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Aiming at the problem of the resolution reduction in a miniaturized grating spectrometer, we presented a method to improve its spectral resolution by inserting a tunable Fabry-Perot filter into its optical path before the grating. The Fabry-Perot filter was designed to filter out a partial spectrogram and separate the original undistinguishable spectral lines so as to make their actual wavelengths can be detected. The different cavity length of the Fabry-Perot filter is corresponding to the different separated partial spectrogram. Combining all the separated partial spectrograms, an entire spectrogram with improved resolution can be achieved. Experimentally, the spectral resolution of a grating dispersive system was improved from 2 nm to 1.2nm in a broad spectral range by insetting a homemade tunable Fabry-Perot filter, which demonstrated the feasibility of this scheme. The tunable Fabry-Perot filter is fit for miniaturization by using MEMS technology and is able to work as an independent module. The method proposed provides a potential way to improve the spectral resolution without reducing the spectral range of the existing miniaturized grating spectrometers.

A recent improvements in charge exchange recombination spectroscopy (CXRS) diagnostic operated at the tokamak HL-2A is reported. With the presented diagnostic half the plasma minor radius at a spatial resolution of ~1.3 cm is covered and temporal resolution is 11 ms. Two spectrometers operating at different wavelengths for impurity ion and beam neutrals emission. Some first results are presented.

Coupling high-power laser diode array (LDA) beams into a multi-mode fiber is an important way to expand the LDA applications. Transforming LDA beam is an essential step for fiber-coupled LDA. Diffractive grating arrays are used to transform a bar LDA beam with the output power of 40 watts to realize the symmetry of BPPs in fast and slow axis directions in the paper. First, the specifications of the diffractive grating are calculated according to focusing and coupling bar LDA. Second, the 8-level binary diffractive gratings are fabricated based on the binary optical elements processing platform in our lab. Third, the experiment was carried out and results are gotten. The results show that the focusing spot size is about 200μm in diameter and the numerical aperture NA is 0.22, which agree with the calculated and simulated.