非晶氮化硅分束－聚焦集成二元位相型光学元件

AMORPHOUS SILICON NITRIDE SPLITTING-FOCUSSING INTEGRATED BINARY-PHASE OPTICAL ELEMENTS

报道了自行设计的将二维Ｄａｍｍａｎｎ光栅和Ｆｒｅｓｎｅｌ波带板集成为一体的同时具有分束和聚焦功能的二元位相型光分束器，并用等离子体增强化学汽相淀积法（ＰＥＣＶＤ）制备的非晶氨化硅（ａ－ＳｉＮｘ：Ｈ）薄膜制作了这样的元件，成功地实现了设计的功能，分束阵列为３×３，焦距１８ｃｍ，分束后的光强分布相对误差小于５％．

We report a self-designed binary-optical beam splitter combined with a two dimensional Dammann grating and a Fresnel zone plate which have functions of both beam splitting and focussing. We achieve this element by means of amorphous silicon nitride (a-SiNx:H) thin films,.taking advantages of the transparent, stable, durable, and variable properlies of the refractive index of such a material.a-SiNx:H thin films are deposited on Corning 7059 glass substrate at 250℃ by r.f.PECVD with the reactant of 10 SCCM SiH4 and 70 SCCM AH3 mixtures. The reactingpressure is 250 mTorr and t.f. power 50W. The film has a refractive index at 633urn of 1.8.The thickness of nitride required for the phase delay is λ/ 2(n-1), for deposition rate of 0.1nm / see, the deposition time is fixed at 3700 sec.We consider combining a Dammann grating and a Fresnel zone plate in the same pattern. Dammann grating is to split optical beam and Fresnel.zone plate is to focus the beam.The transmissives are TDamm = exp[iΦDamm(X,y)] and Tlenx= exp[iΦlens(x,y)] for Dammann grating and Fresnel zone plate, respectively, and the total transmissive is Tsplit= TDamm· Tlens = exp[iΦsplii(x,y)]. The calculated pattern is plotted with a computer and photographed to make a mask. Then the pattern is transferred to silicon nitride film by photolithography.We have obtained an uniform and focused array of beams generated by the beam splitter. The split arrays of Dammann grafting are 3× 3 and the focus of Fresnel zone plate is 18cm. The relative distribution error of optical intensity of split beam is less than 5%.