36 research outputs found
A low-loss photonic silica nanofiber for higher-order modes
Optical nanofibers confine light to subwavelength scales, and are of interest
for the design, integration, and interconnection of nanophotonic devices. Here
we demonstrate high transmission (> 97%) of the first family of excited modes
through a 350 nm radius fiber, by appropriate choice of the fiber and precise
control of the taper geometry. We can design the nanofibers so that these modes
propagate with most of their energy outside the waist region. We also present
an optical setup for selectively launching these modes with less than 1%
fundamental mode contamination. Our experimental results are in good agreement
with simulations of the propagation. Multimode optical nanofibers expand the
photonic toolbox, and may aid in the realization of a fully integrated
nanoscale device for communication science, laser science or other sensing
applications.Comment: 12 pages, 5 figures, movies available onlin
Enhancement of field generation via maximal atomic coherence prepared by fast adiabatic passage in Rb vapor
We have experimentally demonstrated the enhancement of coherent Raman
scattering in Rb atomic vapor by exciting atomic coherence with fractional
stimulated Raman adiabatic passage. Experimental results are in good agreement
with numerical simulations. The results support the possibility of increasing
the sensitivity of CARS by preparing atomic or molecular coherence using short
pulses
Theory of femtosecond coherent anti-Stokes Raman backscattering enhanced by quantum coherence for standoff detection of bacterial spores
Backscattered signal of coherent anti-Stokes Raman spectroscopy can be an extremely useful tool for remote identification of airborne particles, provided the signal is sufficiently large. We formulate a semiclassical theory of nonlinear scattering to estimate the number of detectable photons from a bacterial spore at a distance. For the first time, the theory incorporates enhanced quantum coherence via femtosecond pulses and a nonlinear process into the classical scattering problem. Our result shows a large backscattered signal in the far field, using typical parameters of an anthrax spore with maximally prepared vibrational coherence. Using train pulses of 1 kHz of repetition rate each with energy of 10 mJ, we estimate that about 10(7) photons can be detected by a 1 m diameter detector placed 1 km away from the spore in the backward scattering direction. The result shows the feasibility of developing a real time remote detection of hazardous microparticles in the atmosphere, particularly biopathogenic spores
Media 1: A low-loss photonic silica nanofiber for higher-order modes
Originally published in Optics Express on 29 July 2013 (oe-21-15-18325
Media 2: A low-loss photonic silica nanofiber for higher-order modes
Originally published in Optics Express on 29 July 2013 (oe-21-15-18325