High-efficiency ultra-wideband low-insertion-loss Mach-Zehnder modulator

Abstract

The invention discloses a high-efficiency ultra-wideband low-insertion-loss Mach-Zehnder modulator, and belongs to the fields of microwave photons, photoelectric modulators, high-efficiency photoelectric conversion and the like. The dual-parallel Mach-Zehnder modulator comprises a SiO2 substrate, a dual-parallel Mach-Zehnder modulator is arranged on the SiO2 substrate, and the two ends of the dual-parallel Mach-Zehnder modulator are each provided with a spot size converter. Based on the lithium niobate film modulator process technology, the spot-size conversion waveguide structure is optimized, low insertion loss can be achieved, and the modulation bandwidth is improved through the double parallel modulators. According to the invention, the linearity and the working bandwidth of the microwave photon link can be effectively improved, and the wide application requirements of broadband satellite communication and high-frequency radio-frequency front ends in various fields can be met.

Description

Technical Field

[0001] The invention belongs to the fields of microwave photons, optoelectronic modulators, and efficient optoelectronic conversion, and specifically relates to a high-efficiency ultra-wideband low insertion loss Mach-Zehnder modulator. Background Art

[0002] RF front-end, transmission link and signal processing system are the core functional modules in radar, communication and other systems. The demand for large bandwidth, multi-band, reconfigurable signal processing in electronic information equipment poses new challenges to microwave technology. Traditional microwave technology has many bottleneck problems such as large high-frequency loss, narrow bandwidth, low processing rate, and inflexible modulation, which makes it difficult to meet the further development trend of equipment.

[0003] Microwave photonics integrate the advantages of microwaves and light waves, and have the advantages of large bandwidth and high speed. It is expected to break through the bottleneck problem of traditional electrical domain and meet the needs of electronic information equipment. Microwave photonic technology mainly involves three types of devices: lasers, electro-optic modulators and detectors. The electro-optic modulator is a key unit for realizing electro-optical conversion. It refers to a device that modulates the electrical signal carrying information onto an optical carrier. The characteristic parameters of the optical carrier used to carry information mainly include intensity, phase, frequency and polarization state. It is the core device for realizing optical domain processing. The most typical modulator structure is the Mach-Zehnder modulator, which has the advantages of significant electro-optical effect, small waveguide loss, and mature process manufacturing. It can effectively improve the transmission linearity, increase the bandwidth and operating frequency band of microwave photonic links, and can be used in ultra-wideband signal receiving systems in the fields of ultra-wideband radar, large-capacity communications, and high-performance electronic countermeasures.

[0004] At present, mature modulators are all based on traditional bulk lithium niobate processing, which has large size and power consumption. In addition, there is little research on this modulator in China, and it relies heavily on imports. The modulation bandwidth of the international leading modulation can reach more than 60GHz, but there are no modulators exceeding 20GHz in China. The emergence of thin-film lithium niobate materials is expected to replace the modulation of traditional bulk lithium niobate processing, greatly reduce the size and power consumption of modulators, and catch up with the international first-class level.

[0005] In view of the rapid development of communication technology towards multi-band, large bandwidth, multi-beam, flexible configuration, and the demand for satellite multifunctional fusion technology, which is currently widely used in various fields of satellite communication bandwidth and high-frequency RF front-end needs, we study modulators to achieve low insertion loss and waveguide structures, modulators to achieve high modulation bandwidth, lithium niobate thin film modulator process technology research, high reliability packaging design and technology research, etc., breakthroughs in low-loss optical structure design such as waveguides and couplers, modulator bandwidth theory and traveling wave electrode design, reliability and uniformity process manufacturing technology, optical waveguide mode conversion technology, high reliability packaging and other key technologies, to achieve the ability to improve the bandwidth and frequency band of traditional satellite communications.

[0006] Therefore, the research on high-efficiency, ultra-wideband, low-insertion-loss Mach-Zehnder modulators is of great value and significance for promoting the next generation of higher-capacity optical communication systems, faster data centers, and analog fiber-optic communication systems. It also plays an important role in promoting and facilitating the communication application industry related to high-speed modulators, and has high-value scientific significance. Summary of the invention

[0007] In view of this, the present invention proposes a high-efficiency ultra-wideband low insertion loss Mach-Zehnder modulator. The present invention has the characteristics of ultra-wideband working bandwidth, low insertion loss, and high modulation efficiency, and can achieve indicators such as modulation bandwidth ≥ 60.83GHz, insertion loss ≤ 4.6dB, and extinction ratio ≥ 24dB, and can be widely used in multi-band, high-bandwidth, and large-capacity communication systems.

[0008] To achieve the above object, the technical solution of the present invention is:

[0009] A high-efficiency ultra-wideband low insertion loss Mach-Zehnder modulator comprises a SiO2 substrate, on which a dual parallel Mach-Zehnder modulator is arranged, and at each end of the dual parallel Mach-Zehnder modulator there is a mode spot converter; the mode spot converter is a double-cone structure, comprising a bottom inverted tapered waveguide and a top inverted tapered waveguide, the bottom inverted tapered waveguide comprises a bottom rectangular section and a bottom tapered section, the width of the bottom tapered section is smaller than the width of the bottom rectangular section, a straight waveguide is extended from the end of the bottom tapered section, the top inverted tapered waveguide comprises a top rectangular section and a top tapered section, the width of the top rectangular section is smaller than the width of the bottom tapered section, the length of the top rectangular section is equal to the length of the bottom rectangular section, the width of the top tapered section is equal to the width of the top rectangular section, the end of the top tapered section is a flat head, and the end of the top tapered section is located at 1 / 5 to 3 / 5 of the length of the bottom tapered section;

[0010] The dual parallel Mach-Zehnder modulator includes a waveguide network and five high-frequency electrodes, wherein a gap is provided between two adjacent high-frequency electrodes, and a straight waveguide is provided at each end of the waveguide network. The straight waveguide at one end of the waveguide network is divided into four waveguides, namely, a first waveguide, a second waveguide, a third waveguide, and a fourth waveguide, through a two-stage one-to-two structure. The four waveguides pass through four gaps respectively, and then form a straight waveguide at the other end of the waveguide network through a two-stage two-in-one structure, wherein the first waveguide and the second waveguide are combined into a fifth waveguide, and the third waveguide and the fourth waveguide are combined into a sixth waveguide, and a DC electrode is provided at each of the first waveguide, the third waveguide, and the fifth waveguide;

[0011] The mode spot converters at both ends of the dual parallel Mach Zehnder modulator are mirror-symmetrical, the straight waveguide at each end of the dual parallel Mach Zehnder modulator is connected to the bottom rectangular segment and the top rectangular segment of the mode spot converter at this end, the width of the straight waveguide of the dual parallel Mach Zehnder modulator is equal to the width of the bottom rectangular segment of the mode spot converter, and the height of the straight waveguide of the dual parallel Mach Zehnder modulator is equal to the height of the double-conical structure of the mode spot converter.

[0012] Furthermore, a silicon dioxide upper cladding layer is provided on the double-cone structure of the spot converter.

[0013] Furthermore, the waveguides in the dual parallel Mach-Zehnder modulator and the spot converter are both made of lithium niobate.

[0014] Furthermore, the width of the top rectangular segment is W1=2um, the width of the flat head at the end of the top conical segment is W3=480nm, the width of the bottom conical segment is W2=800nm, the length of the top conical segment is L1=500nm, the length of the bottom conical segment is L2=2.16um, and the width of the straight waveguide at the end of the bottom conical segment is W4=50nm.

[0015] The beneficial effects of the present invention are:

[0016] 1. The present invention realizes a high-efficiency high-bandwidth pattern spot converter and a dual-parallel Mach-Zehnder modulator, thereby realizing a high-efficiency ultra-wideband low insertion loss Mach-Zehnder modulator.

[0017] 2. The present invention can be implemented by adopting a high-uniform processing technology and a high-reliability packaging method, and can achieve indicators of a modulation bandwidth ≥ 60.83 GHz, an insertion loss ≤ 4.6 dB, and an extinction ratio ≥ 24 dB.

[0018] 3. The present invention can solve the problems of microwave photonic link linearity, ultra-wideband, and low insertion loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the structure of a high-efficiency and high-bandwidth spot converter in an embodiment of the present invention.

[0020] Figure 2 Schematic diagram of the structure of a dual parallel Mach-Zehnder modulator in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0022] A high-efficiency ultra-wideband low insertion loss Mach-Zehnder modulator comprises a SiO2 substrate on which a dual-parallel Mach-Zehnder modulator is arranged. Two ends of the dual-parallel Mach-Zehnder modulator are respectively provided with a high-efficiency high-bandwidth pattern spot converter.

[0023] like Figure 1 As shown, the high-efficiency and high-bandwidth pattern spot converter adopts a double-cone pattern spot converter, which mainly includes a top inverted tapered waveguide and a bottom inverted tapered waveguide. The pattern spot converter is a double-cone structure, including a bottom inverted tapered waveguide LN1 and a top inverted tapered waveguide LN2. The bottom inverted tapered waveguide includes a bottom rectangular section and a bottom tapered section. The width of the bottom tapered section is smaller than the width of the bottom rectangular section. A straight waveguide extends from the end of the bottom tapered section. The top inverted tapered waveguide includes a top rectangular section and a top tapered section. The width of the top rectangular section is smaller than the width of the bottom tapered section. The length of the top rectangular section is equal to the length of the bottom rectangular section. The width of the top tapered section is equal to the width of the top rectangular section. The end of the top tapered section is a flat head. The end of the top tapered section is located at 1 / 5 to 3 / 5 of the length of the bottom tapered section.

[0024] In addition, the spot converter has a silicon dioxide upper cladding layer above the double-tapered structure.

[0025] In the high-efficiency and high-bandwidth spot converter, the top inverted tapered waveguide, the bottom inverted tapered waveguide and the upper silica cladding structure can better limit the light wave so that it does not diffuse in the air. In order to guide the light wave from the optical fiber into the bottom inverted tapered waveguide, a straight waveguide with a width of W4 is extended at the end of the tip of the bottom inverted tapered waveguide, which also avoids the damage of the tip of the bottom inverted tapered waveguide due to the polishing process in the actual process.

[0026] like Figure 2 As shown, the dual parallel Mach-Zehnder modulator includes a waveguide network and five high-frequency electrodes (ground electrodes G and signal electrodes S are alternately arranged), a gap is provided between two adjacent high-frequency electrodes, a straight waveguide is provided at each end of the waveguide network, and the straight waveguide at one end of the waveguide network is divided into four waveguides, namely, a first waveguide, a second waveguide, a third waveguide, and a fourth waveguide, through a two-stage one-to-two structure. The four waveguides pass through four gaps respectively, and then form a straight waveguide at the other end of the waveguide network through a two-stage two-in-one structure, wherein the first waveguide and the second waveguide are combined into a fifth waveguide, and the third waveguide and the fourth waveguide are combined into a sixth waveguide, and a DC electrode DC1, DC2, and DC3 are provided at the first waveguide, the third waveguide, and the fifth waveguide.

[0027] The dual parallel Mach-Zehnder modulator is composed of three Mach-Zehnder modulators. The two sub-modulators MZM1 and MZM2 have the same performance and are intensity modulators, that is, the modulated electrical signals and DC bias voltages applied to the upper and lower arms have the same amplitude and opposite phases, and are respectively embedded in the two arms of the main modulator MZM3.

[0028] In the high-efficiency ultra-wideband low insertion loss Mach-Zehnder modulator, the spot converters at both ends of the dual-parallel Mach-Zehnder modulator are mirror-symmetrical, the straight waveguide at each end of the dual-parallel Mach-Zehnder modulator is connected to the bottom rectangular segment and the top rectangular segment of the spot converter at this end, the width of the straight waveguide of the dual-parallel Mach-Zehnder modulator is equal to the width of the bottom rectangular segment of the spot converter, the height of the straight waveguide of the dual-parallel Mach-Zehnder modulator is equal to the height of the double-conical structure of the spot converter, and the waveguides in the dual-parallel Mach-Zehnder modulator and the spot converter are both made of lithium niobate.

[0029] In a specific embodiment, the width W1 of the top rectangular segment is 2um, the width W3 of the flat head at the end of the top tapered segment is 480nm, the width W2 of the bottom tapered segment is 800nm, the length L1 of the top tapered segment is 500nm, the length L2 of the bottom tapered segment is 2.16um, and the width W4 of the straight waveguide at the end of the bottom tapered segment is 50nm.

[0030] The working principle of the present invention is as follows:

[0031] In the double-cone mode spot converter, the light wave is first transmitted in the ridge single-mode waveguide. As the waveguide gradually narrows, the ability to limit the light wave gradually weakens, and the mode field area gradually increases. At the same time, it is restricted by the cladding and will not diffuse into the air. As the waveguide width continues to shrink with the transmission distance, its mode field gradually increases. The small-sized mode field in the ridge single-mode waveguide gradually diffuses into the cladding through the double-layer inverted cone waveguide and becomes a large-sized mode field.

[0032] In the thin-film lithium niobate Mach-Zehnder modulator, after the optical signal output by the double-conical spot converter enters the modulator, it is divided into two equal-power paths through the beam splitter waveguide and injected into MZM1 and MZM2, and intensity modulation is performed on the two sub-modulators respectively; in addition, by adjusting the DC bias on MZM3, a phase difference can be introduced into the signals on the two arms (loading a DC bias on the modulation electrode of the main modulator on a certain arm can introduce a phase shift determined by the DC bias into the optical signal after intensity modulation on the arm), and finally the two signals are coupled and outputted through the beam splitter waveguide to the modulated optical signals of the two arms.

[0033] The functional components are assembled in a certain order in the photolithography, and the principle of assembling electrical components first and then optical components is adopted. A fully functional modulator module is constructed through gradient solder, auxiliary fixtures and metal brackets.

[0034] In summary, the present invention is based on lithium niobate thin film modulator process technology, optimizes the pattern spot conversion waveguide structure, can achieve low insertion loss, and improves the modulation bandwidth through dual parallel modulators. The present invention can achieve the indicators of modulation bandwidth ≥ 60.83GHz, insertion loss ≤ 4.6dB, and extinction ratio ≥ 24dB, which can effectively improve the linearity and working bandwidth of microwave photonic links, and meet the wide application requirements of broadband satellite communications and high-frequency RF front-ends in various fields.

[0035] The above description is only a specific implementation of the present invention in the embodiment, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A high-efficiency ultra-wideband low insertion loss Mach-Zehnder modulator, comprising a SiO2 substrate, characterized in that: A dual parallel Mach-Zehnder modulator is arranged on the SiO2 substrate, and a pattern spot converter is respectively arranged at both ends of the dual parallel Mach-Zehnder modulator; the pattern spot converter is a dual-cone structure, including a bottom inverted conical waveguide and a top inverted conical waveguide, the bottom inverted conical waveguide includes a bottom rectangular section and a bottom conical section, the width of the bottom conical section is smaller than the width of the bottom rectangular section, a straight waveguide is extended from the end of the bottom conical section, the top inverted conical waveguide includes a top rectangular section and a top conical section, the width of the top rectangular section is smaller than the width of the bottom conical section, the length of the top rectangular section is equal to the length of the bottom rectangular section, the width of the top conical section is equal to the width of the top rectangular section, the end of the top conical section is a flat head, and the end of the top conical section is located at 1 / 5 to 3 / 5 of the length of the bottom conical section; The dual parallel Mach-Zehnder modulator includes a waveguide network and five high-frequency electrodes, wherein a gap is provided between two adjacent high-frequency electrodes, and a straight waveguide is provided at each end of the waveguide network. The straight waveguide at one end of the waveguide network is divided into four waveguides, namely, a first waveguide, a second waveguide, a third waveguide, and a fourth waveguide, through a two-stage one-to-two structure. The four waveguides pass through four gaps respectively, and then form a straight waveguide at the other end of the waveguide network through a two-stage two-in-one structure, wherein the first waveguide and the second waveguide are combined into a fifth waveguide, and the third waveguide and the fourth waveguide are combined into a sixth waveguide, and a DC electrode is provided at each of the first waveguide, the third waveguide, and the fifth waveguide; The mode spot converters at both ends of the dual parallel Mach Zehnder modulator are mirror-symmetrical, the straight waveguide at each end of the dual parallel Mach Zehnder modulator is connected to the bottom rectangular segment and the top rectangular segment of the mode spot converter at this end, the width of the straight waveguide of the dual parallel Mach Zehnder modulator is equal to the width of the bottom rectangular segment of the mode spot converter, and the height of the straight waveguide of the dual parallel Mach Zehnder modulator is equal to the height of the double-conical structure of the mode spot converter.

2. A high-efficiency ultra-wideband low insertion loss Mach-Zehnder modulator according to claim 1, characterized in that: The spot converter also has a silicon dioxide upper cladding layer above the double-tapered structure.

3. The high-efficiency ultra-wideband low insertion loss Mach-Zehnder modulator according to claim 1, characterized in that: The waveguides in the dual parallel Mach-Zehnder modulator and the spot converter are both made of lithium niobate.

4. The high-efficiency ultra-wideband low insertion loss Mach-Zehnder modulator according to claim 1, characterized in that: The width of the top rectangular segment is W1=2um, the width of the flat head at the end of the top conical segment is W3=480nm, the width of the bottom conical segment is W2=800nm, the length of the top conical segment is L1=500nm, the length of the bottom conical segment is L2=2.16um, and the width of the straight waveguide at the end of the bottom conical segment is W4=50nm.

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