Phase-modulated single-photon nonreciprocal transport and directional router in a waveguide-cavity-emitter system beyond the chiral coupling

We propose a potentially practical scheme for the controllable single-photon transport via waveguides which are coupled to a microcavity-emitter system. The microcavity-emitter system consists of a V-type three-level emitter and two or one single-mode microcavity. A driving field is used to drive a hyperfine transition between two upper excited states of the V-type three-level emitter. Beyond chiral coupling between waveguides and microcavity-emitter system, we show that the perfectly nonreciprocal single-photon transport in a single waveguide and the single-photon router with 100% routing probability in two waveguides can be achieved. Interesting enough, whether the nonreciprocal single-photon transport or the single-photon router can be switched periodically by adjusting the phase associated with microcavity-emitter coupling strength and the driving field. The complete physical explanation of the underlying mechanism is presented.

Serpent 2 Validation for Radiation Shielding Applications

This paper contributes to the validation of Serpent's photon transport and coupled neutron-photon transport routines. Two benhmarks presenting measurements of neutron and photon flux through different sized iron and lead spheres have been calculated using a development version of Serpent and MCNP6.2. The Serpent results were compared to the measurement results and the MCNP6.2 calculations. Additionally, the development version has been compared to the currently distributed Serpent version 2.1.31. In all cases, the Serpent calculated neutron and photon spectra followed the measured spectra fairly well. For the iron spheres, differences between Serpent and MCNP6.2 calculated neutron spectra were mostly below 2 % at neutron energies below 4 MeV. Differences between photon spectra through the iron spheres were mostly below 3 %. For the lead spheres, differences in the calculated neutron spectra were mostly below 1.5 % in the energy range 0.04-4.0 MeV. Differences between photon spectra through the 10 cm lead sphere were mostly below 5 % and for the larger spheres below 10 % except at higher photon energies above 6.5 MeV. Differences between the development version and the Serpent version 2.1.31 of the order of 3 % were observed in the photon spectra through the largest lead spheres with radius 20 and 30 cm when Gaussian Energy Broadening was not applied. These are probably related to the coupled neutron-photon transport routines in the different versions.