Highly efficient coupling of photons from nanoemitters into single-mode optical fibers is demonstrated using tapered fibers. 7.4 ± 1.2 % of the total emitted photons from single CdSe/ZnS nanocrystals were coupled into a 300-nm-diameter tapered fiber. The dependence of the coupling efficiency on the taper diameter was investigated and the coupling efficiency was found to increase exponentially with decreasing diameter. This method is very promising for nanoparticle sensing and single-photon sources.Collection of fluorescence photons from single nanoemitters is of fundamental importance in fields such as quantum information and biological sensing. For examples, single nanoemitters such

Abstract:We investigated the cause of optical transmittance degradation in tapered fibers. Degradation commences immediately after fabrication and it eventually reduces the transmittance to almost zero. It is a major problem that limits applications of tapered fibers. We systematically investigated the effect of the dust-particle density and the humidity on the degradation dynamics. The results clearly show that the degradation is mostly due to dust particles and that it is not related to the humidity. In a dust free environment it is possible to preserve the transmittance with a degradation of less than the noise (±0.02) over 1 week.

Abstract:The coupling of a microsphere resonator to a tapered fiber was demonstrated at cryogenic temperatures (8 -13 K) and investigated with a probe laser light whose frequency around the zero phonon line of nitrogen vacancy centers in diamond (638 nm). For this purpose, a liquid-heliumflow cryostat with a large sample chamber is developed and a resonance dip with a Q of 2 × 10 6 is observed. The resonance frequency and the coupling condition are found to be stable for a period of one hour.