Figure 2: Probing the photonic part of polaritons at the condensation threshold.
From: Revealing the dark side of a bright exciton–polariton condensate
(a) Time- and momentum-integrated PL intensity as a function of the density of photoexcited electron–hole pairs ρ. Unbound electron–hole pairs are injected by 20-fs pulses centred at ħωp=1.65 eV. The steep increase in the PL intensity above a critical density ρc=6 × 1010 cm−2 has been assigned to bosonic stimulation due to the formation of a dynamic condensate. Broken lines: guides to the eye underpinning the linear increase in PL intensity in the low- and high-density limits. Angle-resolved PL measurements taken for ρ1=5 × 1010 cm−2 (b) and ρ2=15 × 1010 cm−2 (c), that is, below and above the critical density ρc. When ρ exceeds ρc, the broad PL dispersion collapses into a degenerate momentum and energy state indicative of a polariton condensate.
