Quantum and nonlinear optics with surface plasmons
Final Report Abstract
In this research project we have explored different aspects of quantum and nonlinear optics using nanoscale plasmonic waveguides. First, we have studied the general problem of photon scattering by single emitters in one-dimensional waveguides, pointing out several possible applications in quantum metrology and quantum information processing. In particular we have solved the general scattering problem for three-level emitters, including a possible classical driving field. It was shown that these structures can be used to realize a single photon transistor as well as tunable photonic band gap structures. Furthermore, we have designed a fault-tolerant photonic Bell state analyzer, which uses only two-level emitters and passive elements. Our results apply equally well to plasmonic structures as to other waveguides strongly coupled to a single emitter, as for instance tapered optical fibers coupled to a single atom, microwave transmission lines coupled to a flux qubit. Second, we have investigated the optical nonlinearities of plasmonic slab waveguides both theoretically and experimentally. Second-order nonlinearities arise at the surface of a metal and have been studied previously in reflection. Unfortunately, an application of this nonlinearity for second-harmonic generation or down-conversion is forbidden in simple structures due to the symmetry. The Kerr effect of a surface plasmon mode, which can be used to design active plasmonic elements, has been analyzed in detail. It was shown that two effects are present: On short time scales, the absorption in the metal is saturated such that the transmission of a plasmonic waveguide increases with the input power. On longer timescales, the sample heats up which increases losses. One particular drawback in current experimental setups is a reliable incoupling to the plasmon modes. A possible solution of this problem is to implement an adiabatic passage between a plasmonic and a dielectric waveguide. We have developed a general theory of adiabatic mode transfer for electromagnetic waves in dissipative media. These methods are currently applied to optimize setups in ongoing experiments.
Publications
- Photon scattering by a three-level emitter in a one-dimensional waveguide. New J. Phys 12, 043052 (2010)
D. Witthaut and A. S. Sørensen
