Tailoring a nanofiber for enhanced photon emission and coupling efficiency from single quantum emitters.
We present a novel approach to enhance the spontaneous emission rate of single quantum emitters in an optical nanofiber-based cavity by introducing a narrow air-filled groove into the cavity. Our results show that the Purcell factor for single quantum emitters inside the groove of the nanofiber-based cavity can be at least six times greater than for such an emitter on the fiber surface when using an optimized cavity mode and groove width. Moreover, the coupling efficiency of single quantum emitters into the guided mode of this nanofiber-based cavity can reach up to ∼80% with only 35 cavity-grating periods. This new system has the potential to act as an all-fiber platform to realize efficient coupling of photons from single emitters into an optical fiber for quantum information applications.
Optimization of nanofiber gratings for efficient single-photon collection
We report on a simulation of a nanophotonic cavity constructed by designing periodic holes on an optical nanofiber to realize light–matter interaction. The cavity is designed using finite-difference time-domain simulations to maximize the coupling of spontaneous emission from a quantum emitter into fiber-guided modes. We systematically analyze the dependence of spontaneous emission on the quantum emitter position, polarization, and the grating strength (number of periods). We show that coupling efficiencies as high as 87% and 83% can be realized for a dipole emitter placed at the center of the nanofiber with polarization perpendicular (x-pol) and parallel (y-pol) to the hole-axis, respectively. This system may attract various quantum photonic applications based on single-photon sources.
DESIGN CONSIDERATION TO PPM KLYSTRONS FOR INDUSTRIAL LINAC
Toshiba has been developing the C-band and X-band Periodic Permanent Magnet (PPM) focused klystron in collaboration with KEK and manufactured prototypes for the JLC project. [1] The PPM klystron has an advantage to enhance the total efficiency as a result of eliminating the electric power for the focusing magnet. From experience on the development the PPM focused klystrons for the JLC project, we plan to apply the PPM focused klystron to the medical and industrial linac. The periodic magnet focusing scheme has some technical difficulties such as stop band voltage. To design the PPM klystron for the medical and industrial linac, it is necessary to give heed to electron beam instability; so that the tube parameters of the PPM focused klystrons have some constraints. The size of the accelerator system is substantially reduced if a PPM focused klystron is used. The majority of medical and industrial linacs use frequencies of S-band range. We discuss the availability of the S-band PPM focused klystron in this paper.