System for measuring Mueller matrix spectrum in real time and measuring method thereof

Abstract

The invention discloses a system for measuring a Mueller matrix spectrum in real time. The system comprises a light source, an optical fiber, a collimation system, a polarizer, a first delayer, a second delayer, a sample table, a third delayer, a Wollaston prism and a spectrograph group which are sequentially arranged in an incident direction of incident light. The invention further discloses a method for measuring the Mueller matrix spectrum in real time. Fourier transform, channel filtering and inverse Fourier transform are carried out on spectral intensity obtained by spectrographs, a Stokes vector S emitted from the surface of a measured sample can be restored, Fourier transform, channel filtering and inverse Fourier transform are carried out on four Stokes parameters in S such that spectrums of 16 Mueller matrix elements can be restored. According to the invention, the channel crosstalk is avoided, the measurement accuracy is high, and the operability is strong.

Description

technical field [0001] The invention belongs to the technical field of polarization spectrum measurement, relates to a system for real-time measurement of Mueller matrix spectrum, and also relates to a method for real-time measurement of Mueller matrix spectrum. Background technique [0002] The Mueller matrix can completely describe the polarization response properties of the object to light. By obtaining the Mueller matrix spectrum of the tested sample, many optical characteristics of the tested sample can be obtained, such as depolarization effect, anisotropy of surface etching and asymmetry of the cross section. . As a new type of optical detection method, Mueller matrix spectral measurement technology has broad application prospects in the fields of integrated circuit manufacturing, flat panel display, and biomedical diagnosis. At present, only a few scientific research institutions in the world carry out relevant research work. In particular, the instruments for real...

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Problems solved by technology

At present, only a few scientific research institutions in the world carry out relevant research work

In particular, the instruments for real-time acquisition of Mueller matrix spectra are still in the stage of principle exploration and experimental verification, and their technical means are not yet mature.

[0003] At present, there are mainly two types of conventional Mueller matrix spectral measurement methods in the world: one is carried out in time order, and the compensator of the polarizer arm and the polarizer arm is set at a certain rate ratio 5ω:mω (ω is the base of the coaxial motor. Frequency, m is a non-zero integer and not equal to 5 or 10) Rotation produces different time modulation frequencies, and obtaining all 16 Mueller matrix elements of the sample through Fourier transform demodulation requires detector readings N=4m+21 times to ensure The complete waveform analysis is completed within one optical period T=π / ω, and the time spent is t=N×t 0 (t 0 is the readout time of the detector), the longer measurement time is not suitable for the situation where the measured Mueller matrix changes rapidly with time, and the two moving parts in the system increase the probability of system error

The other is to modulate all 16 elements of the measured Mueller matrix to 37 different frequency channels through frequency modulation, and use channel filtering and Fourier transform demodulation to obtain the spectrum of all 16 elements of the Mueller matrix. Since there are no moving parts in the system, static real-time measurement can be realized (the measurement time is determined by the detector readout time), but when the measured Mueller matrix has sharp characteristic peaks, there will be serious channel crosstalk, which will affect the measurement accuracy and precision , and the spectral resolution of the restored Mueller matrix is ​​much smaller than that of the spectrometer, so it is only suitable for the case where the measured Mueller matrix changes slowly with wavelength

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