The optical breakdown thresholds (OBTs) of typical dielectric and semiconductor materials are measured using double 40-fs laser pulses. By measuring the OBTs with different laser energy and different time delays between the two pulses, we found that the total energy of breakdown decrease for silica and increase for silicon with the increase of the first pulse energy.

Thin-film silicon solar cells with light-trapping structures can enhance light absorption within the semiconductor absorber layer. Metasurfaces, consisting of single-layer of planar structures, can be realized inexpensively by means of new nanopatterning techniques. Here we propose an asymmetric metasurface light trapping scheme that enables broadband absorption enhancement within c-Si thin film. Our numerical results demonstrate that the proposed metasurfaces exhibit better light trapping performance than the inverted pyramid that has been widely studied in recent years. Our work illustrates the impressive promise for metasurface structures used in thin film silicon solar cells.

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