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(a) Top view scanning electron microscope (SEM) image of the triangular lattice of high index pillars with lattice constant . The lattice directions and are also labeled. (b) Bird’s eye view SEM image of a PhC laser with a wide ridge and 2.5 PhC periods (five columns of pillars) at the rear and 1.5 PhC periods at the front facet. From a side view SEM image (not shown) we have determined a column diameter of and an etch depth of more than .
(Color online) Spectral dependence of the simulated reflectivity for light incident from the laser ridge on 1.5 periods of the triangular PhC structure in (top) and (bottom) directions. The results for 2D (dashed lines) and 3D simulations (solid lines) are shown for comparison.
(Color online) Temperature dependence of the threshold current for long cavities without (Ref) and with and oriented PhCs. Whereas the device with the PhC in orientation employed one PhC period at the front facet and two periods at the rear facet, the device with the PhC in orientation incorporated 1.5 and 2.5 PC periods, respectively. The inset shows comparatively the current-light output characteristics of the devices at .
(Color online) Emission spectra of the long and PhC QCLs and of the long reference laser (Ref) laser with cleaved facets at comparable temperatures. The determined Fabry-Pérot mode spacings for the two PhC QCLs and the reference QCL are 2.47 and , respectively, yielding the corresponding group refractive indices of 3.37 and 3.33.
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