Enhanced thermal radiation by femtosecond laser fabricating grating patterns on metal surfaces

To manipulate the optical property of object by the patterns on its surface is an heat topic for many applications. Thermal radiation is electromagnetic wave in nature, so that researchers can control it spectrally or on polarization by surface patterns likewise. This technique has a promising application prospect on thermophotovoltaic device, selective thermal radiative device, outer space heat transfer and infrared stealth technology etc. For the characteristic length of the surface patterns is approximate to micrometers which can be contrast with the thermal radiation wavelength at general application temperature, femtosecond laser micro-structure processing is an economical and practical method for fabricating desirable surface patterns which is neat edge and almost no heat affected zone. In this paper, we fabricate the surface grating patterns on Ni, Cu and Cr surfaces by femtosecond laser direct writing technique. To heat these samples to 573K and to detect the thermal radiation spectra by a fourier transform infrared spectrometer at the range of 5∼25 um. The results show that thermal radiation can be enhanced spectrally by the grating surfaces, the enhanced wavelength is approximate to the grating’s period. Surface plasmon polaritons is considered to explain this phenomenon and a numerical simulation result is completed by rigorous coupled wave analysis. The experimental and numerical results show a good agreement.