CN105572796B - A kind of path filter up and down based on antisymmetry multimode Bragg waveguide grating - Google Patents

Abstract

The invention discloses an uplink and downlink filter based on an antisymmetric multimode Bragg waveguide grating. When TE light is input from a single-mode input waveguide, the downlink asymmetrical Y-branched waveguide converts it into a TE fundamental mode of a multimode waveguide. The anti-symmetric Bragg waveguide grating reversely couples the incident light with a wavelength that satisfies the phase matching condition into reflected light, and when passing through the downlink asymmetric Y-branched waveguide, the TE mode that is converted into the downlink single-mode waveguide is output from the downlink end, and the transmitted light Then, the uplink asymmetric Y-branched waveguide is output from the single-mode output waveguide; similarly, the uplink light is input from the uplink single-mode input waveguide, and the uplink asymmetric Y-branched waveguide converts it into the TE first-order mode of the multimode waveguide. The anti-symmetrical Bragg waveguide grating converts the reflected light of the wavelength satisfying the phase matching condition into the TE mode of the single-mode output waveguide when passing through the uplink asymmetric Y-branched waveguide, and outputs it from the output end. It is applied to the optical interconnection system of high-density integration on a chip.

Description

An Add-Drop Filter Based on Antisymmetric Multimode Bragg Waveguide Grating

technical field

The invention relates to an optical add-on and drop-path filter integrated device, in particular to an add-on-drop filter based on an antisymmetrical multimode Bragg waveguide grating.

Background technique

With the rapid development of integrated circuits, the feature size of transistors continues to decrease, and high-speed information inevitably encounters a series of bottlenecks in terms of speed, bandwidth, and power consumption when transmitting electrical interconnections. On-chip optical interconnection based on silicon optics provides a feasible solution to this technical problem, and the exchange of information will be carried out directly on the optical transmission layer.

As a basic functional device of optical interconnection, optical filter can flexibly realize the separation, add and drop of different signals, and is a very important link in dense wavelength division multiplexing optical network. At present, there are three main structures of devices that can realize the optical add and drop filtering function: The first is the micro-ring resonator structure, which can provide a higher Q value, and it does not require two reflective end faces, but it has a series of resonances Wavelength, the filtering of light is affected by the free spectral width, and the filtering bandwidth is small; the second is the F-P cavity structure, which requires two reflective end faces, and has a series of resonance wavelengths and small filtering bandwidth; the third It is a Bragg grating structure, which uses periodic refractive index perturbation regions to achieve optical filtering functions of different bandwidths, but because it is a two-port device, it cannot simultaneously achieve band-pass and band-stop filtering functions, and the reflection spectrum of light cannot It is extracted through a similar optical fiber looper. If a symmetrical Y bifurcated structure is used, a loss of 6 dB will be introduced.

Therefore, it is an important and meaningful work to develop on-chip integrated optical communication technology in the future to develop a simple structure, compact size, complete functions, and easy to integrate and manufacture.

Contents of the invention

The object of the present invention is to provide an up-and-down filter based on an antisymmetric multimode Bragg waveguide grating, which has a simple structure, compact size, complete functions, and is easy to integrate and manufacture.

The present invention is an upper and lower channel filter based on an antisymmetric multimode Bragg waveguide grating, including a single-mode input waveguide, an asymmetrical Y-branched waveguide for a lower channel, a multimode waveguide, an antisymmetrical Bragg waveguide grating, and an asymmetrical Y-forked waveguide for an upper channel , single-mode output waveguide, down-channel single-mode waveguide, and up-channel single-mode input waveguide, wherein the single-mode input waveguide is connected to a branch of the down-channel asymmetric Y-branch waveguide, and the down-channel single-mode waveguide is connected to the down-channel asymmetric Y-branch waveguide The other branch of the asymmetrical Y-branched waveguide is connected, the trunk of the asymmetrical Y-branched waveguide is connected to one end of the multi-mode waveguide, the other end of the multi-mode waveguide is connected to the trunk of the asymmetrical Y-branched waveguide of the upper road, and the single-mode output waveguide is asymmetrical to the upper road One branch of the Y bifurcated waveguide is connected, and the upper single-mode input waveguide is connected to the other branch of the asymmetrical Y bifurcated waveguide. The antisymmetric Bragg waveguide grating is located on the multimode waveguide and is distributed antisymmetrically.

The single-mode input waveguide, the lower asymmetric Y-branch waveguide, the multi-mode waveguide, the antisymmetric Bragg waveguide grating, the upper asymmetric Y-branch waveguide, the lower single-mode waveguide, the upper single-mode waveguide and the single-mode output waveguide Both are strip waveguides.

The structure of the lower asymmetric Y-branch waveguide is the same as that of the upper asymmetric Y-branch waveguide. The two branches of the asymmetric Y-branch waveguide are composed of two single-mode waveguides with different widths. The backbone of the asymmetric Y-branch waveguide is composed of composed of a multimode waveguide.

The period of the anti-symmetrical Bragg waveguide grating satisfies the phase matching condition of reversely coupling the TE fundamental mode in the multimode waveguide into the TE first-order mode.

The periodic refractive index perturbation regions of the antisymmetric Bragg waveguide grating are on both sides of the multimode waveguide.

The shapes of the periodic units constituting the antisymmetric Bragg waveguide grating are all rectangles.

Adopting the technical solution of the present invention, TE light is input from a single-mode input waveguide, and the asymmetrical Y-branched waveguide in the lower path converts it into the TE fundamental mode of the multi-mode waveguide, and the antisymmetric Bragg waveguide grating converts the incident light of wavelength satisfying the phase matching condition Reverse coupling is the TE first-order mode in the multimode waveguide, and the reflected light is converted to the TE mode of the downlink single-mode waveguide when passing through the downlink asymmetric Y-branched waveguide, and is output from the downlink end; the phase matching condition is not satisfied The transmitted light of the wavelength is output from the single-mode output waveguide through the uplink asymmetric Y-branched waveguide; similarly, the uplink light is input from the uplink single-mode input waveguide, and the uplink asymmetric Y-branched waveguide converts it into the TE of the multimode waveguide The first-order mode, the anti-symmetrical Bragg waveguide grating reversely couples the uplink light that meets the phase matching condition wavelength into the TE fundamental mode in the multimode waveguide, and the reflected light is converted into a single-mode output waveguide when it passes through the uplink asymmetric Y-branched waveguide The TE mode is output from the output end of the single-mode output waveguide. The invention simultaneously realizes the function of adding and dropping signals, and has the advantages of simple structure, compact size and large tolerance. It can be manufactured at low cost and can be applied to high-density integrated optical interconnection systems on a chip.

The beneficial effects of the present invention are:

1. Combining the asymmetric Y-branched waveguide and the antisymmetric Bragg waveguide grating to realize the function of the optical filter for the upper and lower channels, which has the characteristics of small insertion loss and large tolerance.

2. The device design is simple in structure and compact in size.

3. The device manufacturing process is compatible with CMOS technology, which makes the device easy to integrate and expand, and is convenient for low-cost manufacturing, and can be widely used in on-chip high-density integrated optical interconnection communication systems.

Description of drawings

Fig. 1 is a structural diagram of the present invention;

Fig. 2 is a sectional view of the strip waveguide in Fig. 1;

Fig. 3 is a schematic diagram of the periodic unit shape of the Bragg waveguide grating in Fig. 1;

Fig. 4 is a top view of the Bragg waveguide grating in Fig. 1;

The present invention will be further described below in conjunction with drawings and embodiments.

Marked in the picture:

1. Single-mode input waveguide 2. Asymmetrical Y-branched waveguide for the drop channel

3. Multimode waveguide 4. Antisymmetric Bragg waveguide grating

5. Asymmetrical Y-branched waveguide on the upper channel 6. Single-mode output waveguide

7. Down channel single-mode waveguide 8. Up channel single-mode input waveguide.

Detailed ways

As shown in Figure 1, the present invention is an uplink and downlink filter based on an antisymmetric multimode Bragg waveguide grating, including a single-mode input waveguide (1), a downlink asymmetric Y-branched waveguide (2), a multimode waveguide (3 ), antisymmetric Bragg waveguide grating (4), uplink asymmetric Y-branched waveguide (5), single-mode output waveguide (6), downlink single-mode waveguide (7) and uplink single-mode input waveguide (8), where single The mode input waveguide (1) is connected to one branch of the downlink asymmetric Y-branch waveguide (2), and the downlink single-mode waveguide (7) is connected to the other branch of the downlink asymmetric Y-branch waveguide (2). The trunk of the asymmetrical Y-branched waveguide (2) is connected to one end of the multimode waveguide (3), and the other end of the multimode waveguide (3) is connected to the trunk of the uplink asymmetrical Y-branched waveguide (5), and the single-mode output waveguide (6) Connected to one branch of the uplink asymmetric Y-branch waveguide (5), the uplink single-mode input waveguide (8) is connected to the other branch of the uplink asymmetric Y-branch waveguide (5), and the antisymmetric Bragg waveguide The grating (4) is located on the multimode waveguide (3) and is distributed antisymmetrically; TE light is input from the single-mode input waveguide (1), and the asymmetrical Y-branched waveguide (2) in the lower path converts it into TE of the multimode waveguide Fundamental mode, anti-symmetrical Bragg waveguide grating (4) reversely couples the incident light of the wavelength satisfying the phase matching condition into the TE first-order mode in the multimode waveguide (3), and the reflected light passes through the downlink asymmetric Y-branched waveguide (2 ) is converted to the TE mode of the downlink single-mode waveguide (7), and output from the downlink end; the transmitted light with a wavelength that does not meet the phase matching condition passes through the uplink asymmetric Y-branched waveguide (5), and is output from the single-mode The output of the waveguide (6); similarly, the uplink light is input from the uplink single-mode input waveguide (8), and the uplink asymmetric Y-branched waveguide (5) converts it into the TE first-order mode of the multimode waveguide (3), which is antisymmetric The Bragg waveguide grating (4) reversely couples the uplink light with a wavelength that satisfies the phase matching condition into the TE fundamental mode in the multimode waveguide (3), and the reflected light is converted into a single mode when passing through the uplink asymmetric Y-branched waveguide (5) The TE mode of the output waveguide (6) is output from the output end of the single-mode output waveguide (6). The present invention realizes the function of adding and dropping signals at the same time, and has the advantages of simple structure, compact size and large tolerance. The manufacturing process has CMOS technology Compatibility, easy integration and expansion, convenient low-cost manufacturing, and can be applied to high-density integrated optical interconnection systems on chips.

The two branches of the lower asymmetric Y-branch waveguide (2) are composed of two single-mode waveguides with different widths, and the backbone of the lower asymmetric Y-branch waveguide (2) is composed of a multi-mode waveguide. When the single-mode When the input mode of the input waveguide (1) is the TE mode, the down-channel asymmetric Y-branched waveguide (2) converts the mode into the TE fundamental mode of the multimode waveguide;

The structure of the uplink asymmetric Y-branch waveguide (5) is consistent with the structure of the downlink asymmetric Y-branch waveguide (2). When the input mode of the uplink single-mode input waveguide (8) is TE mode, the downlink asymmetrical Y-branch waveguide (2) The symmetrical Y-branched waveguide (2) converts this mode to the TE first-order mode of the multimode waveguide;

The periodic refractive index perturbation regions of the antisymmetric Bragg waveguide grating (4) are arranged symmetrically on both sides of the multimode waveguide (3), and are distributed antisymmetrically; when the wavelength of the incident light in the multimode waveguide (3) When the TE fundamental mode that satisfies the phase matching condition passes through the antisymmetric Bragg waveguide grating (4), it is coupled back into the TE first-order mode of the multimode waveguide (3), and the reflected light of the TE first-order mode passes through the down-channel asymmetric Y When the bifurcated waveguide (2) is converted to the TE mode of the downlink single-mode waveguide (7), it is output from the output end of the downlink single-mode waveguide (7); and when the wavelength in the multimode waveguide (3) does not meet the phase matching When the conditional TE fundamental mode passes through the antisymmetric Bragg waveguide grating (4), the transmitted light will not be affected by the antisymmetric Bragg waveguide grating (4), and continues to propagate forward. , is converted to the TE mode of the single-mode output waveguide (6), and is output from the output end of the single-mode output waveguide (6); when the light is input from the upper single-mode input waveguide (8), it passes through the upper asymmetrical Y-branched waveguide (5), it is converted into the first-order mode of the multimode waveguide (3), and the TE first-order mode whose wavelength satisfies the phase matching condition passes through the antisymmetric Bragg waveguide grating (4), and is reversely coupled into the multimode waveguide (3 ), the reflected light of the TE fundamental mode is converted into the TE mode of the single-mode output waveguide (6) when the reflected light of the TE fundamental mode passes through the upper asymmetric Y-branched waveguide (5), and the output from the single-mode output waveguide (6) terminal output.

As shown in Figure 1, Figure 3 and Figure 4, the antisymmetric Bragg waveguide grating (4) is formed by etching a one-dimensional rectangular periodic unit on the waveguide, and the period of the antisymmetric Bragg waveguide grating (4) satisfies multiple The phase-matching condition that the TE fundamental mode of the mode waveguide (3) is reversely coupled to the TE first-order mode.

In order to meet the requirements of the multimode waveguide (3) TE mode reversely coupled to the TE first-order mode, it is necessary to design the Bragg waveguide grating period, which can be obtained by the following formula

(1)

where Λ is the grating period, is the propagation constant of the TE fundamental mode of the multimode waveguide, is the propagation constant of the first-order TE mode of the multimode waveguide.

An embodiment as shown in Figure 1, the present invention is based on an antisymmetric multimode Bragg waveguide grating up and down filter is composed of a single mode waveguide, asymmetric Y bifurcated waveguide, multimode waveguide and antisymmetric Bragg waveguide grating, All components of the device are located in the same plane. All the single-mode waveguides 1, 6, 7 and 8 in Fig. 1, the asymmetric Y-branched waveguides 2 and 5, the multimode waveguides 3 and the Bragg waveguide gratings 4 all adopt the strip waveguide shown in Fig. 2 .

Example:

As shown in Figure 1, Figure 2 and Figure 4, the silicon-on-insulator (SOI) material with a top silicon thickness of 220 nm and a silicon oxide buried layer of 2 µm is used. After the wafer surface is cleaned, deep ultraviolet lithography or electronic A silicon etching mask was obtained by beam direct writing lithography, and a strip waveguide with a height of 220 nm was fabricated by silicon dry etching, in which the widths of the two bifurcated waveguides of the asymmetric Y bifurcated waveguide were 500 nm and 400 nm respectively , the width of the trunk waveguide is 900 nm, the width of the multimode waveguide is 900 nm, the two sides of the multimode waveguide are etched with anti-symmetric Bragg waveguide grating, the rectangular grating tooth is 150 nm, and its period is 308 nm, the Bragg waveguide grating The length is 300 µm.

The grating period parameters in the above embodiments are designed for multimode strip waveguides with a working wavelength of 1550 nm and a width of 900 nm. The device is also suitable for multimode strip waveguides with other working wavelengths and widths, and is also suitable for different top-layer silicon The thickness of the strip waveguide can realize the optical filter function only by changing the size of the tapered waveguide and designing different grating period parameters. The entire device can be fabricated with only one etching.

The above specific embodiments are used to explain the present invention, rather than to limit the present invention. Within the spirit of the present invention and the protection scope of the claims, any modification and change made to the present invention will fall into the protection scope of the present invention.

Claims (6)

1. a kind of path filter up and down based on antisymmetry multimode Bragg waveguide grating, it is characterised in that：It is inputted including single mode Waveguide, lower road Asymmetry Y furcation waveguide, multimode waveguide, antisymmetry Bragg waveguide grating, upper road Asymmetry Y furcation waveguide, list Mould output waveguide, lower road single mode waveguide and upper road singlemode input waveguide, wherein singlemode input waveguide and lower road Asymmetry Y furcation wave Branch connection is led, lower road single mode waveguide is connect with another branch of lower road Asymmetry Y furcation waveguide, lower road Asymmetry Y furcation The trunk of waveguide and one end of multimode waveguide connect, and the other end of multimode waveguide and the trunk of upper road Asymmetry Y furcation waveguide connect It connects, single-mode output waveguide is connect with upper one branch of road Asymmetry Y furcation waveguide, upper road singlemode input waveguide and the asymmetric Y in upper road Another branch of bifurcated waveguide connects, and the antisymmetry Bragg waveguide grating is located on multimode waveguide, antisymmetry Prague The periodic refractive index perturbation area of waveguide optical grating is distributed on the two sides of multimode waveguide in antisymmetry.

2. a kind of path filter up and down based on antisymmetry multimode Bragg waveguide grating according to claim 1, special Sign is：The singlemode input waveguide, upper road Asymmetry Y furcation waveguide, multimode waveguide, lower road Asymmetry Y furcation waveguide, under Road single mode waveguide, upper road singlemode input waveguide and single-mode output waveguide are slab waveguide.

3. special according to a kind of path filter up and down based on antisymmetry multimode Bragg waveguide grating described in claim 2 Sign is：Two branches of the lower road Asymmetry Y furcation waveguide are made of two single mode waveguides of different size, and the upper road/ The trunk of lower road Asymmetry Y furcation waveguide is made of multimode waveguide.

4. special according to a kind of path filter up and down based on antisymmetry multimode Bragg waveguide grating described in claim 2 Sign is：The upper road Asymmetry Y furcation waveguide and lower road Asymmetry Y furcation waveguide are completely the same.

5. special according to a kind of path filter up and down based on antisymmetry multimode Bragg waveguide grating described in claim 2 Sign is：Period of the antisymmetry Bragg waveguide grating meet by multimode waveguide TE basic modes and TE First-Order Modes it is mutual The phase-matching condition coupled.

6. special according to a kind of path filter up and down based on antisymmetry multimode Bragg waveguide grating described in claim 2 Sign is：The periodic unit shape for constituting Bragg waveguide grating is rectangle.