Coherent nonlinear pulse propagation on a free-exciton resonance in a semiconductor

Nielsen, Nils C.; Lindén, Stefan; Kühl, J.; Förstner, Jens; Knorr, Andreas; Koch, S. W.; Gießen, Harald

doi:10.1103/physrevb.64.245202

“…In linear regime interference between the lower (LP) and upper (UP) polariton branches leads to a beating signal, first observed for the 1S quadrupole exciton in Cu 2 O 8 . Nonlinear effects like self-induced transparency at the Aexciton in CdSe and at the bound exciton in CdS have been also studied using frequency-resolved gating 9 and bandwidth limited time-resolved spectroscopy 10 , respectively.Many of the experiments on EP propagation in direct band gap semiconductors like GaAs, CdSe or CdS were performed for resonance conditions on relatively thin crystals (with thicknesses normally below tens of µm) 1,4,6,9,10 . In this case EP in both lower and upper branches propagates through the crystal without significant losses.…”

mentioning

confidence: 99%

“…This phenomenon originates from exciton-photon interaction, which can be considered in terms of an excitonic polariton (EP) quasi-particle [1][2][3] . The EP propagation and its dispersion have been widely studied using various experimental techniques in different semiconductor materials 1,[4][5][6][7][8][9][10][11][12] . Time-of-flight measurements using pulsed lasers in conjunction with time-resolved detection resulted in group index measurements up to several thousand in GaAs, CuCl and CdSe crystals [4][5][6] .…”

mentioning

confidence: 99%

“…In linear regime interference between the lower (LP) and upper (UP) polariton branches leads to a beating signal, first observed for the 1S quadrupole exciton in Cu 2 O 8 . Nonlinear effects like self-induced transparency at the Aexciton in CdSe and at the bound exciton in CdS have been also studied using frequency-resolved gating 9 and bandwidth limited time-resolved spectroscopy 10 , respectively.…”

mentioning

confidence: 99%

“…Many of the experiments on EP propagation in direct band gap semiconductors like GaAs, CdSe or CdS were performed for resonance conditions on relatively thin crystals (with thicknesses normally below tens of µm) 1,4,6,9,10 . In this case EP in both lower and upper branches propagates through the crystal without significant losses.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Subnanosecond delay of light inCdxZn1−xTecrystals

Godde¹,

Акимов²,

Yakovlev³

et al. 2010

View full text Add to dashboard Cite

We study excitonic polariton relaxation and propagation in bulk Cd0.82Zn0.12Te using timeresolved photoluminescence and time-of-flight techniques. Propagation of picosecond optical pulses through 745 µm thick crystal results in time delays up to 350 ps, depending on the photon energy. Optical pulses with 150 fs duration become strongly stretched. The spectral dependence of group velocity is consistent with the dispersion of the lower excitonic polariton branch. The lifetimes of excitonic polariton in the upper and lower branches are 1.5 and 3 ns, respectively. When the energy of a photon is close to that of an exciton resonance in a semiconductor its group velocity for propagation may be significantly decreased. This phenomenon originates from exciton-photon interaction, which can be considered in terms of an excitonic polariton (EP) quasi-particle 1-3 . The EP propagation and its dispersion have been widely studied using various experimental techniques in different semiconductor materials 1,4-12 . Time-of-flight measurements using pulsed lasers in conjunction with time-resolved detection resulted in group index measurements up to several thousand in GaAs, CuCl and CdSe crystals 4-6 . In some materials like anthracene light may propagate even at velocities below that of sound 7 . Additionally several coherent effects may take place during optical pulse propagation. In linear regime interference between the lower (LP) and upper (UP) polariton branches leads to a beating signal, first observed for the 1S quadrupole exciton in Cu 2 O 8 . Nonlinear effects like self-induced transparency at the Aexciton in CdSe and at the bound exciton in CdS have been also studied using frequency-resolved gating 9 and bandwidth limited time-resolved spectroscopy 10 , respectively.Many of the experiments on EP propagation in direct band gap semiconductors like GaAs, CdSe or CdS were performed for resonance conditions on relatively thin crystals (with thicknesses normally below tens of µm) 1,4,6,9,10 . In this case EP in both lower and upper branches propagates through the crystal without significant losses. Although the group velocity is reduced thousand times the optical delay is in the range of several to tens of picoseconds only. It is also known that the EP energy relaxation within the lower branch is strongly suppressed due to the phonon bottleneck in the relaxation path 13 . This effect may be used for long distance coherent EP propagation and realization of long delays for optical pulses. Recently large delays of light in the order of several hundreds of picoseconds were reported in 1 mm thick GaN crystals 12 . Here we report on the direct measurement of sub-nanosecond optical pulse delays in (Cd,Zn)Te crystals which are attributed to propagation of the excitonic polariton in the lower branch. High quality samples with low impurity concentrations result in significant transmission levels in crystals with about 1 mm thickness. The detected group velocity is only 150 times smaller than the speed of light, but the resulting time ...

show abstract

“…Different from the atomic systems which could be modeled as nonlinear two-level systems [5], the many-body effects arising from the macroscopic carrier density in semiconductors [6] may prevent the establishment of complete selfinduced transparency(SIT) [7,8,9]. Nevertheless, the phenomenon self-induced transmission [10,11] is observed in semiconductors, which has many observed features resemble SIT in atomic systems, such as Rabi flopping of the carrier density, coherent nonlinear long-distance propagation, and a high degree of transmission.…”

Section: Introductionmentioning

confidence: 99%