Advances in multi-dimensional coherent spectroscopy of semiconductor nanostructures

Abstract

Multi-dimensional coherent spectroscopy (MDCS) has become an extremely versatile and sensitive technique for elucidating the structure, composition, and dynamics of condensed matter, atomic, and molecular systems. The appeal of MDCS lies in its ability to resolve both individual-emitter and ensemble-averaged dynamics of optically created excitations in disordered systems. When applied to semiconductors, MDCS enables unambiguous separation of homogeneous and inhomogeneous contributions to the optical linewidth, pinpoints the nature of coupling between resonances, and reveals signatures of many-body interactions. In this review, we discuss the implementation of MDCS to measure the nonlinear optical response of excitonic transitions in semiconductor nanostructures. Capabilities of the technique are illustrated with recent experimental studies that advance our understanding of optical decoherence and dissipation, energy transfer, and many-body phenomena in quantum dots and quantum wells, semiconductor microcavities, layered semiconductors, and photovoltaic materials.

Multidimensional Coherent Spectroscopy of Semiconductors

“…Detailed accounts of detection schemes and phase‐stabilization methodology have been discussed in refs. [], which review the MDCS technique from complementary perspectives. Regardless of detection scheme, the time delay between pulses 1 and 2 is then varied to produce a 2D plot of the response as a function of excitation time τ and emission time t as displayed in Figure b, plotted in a rotating frame.…”

“…Although the roots of MDCS can be traced to the development of 2D nuclear magnetic resonance (2D‐NMR) by Ernst and collaborators in the 1970s, advances in both laser development and interferometric stabilization have pushed the technique far beyond its radio‐frequency origins, extending it into the infrared regime, the optical regime, and in a few recent cases even into the ultraviolet . Today, optical MDCS (with a wavelength range of 400–1000 nm) has emerged as a powerful method for studying properties ranging from many‐body dynamics in semiconductors to energy‐transfer processes in photosynthetic light harvesting complexes to interactions and dynamics in atomic and molecular vapors and solutions …”

Communication: Multidimensional triple sum-frequency spectroscopy of MoS2 and comparisons with absorption and second harmonic generation spectroscopies

“…Coherent multidimensional spectroscopy (CMDS) is a useful tool for exploring the rich many-body physics of semiconductors. 1,2 A new CMDS methodology is Triple Sum Frequency (TSF) spectroscopy. TSF is the nondegenerate analog of third harmonic generation (THG), and the four-wave mixing extension of three-wave mixing processes like sum-frequency generation and second harmonic generation (SHG).…”

“…The polarization is expressed as an expansion in electric field and susceptibility (χ) order. Absorption, SHG, and TSF (THG) depend on χ (1) , χ (2) , and χ (3) , respectively. Absorption is proportional to Im χ (1) .…”

“…The additional detuning factors are defined by ∆ 123 gck ≡ ω cgk − ω 321 − iΓ and ∆ 12 gbk ≡ ω bgk − ω 21 − iΓ in which ω ab is the frequency difference between bands a and b at point k in the BZ. The JDOS formalism employed in Equation 2 can be abstracted to describe χ (2) and χ (3) with the introduction of multidimensional joint density functions. These joint densities depend not just on the energy difference between the initial and final states, but also on the energy differences between the intermediate states reached during the sum-frequency process.…”