Highly efficient light trapping of metallic microstructures induced by femtosecond lasers

Microstructuring of NiTi alloy plates by 800 nm femtosecond lasers is investigated through the line-scribing experiment in ambient air. It is found that some distinct surface structures can be generated by varying laser pulse energies and the scan speeds of the samples. Very weak stray light is detected when He-Ne laser beam is directed on the micro-structured targets. The integrated reflectance measurements reveal that the light trapping of these structured metal surfaces can be improved greatly, even up to 90%, within a large spectral range covering the ultraviolet, the visible and the mid-infrared. It is expected that this result could have great potential applications in the designing of efficient energy transfer devices.