Fig. 2. Device characteristics.
(A) Measured subthreshold emission spectra (T = 10 K). Two peaks separated by the AlAs reststrahlen band were observed, stemming from the emission from the lower and upper phonon-polariton branches, respectively. The low-temperature laser spectrum at 880 mA is also shown. a.u., arbitrary units. (B) Measured Raman spectrum taken from the active region in the geometry. (C) Room-temperature direct transmission spectrum using a room-temperature deuterated triglycine sulfate detector. (D) Light output versus current characteristic. A single threshold current (=880 mA) was observed. The inset shows the transport curve of the device. The ridge width of the device is ~30 μm, and the length was 250 μm.