Comparison and application of wavelet transform and Kalman filtering for denoising in δ13CO2 measurement by tunable diode laser absorption spectroscopy at 2.008 µm: retraction.

The referenced article [Opt. Express25, A896 (2017)] has been retracted.

Comparison and application of wavelet transform and Kalman filtering for denoising in δ13CO2 measurement by tunable diode laser absorption spectroscopy at 2.008 µm.

We propose to use the wavelet transform and Kalman filter methods for processing noise in δ13CO2 measurement using laser absorption spectroscopy at 2.008 µm and they have been shown to be useful tool for reducing the intrinsic noise of the optical system. Through the performance comparison and analysis of these two denoising techniques for the intrinsic noise reduction of optical system, it can be found that the Kalman filter is a more suitable approach for the extraction of gas isotope measurement signal from a contaminated signal.

[Precision measurement of the birefringence of quartz crystal at 1 310 nm based on the spectroscopic ellipsometer].

In order to get the precision measurement of birefringence of quartz crystal at the communication wavelength 1310nm, based on the principle of precision measurement of phase difference between P and S polarized lights of spectroscopic ellipsometer, a method for precision measurement of birefringence of crystal was designed through the analysis of the Jones matrix under the transmission mode, and the precision measurement of birefringence of quartz crystal at 1 310 nm at room temperature (22 degrees C) was made, the measuring results and error analysis show that the precision reached 10(-6) level, this is the most precise birefringence parameter available, and it is of important significance for the improvement of designing precision of phase retardation devices of quartz.

[Spectral analysis method for precisely measuring specific rotation of quartz].

A spectral analysis method for precisely measuring specific rotation of quartz is proposed. The measuring principle is analyzed by using the method of optical matrix. The result indicates that the specific rotation of quartz can be exactly calculated by measuring the transmittance curve of a sample quartz plate sandwiched between two paralleled polarizing prisms, and the correctness of the method is validated by a designed experiment using a spectrophotometer. The data is analyzed, and the rotary dispersion formula of quartz is fitted. Compared with Lowry' formula, our formula is more accurate in visible spectral scope. Errors in the experiment is analyzed and the result shows that the measuring accuracy will be improved by choosing thicker quartz plate, longer wave band, lower scan speed, and smaller slit width.