Fig. 1.

Different light sources. (a) The top and (b) the reverse side of a VCSEL ($\lambda =680\mathrm{nm}$). The dimension is $250\times 250\times 200\mu {\mathrm{m}}^3$ and its maximum output power is about 4 mW. (c) and (d) The top and bottom of a $5\times 7$ VCSEL array, ($\lambda =1860\mathrm{nm}$). The dimension is $450\times 250\times 200\mu {\mathrm{m}}^3$ and its maximum output power is about 7.5 mW. Each circle in (c) represents one VCSEL. (d) The light emitting window and the cathode, (e) and (f) a SELD ($\lambda =1850\mathrm{nm}$). The dimension is $450\times 350\times 100\mu {\mathrm{m}}^3$ and its maximum output power is about 50 mW. (g) The original appearance of a blue $\mu \mathrm{LED}$ ($\lambda =470\mathrm{nm}$) before being resized. The dimension is $1000\times 600\times 200\mu {\mathrm{m}}^3$ and its maximum output power is about 34 mW. Scale bars are the same for (a)–(f) [shown in (b)] and (g)–(h) [shown in (h)]: $100\mu \mathrm{m}$. The power ratings are given for continuous wavemode operation.