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Role of spurious reflections in ring-down spectroscopy
Optics Letters
|November 23, 2007
Summary
Spurious reflections in ring-down cavities significantly alter decay times. Even weak reflections (10^-4) can change cavity decay time by +/-0.4 microseconds.
Area of Science:
- Physics
- Optical Engineering
- Spectroscopy
Background:
- Ring-down cavities are crucial for high-sensitivity measurements.
- Optical elements can cause spurious reflections.
- These reflections can affect cavity performance.
Purpose of the Study:
- To investigate the impact of spurious coherent reflections on ring-down cavity decay time.
- To quantify the relationship between reflection magnitude and decay time perturbation.
Main Methods:
- Utilized a 25-cm-long Fabry-Perot cavity with a baseline decay constant of 40 microseconds.
- Introduced controlled spurious reflections (10^-4 of transmitted power) mode-matched back into the cavity.
- Demonstrated the effect using a continuous-wave (cw) system.
Main Results:
- A spurious reflection of 10^-4 can alter the decay time by up to +/-0.4 microseconds.
- The perturbation is proportional to the electric field of the reflection.
- A 100-fold decrease in reflected power reduces perturbation only 10-fold.
Conclusions:
- Spurious reflections pose a significant challenge in precision ring-down spectroscopy.
- Careful optical design and alignment are necessary to minimize these effects.
- Understanding this phenomenon is key to accurate decay time measurements.
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