Study of Fabry-Perot Etalon Stability and Tuning for Spectroscopic Rayleigh Scattering

Rayleigh Scattering Measurements Using a Tunable Liquid Crystal Fabry-Perot Interferometer

“…The resulting Rayleigh interference fringe pattern has no distinguishable peak to use for determining velocity or temperature measurements. These observations along with the results from a previous study of the LC etalon 13 led to the decision to collect data at 45 o scattering to reduce the width of the Rayleigh spectrum. Fig.…”

“…In previous characterization experiments Clem, et al 13 discovered that the LC etalon has a much lower free spectral range (FSR) than originally thought; the fringes are only about 2.5 GHz apart. Typical FP's used in IRS have a FSR of about 8-10 GHz.…”

“…This made it difficult to measure the Doppler shift and the Rayleigh linewidth very accurately in order to obtain velocity and temperature estimates. The experiment presented here was set up initially in a 90 o scattering configuration using a single-point, fiber-coupled imaging approach, rather than the direct-imaging configuration used previously 13 to simplify the optical system and concentrate on the analysis of only the centermost fringe in the interference pattern in an effort to investigate the capabilities of the LC etalon. Data was acquired with the LC etalon as well as a fused silica (FS) solid etalon with similar spectral frequency resolution but with a higher FSR for comparison.…”

Simulation and high-precision wavelength determination of noisy 2D Fabry–Pérot interferometric rings for direct-detection Doppler lidar and laser spectroscopy

“…A FI-type FPI was the first one to be tested on aircraft [25,26] for wind speed measurements. FPIs are applied in scanning mode for plasma jet Rayleigh scattering measurements to determine gas temperature and velocity profiles of plasmas [27], in planar Doppler velocimetry [28] or, similar to our approach, in imaging mode to measure the flow properties by Rayleigh scattering in a small supersonic wind tunnel [29] via the locations of interference fringes [30] on a two-dimensional (2D) charge-coupled device (CCD). Among other Doppler lidar methods that use FPIs with 2D information are the image plane detector (IPD) for the Dynamics Explorer spacecraft [31], which allows for circular-pixel ringdetection, and the circle-to-line interferometer optical system (CLIO) [32,33], which uses a reflective cone to convert circular fringes from a FPI into a linear series of spots on a CCD.…”

Two-dimensional interferometric Rayleigh scattering velocimetry using multibeam probe laser

“…For example, the change of ambient temperature can cause the movement of the interference fringes, which leads to an increase in the measurement error and even the failure of the velocity. 12 Aiming at this problem, a method of simultaneously recording the reference interference signal and flow interference signal is needed. But the detection method of a laser sheet can result in the overlap of the reference interference signal and flow interference signal, which causes identification difficulty.…”