Abstract
The transmission peaks of Faraday anomalous dispersion optical filters (FADOF) are located in the wings of the atomic vapor absorption bands. There are four transmission peaks for typical Rb and Cs FADOFs due to the isotopic splitting and hyperfine structure of these atoms. The signal is transmitted on only one passband, the other passbands contributing only to the background noise. A composite filter system can be used to isolate the signal transmission band and eliminate the other transmission bands. In this system, a Zeeman absorption cell is placed in series with a FADOF. The absorption cell operates under different conditions from the FADOF to shift absorption bands, so that the shifted absorption bands may cancel the other three undesirable transmission peaks. The results show that a composite system may provide a single ultra-narrow passband (~0.7 GHz) in the transmission spectrum, improving the noise rejection factor by about 6 dB with high throughput (~90%) and low equivalent noise bandwidth (~1 GHz). Also, the transmission peak in the composite filter is independent from the Zeeman absorption cell, which means that the peak bandwidth and position can be fine tuned by changing the operating condition of the FADOF. The results of both theoretical analysis and experimental measurements will be presented.
© 1993 Optical Society of America
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