Polariton Laser Using Single Micropillar $\mathrm{GaAs}\mathrm{\text{−}}\mathrm{GaAlAs}$ Semiconductor Cavities

Polariton lasing is demonstrated on the zero-dimensional states of single $\mathrm{GaAs}/\mathrm{GaAlAs}$ micropillar cavities. Under nonresonant excitation, the measured polariton ground-state occupancy is found as large as ${10}^4$. Changing the spatial excitation conditions, competition between several polariton lasing modes is observed, ruling out Bose-Einstein condensation. When the polariton state occupancy increases, the emission blueshift is the signature of self-interaction within the half-light half-matter polariton lasing mode.

Figure 1

(a) PL spectrum measured on a single $4\mu \mathrm{m}$ diameter micropillar; inset: scanning electron micrography of a micropillar array; (b) (black circles) emission energy of the discrete polariton PL lines and (open circles) of the exciton line measured on several $4\mu \mathrm{m}$ diameter micropillars along the cavity wedge, (thick black lines) calculated energy of the 0D polariton modes. $T=10\mathrm{K}$.

Figure 2

Emission spectra measured for several excitation powers in a single $6\mu \mathrm{m}$ diameter micropillar. (a) Corresponds to the polariton lasing regime; (inset) emission spectrum measured for $P=30\mu \mathrm{W}$. (b) Corresponds to the loss of the strong coupling regime and the onset of photon lasing. $T=10\mathrm{K}$.

Figure 3

(a) Integrated intensity and measured occupancy, (b) emission energy and (c) emission linewidth measured on the lowest energy emission line as a function of the excitation power; dashed areas highlight the excitation range for polariton lasing or photon lasing.

Figure 4

(a) Emission spectra measured on a single $6\mu \mathrm{m}$ diameter micropillar for several excitation powers with a laser spot centered on the pillar surface, (b) measured integrated intensity of the three lowest energy polariton mode as a function of the excitation power in this centered excitation geometry; (c) and (d) same as (a) and (b) but with an edge excitation geometry as schematically indicated in the figure; (e) spectral blueshift of the polariton lasing modes as a function of their occupancy. $T=10\mathrm{K}$.