Efficient nitrogen-vacancy centers' fluorescence excitation and collection from micrometer-sized diamond by a tapered optical fiber

Efficiently excite nitrogen-vacancy (NV) centers in diamond and collect their fluorescence significantly benefit the fiber-optic-based NV sensors. Here, using a tapered optical fiber (TOF) tip, we significantly improve the efficiency of the laser excitation and fluorescence collection of the NV, thus enhance the sensitivity of the fiber-optic based micron-sized diamond magnetic sensor. Numerical calculation shows that the TOF tip delivers a high numerical aperture (NA) and has a high fluorescence excitation and collection efficiency. Experiments demonstrate that using such TOF tip can obtain up to over 7-fold the fluorescence excitation efficiency and over15-fold the fluorescence collection efficiency of a flat-ended (non-TOF) fiber. Such fluorescence collection enhances the sensitivity of the optical fiber-based diamond NV magnetometer, thus extending its potential application region.Comment: 11 pages, 13 figure

Methane concentrations and aerobic methane oxidation rates in the East China Sea and Yellow Sea

We measured the methane concentrations and aerobic methane oxidation rates (MOx) in the seawater of East China Sea and Yellow Sea. Seawater samples were collected onboard "Dong Fang Hong 3" in April 2021 using a rosette system equipped with 24-liter Niskin bottles and a Seabird 911 CTD. Methane concentrations were measured using a purge-and-trap preconcentration method with a gas chromatography (Shimadzu GC-2014B) with a flame ionization detector. The rate constants of MOx and MOx rates were determined using a radiotracer approach through quantifying the conversion of added 3H-methane tracer to the oxidation product 3H-H2O