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Nonlinear estimation of ring-down time for a Fabry-Perot optical cavity
Abhijit G Kallapur1, Toby K Boyson, Ian R Petersen
1School of Engineering and Information Technology, University of New South Wales at the Australian Defence Force Academy, Canberra, ACT, Australia. abhijit.kallapur@gmail.com
Optics Express
|April 1, 2011
Summary
This study applies an extended Kalman filter (EKF) to estimate the decay time constant in cavity ring-down spectroscopy (CRDS). The EKF accurately determines the optical cavity
Area of Science:
- Optical Spectroscopy
- Metrology
- Control Systems
Background:
- Cavity Ring-Down Spectroscopy (CRDS) relies on precise measurement of light decay within an optical cavity.
- Estimating the decay time constant is crucial for CRDS applications, but can be challenging with experimental noise and initial parameter uncertainties.
- Traditional methods may require significant computational resources or be sensitive to initial conditions.
Purpose of the Study:
- To apply a discrete-time extended Kalman filter (EKF) for estimating the decay time constant of a Fabry-Perot optical cavity.
- To evaluate the performance of the EKF in a practical CRDS experimental setup.
- To compare EKF estimation results with those from the Levenberg-Marquardt algorithm.
Main Methods:
- Utilized a cavity ring-down spectroscopy (CRDS) experimental setup.
- Employed a proportional-integral (PI) controller to maintain laser frequency lock by adjusting cavity mirror distance.
- Applied a discrete-time extended Kalman filter (EKF) to estimate the decay time constant from output light intensity data.
Main Results:
- The EKF demonstrated robust convergence to the expected decay time constant, even with initial uncertainties.
- Accurate estimates were achieved within a few ring-down cycles.
- EKF performance was comparable to the Levenberg-Marquardt estimation scheme.
Conclusions:
- The discrete-time extended Kalman filter is a viable and effective method for real-time decay time constant estimation in CRDS.
- The EKF offers reliable performance and rapid convergence, making it suitable for dynamic spectroscopic measurements.
- This approach enhances the precision and efficiency of optical cavity characterization in CRDS.
