CN110286540A - A 1×4 lithium niobate waveguide optical switch based on Mach-Zehnder interference structure - Google Patents

Abstract

The invention discloses a 1×4 lithium niobate waveguide optical switch based on a Mach-Zehnder interference structure, which can be applied to optical communication, optical interconnection, optical calculation, etc., and belongs to the field of optoelectronic technology. The invention has one light wave input port and four light wave output ports. The present invention is composed of three switch unit arrays of 1*2 MZI structure in two stages. There is a 1×2 MZI in the first-stage optical switch unit, and the light enters the upper and lower interference arms respectively through the Y-shaped waveguide beam splitter, and then is output through the interference of the 2×2 directional coupler. The input ends of the Y-shaped waveguide beam splitter in the two parallel MZI optical switch units of the second stage are respectively connected in parallel with the two output ports of the directional coupler of the first stage. In MZI, when the phase difference of the interference arm reaches π/2, the switching of the optical path between the two output ports can be realized. For the two-stage MZI, the function of four-way gating can be realized, which provides a great support for the production of large-scale optical switch arrays. greater flexibility.

Description

A 1×4 lithium niobate waveguide optical switch based on Mach-Zehnder interference structure

technical field

The invention relates to optical components, in particular to a 1×4 lithium niobate waveguide optical switch based on a Mach-Zehnder interference structure, which can be applied to optical communication, optical interconnection, optical computing, etc., and belongs to the field of optoelectronic technology.

Background technique

The optical switch is the core device of optical switching, and it is also one of the main factors affecting the performance of the optical network. As a key device of the new-generation all-optical networking network, the optical switch is mainly used to realize functions such as routing selection, wavelength selection, optical cross-connection and self-healing protection on the optical level. In an all-optical network, optical add-drop multiplexing devices (OADM) and optical cross-connects (OXC) are indispensable network node devices, and optical switches and optical switch arrays are the core devices in these devices. With the increasing demands of communication capacity in the information society, the transmission bandwidth of optical fiber communication network is increasing rapidly. Correspondingly, the high-speed communication network also puts forward higher and higher requirements on the switching rate of the optical switch. The switching rate of microelectromechanical system (MEMS) optical switch is on the order of milliseconds, and the switching rate of thermo-optic optical waveguide switch can reach tens of microseconds after structural optimization design, but it still cannot meet the requirements of ultra-high-speed optical switching. Electro-optic switches can quickly change the state of the switch on the order of nanoseconds. LiNbO ₃ has a large electro-optic coefficient (30.8×10 ^-12 V/m) and an extremely fast electro-optic response (t=10-19s). The optical waveguide device made of LiNbO ₃ is a modern ultra-high-speed, large-capacity, long-term The key components of optical fiber communication and optical switching systems.

Optical switches using Mach-Zehnder-Interferometer (MZI) have excellent characteristics such as high extinction ratio, low crosstalk, and low loss, and have attracted widespread attention. The switching power can be reduced by increasing the length difference between the two interference arms, but this is not conducive to the miniaturization and integration of the device. Therefore, designing a reasonable waveguide structure is of great significance for reducing switching power and increasing switching speed. In addition, in order to meet the requirements of optical computing, communication and optical network with a large amount of data, it is also necessary to increase the number of circuits of a single switching element. At present, commercial lithium niobate waveguide optical switches are large in size and low in integration, and are mostly used in 1×2, 2×2 low-port switching systems, which can only realize optical path switching between two output ports, and integration The degree and chip utilization are not high. Therefore, it is necessary to develop a new device structure to improve its integration and realize light switching between as many ports as possible without increasing the chip size and process difficulty.

Contents of the invention

A 1×4 lithium niobate waveguide optical switch based on a Mach-Zehnder interference structure, consisting of one input optical fiber (1), a lithium niobate waveguide chip (3), and four output optical fibers (12), characterized in that: The lithium niobate waveguide chip (3) includes a first-level optical switch unit (I) composed of a 1×2 MZI and a second-level optical switch unit (II) composed of two parallel 1×2 MZIs, The 1×2 MZI includes a lithium niobate substrate (13) and a buffer layer (14) formed on its surface, a traveling wave electrode (4) and an optical waveguide (5), and the traveling wave electrode (4) consists of a central electrode (9) and ground electrodes (10) on both sides thereof, the optical waveguide (5) constitutes a Y-type waveguide beam splitter (6), a waveguide interference arm (7) parallel up and down, and a 3dB directional coupler ( 8); the Y-shaped waveguide beam splitter (6) of the 1×2 MZI in the first-level optical switch unit (I) divides the light input by the input optical fiber (1) into two paths, and enters the waveguide respectively The upper and lower two arms of the interference arm (7), the output end of the waveguide interference arm (7) is connected with the 3dB directional coupler (8), and the light of the two paths at the upper and lower arms of the waveguide interference arm (7) passes through the traveling wave electrode The phase difference is generated under the action of (4), when the phase difference reaches π/2, the output port interference output from the 3dB directional coupler (8), when the phase difference reaches -π/2, from the 3dB directional coupler (8) ) on the output port interference output, the switching of the optical path between the two output ports of the 1×2 MZI is realized, that is, the function of two-way gating; the two 1 in the second-stage optical switch unit (II) The Y-type waveguide beam splitter (6) of the MZI of ×2 is connected in parallel with the output port of the upper-stage 3dB directional coupler (8), and the light output from a certain output port of the upper-stage 3dB directional coupler (8) Enter the Y-shaped waveguide beam splitter (6) of a certain 1×2 MZI optical switch unit in the second-stage optical switch unit (II), also under the action of the traveling wave electrode (4), from 3dB directional coupling One of the output ports of the device (8) interferes with the output; by controlling the traveling wave electrodes (4) in the three 1×2 MZIs respectively, the function of four-way gating is realized; the four output ports are respectively connected to the four-way Output optical fiber (12).

In order to solve the above-mentioned technical problems, the present invention provides a 1×4 lithium niobate waveguide optical switch based on Mach-Zehnder interference structure, which is composed of one input optical fiber, lithium niobate waveguide chip, and four output optical fibers, wherein lithium niobate The waveguide chip includes a first-level optical switch unit composed of a 1×2 MZI and a second-level optical switch unit composed of two parallel 1×2 MZIs, and the 1×2 MZI includes a lithium niobate substrate And a buffer layer formed on its surface, a traveling wave electrode and an optical waveguide, the traveling wave electrode is composed of a central electrode and ground electrodes on both sides thereof, and the optical waveguide sequentially constitutes a Y-shaped waveguide beam splitter, a waveguide parallel up and down Interference arm, 3dB directional coupler; the 1×2 MZI Y-shaped waveguide beam splitter in the first-stage optical switch unit divides one path of light input by the input fiber into two paths, and enters the upper and lower portions of the waveguide interference arm respectively Two arms, the output end of the waveguide interference arm is connected to the 3dB directional coupler, and the two-way light in the upper and lower arms of the waveguide interference arm produces a phase difference under the action of the traveling wave electrode. When the phase difference reaches π/2, The interference output from the lower output port of the 3dB directional coupler, when the phase difference reaches -π/2, the interference output from the upper output port of the 3dB directional coupler realizes the switching of the optical path between the two output ports of the 1×2 MZI , that is, the function of two-way gating; the Y-type waveguide beam splitters of two 1×2 MZIs in the second-stage optical switch unit are connected in parallel with the output port of the upper-stage 3dB directional coupler, from the previous stage The light output by a certain output port of the first-stage 3dB directional coupler enters the Y-shaped waveguide beam splitter of a certain 1×2 MZI optical switch unit in the second-level optical switch unit, and is also under the action of the traveling wave electrode. Interference output from one of the output ports of the 3dB directional coupler; by separately controlling the traveling-wave electrodes in the three 1×2 MZIs, for the entire optical switch device, the function of four-way gating is realized; four The output ports are respectively connected with four output optical fibers (12).

The lithium niobate substrate adopts X-cut Y-type transfer.

The Y-shaped waveguide beam splitter, the upper and lower parallel waveguide interference arms, and the 3dB directional coupler are all composed of optical waveguides. The optical waveguides have the same width, and annealed proton-exchanged lithium niobate single-mode waveguides are used. After cleaning the substrate sheet and preparing Masking, photolithography, proton exchange, annealing, end face polishing, waveguide adjustment and inspection steps are fabricated.

The waveguide bending part of the Y-shaped waveguide beam splitter and the 3dB directional coupler is bent by a raised cosine curve.

The input optical fibers are aligned using U-shaped grooves, and the output optical fibers are aligned using V-shaped groove arrays arranged at equal intervals.

The beneficial effects of the present invention are: (1) the present invention is a 1×4 optical switch, which has one light wave input port and four light wave output ports, and can realize the four-way gating function of the optical switch. The present invention is simple in structure and smaller in size. Small size, which provides greater flexibility for the production of large-scale optical switch arrays; (2) Utilizing the excellent electro-optic properties of lithium niobate materials, annealed proton-exchanged lithium niobate optical waveguides are used in the process, and the manufacturing process is mature and the cost is small. Potential economic and application value can be widely used in the field of optical communication.

Description of drawings

Fig. 1 is the structural representation of the novel 1 * 4 lithium niobate waveguide optical switch based on the Mach-Zehnder interference structure of the present invention;

Fig. 2 is the sectional structure schematic diagram of the lithium niobate waveguide chip of the present invention;

FIG. 3 is a simulation result diagram of the four-way gating of the novel 1×4 lithium niobate waveguide optical switch based on the Mach-Zehnder interference structure of the present invention.

In the figure: 1. Input optical fiber, 2. U-groove optical fiber fixing device, 3. Lithium niobate waveguide chip, 4. Traveling wave electrode, 5. Optical waveguide, 6. Y-shaped waveguide beam splitter, 7. Waveguide interference arm , 8.3dB directional coupler, 9. center electrode, 10. ground electrode, 11. V-groove fiber fixture, 12. output fiber, 13. lithium niobate substrate, 14. buffer layer, Ⅰ. first-stage optical switch Unit, Ⅱ. The second level optical switch unit.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the present invention is not limited to this embodiment.

A schematic structural diagram of a 1×4 lithium niobate waveguide optical switch based on a Mach-Zehnder interference structure in this embodiment is shown in FIG. 1 .

This embodiment includes an input optical fiber 1 arranged in sequence along the beam transmission direction, a U-groove fiber fixing device 2, a first-stage optical switch unit I composed of a 1×2 MZI and two parallel 1×2 MZIs The second stage optical switch unit II, the V-groove optical fiber fixing device 11 and the output optical fiber 12 are formed. When the input optical fiber 1 is coupled and connected with the first-stage optical switch unit I, considering that there is only one input optical fiber, U-shaped grooves are used for alignment; the output optical fibers are four optical fibers arranged at equal intervals, and V-shaped groove arrays are used for alignment . The 1×2 MZI includes a lithium niobate substrate 13 as shown in FIG. 2 and a buffer layer 14 formed on its surface, a traveling wave electrode 4 and an optical waveguide 5. The traveling wave electrode 4 includes a central electrode 9 and a ground electrode 10, The optical waveguide 5 includes a Y-shaped waveguide beam splitter 6 , a waveguide interference arm 7 , and a 3dB directional coupler 8 . The waveguide bending part of the Y-shaped waveguide beam splitter and the 3dB directional coupler adopts a rising cosine curve to reduce the bending loss of the waveguide. One path of light input by the input optical fiber 1 is divided into two paths by the Y-shaped waveguide beam splitter 6, and enters the upper and lower interference arms of the waveguide interference arm 7 respectively, and the two paths of light generate a phase difference under the action of the traveling wave electrode 4, thereby By deciding which output port of the directional coupler to interfere with the output, the switching of the optical path between the two output ports of the first-stage optical switch unit I can be realized, that is, the optical switch function. The two outputs of the first-stage optical switch unit I respectively enter the two 1×2 MZIs of the second-stage optical switch unit II. After passing through the second-stage optical switch unit II, for the entire optical switch device, it can realize Four-way strobe function.

The manufacturing process of the present invention is simple, the lithium niobate substrate 13 adopts X-cut Y-type transmission, and the optical waveguide 5 adopts annealed proton-exchanged lithium niobate single-mode waveguide. In this example, a 1×4 lithium niobate waveguide optical switch device The total length is 3.7cm. The waveguide width of the Y-shaped waveguide beam splitter, the upper and lower parallel waveguide interference arms, and the 3dB directional coupler are the same as 6.5 μm. A push-pull electrode structure is adopted, which can simultaneously apply an electric field to the two interference arms of the MZI optical switch to realize phase modulation. Compared with the single-arm modulation, the push-pull electrode structure can obtain a smaller switching voltage and improve the working stability of the switching device. In this example, the electrode thickness is 15 μm, the electrode width is 8 μm, and the electrode spacing is 12 μm. In order to reduce The length of the device ensures that the device has a low switching voltage, and the length of the interference arm needs to be set reasonably. In this example, the length of the interference arm is 1cm. The coupling spacing of the 3dB directional couplers in the first-stage 1×2 MZI optical switch unit is 10 μm, and the coupling length is 261.5 μm. The coupling spacing of the second-stage 3dB directional couplers is 10 μm, and the coupling length is set to 432.5 μm. Considering that the light at the output port is output by the optical fiber, in this example, the output ports of the four lithium niobate waveguides are arranged at equal intervals with a pitch of 127 μm.

Fig. 3 is the simulation result figure of the novel 1×4 lithium niobate waveguide optical switch four-way gating based on the Mach-Zehnder interference structure of the present invention, for the input light of 1550nm wavelength, the maximum extinction ratio can reach 48dB, which can be well Realize the function of four-way strobe.

In summary, the present invention proposes a novel 1×4 lithium niobate waveguide optical switch based on the Mach-Zehnder interference structure, which can well realize the arbitrary switching of the optical path at the four output ports, has potential economic and application value, and is expected to It is widely used in the field of optical communication.

Claims (5)

1. a kind of 1 × 4 lithium niobate waveguides photoswitch for increasing Dare interference structure based on Mach, by input optical fibre all the way (1), niobic acid Lithium waveguide chip (3), four road output optical fibres (12) are constituted, it is characterised in that: wherein lithium niobate waveguides chip (3) includes by one The first order optical switch element (I) that 1 × 2 MZI is constituted and the second level photoswitch list being made of two 1 × 2 parallel MZI First (II), described 1 × 2 MZI includes lithium niobate base bottom (13) and buffer layer (14), the traveling wave electrode for being formed in its surface (4) it is made of with optical waveguide (5), the traveling wave electrode (4) the ground electrode (10) of central electrode (9) and its two sides, the light wave It leads (5) and successively constitutes Y type waveguide beam splitter (6), up and down parallel Waveguide interference arm (7), 3dB directional coupler (8)；It is described The light all the way that the Y type waveguide beam splitter (6) of 1 × 2 MZI in first order optical switch element (I) will be inputted by input optical fibre (1) It is divided into two-way, respectively enters two arms up and down of Waveguide interference arm (7), the output end and 3dB of Waveguide interference arm (7) orient coupling Clutch (8) connection, two-way generate phase under the action of the light of two arms up and down of Waveguide interference arm (7) is in traveling wave electrode (4) Difference, when phase difference reaches pi/2, from output port interference output under 3dB directional coupler (8), when phase difference reaches-pi/2 when, From output port interference output on 3dB directional coupler (8), optical path is just realized between two output ports of 1 × 2 MZI Switching, i.e. two roads gating function；The Y type waveguide of two 1 × 2 MZI in the second level optical switch element (II) point Beam device (6) is parallel with the output port of upper level 3dB directional coupler (8) to be connected, from upper level 3dB directional coupler (8) The light of a certain output port output enters the Y type of a certain 1 × 2 MZI optical switch element in second level optical switch element (II) In waveguide beam splitter (6), equally under the action of traveling wave electrode (4), from 3dB directional coupler (8) one of output port Interference output；By controlling the traveling wave electrode (4) in three 1 × 2 MZI respectively, the function of four roads gating is just realized； Four output ports are separately connected four road output optical fibres (12).

2. a kind of 1 × 4 lithium niobate waveguides photoswitch for increasing Dare interference structure based on Mach as described in claim 1, special Sign is: the lithium niobate base bottom (13) cuts Y biography type using X.

3. a kind of 1 × 4 lithium niobate waveguides photoswitch for increasing Dare interference structure based on Mach as claimed in claim 1 or 2, Be characterized in that: the Y type waveguide beam splitter (6), up and down parallel Waveguide interference arm (7), 3dB directional coupler (8) are all by light Waveguide (5) is constituted, and the optical waveguide (5) is of same size, lithium niobate single mode waveguide is exchanged using annealed proton, through over cleaning substrate Piece, prepare mask, photoetching, proton exchange, annealing, end face polishing, waveguide adjustment and checking step are made.

4. a kind of 1 × 4 lithium niobate waveguides photoswitch for increasing Dare interference structure based on Mach as claimed in claim 3, special Sign is: the waveguide bend part of the Y type waveguide beam splitter (6) and 3dB directional coupler (8) is curved using rised cosine curve It is bent.

5. a kind of 1 × 4 lithium niobate waveguides photoswitch for increasing Dare interference structure based on Mach as described in claim 1 or 4, Be characterized in that: the input optical fibre (1) is aligned using U-type groove, and four road output optical fibre (12) is using the V-type equidistantly arranged The alignment of slot array.