Room Temperature Ultralow Threshold GaN Nanowire Polariton Laser

We report ultralow threshold polariton lasing from a single GaN nanowire strongly coupled to a large-area dielectric microcavity. The threshold carrier density is 3 orders of magnitude lower than that of photon lasing observed in the same device, and 2 orders of magnitude lower than any existing room-temperature polariton devices. Spectral, polarization, and coherence properties of the emission were measured to confirm polariton lasing.

Figure 1

(a) Schematic representation of the dielectric microcavity with a single GaN nanowire of diameter 60 nm (inset) buried in the center of a $\lambda$-sized cavity; (b) photoluminescence spectrum from a single GaN nanowire measured at 25 K showing free and bound exciton transitions; (c) angle-resolved photoluminescence measured at room temperature; (d) polariton dispersion curves obtained from the data of (c). The solid curves indicate the calculated polariton dispersion from a coupled harmonic oscillator model.

Figure 2

(a) Measured polariton emission intensity at 200 K as a function of incident optical excitation energy showing strong nonlinearity at threshold. The inset shows the emission spectra; (b) variation of the emission linewidth and peak energy corresponding to the data in (a); (c) variation of the emission intensity with excitation energy at 300 K clearly showing the two thresholds for polariton and photon lasing. The insets show the corresponding emission spectra; (d) variation of linewidth and emission energy at 300 K for polariton lasing.

Figure 3

Angle-resolved lower polariton luminescence spectra measured at 300 K (a) below and (b) above the polariton lasing threshold; (c) polariton occupancy for different $k_{\parallel }$ states deduced from the data of (a) and (b).