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Dissertation
Narrow band optical filter for lidar
Doctor of Philosophy (Ph.D.), Drexel University
1996
DOI:
https://doi.org/10.17918/00007879
Abstract
A narrow-band, gate-able matched optical filter with large extinction ratio and high transmission is required for ocean lidar applications at wavelength of 532 nm. Two types of filters, the induced dichroism excited-state atomic line (IDEAL) and excited state anomalous Faraday dispersion optical filter (ESFADOF), are studied. They are operating on the 4P1/2 to 8S1/2 excited states transition line of potassium vapor and a narrow band at 532 nm. The measured critical features of the IDEAL filter are: 1.3 GHz (i.e..01A) narrow pass band, approximately 45% peak transmission, high extinction coefficient in the order of 10-5, very fast rise time (<3ns) and a 15 ns decay time determined by resonant enhanced two photon transition. The physical mechanism of the IDEAL filter operation is explained in terms of resonant enhanced two photon transition. Good agreement between experiment and the derived theoretical model is achieved. The pertinent features of the excited (ESFADOF) filter were measured to be: approximately 15% peak transmission, high extinction coefficient in the order of 10-5, very fast rise time (<3ns), and a decay time in the tens of microsecond range governed by resonant photon trapping. The physical processes contributing to the ESFADOF filter action are resonant photon trapping and Faraday anomalous dispersion. The experimental results confirmed theoretical predictions. The applications of these filters are discussed in terms of improving the lidar system performance. Specifically, the narrow bandwidth of these filters eliminates the background noise caused by stray solar radiation and thereby enhances the dynamic range of the lidar system. Furthermore the fast efficient gating of the filters minimizes reflection from the ocean surface, which is several orders of magnitude higher than the return signal from underwater targets.
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Details
- Title
- Narrow band optical filter for lidar
- Creators
- Guangning Yang
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xi, 146 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Arts and Sciences; Drexel University
- Other Identifier
- 991021888991904721