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Teaching polaritons new tricks
No full textSemiconductor microcavities have attracted much recent interest because they utilize simultaneously 2D confinement of both excitons and photons in the same heterostructure. Strong coupling of these two states produces unique dynamics that can be well described in a quasiparticle state, the cavity polaritons. Their dispersion relation is dramatically modified with an apparent trap in k-space offering exciting new possibilities for tailoring nonlinear optical properties in microcavities. The reduced density of states inside the trap allows the macroscopic occupancy of polaritons producing much of the new physics. This paper describes recent work on nonlinear effects in semiconductor microcavities including stimulated scattering, parametric oscillation and non-equilibrium phase transition. By teaching polaritons new tricks, both fundamental questions about their bosonic nature can be answered and practical applications in a variety of optoelectronic and interferometric devices can be found
Asymmetric angular emission in semiconductor microcavities
Get PDFStrongly 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
Off-branch polaritons and multiple scattering in semiconductor microcavities
No full textAngle-resolved measurements show unexpected emission resonances of the polaritons in a semiconductor microcavity. These resonances appear when more than one in-plane polariton mode is macroscopically occupied. The new resonances observed in angle-resolved luminescence do not lie on the expected polariton branches and possess different dispersion relations with negative effective mass. The experimental results can be well explained using an interacting polariton model that treats multiple scattering. The k dispersion of the luminescence resonances is reproduced using the Bogolubov approximation that deals with the macroscopic coherence of the signal, pump, and idler modes. This model also explains many puzzling features such as the stimulation of resonant Rayleigh scattering in the backward direction. In addition, the use of nonresonant control beams for coherent control of the polaritons is shown both experimentally and theoretically. The rich complexity of new phenomena in optically excited semiconductor microcavities can be attributed to the distinctive anti-Hermitian or anomalous coupling between polaritons
Angle-resonant stimulated polariton amplifier
Get PDFWe 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
Get PDFTime-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
Data for Optical bistability under non-resonant excitation in spinor polariton condensates
No full textExperimental data and numerical simulation results used to create the figures in the paper Pickup, L., Kalinin, K., Askitopoulos, A. M., Hatzopoulos, Z., Savvidis, P. G., Berloff, N. G., & Lagoudakis, P. (2018). Optical bistability under nonresonant excitation in spinor polariton condensates. Physical Review Letters.
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Ring emission and exciton pair scattering in semiconductor microcavities
No full textPolariton microemitters are semiconductor devices that take advantage of the strong coupling of light and matter to produce efficient optical sources. Injecting an exciton gas into such a semiconductor microcavity can produce annular optical emission of a specific cone angle. We demonstrate that at higher exciton densities or temperatures, this ring continuously decreases in diameter due to the greater energy that can be carried off in exciton-pair scattering processes. These Coulomb-mediated exciton-exciton scatterings are shown to dominate the polariton relaxation and optical emission
Ultrafast polariton dynamics in strongly coupled zinc porphyrin microcavities at room temperature
Get PDFTime 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
Get PDFA 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
Polariton traps in semiconductor microcavities
No full textThe strong coupling of excitons and photons inside a semiconductor microcavity forms a trap in k-space for the coupled polaritons. This trap produces new behaviour from the strong parametric scattering of polaritons on the walls of the trap, from condensation of polaritons at the bottom of the trap and from the bottleneck in relaxation at the neck of the trap. We predict the operation of polariton lasers pumped non-resonantly, either electrically or optically, based on efficient scattering of polaritons into the trap
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