Hongzhu Yu

Practical method study on correcting yaw error of 500 mm grating blank carriage in real time

We provided a method to correct the yaw error of a 500 mm grating blank carriage in real time, as the yaw error will bring down the quality of wavefront. We designed a structure with double piezoelectric devices to correct the yaw error. At the same time, to evaluate the correcting ability of our structure, we proposed a relative optical testing structure to verify the correcting accuracy by experiments. The experiment result showed that our method can accomplish the correction of yaw error in real time effectively, at the same time guaranteeing the grating quality.

Measuring method of diffraction efficiency for plane grating based on Fourier spectral technology.

A traditional double monochromatic measurement instrument of diffraction efficiency for a plane grating involves two major problems: one is the differences of output spectrum bandwidths during measurement of a standard reflection mirror and the tested grating; the other is overlapping of diffracted spectra, which influence testing accuracy of diffraction efficiency. In this paper, a new measuring method of diffraction efficiency based on Fourier spectral technology is presented. The mathematical model of diffraction efficiency is first deduced and then verified by ray tracing and Fourier optics simulation. The influences of the moving cube corners tilt error, lateral shift error, and maximal moving distance error on the measurement accuracy are analyzed in detail. The analyses provide theoretical references for designing diffraction efficiency instruments. Compared with the traditional diffraction efficiency measurement instrument with double monochromator structure, our method not only improves the measurement accuracy of diffraction efficiency but also has the advantage of high luminous flux, high spectral resolution, multiwavelength measurement in mean time, and high wavenumber accuracy.

Correcting groove error in gratings ruled on a 500-mm ruling engine using interferometric control

Groove error is one of the most important factors affecting grating quality and spectral performance. To reduce groove error, we propose a new ruling-tool carriage system based on aerostatic guideways. We design a new blank carriage system with double piezoelectric actuators. We also propose a completely closed-loop servo-control system with a new optical measurement system that can control the position of the diamond relative to the blank. To evaluate our proposed methods, we produced several gratings, including an echelle grating with 79  grooves/mm, a grating with 768  grooves/mm, and a high-density grating with 6000  grooves/mm. The results show that our methods effectively reduce groove error in ruled gratings.

Application of photoresist melting method to the fabrication of holographic grating

A new technique of reducing surface roughness of photoresist grating is presented. In this paper, photoresist melting method, which is low-cost, short-period and easy realization, is presented. In addition, the influence of photoresist melting on the groove profile of the photoresist grating is investigated. Experimental results show that the surface roughness reduces due to surface tension, when developed photoresist is heated to be melting state by this method. In experiment, when the melted photoresist grating is etched by ion beam, the surface relief grating possessing preferable groove profile is obtained on K9 glass substrate, then the surface is evaporated by aluminum using vacuum evaporation, holographic grating with preferable groove profile is successively fabricated.