We describe a new kind of symmetric color separation grating (SCSG), which can be applied to separate the frequency-tripling (3ω)light from the basic (1ω) and frequency-doubling (2ω)lights. The profile of the proposed SCSG is a three-level symmetric structure in one period, thus it is easy to fabricate it with the much improved tolerance of mask misalignment without the decrese of the efficiency of the frequency-tripling light. We have analyzed the principles of the SCSGs by employing the scalar diffraction theory and fabricated them experimentally by means of binary optics technology. The theoretical and experimental results demonstrated that the proposed SCSGs can be made in a comparatively easy way for the symmetric structure that can effectively avoid the effect of the fabrication error due to mask misalignment, thus higher manufacturing yield and lower cost can be achieved.
Inductively Coupled Plasma (ICP)can achieve high density plasma in low pressure,so it has a number of significant advantages such as improved etching rates,better profile control,improved uniformity, greatly increased selectivity and a dramatic reduction in radiation damage and contamination. In optics,quartz is an ideal optical material with transmitting spectral range from deep ultraviolet to far infrared.So we systematically studied the etching characteristics
of quartz by using a Inductively Coupled Plasma (ICP)etching system.In the xperim nts,the gas was the mixture of CHF<sub>3</sub>,O<sub>2</sub> and Ar,and the chamber pressure was about 10 mTorr.Th influences of gas flow rate and the power of the
radio frequency on etching rate were optimized. The uniformity and repeatability of the etching technology were also studied. After residue mask material was removed by wet chemical solution, no polymer was observed on the surfaces of samples,and the surfaces of the fabricated quartz elements were smooth and clean. The optimized etching process is important for the fabrication of micro-optical lements based on quartz. Using this etching process, many gratings such as Dammann grating, rectangular groove grating, and optical disk grating can be fabricated successfully.