Broadband solar distributed Bragg reflector design using numerical optimization

In this paper, we optimize the structure of the multi-paired SiO2/TiO2 Bragg reflector to obtain broad-band and broad-angled high solar reflectivity in visible to near-infrared frequencies. To control the refractive index contrast in the BR pairs, the porosity of SiO2 (same across all layers) is also allowed to change. We study the trade-off between the number of pairs and porosity and the overall performance of the structure. As a result of the optimization, we demonstrate that a 15-pair structure can yield an average reflectivity twice that of a quarter-wavelength stack rule design for extraterrestrial irradiance.

Automated summary

In this paper, the structure of the multi-paired SiO2/TiO2 Bragg reflector was optimized to achieve broad-band and broad-angled high solar reflectivity. By allowing the porosity of SiO2 to change, the refractive index contrast in the BR pairs was controlled. The trade-off between the number of pairs and porosity was studied, leading to the demonstration that a 15-pair structure can significantly outperform a quarter-wavelength stack rule design for extraterrestrial irradiance.