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Efficient Optical Fiber Technique Shown to Probe Individual Emitters
For Immediate Release: July 26, 2010
Using electromagnetic simulations, researchers from the Center for Nanoscale Science and Technology have shown that fiber taper waveguides can be a very efficient tool for optical spectroscopy on individual light emitters, such as single molecules, atoms, or semiconductor quantum dots, deposited on the surface of a dielectric membrane.* Optical fiber taper waveguides, sometimes called micro- or nanofiber waveguides, are single mode optical fibers whose diameter is slowly and symmetrically reduced to a wavelength-scale minimum. CNST researchers are developing these structures for a range of light measurement solutions. In this work, the team simulated how, when placed in proximity to single emitters on a dielectric membrane, the fiber probe would form an optical waveguide supporting modes in the low refractive index gap between the fiber and the membrane. The high concentration of the optical field of these gap modes, when interacting with vertical electric dipoles, is predicted to enhance light emission rates by a factor of 20. Additionally, efficient power transfer from the gap modes into the optical fiber should improve collection efficiencies to values of more than 20%. These two factors combined should significantly improve the signal to noise ratio in light detection from single emitters compared with standard lens-based collection methods.