84
3 Light–Matter Interactions for Photonic Applications
Fig. 3.10 Temporal photon statistics measured for oppositely circularly-polarised spinor condensate emission. Second-order temporal autocorrelation functions were acquired as a function of an
external magnetic field B (see [214]). a At fixed pump density, spin-split polariton modes featured
a magnetic-field dependent degree of circular polarisation above the condensate threshold, which
had a direct impact on the photon correlations measured for coexisting spinor condensates with
opposing polarisations. b At 5 T, an increase in pump density above the threshold resulted in a considerable increase in coherence for the spinor condensate with lower-energetic mode in the external
magnetic field, reflected by a decrease in polarisation-resolved G (2) (0) towards unity. In contrast,
the oppositely polarised condensate exhibited an elevated level of intensity fluctuations. Note that
the use of symbols in a and b differs. Reused with permission [214] Copyright 2016 Springer Nature
ton statistics measurements that with increasing field, spinor condensates of opposing
polarisations approached each others G
(2)
(0), which exhibited noticeable intensity
fluctuations, whereas at 0 T, one of the two circularly-polarised condensate signals
featured a high degree of coherence with near unity value (signal from the lowerenergetic condensate in magnetic field series) [214]. This result indicated that the
symmetry break through condensation gives preference to one polariton polarisation
intrinsically without external field.
13
Ultimately, the understanding of conditions for good second-order coherence and
low intensity noise are expected to pave the way for coherent exciton–polariton
devices, such as described in the literature [54, 57].
Polaritons and Terahertz Radiation
Furthermore, the relationship of polaritons with terahertz radiation in terms of the
Rabi-oscillation frequency being of the order of terahertz waves in common polariton systems has also triggered research activities which promise the realisation of
bosonic lasers, e.g. proposed bosonic cascade lasers [77], and novel polariton-based
13 In fact, the low-density (below-threshold) lower-polariton mode remained unpolarised over the
whole flux range of such experiment, whereas in stark contrast the helicity for the dynamical
BEC was initially high at 0 T, where no energy-degeneracy lifting through an external magnetic
field occurred, and vanished towards 5 T, where the intensity noise (measured G (2) (0)) became
comparable. In the absence of the external field, polariton-condensate formation was accompanied
by an abrupt change in the degree of circular polarisation from 0 below to 80% above the bosonic
stimulated polariton–polariton scattering threshold.
3 Light–Matter Interactions for Photonic Applications
Fig. 3.10 Temporal photon statistics measured for oppositely circularly-polarised spinor condensate emission. Second-order temporal autocorrelation functions were acquired as a function of an
external magnetic field B (see [214]). a At fixed pump density, spin-split polariton modes featured
a magnetic-field dependent degree of circular polarisation above the condensate threshold, which
had a direct impact on the photon correlations measured for coexisting spinor condensates with
opposing polarisations. b At 5 T, an increase in pump density above the threshold resulted in a considerable increase in coherence for the spinor condensate with lower-energetic mode in the external
magnetic field, reflected by a decrease in polarisation-resolved G (2) (0) towards unity. In contrast,
the oppositely polarised condensate exhibited an elevated level of intensity fluctuations. Note that
the use of symbols in a and b differs. Reused with permission [214] Copyright 2016 Springer Nature
ton statistics measurements that with increasing field, spinor condensates of opposing
polarisations approached each others G
(2)
(0), which exhibited noticeable intensity
fluctuations, whereas at 0 T, one of the two circularly-polarised condensate signals
featured a high degree of coherence with near unity value (signal from the lowerenergetic condensate in magnetic field series) [214]. This result indicated that the
symmetry break through condensation gives preference to one polariton polarisation
intrinsically without external field.
13
Ultimately, the understanding of conditions for good second-order coherence and
low intensity noise are expected to pave the way for coherent exciton–polariton
devices, such as described in the literature [54, 57].
Polaritons and Terahertz Radiation
Furthermore, the relationship of polaritons with terahertz radiation in terms of the
Rabi-oscillation frequency being of the order of terahertz waves in common polariton systems has also triggered research activities which promise the realisation of
bosonic lasers, e.g. proposed bosonic cascade lasers [77], and novel polariton-based
13 In fact, the low-density (below-threshold) lower-polariton mode remained unpolarised over the
whole flux range of such experiment, whereas in stark contrast the helicity for the dynamical
BEC was initially high at 0 T, where no energy-degeneracy lifting through an external magnetic
field occurred, and vanished towards 5 T, where the intensity noise (measured G (2) (0)) became
comparable. In the absence of the external field, polariton-condensate formation was accompanied
by an abrupt change in the degree of circular polarisation from 0 below to 80% above the bosonic
stimulated polariton–polariton scattering threshold.