Fig. 4 | Nature Communications

Fig. 4

From: High power surface emitting terahertz laser with hybrid second- and fourth-order Bragg gratings

Fig. 4

Experimental results. a Scanning electron microscope image of the fabricated terahertz QCLs with hybrid DFB gratings as in Fig. 2a. b Current–voltage (IV), and spectral intensity (inset) at different electric bias at a heat-sink temperature of 62 K, and light–current characteristics at different temperatures measured in pulsed mode of operation. The terahertz QCL is of dimensions 10 μm×200 μm×1.5 mm, grating period Λ = 28 μm, and d/Λ = 3/8. c Far-field radiation pattern (optical intensity) measured at 62 K close to the peak-bias (~405 A cm−2) at a distance of 40 mm from the QCL in the surface-normal direction. θ x and θ y are angles with respect to the surface normal along the longitudinal and lateral dimensions of the QCL cavity, respectively. d Spectral characteristics of three different QCLs located neighboring each other on the wafer with different grating periods, and d/Λ = 3/8 for each QCL

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