Passive Fraunhofer-wavelength atomic filter at 460.7 nm

A passive Fraunhofer-wavelength atomic filter in the spectral region of minimum seawater attenuation is reported. Signal light at 460.7 nm is strongly absorbed by strontium atoms contained in a heated vapor cell. Collisions with rare gases transfer population into the Sr(5p/sup 3/P/sub j/) level, which subsequently emits 689.3-nm photons. Up to 45% photon conversion efficiency was recorded. The strontium filter exhibits a 50- mu s decay time and a single noise passband.<
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