects, giving rise to peaks due to different biexciton states, unbound two-exciton correlations between various combinations of single-exciton states, and even triexciton states. All of these multiexciton coherences may interfere with each other and single-exciton peaks.…”