CN102879859A - Integrated optical branching device - Google Patents

Abstract

An integrated optical splitter, comprising: a substrate, a lower cladding layer is arranged on the substrate, a core layer is arranged on the lower cladding layer, and the core layer is composed of an input waveguide, a tapered waveguide, a first output waveguide and a second The output waveguide is composed of, the output end of the input waveguide is connected with the input end of the tapered waveguide, and the output end of the tapered waveguide is respectively connected with the input end of the first output waveguide and the input end of the second output waveguide. It is characterized in that, in the tapered waveguide A groove is provided on the waveguide, and the groove is located on the central axis of the tapered waveguide and adjacent to the output end of the tapered waveguide. The introduction of grooves in the tapered waveguide improves the matching degree of the mode field, so that the integrated optical splitter has the advantages of uniform power division ratio, low insertion loss, and large operating wavelength range. At the same time, the device has a compact structure, low processing difficulty, and The yield rate is high, and the application field of the device is expanded.

Description

The integrated-type optical branching device

Technical field

The present invention relates to a kind of waveguide type optical branching device for optical communication system, optical computer system and photon/optoelectronic integrated circuit, belong to the integrated optics technique field.

Background technology

Optical branching device is the base components of optical communication system, optical computer system and integrated optical device, and they are used as optical branching device or combiner in power splitter and optical interferometer, for example photoswitch, attenuator, modulator.Optical branching device mainly contains two kinds of fused tapered and planar waveguide-types.The production technology of fused tapered optical branching device is inconsistent because of the thermal expansivity that solidifies glue and quartz substrate, stainless-steel tube, and the degree of expanding with heat and contract with cold when variation of ambient temperature is just inconsistent, and this kind situation easily causes the optical branching device damage.The fused tapered optical branching device is discrete component, is not easy to realize that with other photonic device monolithic is integrated.

The planar waveguide-type optical branching device is to have the advantages such as volume is little, along separate routes way is many, and is easily integrated with photonic device realization monolithics such as waveguide type filter, laser instrument, detectors.At present, the planar waveguide-type optical branching device mainly adopts semiconductor technology (photoetching, burn into develop) to make, and the gap between output branch can not be eliminated fully; And along with the refringence of material increases, the relative width phase strain of output branch gap is large, the single mode waveguide width further dwindles, and the minimum clearance between the output branch still remains unchanged, and so in single mode waveguide, it is large that the relative width between output branch further becomes.Thereby for single mode waveguide, the high index-contrast material will cause the pattern match degree to reduce, to such an extent as to added losses increase, further increase difficulty of processing, reduce the yields of device, dwindle operating wavelength range, be difficult for being applied in the dense wavelength division multiplexing optical networks.And introduce catoptron in the Y bifurcation, and can further make the merit proportion by subtraction even, but can bring larger added losses then to increase insertion loss, generally to adopt multi-layer fabric decoration, difficulty of processing is large.

Summary of the invention

The invention provides a kind of have compact conformation, insertion loss is low, merit minute homogeneity is high and operating wavelength range is large integrated-type optical branching device.

The present invention adopts following technical scheme:

A kind of integrated-type optical branching device, comprise: substrate, be provided with under-clad layer at substrate, be provided with sandwich layer at under-clad layer, sandwich layer is comprised of input waveguide, tapered transmission line, the first output waveguide and the second output waveguide, the output terminal of input waveguide is connected with the input end of tapered transmission line, the output terminal of tapered transmission line is connected with the input end of the first output waveguide and the input end of the second output waveguide respectively, it is characterized in that, be provided with groove in tapered transmission line, and groove is positioned on the axis of tapered transmission line and is adjacent with the output terminal of tapered transmission line.

Compared with prior art, the present invention has following advantage:

Introduce groove (low-index regions) at the tapered transmission line place, improved the matching degree of mould field, make the integrated-type optical branching device have that the merit proportion by subtraction is even, insertion loss is low, the advantage that operating wavelength range is large.With respect to the optical branching device of making prism or growth low-refraction wedge district at the tapered transmission line place, its compact conformation, difficulty of processing is low, and the device yields is high, has expanded the application of device.

Description of drawings

Fig. 1 is the structural drawing of first example of integrated-type optical branching device sandwich layer.

Fig. 2 is the structural drawing of tapered transmission line.

Fig. 3 is the cross-sectional view of tapered transmission line.

Fig. 4 is the longitdinal cross-section diagram of tapered transmission line.

Fig. 5 is preparation technology's process flow diagram of waveguide.

Fig. 6 is the graph of a relation of groove width and number and branch's output energy.

Fig. 7 is the graph of a relation of groove number and branch's angle and branch's output energy.

Fig. 8 is the mould field pattern of tapered transmission line input end when operation wavelength is 1.55 μ m.

Fig. 9 is the mould field pattern of tapered transmission line output terminal when operation wavelength is 1.55 μ m.

Figure 10 is the output mould field pattern of the first output waveguide when operation wavelength is 1.55 μ m.

Figure 11 is the output mould field pattern of the second output waveguide when operation wavelength is 1.55 μ m.

Figure 12 is the structural drawing of second example of integrated-type optical branching device sandwich layer.

Figure 13 is the optical field distribution figure of integrated-type optical branching device when operation wavelength is 1.55 μ m.

1. input waveguides among the figure, 2. tapered transmission line, 3. groove, 4. the first output waveguide, 5. the second output waveguide, the 6. angle between the first output waveguide and the second output waveguide; I. substrate, II. under-clad layer, III. sandwich layer, IV. top covering.

Embodiment

A kind of integrated-type optical branching device, comprise: the substrate I, be provided with the under-clad layer II in the substrate I, be provided with the sandwich layer III in the under-clad layer II, the sandwich layer III is by input waveguide 1, tapered transmission line 2, the first output waveguide 4 and the second output waveguide 5 form, the output terminal of input waveguide 1 is connected with the input end of tapered transmission line 2, the output terminal of tapered transmission line 2 is connected with the input end of the first output waveguide 4 and the input end of the second output waveguide 5 respectively, it is characterized in that, be provided with groove 3 in tapered transmission line 2, and groove 3 is positioned on the axis of tapered transmission line 2 and is adjacent with the output terminal of tapered transmission line 2.In the present embodiment,

Upper surface in under-clad layer II and sandwich layer III is provided with the top covering IV; The quantity of groove 3 is 1 ~ 4, that is: the quantity of groove 3 is 1,2,3 or 4.

Fig. 1 is first example of the present invention, by input waveguide 1, and tapered transmission line 2, the first output waveguides 4 and the second output waveguide 5, groove 3 forms.1.55 the single-mode optics signal of mum wavelength is from input waveguide 1 input, through tapered transmission line 2, fraction light loss, remainder are coupled in the first output waveguide 4 and the second output waveguide 5.

Theoretical according to pattern analysis, be that z is constant to the lateral dimension of waveguide in direction of wave travel, frequency of light wave is fixed, propagation factor exp[j (β z-ω t) is namely arranged], wherein ω is circular frequency, β is propagation constant, by the Maxwell equation group, obtain following wave equation:

${\▿}^2\stackrel{\→}{E}+K_0^2{\mathrm{\ϵ}}_r\stackrel{\→}{E}=0---\left(1\right)$

K wherein ₀Be free space wave number, ε _r(x, y) described the waveguide cross-section index distribution, ε in the anisotropic medium _r(x, y) is tensor form.Follow according to the waveguide situation, reducible corresponding scalar or half vector equation of turning to of equation calculates thereby simplify.The task of pattern analysis is for given waveguide dimensions and certain frequency of light wave, determines propagation constant β value and corresponding mode profile.

A little less than not only can processing, bundle Law of Communication (BPM) leads device, and can process the waveguide device with sudden change refraction distribution, be widely used at present in the board design of optoelectronic device light transmission, lightwave transmission characteristics that can analysis device, the parameter of optimizing structure, to the transmission of mould field in device develop have advantages of directly perceived as can be known.BPM can do unified the processing to guided mode and radiation mode, does not need to discuss in addition the impact of branches angle size.And under certain conditions, only utilize the wave equation under the holography can process wide-angle light transmission problem.The BPM concept succinctly (is namely directly transmitted forward), counting yield is high, the program highly versatile, is the foundation of many commercial simulation softwards.

Be similar to down weak leading, can get monochromatic scalar Helmholtz (Helmholtz) equation by equation (1)

$\frac{{\&PartialD;}^2\mathrm{\&Phi;}}{\&PartialD;x^2}+\frac{{\&PartialD;}^2\mathrm{\&Phi;}}{\&PartialD;{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HDA00002034429700022.png,HDA00002034429700052.png"\; state="\{\{state\}\}">y</figure-callout>}}^2}+\frac{{\&PartialD;}^2\mathrm{\&Phi;}}{\&PartialD;{\mathrm{<figure-callout\; id="2"\; label="z"\; filenames="HDA00002034429700022.png,HDA00002034429700052.png"\; state="\{\{state\}\}">z</figure-callout>}}^2}+k{(x,y,z)}^2\mathrm{\&Phi;}=0---\left(2\right)$

Wherein scalar electric field E (x, y, z, t) is write as

E(x,y,z,t)＝Φ(x,y,z)e ^-jωt (3)

Form, K (x, y, z)=k ₀N (x, y, z), k ₀Be the wave number of free space, n (x, y, z) has described the refractive index spatial distribution.Order

$\mathrm{\&Phi;}(x,y,z)=u(x,y,z)e^{j\stackrel{\&OverBar;}{k}z}---\left(4\right)$

Wherein

Be a constant, represent the average phase of amount Φ and change, be referred to as with reference to wave number,

Be referred to as with reference to refractive index, obviously u is the slow variable of electric field Φ.In equation (4) substitution equation (2), obtain

$\frac{{\&PartialD;}^{2}u}{\&PartialD;z^2}+2j\stackrel{\&OverBar;}{k}\frac{\&PartialD;u}{\&PartialD;z}+\frac{{\&PartialD;}^{2}u}{\&PartialD;x^2}+\frac{{\&PartialD;}^{2}u}{\&PartialD;{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HDA00002034429700022.png,HDA00002034429700052.png"\; state="\{\{state\}\}">y</figure-callout>}}^2}+(k^2-{\stackrel{\&OverBar;}{k}}^2)u=0---\left(5\right)$

Consider that u changes slowly with z, in the equation (5) can ignore in first on the left side, then has

$\frac{\&PartialD;u}{\&PartialD;z}=\frac{j}{2\stackrel{\&OverBar;}{k}}(\frac{{\&PartialD;}^{2}u}{\&PartialD;x^2}+\frac{{\&PartialD;}^{2}u}{\&PartialD;{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HDA00002034429700022.png,HDA00002034429700052.png"\; state="\{\{state\}\}">y</figure-callout>}}^2}+(k^2-{\stackrel{\&OverBar;}{k}}^2)u)---\left(6\right)$

Equation (6) is the fundamental equation of three-dimensional BPM, ignores relevant y(or x) Xiang Zeke get simpler two-dimentional BPM fundamental equation.Can find out from equation (6), as long as given input field u (x, y, z=0), just can calculate Z the field distribution in 0 space.

Theoretical and bundle Law of Communication can realize the pre-separation of light signal through the light signal of the groove in the tapered transmission line, and the matching degree of the pattern of the first output waveguide 4 and the second output waveguide 5 improves the coupling loss reducing of optical branching device as can be known according to pattern analysis.Whole device layout is simple, and difficulty of processing is little; The design of the S type of the first output waveguide 4 and the second output waveguide 5 so that the separation of output waveguide light preferably, has further reduced the excessive loss of light signal.We can see that light just realized the even pre-separation of light signal before output waveguide in Fig. 9, and the even separation of light signal of having taken advantage of a situation progressively mild realization.

Fig. 2 is the structural drawing of tapered transmission line 2, and the embedding of groove 3 is so that light signal is in the situation that the very little pre-separation that realizes light signal of loss has improved the matching degree of tapered transmission line 2 outputs with the light patterns of the first output waveguide 4 and the second output waveguide 5.Fig. 3 is the cross-sectional view of waveguide.Fig. 4 is the longitdinal cross-section diagram of tapered transmission line.Fig. 5 is preparation technology's process flow diagram of waveguide, can find out that this waveguide difficulty of processing is low, practical.

The integrated-type optical power distributor manufacturing process that provides of the present invention is with reference to Fig. 5, and at first, layer overlay thickness is that 20 μ m refractive indexes are 1.46 pure silicon dioxide on silica-based.Then, the silicon dioxide that mixes of layer overlay again on pure silicon dioxide, the refractive index contrast of itself and pure silicon dioxide is between the 0.4%-1.5%.Subsequently, utilize the standard fine process on the silicon dioxide that mixes, to apply one deck photoresist and photoetching.At last, the silicon dioxide of layer overlay 20 μ m again above the waveguide after the photoetching again.

Can find out in Fig. 6,7,8,9,10,11,13 with respect to not having fluted integrated-type optical branching device, integrated-type optical power distributor provided by the invention makes the integrated-type optical branching device have that the merit proportion by subtraction is even, insertion loss is low, the advantage that operating wavelength range is large.With respect to the optical branching device of making prism or growth low-refraction wedge district at the tapered transmission line place, its compact conformation, difficulty of processing is low, and the device yields is high, has expanded the application of device.

With reference to Fig. 6, the graph of a relation of groove width and branch output energy, when groove width was the 1 μ m left and right sides, insertion loss was minimum, and the groove number when being three insertion loss drop to minimum.

With reference to Fig. 7, the graph of a relation of groove number and branch-waveguide energy has increased that the energy of Waveguide branching output obviously increases after the groove, and is that 7 insertion loss when spending are minimum in branch's angle.

With reference to Fig. 8, the mould field pattern of input waveguide.

With reference to Fig. 9, the mould field pattern of tapered transmission line output terminal has as can be seen from the figure been realized the pre-separation of the light under the low-loss state.

With reference to Figure 10, the output mould field pattern of the first output waveguide when operation wavelength is 1.55 μ m.

With reference to Figure 11, the output mould field pattern of the second output waveguide when operation wavelength is 1.55 μ m, and Figure 10 can find out that relatively their mould field distribution is almost identical, the merit minute homogeneity that demonstrates shunt is very high.

With reference to Figure 13, the transmission of input mould field in the integrated-type optical branching device develops situation when being 1.55 μ m for operation wavelength.Can find out at tapered transmission line 2 places, light signal is walked unhurriedly and has been realized the pre-separation of light, and then the low-loss output mould field amplitude that has entered the first output waveguide 4 and 5, two output waveguides of the second output waveguide of light signal is almost consistent, and the merit proportion by subtraction is even.

Claims (3)

1. An integrated optical splitter, comprising: a substrate (I), with a lower cladding layer (II) on the substrate (I), and a core layer (III) on the lower cladding layer (II), The core layer (Ⅲ) is composed of an input waveguide (1), a tapered waveguide (2), a first output waveguide (4) and a second output waveguide (5). The output end of the input waveguide (1) is connected to the tapered waveguide (2 ), the output end of the tapered waveguide (2) is respectively connected to the input end of the first output waveguide (4) and the input end of the second output waveguide (5). It is characterized in that the tapered waveguide (2) ) is provided with a groove (3), and the groove (3) is located on the central axis of the tapered waveguide (2) and adjacent to the output end of the tapered waveguide (2). 2. The integrated optical splitter according to claim 1, characterized in that an upper cladding layer (IV) is provided on the upper surfaces of the lower cladding layer (II) and the core layer (III). 3. The integrated optical splitter according to claim 1 or 2, characterized in that the number of grooves (3) is 1-4.

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