CN104570207A - Large-angle auto-collimation photonic crystal and collimation quantitative method thereof - Google Patents

Abstract

The invention provides a large-angle auto-collimation photonic crystal and a collimation quantitative method of the photonic crystal. The large-angle auto-collimation photonic crystal at least comprises a rectangular lattice photonic crystal dielectric cylinder and a single-row anti-reflection dielectric cylinder which is located outside the photonic crystal and has the anti-reflection layer effect. The photonic crystal dielectric cylinder and the anti-reflection dielectric cylinder are located in air dielectric and can be obtained by etching silicon on a top layer of an SOI substrate. The photonic crystal has the advantages that collimation of constant-frequency contours of the photonic crystal is quantified on the basis of a least square method, and auto-collimation light beam propagation can be achieved by changing the lattice symmetry of the photonic crystal; meanwhile, by optimizing structure parameters of the single-row photonic crystal dielectric cylinder, large-angle incident beams can be efficiently coupled to enter the auto-collimation photonic crystal, the manufacturing process and the CMOS process are compatible completely, the complex process is avoided, and the processing cost is low.

Description

A kind of accurate autocollimation photonic crystal of wide-angle and collimation quantivative approach thereof

Technical field

The present invention relates to semi-conductor photoelectronic field, particularly relate to the accurate autocollimation photonic crystal of a kind of wide-angle and collimation quantivative approach thereof.

Background technology

Along with the continuous reduction of si-substrate integrated circuit characteristic dimension, the electrical interconnection technology based on copper-connection due to the factors such as power consumption is large, signal delay more and more difficulty meet the highdensity communication requirement of chip chamber.Light network technology due to possess band roomy, low in energy consumption, postpone short, without crosstalk and the advantage such as coupling and electromagnetic compatibility, become the gordian technique meeting supercomputing and magnanimity information transmission requirement.It is integrated that silicon based opto-electronics integrated technology can realize photoelectricity, can be mass-produced, and has the advantage of low cost and two-forty simultaneously, becomes the gordian technique solving interconnection problems gradually.

Isolate supports (Silicon-on-Insulator, SOI) is a kind of silica-base material system of uniqueness, adopts this material to make optoelectronic device and is conducive to compatible ripe CMOS technology, realize large-scale photoelectricity integrated.But common SOI optical waveguide size is comparatively large, and corresponding devices difficult realizes highdensity integrated chip, so the concept of photonic crystal is arisen at the historic moment.

So-called photonic crystal, refers to the artificial micro-structure of the medium wavelength dimension periodic arrangement of different refractivity, has photon band gap (PBG), photon local, negative refraction, the characteristics such as autocollimation.Photonic crystal can to the manipulation of photon based on these characteristics, for photoelectricity in the future and photon integrated chip open a new road.

Photonic crystal is divided into 1D, 2D and 3D photonic crystal with the space periodic of material arrangement difference.The 3D photonic crystal producing complete photonic band gap also has certain difficulty in making, and therefore, the 2D photonic crystal with advantages such as flexible design, manufacture craft are relatively simple is the optimal selection constructing photon crystal device at present.

Autocollimation phenomenon is the key property of photonic crystal, and its light beam is overcome characteristic that diffraction effect weakening demonstrates rectilinear propagation, has the technological advantage of low cost, high integration.New-type photon crystal device based on autocollimation phenomenon is developed in succession, as without channel waveguide, sub-wavelength imaging etc., but traditional autocollimation phenomenon limits by incident angle, and because the factors such as refractive index, mould field and group-velocity mismatch make photonic crystal coupling efficiency very low, these factors limit the application of device in large-scale integrated photon chip based on photon crystal self-aligning phenomenon.

Summary of the invention

The shortcoming of prior art in view of the above, the object of the present invention is to provide the accurate autocollimation photonic crystal of a kind of wide-angle and collimation quantivative approach thereof, for solving the problems such as autocollimation phenomenon limits by incident angle, photonic crystal coupling efficiency is low in prior art.

For achieving the above object and other relevant objects, the invention provides the accurate autocollimation photonic crystal of a kind of wide-angle, the accurate autocollimation photonic crystal of described wide-angle at least comprises:

The photonic crystal dielectric posts of rectangle crystalline network arrangement, for realizing the accurate autocollimation transmission of wide-angle;

And the anti-reflecting layer between described photonic crystal dielectric posts and incident beam, described anti-reflecting layer comprises the antireflection dielectric posts of single periodic arrangement.

Preferably, described photonic crystal dielectric posts and described antireflection dielectric posts can utilize mask, electron beam exposure, ion etching, dry etching, wet etch techniques to be formed on semiconductor material substrate silicon-on-insulator.

Preferably, the material of described photonic crystal dielectric posts and described antireflection dielectric posts is silicon, and refractive index is 3.5.

Preferably, the radius r=0.3a of described photonic crystal dielectric posts, grating constant ratio beta=b/a, wherein, a, b are respectively the grating constant of photonic crystal in x, y direction, the spacing namely on x, y direction between adjacent photonic crystal dielectric posts.

Preferably, described photonic crystal is set as 400nm at the grating constant a in x direction.

Preferably, described grating constant ratio beta is not less than 2.3.

Preferably, the cycle of described antireflection dielectric posts is b.

Preferably, the distance d of described anti-reflecting layer and described photonic crystal interfacial medium post is optimized by the incident angle demarcation interval of described incident beam _arland the radius r of described antireflection dielectric posts _arl; Make the radius r of described antireflection dielectric posts _arl=r, wherein r is the radius of described photonic crystal dielectric posts, the distance d of scanning coupling efficiency and described anti-reflecting layer and described photonic crystal interfacial medium post _arland the relation between the incident angle θ of described incident beam, optimize the distance d of described anti-reflecting layer and described photonic crystal interfacial medium post _arl; Scan the radius r of coupling efficiency and described antireflection dielectric posts on this basis _arland the relation between the incident angle θ of described incident beam, optimize the radius r of described antireflection dielectric posts _arlto improve the coupling efficiency of described incident beam.

Preferably, if the incident angle θ of described incident beam is between 0 ° ~ 20 °, then the distance d of described anti-reflecting layer and described photonic crystal interfacial medium post _arl=3.28a, the radius r of described antireflection dielectric posts _arl=0.26a.

Preferably, if the incident angle θ of described incident beam is between 20 ° ~ 30 °, then the distance d of described anti-reflecting layer and described photonic crystal interfacial medium post _arl=3.44a, the radius r of described antireflection dielectric posts _arl=0.26a.

For achieving the above object and other relevant objects, the present invention also provides the collimation quantivative approach of the accurate autocollimation photonic crystal of above-mentioned wide-angle, and described collimation quantivative approach at least comprises:

Utilize least square method to define the straight line factor of equifrequency line, determine described grating constant ratio beta according to the straight line factor of described equifrequency line, the accurate autocollimation realizing described photonic crystal by adjusting described grating constant ratio beta is propagated.

As mentioned above, the accurate autocollimation photonic crystal of wide-angle of the present invention and collimation quantivative approach thereof, have following beneficial effect:

The accurate autocollimation that wide-angle of the present invention accurate autocollimation photonic crystal and collimation quantivative approach thereof realize wide-angle light beam by the photonic crystal dielectric posts that rectangle crystalline network arranges is propagated, arrange by introducing one the high-level efficiency coupling that dielectric posts realizes incident beam again, the complicacy of preparation technology can be reduced.Meanwhile, the quantivative approach proposed based on least square method can mathematically describe photonic crystal collimation, for photonic crystal practical application in optoelectronic devices provides the foundation.

Accompanying drawing explanation

Fig. 1 is shown as wide-angle of the present invention accurate autocollimation photonic crystal two-dimensional structure schematic diagram.

Fig. 2 ~ Fig. 5 is shown as the relation schematic diagram between wide-angle of the present invention accurate autocollimation photonic crystal equifrequency line and grating constant ratio.

Fig. 6 is shown as the relation schematic diagram between the linearity factor based on least square method of the present invention and grating constant ratio.

Fig. 7 ~ Fig. 9 is shown as the mould field pattern of the accurate autocollimation photonic crystal of wide-angle of the present invention.

Figure 10 is shown as the relation schematic diagram between the distance of coupling efficiency and described anti-reflecting layer and described photonic crystal interfacial medium post and the incident angle of described incident beam.

Figure 11 ~ Figure 12 is shown as the relation schematic diagram between the radius of coupling efficiency and described antireflection dielectric posts and the incident angle of described incident beam.

Figure 13 is shown as photonic crystal of the present invention and the coupling efficiency relation schematic diagram after adding anti-reflecting layer under different angles.

Element numbers explanation

1 photonic crystal dielectric posts

2 antireflection dielectric posts

3 air dielectrics

Embodiment

Below by way of specific instantiation, embodiments of the present invention are described, those skilled in the art the content disclosed by this instructions can understand other advantages of the present invention and effect easily.The present invention can also be implemented or be applied by embodiments different in addition, and the every details in this instructions also can based on different viewpoints and application, carries out various modification or change not deviating under spirit of the present invention.

Refer to Fig. 1 ~ Figure 13.It should be noted that, the diagram provided in the present embodiment only illustrates basic conception of the present invention in a schematic way, then only the assembly relevant with the present invention is shown in graphic but not component count, shape and size when implementing according to reality is drawn, it is actual when implementing, and the kenel of each assembly, quantity and ratio can be a kind of change arbitrarily, and its assembly layout kenel also may be more complicated.

As shown in Figure 1, the invention provides the accurate autocollimation photonic crystal of a kind of wide-angle, the accurate autocollimation photonic crystal of described wide-angle at least comprises:

The photonic crystal dielectric posts 1 of rectangle crystalline network arrangement, for realizing the accurate autocollimation transmission of wide-angle.Radius r=the 0.3a of described photonic crystal dielectric posts 1, grating constant ratio beta=b/a, wherein, a, b are respectively the grating constant of photonic crystal in x, y direction, the spacing namely on x, y direction between adjacent photonic crystal dielectric posts.In order to ensure that photon crystal device is operated in the smaller wave band of loss, in the present embodiment, described photonic crystal is set as 400nm at the grating constant a in x direction.By adjusting described grating constant ratio beta, the accurate autocollimation that can realize photonic crystal is propagated, and described grating constant ratio beta is not less than 2.3.

And the anti-reflecting layer between described photonic crystal dielectric posts 1 and incident beam, described anti-reflecting layer comprises the antireflection dielectric posts 2 of single periodic arrangement.Described antireflection dielectric posts 2 is d with the distance of described photonic crystal interfacial medium post _arl, the radius of described antireflection dielectric posts 2 is r _arl, the cycle is b (namely described antireflection dielectric posts 2 aligns in the x direction with described photonic crystal dielectric posts 1), by optimizing d _arl, r _arlthe high-level efficiency that can the realize large angle incidence light beam accurate autocollimation that is coupled is propagated.

Described photonic crystal dielectric posts 1 and described antireflection dielectric posts 2 are in air dielectric 3.

Particularly, described photonic crystal dielectric posts 1 and described antireflection dielectric posts 2 can utilize mask, electron beam exposure, ion etching, dry etching, wet etch techniques to be formed on semiconductor material substrate silicon-on-insulator.

Particularly, the material of described photonic crystal dielectric posts 1 and described antireflection dielectric posts 2 is silicon, and refractive index is 3.5, and the refractive index of described air dielectric 3 is 1.

Incident beam all can realize accurate autocollimation afterwards with different angles incidence and propagate along x direction.

The present invention also provides the collimation quantivative approach of the accurate autocollimation photonic crystal of above-mentioned wide-angle, and described collimation quantivative approach is as follows:

The accurate autocollimation realizing described photonic crystal by adjusting described grating constant ratio beta is propagated:

There is provided an above-mentioned wide-angle accurate autocollimation photonic crystal, wherein a, b are respectively x, y direction grating constant, as shown in Figure 2, the pure silicon photonic crystal dielectric posts 1 (refractive index is 3.5) of radius r=0.3a is in air dielectric (refractive index is 1), definition grating constant ratio beta=b/a.Increase described grating constant ratio beta and change photonic crystal lattice symmetry, normalized frequency f=0.2 (c/a) equifrequency line can be realized and become straight in whole first Brillouin zone by bending.As the equifrequency line of Fig. 2 ~ Figure 5 shows that normalized frequency f=0.2 (c/a), wherein, the equifrequency line that Figure 2 shows that grating constant ratio beta=1.25, the equifrequency line that Figure 3 shows that grating constant ratio beta=1.75, Figure 4 shows that the equifrequency line of grating constant ratio beta=2.3, Figure 5 shows that the equifrequency line of grating constant ratio beta=3.5, corresponding different grating constant ratio beta, with the increase of described grating constant ratio beta, the equifrequency line of normalized frequency f=0.2 (c/a) is tending towards smooth.

Utilize the method for least square to quantize the straight line quality of equifrequency line.First consider an accurate autocollimation equifrequency line, this curve can be expressed as Y=F (X), X and Y is in κ space, supposes straight-line equation

$\stackrel{\‾}{Y}=\mathrm{AX}+B---\left(1\right)$

Can mate this accurate autocollimation equifrequency line, A and B is coefficient, definition i is the sequence number of sampled point, utilizes minimal condition method, can obtain

A∑X _i ²+B∑X _i＝∑X _iY _i(2)

A∑X _i+nB＝∑Y _i(3)

And then can try to achieve

$A=\frac{\mathrm{n\Σ}{X}_i{Y}_i-\mathrm{\Σ}{X}_i\mathrm{\Σ}{Y}_i}{\mathrm{n\Σ}{X_i}^2-{\left(\mathrm{\Σ}{X}_i\right)}^2}B=\frac{\mathrm{\Σ}{Y}_i\mathrm{\Σ}{X_i}^2-\mathrm{\Σ}{X}_i\mathrm{\Σ}{X}_i{Y}_i}{\mathrm{n\Σ}{X_i}^2-{\left(\mathrm{\Σ}{X}_i\right)}^2}---\left(4\right)$

Finally, the straight line factor can be defined

L＝ΔL _max-ΔL _min(5)

Here ${\mathrm{\ΔL}}_{\max }={[Y-\stackrel{\‾}{Y}]}_{\max }={[Y-\mathrm{AX}-B]}_{\max }$ With ${\mathrm{\ΔL}}_{\min }={[Y-\stackrel{\‾}{Y}]}_{\min }={[Y-\mathrm{AX}-B]}_{\min }$ Minimum and maximum convexity respectively.Utilize formula (5) that the straight line factor L of equifrequency line can be obtained, as shown in Figure 6, the straight line factor L=8.09 × 10-4 of the straight line factor L=0.1743 of described grating constant ratio beta=1.25 correspondence, the straight line factor L=0.041 of described grating constant ratio beta=1.75 correspondence, the straight line factor L=0.01 of described grating constant ratio beta=2.3 correspondence, described grating constant ratio beta=3.5 correspondence, become large along with described grating constant ratio beta as seen, factor L is more and more less for straight line.Propagate when L=0 can realize strict autocollimation, corresponding described grating constant ratio beta is comparatively large, but for practical application, as long as L value is suitable just can meet application request.

For the light beam transmitted in accurate autocollimation photonic crystal, waist width can be expressed as λ is air medium wavelength, W0 and D (supposes D>=λ, D>=W ₀) represent initial waist width and transmission range.The corresponding more and more straight curve of less straight line factor L and more obvious autocollimation phenomenon.Strictly straight equifrequency line can be obtained as L=0, there is no the strict autocollimator beam of beam broadening, namely for any transmission range D, W (D)=W ₀.In the present embodiment, L is advised ₀=0.01 (now described grating constant ratio beta=2.3) are as the critical straight line factor, in this case, when Gaussian beam is initially girdled the waist, when transmission range reaches 100 λ, beam spread is less than 1%, can meet most of application request for so accurate autocollimator beam.

As shown in Fig. 7 ~ Fig. 9, choosing described grating constant ratio beta=2.3, described photonic crystal is set as 400nm at the grating constant a in x direction, radius r=the 0.3a of described photonic crystal dielectric posts, when normalized frequency f=0.2 (c/a), from different angle incident beams, all can realize accurate autocollimation and propagate.

By optimizing the distance d of described anti-reflecting layer and described photonic crystal interfacial medium post _arland the radius r of described antireflection dielectric posts _arlimprove the coupling efficiency of described incident beam:

Make the radius r of described antireflection dielectric posts _arl=r (wherein r is the radius of described photonic crystal dielectric posts), the distance d of scanning coupling efficiency and described anti-reflecting layer and described photonic crystal interfacial medium post _arland the relation between the incident angle θ of described incident beam.As shown in Figure 10, there is a d _arl(in the present embodiment, described anti-reflecting layer is preferably 3.28a with the distance of described photonic crystal interfacial medium post) high-level efficiency within the scope of 0 ° ~ 20 ° can be realized be coupled, be in like manner 20 ° ~ 30 ° at the incident angle θ of described incident beam and also there are d _arl(in the present embodiment, described anti-reflecting layer is preferably 3.44a with the distance of described photonic crystal interfacial medium post) can realize high-level efficiency and be coupled.At the distance d of the described anti-reflecting layer optimized and described photonic crystal interfacial medium post _arlbasis on, be the radius r optimizing described antireflection dielectric posts in 0 ° ~ 20 ° and 20 ° ~ 30 ° respectively at the incident angle θ of described incident beam _arlimprove coupling efficiency further.The radius r of scanning coupling efficiency and described antireflection dielectric posts _arland the relation between the incident angle θ of described incident beam.As shown in figure 11, in the present embodiment, in the scope that the incident angle θ of described incident beam is 0 ° ~ 20 °, the radius r of described antireflection dielectric posts _arlbe preferably 0.26a; As shown in figure 12, in the present embodiment, in the scope that the incident angle θ of described incident beam is 20 ° ~ 30 °, the radius r of described antireflection dielectric posts _arlbe preferably 0.26a.In the present embodiment only for 0 ° ~ 30 °, be divided into 2 intervals, different interval division can be done to larger angular range as the case may be in practical application, not repeat one by one in the present embodiment.

As shown in figure 13, not adding curve no ARL corresponding to described anti-reflecting layer at the incident angle θ of described incident beam is that within the scope of 0 ° ~ 30 °, coupling efficiency only has about 0.5; Add anti-reflecting layer ARL1 (d _arl=3.28a, r _arl=0.26a), the incident angle θ that greatly can improve described incident beam is the coupling efficiency between 0 ° ~ 20 °; Add anti-reflecting layer ARL2 (d _arl=3.44a, r _arl=0.26a), the incident angle θ that greatly can improve described incident beam is the coupling efficiency between 20 ° ~ 30 °.

Wide-angle of the present invention accurate autocollimation photonic crystal and collimation quantivative approach thereof carry out the collimation of quantitative photonic crystal equifrequency line based on least square method, change photonic crystal lattice symmetry and can realize the propagation of accurate autocollimator beam, simultaneously by optimizing the structural parameters of single photonic crystal dielectric posts, large angle incidence light beam energy efficient coupling can be made to enter accurate autocollimation photonic crystal, manufacture craft and CMOS technology are completely compatible, without the need to complicated technology, processing cost is low.

In sum, the invention provides the accurate autocollimation photonic crystal of a kind of wide-angle and collimation quantivative approach thereof, at least comprise the photonic crystal dielectric posts of rectangle crystalline network arrangement, for realizing the accurate autocollimation transmission of wide-angle; And the anti-reflecting layer between described photonic crystal dielectric posts and incident beam, described anti-reflecting layer comprises the antireflection dielectric posts of single periodic arrangement.Utilize least square method to define the straight line factor of equifrequency line, determine described grating constant ratio beta according to the straight line factor of described equifrequency line, the accurate autocollimation realizing described photonic crystal by adjusting described grating constant ratio beta is propagated; Make the radius r of described antireflection dielectric posts _arl=r, wherein r is the radius of described photonic crystal dielectric posts, the distance d of scanning coupling efficiency and described anti-reflecting layer and described photonic crystal interfacial medium post _arland the relation between the incident angle θ of described incident beam, optimize the distance d of described anti-reflecting layer and described photonic crystal interfacial medium post _arl; Scan the radius r of coupling efficiency and described antireflection dielectric posts on this basis _arland the relation between the incident angle θ of described incident beam, optimize the radius r of described antireflection dielectric posts _arlto improve the coupling efficiency of described incident beam.Wide-angle of the present invention accurate autocollimation photonic crystal and collimation quantivative approach thereof carry out the collimation of quantitative photonic crystal equifrequency line based on least square method, change photonic crystal lattice symmetry and can realize the propagation of accurate autocollimator beam, simultaneously by optimizing the structural parameters of single photonic crystal dielectric posts, large angle incidence light beam energy efficient coupling can be made to enter accurate autocollimation photonic crystal, manufacture craft and CMOS technology are completely compatible, without the need to complicated technology, processing cost is low.So the present invention effectively overcomes various shortcoming of the prior art and tool high industrial utilization.

Above-described embodiment is illustrative principle of the present invention and effect thereof only, but not for limiting the present invention.Any person skilled in the art scholar all without prejudice under spirit of the present invention and category, can modify above-described embodiment or changes.Therefore, such as have in art usually know the knowledgeable do not depart from complete under disclosed spirit and technological thought all equivalence modify or change, must be contained by claim of the present invention.

Claims (11)

1. the accurate autocollimation photonic crystal of wide-angle, is characterized in that, the accurate autocollimation photonic crystal of described wide-angle at least comprises:

The photonic crystal dielectric posts of rectangle crystalline network arrangement, for realizing the accurate autocollimation transmission of wide-angle;

And the anti-reflecting layer between described photonic crystal dielectric posts and incident beam, described anti-reflecting layer comprises the antireflection dielectric posts of single periodic arrangement.

2. the accurate autocollimation photonic crystal of wide-angle according to claim 1, is characterized in that: described photonic crystal dielectric posts and described antireflection dielectric posts can utilize mask, electron beam exposure, ion etching, dry etching, wet etch techniques to be formed on semiconductor material substrate silicon-on-insulator.

3. the accurate autocollimation photonic crystal of wide-angle according to claim 1, is characterized in that: the material of described photonic crystal dielectric posts and described antireflection dielectric posts is silicon, and refractive index is 3.5.

4. the accurate autocollimation photonic crystal of wide-angle according to claim 1, it is characterized in that: the radius r=0.3a of described photonic crystal dielectric posts, grating constant ratio beta=b/a, wherein, a, b are respectively the grating constant of photonic crystal in x, y direction, the spacing namely on x, y direction between adjacent photonic crystal dielectric posts.

5. the accurate autocollimation photonic crystal of wide-angle according to claim 4, is characterized in that: described photonic crystal is set as 400nm at the grating constant a in x direction.

6. the accurate autocollimation photonic crystal of wide-angle according to claim 4, is characterized in that: described grating constant ratio beta is not less than 2.3.

7. the accurate autocollimation photonic crystal of wide-angle according to claim 1, is characterized in that: the cycle of described antireflection dielectric posts is b.

8. the accurate autocollimation photonic crystal of wide-angle according to claim 1, is characterized in that: the distance d optimizing described anti-reflecting layer and described photonic crystal interfacial medium post by the incident angle demarcation interval of described incident beam _arland the radius r of described antireflection dielectric posts _arl; Make the radius r of described antireflection dielectric posts _arl=r, wherein r is the radius of described photonic crystal dielectric posts, the distance d of scanning coupling efficiency and described anti-reflecting layer and described photonic crystal interfacial medium post _arland the relation between the incident angle θ of described incident beam, optimize the distance d of described anti-reflecting layer and described photonic crystal interfacial medium post _arl; Scan the radius r of coupling efficiency and described antireflection dielectric posts on this basis _arland the relation between the incident angle θ of described incident beam, optimize the radius r of described antireflection dielectric posts _arlto improve the coupling efficiency of described incident beam.

9. the accurate autocollimation photonic crystal of wide-angle according to claim 1, is characterized in that: if the incident angle θ of described incident beam is between 0 ° ~ 20 °, then the distance d of described anti-reflecting layer and described photonic crystal interfacial medium post _arl=3.28a, the radius r of described antireflection dielectric posts _arl=0.26a.

10. the accurate autocollimation photonic crystal of wide-angle according to claim 1, is characterized in that: if the incident angle θ of described incident beam is between 20 ° ~ 30 °, then the distance d of described anti-reflecting layer and described photonic crystal interfacial medium post _arl=3.44a, the radius r of described antireflection dielectric posts _arl=0.26a.

The collimation quantivative approach of 11. 1 kinds of accurate autocollimation photonic crystals of the wide-angle as described in claim 1 ~ 10 any one, is characterized in that, described collimation quantivative approach at least comprises:

Utilize least square method to define the straight line factor of equifrequency line, determine described grating constant ratio beta according to the straight line factor of described equifrequency line, the accurate autocollimation realizing described photonic crystal by adjusting described grating constant ratio beta is propagated.