Enhanced and shortened Mn 2+ emissions by Cu + co-doping in borosilicate glasses for W-LEDs

A novel pair of transition metal ions Cu+, Mn2+ is co-doped in borosilicate glasses. Both copper and manganese ions exist in lower valence states (Cu+, Mn2+) in the as-prepared glasses. Around 5-time enhanced Mn2+ emission under the UV excitation is observed, which, as demonstrated by excitation spectra and emission decay curves, is due to an energy transfer from Cu+ ions resulting in greatly increased absorption of Mn2+ ions in the UV region, and relaxation on doubly-forbidden transition of Mn2+ leading to the much shortened Mn2+ emission lifetime from millisecond to microsecond level. Besides, a composite white emission is generated by combining the blue-green part from Cu+ ions with the green-red part from Mn2+ ions and it can be effectively tuned from cold to warm by adjusting host glass composition and altering excitation wavelength. Relevant mechanisms are discussed

Symmetrical triangular LFM for underwater acoustic communications

Synchronous detection acts as a key role in underwater acoustic communications. It is discovered that the Symmetrical Triangular Linear Frequency Modulation (STLFM) signal has double energy peaks in their fractional Fourier transform domain and these two peaks have symmetry in their amplitude if the STLFM signal is captured in the accurate time windows for the synchronization. In this paper, we propose a synchronization detection method based on the STLFM. To verify the effectiveness of the proposed method, we apply simulations based on the Bellhop program and sea trial data collected at Wuyuan Bay, Xiamen, China. The results show that the proposed STLFM method outperforms the LFM method