Figure 2 | Scientific Reports

Figure 2

From: Ring quantum cascade lasers with twisted wavefronts

Figure 2

Scanning electron microscopy (SEM) images of gradient index metamaterials with different discontinuity counts. (a) Counter-clockwise gradient with a discontinuity count of 1 (ccw1). (b) Clockwise gradient with a discontinuity count of 1 (cw1). Counter-clockwise gradient with a discontinuity count of 2 (ccw2). (d) Close-up of the etched holes. (e) Experimentally determined (solid) and theoretical (dashed) refractive index gradients for different discontinuity counts.

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