Figure 4

(a) Magnified cross-sectional 2D OCT image of the packaged LED device obtained near the LED chip area. (b) Depth-resolved OCT signal curves of the packaged LED device under different injected currents (I = 0/250/500 mA). Magnified images of the first (at 0 μm) and second (at ~1500 μm) peaks are also included in the figure to calculate the corresponding depth position shift under different injected currents.