Passive atomic-scale optical sensors for mapping light flux in ultra-small cavities

Four rock cores were first irradiated with gamma rays to create trapped electrons (mapped using IRPL), and then cut in half along the axis. Cracks of different widths were simulated by placing spacers between the two halves. All these steps were done under dark conditions. The ‘cracked’ rock cores were then positioned under a solar simulator as shown in Figs. 1a and S1. To investigate the dependence of crack orientation on irradiance^9,24, three cracks (0.05, 0.3 and 1 mm) were positioned radially outwards of the center of the light illumination allowing all the light to enter…