A metamaterial perfect absorber working in the ultraviolet-to-near infrared region is proposed. It consists of a periodic nanoarray of quadrangular frustum pyramids with a homogeneous titanium nitride (TiN) film as the ground. Each unit cell of the nanoarray is composed of alternately stacked TiN and dielectric patches with their width tapered linearly from the bottom to the top. The absorption mechanism was qualitatively explained by analyzing the electric and magnetic field distributions at the resonance wavelengths, and the absorption performance was simulated as a function of its geometric parameters and the angle and polarization of incident beam as well. Optimal geometric parameters are presented. With the optimal parameters, the absorption efficiency at normal incidence is above 99.3% over the entire spectral region from 300 to 2500 nm, and a high average absorption of 99.9% is achieved. The ultrabroadband perfect absorption behaviors are attributed to the localized surface plasmonic resonance effect of the pyramid, the intrinsic loss of the TiN material and the coupling of resonance modes between two adjacent pyramids. In addition, the absorber also shows polarization insensitivity and good angular acceptance capability of oblique incidence up to 70°. The unique and compact structure provides a new way for achieving an ultrabroadband solar absorber, showing great application prospects in the fields of solar energy harvesting and the corresponding (thermo-)photovoltaics.
We present z-propagation single-mode Ti: Er: Tm: LiNbO3 strip waveguides on X-Cut congruent LiNbO3 substrate. The
waveguide has been fabricated by a technological process, starting with the preparation of the Er3+/Tm3+codoped
LiNbO3plate, followed by the fabrication of 8-μm-wide Ti-diffused strip waveguide. The results of surface refractive
indices by employing prism coupling technique shows Er3+/Tm3+codoped have no effects on the substrate index, and the
surface composition was evaluated from the measured indices with the help of Sellmeier equation. We demonstrated the
amplified simultaneous emission (ASE) spectra from the waveguide pumped at 980nm and 795nm without optical
damage observed. The results shows that the co-doping combines the laser property of both ions, and the emission band
around 1.5μm is about 150 nm, as a result, opening up a series of possibilities for stable, broadband amplifier devices by
employing pump sources under 980nm and 795nm laser diodes.