Linear flip-chipped resonant-cavity green μLEDs arrays for low-crosstalk optogenetic probes with low damage

Abstract

Optogenetics with high temporal and spatial resolution hold great potentials to replace the traditional drug and electrical stimulation techniques, which calls for optical probing devices with low crosstalk and organic damages. Here, we report a fabrication method of optoelectrical probes for precise modulation of neurons. A linear array of flip-chipped green resonant-cavity μLEDs (RCLED) with an emitting aperture of 50 μm is integrated on Si platform as the stimulation source. Due to the top/bottom Bragg reflectors, the RCLEDs' output light view-angle is narrowed to <90°. The emission wavelength demonstrates remarkable stability under various injection current densities. Under the 50 A/cm2 driving current density, the RCLEDs' output optical density is 100 mW/mm2 and maximum temperature rise is 0.5 °C, both of which exhibit great improvement compared with those of the optical probes on sapphire substrate. Using these green RCLED probes to stimulate Mac-mCherry photosensitive protein, the analgesia and inhibition effects for medium prefrontal cortex GABAergic neurons are verified. This work provides an effective approach to fabricate integrated microscale light sources for precise stimulation and modulation of neurons, which facilitate the study of complex neural functions.