Fig. 3
From: Continuous-wave highly-efficient low-divergence terahertz wire lasers
Electrical and optical characterization. a Voltage–current density (V–J) and power–current density (L–J) characteristics measured at 20 K for a set of devices with different η values, in a nitrogen-purged atmosphere. All lasers are driven in pulsed mode with a pulse width of 200 ns and pulse repetition rate of 100 kHz. Optical power scales were corrected to account for the detector collection efficiency and the absorption of the polyethylene cryostat window. The device area is 0.074 mm2. b Slope efficiency measured at 20 K plotted as a function of η, under the same experimental conditions shown in a, with error bars derived from the linear fitting procedure of the slope. c Fourier transform infrared emission spectra for selected devices from a, measured in rapid scan mode. d Threshold current density of the device with η = 0.95 as a function of the heat-sink temperature. The red line is the fit based on the empirical formula Jth (T) = J1 + J2 exp(T/T2). The error bars account for errors on the extrapolated threshold current densities
