1,721,122 research outputs found
Suppressed polariton scattering in semiconductor microcavities
No full textUltrafast time-resolved measurements on a semiconductor microcavity distinguish polariton dynamics dependent on the detuning between the constituent photon and exciton modes. Spectral synthesis allows the injection of specific polariton pulses into the sample. Scattering which results in absorption is found to be suppressed in the lower polariton branch by the combined action of normal mode splitting and motional narrowing. The experimental difference between angle and position tuning demonstrates the role of the polariton dispersion in polariton-polariton interactions
Asymmetric angular emission in semiconductor microcavities
Full text linkStrongly angular-dependent emission properties are observed from a semiconductor microcavity pumped
along a critical angle of incidence. In contrast to the luminescence from conventional semiconductor heterostructures,the emission is completely asymmetrical with respect to the sample normal. The results imply that
parametric scattering dominates the energy relaxation of polaritons, and is enhanced by the deformed shape of
the dispersion relations
Angle-resonant stimulated polariton amplifier
Full text linkWe experimentally demonstrate resonant coupling between photons and excitons in microcavities which can efficiently generate enormous single-pass optical gains approaching 100. This new parametric phenomenon appears as a sharp angular resonance of the incoming pump beam, at which the moving excitonic polaritons undergo very large changes in momentum. Ultrafast stimulated scattering is clearly identified from the exponential dependence on pump intensity. This device utilizes boson amplification
induced by stimulated energy relaxation
Stimulated spin dynamics of polaritons in semiconductor microcavities
Full text linkTime-resolved polarization spectroscopy of polariton pair scattering in semiconductor microcavities enables complete measurement of the polariton spin dynamics. In addition to spin-preserving interactions previously reported, we observe two additional even stronger scattering processes, which mix polaritons of opposite spin. Because of the polaritons' bosonic character, this results in the stimulation of spin flips. Such mechanisms should allow realization of spin-sensitive interferometers
Ultrafast polariton dynamics in strongly coupled zinc porphyrin microcavities at room temperature
Full text linkTime and angle-resolved measurements reveal ultrafast dynamics of excitations in organic microcavities leading to dramatic modulation of probe transmission (~30%). We find that the induced changes have both fast and long-lived components. Fast response times are defined by vibronic relaxation and intersystem crossing (S1 ? T1), whereas long-lived changes are attributed to a build up of carriers in the nonradiative triplet state whose lifetime is longer than the repetition rate of the laser pulses, resulting thus in incomplete recovery of the ground state. Blueshifts of the lower polariton branch in the presence of the pump pulse indicate the presence of nonlinear interactions in the sample. However, there is no evidence yet for the pair-type scattering processes in porphyrin microcavities
Continuous wave observation of massive polariton redistribution by stimulated scattering in semiconductor microcavities
Full text linkA massive redistribution of the polariton occupancy to two specific wave vectors is observed under conditions of continuous wave excitation of a semiconductor microcavity.
The “condensation” of the polaritons to the two specific states arises from stimulated scattering at final
state occupancies of order unity. The stimulation phenomena, arising due to the bosonic character of
the polariton quasiparticles, occur for conditions of resonant excitation of the lower polariton branch.
High energy nonresonant excitation, as in most previous work, instead leads to conventional lasing in
the vertical cavity structure
Relaxation bottleneck and its suppression in semiconductor microcavities
Full text linkA polariton relaxation bottleneck is observed in angle-resolved measurements of photoluminescence emission from a semiconductor microcavity. For low power laser excitation, low k polariton states are found to have a very small population relative to those at high k. The bottleneck is found to be strongly suppressed at higher powers in the regime of superlinear emission of the lower polariton states. Evidence for the important role of carrier-carrier scattering in suppression of the bottleneck is presented
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Parametric oscillation in a vertical microcavity: a polariton condensate or micro-optical parametric oscillation
Full text linkSemiconductor microcavities can support quasiparticles which are half-light and half-matter with interactions
possessed by neither component alone. We show that their distorted dispersion relation forms the basis of
a quasiparticle ‘‘trap’’ and elicits extreme enhancements of their nonlinear optical properties. When driven by
a continuous wave laser at a critical angle, the quasiparticles are sucked into the trap, condensing into a
macroscopic quantum state which efficiently emits light.
This device is thus an optical parametric oscillator
based on quasiparticle engineering. In contrast to a laser, macroscopic coherence is established in the electronic excitations as well as the light field. This paves the way to new techniques analogous to those established in atomic and superconducting condensates, such as ultrasensitive solid-state interferometers
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