报道了一种新型的Mn⁴⁺掺杂水合六氟钛酸钙CaTiF₆·2H₂O∶Mn⁴⁺红色荧光粉，详细研究了基质的结构转变和荧光粉的发光性能及高显色指数（显指）暖白光LED应用。CaTiF₆·2H₂O∶Mn⁴⁺在130~200 ℃间脱水转化为CaTiF₆∶Mn⁴⁺，荧光光谱发生改变，重新吸附水分子可恢复到CaTiF₆·2H₂O∶Mn⁴⁺，发光性能不可逆。重要的是，该荧光粉在较长波626 nm和635 nm处分别发射锐线极强的零声子线（ZPL）和ν₆振动峰，色坐标为（0.701，0.299），更接近人眼敏感的红光边界650 nm（色坐标x~0.72，y~0.28），有助于提高暖白光LED的显色指数、拓宽背光源的色域。晶体结构和晶体场强度计算指出，Mn⁴⁺在CaTiF₆·2H₂O∶Mn⁴⁺中占据低对称性的格位，所受到的晶体场强度较弱，Mn—F键的共价性较强。另外，通过表面疏水化显著提升了荧光粉耐湿性能，共掺小离子半径的Si⁴⁺增强了荧光粉发光热稳定性。以CaTiF₆·2H₂O∶Mn⁴⁺作为红光成分，获得了高显色指数（R_a=90，R₉=68）的暖白光LED，在高品质的暖白光照明中具有潜在的应用。

In order to meet the practical needs of all-fiber conductivity-temperature-depth sensors with high sensitivity, compact structure, and easy packaging, this Letter uses a microfiber coupler combined with fiber loop (MCFL) reflective photonic device to conduct salinity, temperature, and deep sensing experiments. These MCFLs’ dynamic range and resolution of salinity, temperature, and depth can meet the requirements of actual marine environment monitoring. This structure opens up a new design idea for the practical research of microfiber coupler-based marine environmental parameter sensors.

We modify the pulse-reference-based compensation technique and propose a low-noise and highly stable optical fiber temperature sensor based on a zinc telluride film-coated fiber tip. The system noise is measured to be 0.0005 dB, which makes it possible for the detection of the minor reflectivity change of the film at different temperatures. The temperature sensitivity is 0.0034 dB/°C, so the resolution can achieve 0.2°C. The maximum difference of the temperature output values of the sensor at 20°C at different points in time is 0.39°C. The low cost, ultra-small size, high stability, and good repeatability of the sensor make it a promising temperature sensing device for practical application.

An all-optical intensity modulator based on an optical microfiber coupler (OMC) is presented. The modulator works at 1550 nm wavelength and is modulated directly by heating the coupling region with 980 nm pump light injected through the coupling port of the OMC. The OMC is controlled to have at least a 30 mm long coupling region with diameter smaller than 8 μm, and the uniform waist region diameter is about 3 μm. This is helpful to ensure the optical modulation function based on the light induced thermal effect in the coupling region, while pump light is injected. The modulation response is measured to show good linearity when the 980 nm pump light has a lower intensity (with power below 2.5 mW), which proves that the OMC acts as an all-optical modulator. The bandwidth of the modulator can be at 0.2–50 kHz with the average power of the intensity-modulated pump light about 2 mW, which can be further improved by optimizing the design of the coupler. The demonstrated modulator may have potential value for the application in an all-optical integration system.

We propose a compensation technique based on pulse reference for intensity-modulated optical fiber sensors that can compensate the power fluctuation of the light source, the change of optical components transmission loss, and the coupler splitting ratio. The theoretical principle of this compensation technique is analyzed and a temperature sensor based on fiber coating-covered optical microfiber is carried out to demonstrate the compensation effect. The system noise is measured to be 0.0005 dB with the temperature sensitivity reaching 0.063 dB/°C, and the output drift is 0.006 dB in 2 h at room temperature. The output shows a slight variation (0.0061 dB) when the light source and the common light path suffer a 3 dB attenuation fluctuation.