5 research outputs found
Efficient coupling to an optical resonator by exploiting time-reversal symmetry
The interaction of a cavity with an external field is symmetric under time
reversal. Thus, coupling to a resonator is most efficient when the incident
light is the time reversed version of a free cavity decay, i.e. when it has a
rising exponential shape matching the cavity lifetime. For light entering the
cavity from only one side, the maximally achievable coupling efficiency is
limited by the choice of the cavity mirrors' reflectivities. Such an
empty-cavity experiment serves also as a model system for single-photon
single-atom absorption dynamics. We present experiments coupling exponentially
rising pulses to a cavity system which allows for high coupling efficiencies.
The influence of the time constant of the rising exponential is investigated as
well as the effect of a finite pulse duration. We demonstrate coupling 94% of
the incident TEM00 mode into the resonator.Comment: 7 pages, 5 figure
Viral Infections of the Lower Respiratory Tract: Old Viruses, New Viruses, and the Role of Diagnosis
Viral infections of the lower respiratory tract cause an enormous disease burden in children, and the role of respiratory viruses in serious lower respiratory tract infections (LRTIs) in older adults is increasingly appreciated. Although viruses are responsible for a large proportion LRTIs, antibiotics are often prescribed. New diagnostic platforms have the potential to detect a wider range of established and newly discovered viruses with greater sensitivity. This will create additional challenges. Although it is clear that influenza, parainfluenza, respiratory syncytial virus, human metapneumovirus, and adenovirus are important causes of pneumonia, the role of rhinoviruses and some of the newly described viruses, including human coronaviruses and bocavirus, is harder to determine. Better diagnostic tests that establish the cause of LRTIs in children have the potential to both reduce overall antibiotic use and to improve the targeted use of antibiotics. In addition, rapid identification of viral infections can help control nosocomial transmission