Shanwen Zhang

300 mm ruling engine producing gratings and echelles under interferometric control in China

The designs of 300xa0mm ruling engine producing gratings and echelles under interferometric control (CIOMP-2) are presented. A new ruling-tool carriage system and its driving mechanism—which are easy to manufacture—are proposed. A new blank carriage system, controlled by a dual-frequency laser interferometer and a piezoelectric actuator, is designed. The CIOMP-2 ruling engine can now rule grating blanks with dimensions up to 300u2009u2009mm×300u2009u2009mm, and mainly rules gratings with grating constants between 10 and 2400u2009u2009lines/mm. The wavelength range of CIOMP-2 gratings is from ultraviolet to mid-infrared wavelengths. Experiments show that the new ruling-tool carriage system works well and stability of motion is improved with the help of a flexure-hinge structure, and the threefold standard deviation values of the blank carriage positioning errors are less than ∼5u2009u2009nm. For 600u2009u2009line/mm gratings (diffraction order m=−1), the scatter intensities and ghosts reach 10−5 of the maximum intensity. The scatter intensities and ghost of gratings ruled with CIOMP-2 are low, and no Rowland ghosts are visible. The gratings ruled by CIOMP-2 have high diffraction efficiency and resolving power. CIOMP-2 can also produce varied-line-space, bend-line, and aberration-reducing gratings and echelles.

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.

0.95 W high-repetition-rate, picosecond 335 nm laser based on a frequency quadrupled, diode-pumped Nd:YVO(4) MOPA system.

An efficient all-solid-state picosecond (ps) ultraviolet (UV) laser at 335 nm was demonstrated based on frequency quadrupling of a mode-locked 1342 nm MOPA system. An output power of 0.95 W was obtained under a fundamental wave power of 16.38 W, corresponding to a conversion efficiency of 5.8% from infrared to UV. The repetition rate and pulse duration were 77 MHz and 20.2 ps, respectively. The beam quality factor M(2) was measured to be 1.56. This is, to the best of our knowledge, the highest output power at 335 nm.

Ruling of echelles and gratings with a diamond tool by the torque equilibrium method

Ruling of echelles and gratings by the torque equilibrium method is proposed to eliminate corrugated grating lines, rough blazed grating surfaces, and complex fabrication work such as step-by-step diamond tool deflection. A mathematical model of the torque equilibrium between the diamond tool and the metallic film during the ruling process is deduced to realize optimized diamond tool geometrical parameter design. Then, two echelles with identical areas of 80u2009u2009mm×100u2009u2009mm are separately ruled using the traditional deflecting tool ruling method and the proposed method, and the scatter light results for the two echelles are 9.6×10−4 and 3.1×10−4, respectively.

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 79u2009u2009grooves/mm, a grating with 768u2009u2009grooves/mm, and a high-density grating with 6000u2009u2009grooves/mm. The results show that our methods effectively reduce groove error in ruled gratings.