A kind of polarization beam splitting/close nanoscale grating of bundle and preparation method thereof that is used for
Technical field
The present invention relates to a kind of polarization beam splitting/close nanoscale grating of bundle and preparation method thereof that is used for, be specifically related to a kind of artificial optical crystal material of nanoscale that utilizes and make micro-optical device, especially for polarization beam splitting/the close design and the method for making of bundle nanoscale grating.
Background technology
Optical polarization beam splitter/the bundling device that adopts the artificial optical crystal material of nanoscale to make, the device that its performance has reached even has been better than adopting the traditional double refractive material to be made have been demonstrated by NanoOpto company in U.S. NFOEC in 2002 meeting.Be subjected to the common concern of optic communication device industry.Its nanocomposite optical crystalline material sample has entered the laboratory of many large-scale optical devices manufacturer.
Adopting the artificial optical crystal of nanoscale to make optical communication is a simple application of nanocomposite optical crystal with polarization beam splitting/bundling device.The nanoscale grating that utilizes its surface with P polarized light and S polarized light separately or the function that merges can also be used to constituting the basic components and parts of various optical communication systems such as photoswitch, electric-controlled adjustable optical attenuator, Interleaver, light circulator.For visible light and near infrared light, when the working ability of grating when micron dimension is brought up to nanometer scale, the Light Diffraction Effect complete obiteration at this moment that past people is familiar with.This nanoscale grating pair lambda1-wavelength is insensitive, and is but very responsive to the polarization of incident light attitude, and its first application is to can be used as a kind of synthetic birefringence crystalline material, can be written as for two kinds of polarized light refractive index:
IE mould n
Te 2=fn
1 2+ (1-f) n
2 2
TM mould n
Tm 2=n
1 2n
2 2/ [fn
2 2+ (1-f) n
1 2]
N wherein
1Be the refractive index of grating backing material, n
2Being the refractive index of packing material in the grating gap, can be air or vacuum.F is the grating fill factor, curve factor, is defined as f=t/a.Compare with traditional natural birefringence crystal, this artificial lens can directly be brought the wave plate of doing zero level, as 1/4 or 1/2 wave plate or the like.Make it be particularly suitable for being used for the optic communication device of structural wideband to the insensitivity of wavelength.Above-mentioned artificial crystal material is transformed a little, can be made a kind of optical element of directly two kinds of polarization states being separated or being merged.
Do the polarized light partial wave and wave multiplexer has had report abroad with grating, former existing United States Patent (USP) comprises 6243199,6288840,6122103.Up to the present, the structure of report mainly is the top that the metal film grizzly bar is positioned at the grating back both at home and abroad.As United States Patent (USP) 6122103 is exactly this structure, sees shown in Figure 1ly, and the metal grizzly bar on the grating back plays reflex to the TM mould.Can cause the surface of artificial material fragile after introducing the metal grizzly bar.Though existing in the past people attempts covered with protective film on grating, as United States Patent (USP) 6288840.But diaphragm adheres to too poor on metal gate, in fact is difficult to realize.Therefore how to protect the surface of nanometer grating to be actually a key that realizes nanometer grating practicability.
The method for making of nanoscale grating mainly contains the deep ultraviolet holographic exposure before on the scheme of specific implementation nanoscale grating, electron beam exposure method and Nanoimprint technology, and the United States Patent (USP) that comprises has 5772905.But grating or area that said method is made are less, or the live width of grating is thin inadequately.Therefore how breaking through the restriction on the live width, realize the microfabrication of nanometer scale, obtain the large tracts of land size simultaneously, also is the major obstacle of pendulum in nanometer grating practicability process.
Summary of the invention
The present invention is in order to overcome the prior art above shortcomings, adopts synchrotron radiation light source to make and a kind ofly has the polarized light branch and involve the Performances of Novel Nano-Porous meter level grating that closes wave energy.The nanoscale grating is all had breakthrough on large tracts of land and live width; And the structure of nanoscale grating improved, overcome nanoscale grating fragile obstacle in surface in the practicability process.
Technical scheme of the present invention: nanoscale grating of the present invention; it is made of successively nanometer grating, metal grizzly bar, diaphragm; the metal grizzly bar that it is characterized in that the nanoscale grating is positioned at channel bottom, and deposits the diaphragm of one deck and substrate homogeneity on the upper strata of optical grating construction.
A kind of method for making of above-mentioned nanoscale grating comprises and makes common nanometer grating, plated film, throwing erosion grizzly bar, deposition protective seam, may further comprise the steps:
(1) at first makes common nanometer grating with the synchrotron radiation X-ray photoetching method;
(2) evenly be coated with metal film on the nanometer grating surface with highly reflective;
(3) remove metal film on the grating back;
(4) will cover grating surface with the material of substrate homogeneity with deposition process.
The method for making of described nanoscale grating, its deposition concrete grammar is:
(1) grating is placed with the right bank angle, will be deposited on grating back one side upper end face with the material of substrate homogeneity;
(2) the grating left bank is placed again, material is deposited on grating back opposite side upper end face, the sediment up to two ends links to each other;
(3) at last angle of deposit is just pulled, deposition materials covers grating surface.
The method for making of described nanoscale grating, its metal membrane material are Au/Cr film or other metallized multilayer film, the structure of metal film can be two-layer or two-layer more than.Why doing the Cr film earlier below the Au film, is because Cr film and general dielectric substrate material adhere to better.
Advantage of the present invention: the grating of new structure has comparatively ideal firm surface, can stand general acid, alkali, organic solvent scouring, also can be bonding with general optical cement and other opticses.It will overcome the major obstacle of nanometer grating in the practicability process, i.e. the very fragile problem in surface.Thereby give full play to the usefulness of this artificial optical material, increase work efficiency greatly.
Description of drawings
Fig. 1 is basic nanometer grating structure;
Fig. 2-the 6th, the present invention realize the manufacture craft flow process of this novel nano grating;
Fig. 2 is the basic nanometer grating that adopts the synchrotron radiation X-ray photoetching process to realize;
Fig. 3 evenly is coated with the metal film with highly reflective on the nanometer grating surface;
Fig. 4 removes metal film on the grating back with ion beam bevel etched method;
Fig. 5 removes the nanometer grating behind the metal film on the grating back;
Fig. 6 will cover grating surface with the material of substrate homogeneity with deposition process.
Fig. 7-9 adopts the method at angle of inclination to take logical with " bridge " on the grating back and deposition grating surface protective seam process synoptic diagram;
Fig. 7 places grating with the right bank angle, will be deposited on grating back one side upper end face with the material of substrate homogeneity;
Fig. 8 places the grating left bank, and material is deposited on grating back opposite side upper end face, and the sediment up to two ends links to each other;
Fig. 9 pulls angle of deposit just, and deposition materials covers grating surface.
Embodiment
Major technique of the present invention basis is to adopt the synchrotron radiation X-ray photoetching process to realize common nanoscale optical grating construction.Utilize X-ray lithography to obtain nano-micro structure and in the laboratory, had comparatively ripe technology basis, but in the practicability process, large tracts of land, inhomogeneity requirement have proposed new requirement to photoetching process.By improving photoetching step device, further investigation photoetching process, can realize the making of large-area nano grating and the homogeneity of assurance microstructure.With respect to the deep ultraviolet laser holographic exposure method of present employing, its live width can be from improving about 200nm to the 100nm.With respect to the electron beam exposure method, on the area size of material, can expand 10 centimetres of magnitudes to from the millimeter magnitude.We adopt synchrotron radiation light source to make nanometer grating, on the large tracts of land of nanometer grating and live width important breakthrough are arranged all.
Fig. 1 be traditional nanometer grating structure it be the channel bottom of grating by common nanometer grating 1, metal grizzly bar 1-3,1-2.
The present invention proposes a kind of new construction in order to overcome the fragile shortcoming in surface of nanometer grating in practicality.Its key is that the metal grizzly bar 2-2 of nanoscale grating is positioned at channel bottom 1-2, and deposits the diaphragm 4 of one deck and substrate homogeneity on the upper strata of optical grating construction.
The concrete manufacturing process of this structure nano level grating is that common nanometer grating 1 can be made by the synchrotron radiation X-ray photoetching method; Evenly plate metallic reflective coating on 1 surface; The method of utilizing ion beam bevel etched or mechanical buffing etc. to have the removal function is removed the metallic reflective coating 2-2 on the back 1-2; Utilize sputter or electron beam evaporation or other membrane deposition methods then, will cover grating surface with substrate 1 connatural material and form diaphragm 4.
Adopt synchrotron radiation X-ray stepping exposure to make method such as Fig. 2-6 of nanoscale grating, may further comprise the steps:
(1) at first be to make basic nanometer grating, as Fig. 2 with the synchrotron radiation X-ray photoetching method;
(2) evenly be coated with the metal film with highly reflective on the nanometer grating surface, metal material can be Au/Cr film or other metallized multilayer film, the structure of metal film can be two-layer or two-layer more than, as Fig. 3;
(3) mechanical buffing or ion beam bevel etched method are removed the metal film on the grating back, as Fig. 4: by the ion beam of plasma generation be etched storeroom generation physics, chemical reaction, the microfabrication process of carrying out is ion beam etching, if microfabrication is carried out at the inclination angle between adjustment substrate and the ion beam, be angle-tilt ion bundle etching.Be ion beam direct projection direction and grating surface out of plumb, the angle of grating slope is as the criterion to the direct projection of channel bottom metal film to avoid ion beam.Grating after the etching such as Fig. 5.
(4) will cover grating surface with the material of substrate homogeneity with the inclined deposition method.Fig. 6 promptly is a nanoscale grating of the present invention.
The deposition process step is as follows:
(1) will place with the right bank angle as the grating after Fig. 5 etching, and adopt the deposition process at angle of inclination will be deposited on grating back one side upper end face 4-1, as Fig. 7 with the material of substrate homogeneity;
(2) the grating left bank is placed again, still adopt the method at angle of inclination that material is deposited on grating back opposite side upper end face 4-2, it is logical that " bridge " on the grating back taken, as Fig. 8;
(3) at last angle of deposit is just pulled, continued material is deposited on grating surface, up to the protective seam 4 that adequate thickness is arranged, as Fig. 9.