Sr 3 ( Al 2 O 5 ) Cl 2 phosphor doped with Eu2+ was prepared by a soli-state reaction. This phosphor emits a broad orange-yellow luminescence with a peak wavelength of 620nm and a full width at half maximum of about 175nm under near-ultraviolet (NUV) excitation at ∼400nm. Yellow light-emitting diodes (LEDs) for general lighting were fabricated by combining Sr3(Al2O5)Cl2:Eu2+ phosphor with an NUV chip. The phosphor-converted LEDs had a color temperature of about 2300K and their color rendering index was 74.

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BaMgAl10normalO17 co-doped with Eu2+ and Mn2+ was synthesized in a solid-state reaction and their luminescence properties were investigated as functions of the concentrations of the sensitizer and activator. The energy transfer from Eu2+ to Mn2+ was mainly of the resonance-type via an electric dipole–quadrupole interaction. Additionally, the addition of various fluxes such as AlF3 and BaF2 in the synthesis improves the moist stability. This is particularly important for the phosphor in white light-emitting diodes (LEDs). The white LEDs with a color rendering index of 95 were fabricated by coating the synthesized phosphors on a UV LED chip to verify the real application capability.

The improved heterodyne system is presented to measure the frequency response of photodetectors (PDs) with bandwidth about 100 MHz utilized in ultrasonic applications. In order to eliminate the periodic oscillation following the frequency tuning of the acousto-optic frequency shifters (AOFSs) in the measurement results, the AOFSs’ double-passed scheme in Michelson interferometer is used. Compared with the AOFSs’ single-passed configuration in Mach-Zehnder interferometer, the double-passed scheme can avoid additional optical alignment during the process of the frequency tuning and then reduce its induced measurement uncertainty. With two double-passed AOFSs connected in parallel, the experimental setup is designed to demonstrate the feasibility of the improved heterodyne system in the frequency range from 500 kHz to 135 MHz. Experimental results with measurement uncertainty are provided and discussed.

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