Fig. 2.

Optrodes fabricated with small optical sources. (a) A three-channel optrode. The two infrared sources in (a) are VCSELs ($\lambda =1860\mathrm{nm}$, larger dies to the left). A red source ($\lambda =680\mathrm{nm}$, smaller die to the right) serves as a pilot light, which helps to orient the implant. (b) The completed electrode ready for implantation. At the bottom right, the transcutaneous connector is shown. (c) A picture of a two-channel optical array made of SELDs. The size of the given emitters is $450\mu \mathrm{m}\times 300\mu \mathrm{m}\times 100\mu \mathrm{m}$. The anode of each emitter was connected with a thin gold wire, and then to a Teflon-insulated silver wire. The cathodes of both emitters were connected to a single silver wire, which also served as a heat sink for the light sources. The direction of the light emission is indicated by the arrow. (d) A picture of a silicone-embedded single-channel optical array made with a SELD. The anode and cathode connections are the same as shown in panel (c). The array is embedded in silicone. (e) An array of $15\mu \mathrm{LEDs}$ connected with a silver wire to the cathodes and platinum wires to the anodes. (f) An optrode made with 15 light sources. (g) The insertion of this optrode into a human scala tympani model. (g) and (i) The radiation of a single $\mu \mathrm{LED}$ and multiple $\mu \mathrm{LEDs}$. $\text{Scale bars}=900\mu \mathrm{m}$.