CN107238951B - Low bias large bandwidth electro-optic modulator - Google Patents

Abstract

The invention discloses a low bias voltage and large bandwidth electro-optical modulator. The electro-optic modulator is a phase modulator with an electro-optic modulation waveguide, a Mach-Zehnder type electro-optic intensity modulator and a micro-ring resonant cavity type electro-optic intensity modulator. Modulation electrodes are used to apply an electric field to the electro-optic modulation wave guide to achieve phase or light intensity control. Modulation, the modulation electrode forms an electrical connection with the electro-optical modulation waveguide; the electro-optical modulation waveguide is a waveguide structure composed of alternating arrangements with the same periodicity or varying periods along the transmission direction. The invention can be used for electro-optical phase modulation and electro-optical intensity modulation in optical communication systems, and has the advantages of large modulation bandwidth, low operating voltage, high modulation efficiency, low operating energy consumption, small device size, simple structure, simple design, and simple process.

Description

Low bias large bandwidth electro-optical modulator

Technical field

The invention belongs to the technical field of optical communication, and in particular relates to a low-bias large-bandwidth electro-optical modulator based on an electro-optical modulation waveguide, which is suitable for modulating the phase and intensity of light in an optical communication system.

Background technique

In the 21st century, human society has entered the information age. The rapid development of Internet technology has triggered a new technological revolution, and the demand for communication capacity has increased exponentially. Optical communication technology has become the mainstream technology of current communications due to its advantages such as high bandwidth, low crosstalk, anti-interference, and low loss. As the core device in optical communication technology, the performance indicators of optoelectronic devices have been unable to meet the growing demand for ultra-high-speed transmission, and have gradually become a bottleneck in the development of ultra-large-capacity optical communication technology. Among the various solutions that have been proposed, silicon-based photonic integrated circuits, as one of the most promising solutions, have received great attention since their concept was proposed, and have made considerable progress in the performance of individual devices. , especially the maturity of silicon photonics technology in recent years, has attracted widespread attention from related industries around the world. For passive photonic integrated devices, silicon photonics technology has realized various high-performance devices by virtue of its inherent advantages. However, for active devices, silicon material is limited due to its own characteristics. As one of the most important active devices, the electro-optical modulator functions to convert electrical signals into optical signals. It is the core component of the transmitter and has always been a key technology in urgent need of breakthroughs in silicon-based integrated optoelectronic devices.

One of the most effective methods to achieve high-speed electro-optical modulation is to utilize the electro-optical effect, that is, in electro-optical materials, the change in refractive index is linearly related to the change in the external electric field. However, this linear electro-optical effect in silicon materials is very small, so it cannot be directly used to realize high-speed optical modulators based on the electro-optical effects of silicon materials. Another method is to use technology based on the plasma dispersion effect, that is, by regulating the carrier concentration in the semiconductor through an external electric field, causing changes in the real and imaginary parts of the refractive index of the semiconductor material, thus achieving the light modulation function. The control of carrier concentration in silicon materials is a nanosecond-picosecond level process, which can achieve high-speed light modulation of tens of Gbps. For the reported all-silicon modulator based on the plasma dispersion effect, its size is about ^10mm2 , the half-wave voltage is about 8V, and the bias voltage is about 5V. At the same time, it requires more thermo-optical phase shifters to assist the work, and there is still a device size Disadvantages include larger size, higher power consumption, and higher bias voltage. Therefore, taking into account device size, power consumption, driving voltage, insertion loss and other indicators, there is still a big gap between all-silicon modulators and existing commercial discrete electro-optical modulators based on lithium niobate.

Another promising modulator implementation method in silicon photonic integrated circuits is to combine electro-optical materials (such as the most commonly used electro-optical material lithium niobate, which has been widely used in commercial discrete electro-optical modulator devices) with silicon nanowaveguides. Combine. Electro-optical polymer material is an electro-optical material commonly used in silicon-based integrated devices. It has the advantages of large electro-optical coefficient, simple thin film process, and basic integration with existing processes. It is very suitable for producing low operating voltage, high modulation efficiency, and small device size. Modulators, and because electro-optical polymer materials are usually insulating media, ultra-low power electro-optic modulators can be realized. Although there have been some reports on silicon-based electro-optical polymer material modulators, they are still only breakthroughs in a single performance indicator (modulation rate/bandwidth, operating voltage, device size), and there are still many shortcomings in comprehensive performance. Therefore, silicon-based Electro-optical modulators with large modulation bandwidth, low operating voltage, high modulation efficiency, low operating energy consumption and small device size are still a challenge.

Contents of the invention

In view of the problems existing in the background technology, the purpose of the present invention is to provide a low-bias large-bandwidth electro-optic modulator based on electro-optic modulation waveguide, which can achieve smaller driving voltage, more compact size, larger modulation bandwidth and Lower operating energy consumption, and at the same time, the invention has the advantages of simple structure, simple design, simple process, etc., and plays an important role in silicon photonic integrated circuits.

The technical solution adopted by the present invention is:

The electro-optic modulator is a phase modulator with an electro-optic modulation waveguide, a Mach-Zehnder type electro-optic intensity modulator and a micro-ring resonant cavity type electro-optic intensity modulator. The modulation electrode is used to apply an electric field to the electro-optic modulation wave guide to achieve light intensity or phase adjustment. Modulation, the modulation electrode forms an electrical connection with the electro-optical modulation waveguide.

The electro-optical modulation waveguide is a waveguide structure composed of multiple waveguide units arranged in an alternating interdigital manner with the same period or changing period along the transmission direction. The gaps between the waveguide units and the size of the waveguide units may be the same or different. The periodic size of the waveguide structure is less than or equal to the operating wavelength.

The phase modulator with an electro-optical modulation waveguide includes a cladding structure and an input waveguide wrapped in the cladding structure, an electro-optical modulation waveguide, a first modulation electrode, a second modulation electrode and an output waveguide; the input waveguide, the electro-optical modulation The waveguide and the output waveguide are connected in sequence. The first modulation electrode and the second modulation electrode are respectively located on both sides near the electro-optical modulation waveguide and are electrically connected to the periodic structure waveguides on both sides of the electro-optical modulation waveguide respectively. The two sides can be the left and right sides or the upper and lower sides along the transmission direction.

The described Mach-Zehnder type electro-optical intensity modulator with electro-optical modulation waveguide includes a cladding structure and an input waveguide wrapped in the cladding structure, a power divider, a first connecting waveguide, a second connecting waveguide, and a third connecting waveguide. An electro-optical modulation waveguide, a second electro-optical modulation waveguide, a first modulation electrode, a second modulation electrode, a third modulation electrode, a third connection waveguide, a fourth connection waveguide, a power combiner and an output waveguide; an input waveguide and a power divider The input ports are connected, and the two output ports of the power splitter are respectively connected to the first connection waveguide and the second connection waveguide input end. The first connection waveguide output end is connected through the first electro-optical modulation waveguide and the third connection waveguide input end. The output end of the second connection waveguide is connected through the second electro-optical modulation waveguide and the input end of the fourth connection waveguide. The output ends of the third connection waveguide and the fourth connection waveguide are respectively connected to the two input ports of the power combiner. The output port of the power combiner connected to the output waveguide; the first modulation electrode and the third modulation electrode are respectively located on both sides of the first electro-optical modulation waveguide and the second electro-optical modulation waveguide, and the second modulation electrode is located between the first electro-optical modulation waveguide and the second electro-optical modulation waveguide, Thus, the first modulation electrode and the second modulation electrode are respectively located on both sides near the first electro-optical modulation waveguide, and are respectively electrically connected to the periodic structure waveguides on both sides of the first electro-optical modulation waveguide; at the same time, the second modulation electrode and the third modulation electrode The electrodes are respectively located on both sides near the second electro-optical modulation waveguide, and are electrically connected to the periodic structure waveguides on both sides of the second electro-optical modulation waveguide. The two sides can be the left and right sides or the upper and lower sides along the transmission direction.

The microring resonant cavity type electro-optic intensity modulator with electro-optic modulation waveguide includes a cladding structure and an input waveguide wrapped in the cladding structure, a first coupling waveguide, a second coupling waveguide, an electro-optic modulation waveguide, a third A modulation electrode, a second modulation electrode and an output waveguide; the input waveguide, the first coupling waveguide and the output waveguide are connected in sequence, the first coupling waveguide and the second coupling waveguide are coupled and arranged, and the second coupling waveguide and the electro-optical modulation waveguide are connected end to end to form a Microring resonant cavity; the first modulation electrode and the second modulation electrode are respectively arranged on both sides near the electro-optical modulation waveguide, and are electrically connected to the periodic structure waveguides inside and outside the electro-optical modulation waveguide respectively. The two sides can be the left and right sides or the upper and lower sides along the transmission direction.

The cladding structure is a cladding structure having a symmetrical or asymmetrical waveguide cross section (a cross section perpendicular to the transmission direction). Specifically, the waveguide serves as the core layer and is covered by an upper cladding layer and a lower cladding layer. The upper cladding layer and the lower cladding layer can be made of the same electro-optical material or different electro-optical materials, and the refractive index and electro-optical coefficient can be the same or different.

The cladding structure is mainly composed of an upper cladding layer and a lower cladding layer. The waveguide serves as the core layer. The upper cladding layer covers the core layer. The lower cladding layer is located below the core layer. The refractive index of the upper cladding layer and the lower cladding layer are equal. .

The cladding structure is asymmetrical up and down or left and right with the core layer as the center in the cross section along the transmission direction. Asymmetry means that the refractive index is different or at least one of the thickness and width is different.

The asymmetry of the cross section of the cladding structure along the transmission direction means that the upper and lower cladding layers on the upper and lower sides of the waveguide as the core layer have different refractive indexes or at least one of the thickness and width is different.

The left-right asymmetry of the cross-section of the cladding structure along the transmission direction means that the refractive index of the cladding on the left and right sides of the waveguide as the core layer is different or at least one of the thickness and width is different.

As a core layer, each of the waveguides is a fully etched waveguide, a single-sided ridge waveguide or a double-sided ridge waveguide; when it is a double-sided ridge waveguide, the number of layers, height or length of the ridges on both sides may be equal or unequal. .

The cladding structure is mainly composed of an upper cladding layer covering the core layer and a lower cladding layer located below the core layer. The waveguide serves as the core layer; each of the modulation electrodes is located on the upper part of the upper cladding layer and inside the upper cladding layer. , inside the lower cladding layer or between the upper cladding layer and the lower cladding layer, or each of the modulation electrodes is located on the upper part of the upper cladding layer, inside the upper cladding layer, inside the lower cladding layer, or between the upper cladding layer and the lower cladding layer. Multiple different positions (preferably symmetrical positions on both sides). Each of the modulation electrodes is directly electrically connected to the waveguide core layer or is connected point-to-point through other conductive materials.

At least one of the upper and lower cladding layers uses an electro-optical material with a high electro-optical coefficient. The electro-optical coefficient r ₃₃ is as high as ~192pm/V. The electro-optical coefficient of ordinary commercial electro-optical materials generally does not exceed 100pm/V.

The beneficial effects of the present invention are:

The invention has a simple structure, simple design and simple process, and is basically compatible with the mature CMOS (complementary metal oxide semiconductor) process. In terms of performance, in the periodic structure of the present invention, most of the light energy is distributed in the electro-optical material. Compared with ordinary silicon nanowire optical waveguides, the interaction between light and electro-optical materials is significantly enhanced. The equivalent refractive index of the mode in the waveguide The ratio between the change and the change in the refractive index of the electro-optical material is greater than 1, that is, Δn _eff /Δn _EOP > 1. In ordinary waveguides, this coefficient is generally 0.5. At the same time, since the spacing between adjacent waveguides in the periodic structure is very small, as small as ∼100 nm, the modulated electric field is enhanced in it.

At the same time, benefiting from the high electro-optic coefficient of the electro-optic polymer material, the electro-optic modulator of the present invention can achieve extremely low operating voltage and extremely small device size (V _π L = 0.23 V·mm), which is far superior to the niobate in the background introduction Lithium discrete modulators and silicon-based plasmon dispersion effect electro-optic modulators, as well as most of the silicon-organic hybrid electro-optic modulators that have been reported.

The electrode structure in the present invention has a small RC constant, and combined with the extremely fast response speed of the electro-optical polymer material, a very large modulation bandwidth (3dB bandwidth is 176GHz) can be achieved, which is tens to dozens larger than most reported modulators. 3dB bandwidth in GHz. At the same time, since the electro-optical polymer material is an insulating dielectric material and the current is extremely small during operation, the electro-optical modulator of the present invention has extremely low operating energy consumption (~1fJ/bit), which is better than the reported tens to several times. Power consumption of hundreds of fJ/bit.

In summary, compared with the existing electro-optical modulators in the background introduction, the present invention can achieve lower operating voltage, smaller device size, larger modulation bandwidth, higher modulation efficiency, and lower operating energy consumption. At the same time, its manufacturing process It is compatible with the existing mature CMOS process and has the advantages of simple structure, simple design, and simple process.

Description of the drawings

Figure 1 is a schematic structural diagram of a high-speed electro-optical phase modulator using an electro-optical modulation waveguide according to the present invention.

Figure 2 is a schematic structural diagram of the Mach-Zehnder electro-optic intensity modulator using electro-optic modulation waveguide according to the present invention.

Figure 3 is a schematic structural diagram of a micro-ring resonant cavity electro-optical intensity modulator using an electro-optical modulation waveguide according to the present invention.

Figure 4 is a schematic cross-sectional view of a single-sided ridge waveguide structure with symmetrical cladding according to the present invention.

Figure 5 is a schematic cross-sectional view of the first double-sided ridge waveguide structure with symmetrical cladding of the present invention.

Figure 6 is a schematic cross-sectional view of the second ridge-type waveguide structure with symmetrical cladding on both sides of the present invention.

Figure 7 is a schematic cross-sectional view of the third double-sided ridge waveguide structure with symmetrical cladding of the present invention.

Figure 8 is a schematic cross-sectional view of the fourth ridge-type waveguide structure with symmetrical cladding on both sides of the present invention.

Figure 9 is a schematic cross-sectional view of a single-sided ridge waveguide structure with asymmetric cladding according to the present invention.

Figure 10 is a schematic cross-sectional view of the first double-sided ridge waveguide structure with asymmetric cladding of the present invention.

Figure 11 is a schematic cross-sectional view of the second double-sided ridge waveguide structure with asymmetric cladding of the present invention.

Figure 12 is a schematic cross-sectional view of the third double-sided ridge waveguide structure with asymmetric cladding of the present invention.

Figure 13 is a schematic cross-sectional view of the fourth double-sided ridge waveguide structure with asymmetric cladding of the present invention.

Figure 14 is a schematic cross-sectional view of the first electrode position of the present invention.

Figure 15 is a schematic cross-sectional view of the second electrode position of the present invention.

Figure 16 is a schematic cross-sectional view of the third electrode position of the present invention.

Figure 17 is a schematic cross-sectional view of the fourth electrode position of the present invention.

Figure 18 is a schematic cross-sectional view of the fully etched waveguide structure and the fifth electrode position of the present invention.

Figure 19 is a schematic top cross-sectional view of the period-invariant waveguide structure of the present invention.

Figure 20 is a schematic top cross-sectional view of the periodically changing waveguide structure of the present invention.

Figure 21 is the mode field distribution along the electro-optical modulation waveguide direction of the present invention.

Figure 22 is a curve of the equivalent refractive index of the electro-optical modulated waveguide mode of the present invention changing with the refractive index of the electro-optical material.

Figure 23 is a schematic diagram of the modulation principle of the electro-optic modulation waveguide electro-optic phase modulator of the present invention.

Figure 24 is a schematic circuit diagram of the electro-optical phase modulator using electro-optical modulation waveguide according to the present invention.

Figure 25 is a frequency response curve diagram of the electro-optical phase modulator using electro-optical modulation waveguide according to the present invention.

Figure 26 is a schematic diagram of the principle of the Mach-Zehnder electro-optic intensity modulator using electro-optic modulation waveguide according to the present invention.

Figure 27 is a schematic circuit diagram of a Mach-Zehnder electro-optic intensity modulator using an electro-optic modulation waveguide according to the present invention.

Figure 28 is a schematic equivalent circuit diagram of the Mach-Zehnder electro-optic intensity modulator using electro-optic modulation waveguide according to the present invention.

In Figure 1: 1-input waveguide, 4-electro-optical modulation waveguide, 5a-first modulation electrode, 5b-second modulation electrode, 8-output waveguide.

In Figure 2: 1-input waveguide, 2-power divider, 3a-first connecting waveguide, 3b-second connecting waveguide, 4a-first electro-optical modulation waveguide, 4b-second electro-optical modulation waveguide, 5a-first modulation Electrode, 5b - second modulation electrode, 5c - third modulation electrode, 6a - third connection waveguide, 6b - fourth connection waveguide, 7 - power combiner, 8 output waveguide.

In Figure 3: 1-input waveguide, 9a-first coupling waveguide, 9b-second coupling waveguide, 4-electro-optic modulation waveguide, 5a-first modulation electrode, 5b-second modulation electrode, 8-output waveguide.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and examples.

As shown in Figure 1, a phase modulator with an electro-optical modulation waveguide includes a cladding structure and an input waveguide 1 wrapped in the cladding structure, an electro-optical modulation waveguide 4, a first modulation electrode 5a, a second modulation electrode 5b and Output waveguide 8; input waveguide 1, electro-optical modulation waveguide 4 and output waveguide are connected in sequence 8. The first modulation electrode 5a and the second modulation electrode 5b are respectively located on the left and right sides or the upper and lower sides near the electro-optical modulation waveguide 4, and are connected to the electro-optical modulation waveguide 4 respectively. The periodic structure waveguides on both sides of the modulation waveguide 4 are electrically connected.

As shown in Figure 2, the Mach-Zehnder type electro-optic intensity modulator with electro-optic modulation waveguide includes a cladding structure and an input waveguide 1 wrapped in the cladding structure, a power divider 2, a first connection waveguide 3a, The second connection waveguide 3b, the first electro-optical modulation waveguide 4a, the second electro-optical modulation waveguide 4b, the first modulation electrode 5a, the second modulation electrode 5b, the third modulation electrode 5c, the third connection waveguide 6a, the fourth connection waveguide 6b, The power combiner 7 and the output waveguide 8; the input waveguide 1 is connected to the input port of the power divider 2, and the two output ports of the power divider 2 are respectively connected to the input ends of the first connection waveguide 3a and the second connection waveguide 3b. The output end of the first connection waveguide 3a is connected through the first electro-optical modulation waveguide 4a and the input end of the third connection waveguide 6a, the output end of the second connection waveguide 3b is connected through the input end of the second electro-optical modulation waveguide 4b and the fourth connection waveguide 6b, and the third connection The output ends of the waveguide 6a and the fourth connection waveguide 6b are respectively connected to the two input ports of the power combiner 7, and the output port of the power combiner 7 is connected to the output waveguide 8; the first modulation electrode 5a and the third modulation electrode 5c are respectively located at On both outer sides of the first electro-optical modulation waveguide 4a and the second electro-optical modulation waveguide 4b, the second modulation electrode 5b is located between the first electro-optical modulation waveguide 4a and the second electro-optical modulation waveguide 4b, so that the first modulation electrode 5a and the second modulation waveguide 4b The electrodes 5b are respectively located on both sides near the first electro-optical modulation waveguide 4a, and are respectively electrically connected to the periodic structure waveguides on both sides of the first electro-optical modulation waveguide 4a; at the same time, the second modulation electrode 5b and the third modulation electrode 5c are respectively located on the second The left and right sides or the upper and lower sides near the electro-optical modulation waveguide 4b are electrically connected to the periodic structure waveguides on both sides of the second electro-optical modulation waveguide 4b respectively.

As shown in Figure 3, a microring resonant cavity type electro-optic intensity modulator with an electro-optic modulation waveguide includes a cladding structure and an input waveguide 1, a first coupling waveguide 9a and a second coupling waveguide 9b wrapped in the cladding structure. , the electro-optical modulation waveguide 4, the first modulation electrode 5a, the second modulation electrode 5b and the output waveguide 8; the input waveguide 1, the first coupling waveguide 9a and the output waveguide 8 are connected in sequence, and the first coupling waveguide 9a and the second coupling waveguide 9b are in phase. Coupling arrangement, the second coupling waveguide 9b and the electro-optical modulation waveguide 4 are connected end to end to form a micro-ring resonant cavity; the first modulation electrode 5a and the second modulation electrode 5b are respectively arranged on the left and right sides or the upper and lower sides near the electro-optical modulation waveguide 4, And are electrically connected to the periodic structure waveguides inside and outside the electro-optical modulation waveguide 4 respectively.

The specifically implemented periodic structure waveguide is a waveguide structure composed of alternating arrangements with the same periodicity or varying periods along the transmission direction. The gaps and sizes of the waveguide periodic structures can be the same or different periodic structures.

As shown in Figures 4 to 13, the cladding structure is a cladding structure with a symmetrical or asymmetrical waveguide cross section (section along the transmission direction). The cladding structure is mainly composed of an upper cladding layer 100 and a lower cladding layer 102. The waveguide serves as the core layer 101. The upper cladding layer 100 covers the core layer 101, and the lower cladding layer 102 is located under the core layer 101. The core layer 101 is a single-sided ridge waveguide or a double-sided ridge waveguide.

As shown in Figure 4, the upper cladding layer 100 and the lower cladding layer 102 are made of the same electro-optical material and have the same refractive index. The core layer 101 is a single-sided ridge waveguide, one side of the ridge is etched, and the number of ridge layers is one.

As shown in Figure 5, the upper cladding layer 100 and the lower cladding layer 102 are made of the same electro-optical material and have the same refractive index. There are ridge waveguides on both sides of position 101 of the core layer. Both sides of the ridge are etched, with the same etching depth on both sides. The number of ridge layers is one, and the number of ridge layers on both sides is the same.

As shown in FIG. 6 , the upper cladding layer 100 and the lower cladding layer 102 are made of the same electro-optical material and have the same refractive index. There are ridge waveguides on both sides of position 101 of the core layer. Both sides of the ridge are etched, with different etching depths on both sides. The number of ridge layers is one, and the number of ridge layers on both sides is the same.

As shown in FIG. 7 , the upper cladding layer 100 and the lower cladding layer 102 are made of the same electro-optical material and have the same refractive index. There are ridge waveguides on both sides of position 101 of the core layer. Both sides of the ridge are etched. The etching depths on both sides are different, and the number of layers on the ridges on both sides is different.

As shown in FIG. 8 , the upper cladding layer 100 and the lower cladding layer 102 are made of the same electro-optical material and have the same refractive index. There are ridge waveguides on both sides of position 101 of the core layer. Both sides of the ridge are etched. The etching depths on both sides are different, and the number of layers on the ridges on both sides is different.

As shown in FIG. 9 , the upper cladding layer 100 and the lower cladding layer 102 are made of different materials, at least one of which is an electro-optical material. The core layer 101 is a single-sided ridge waveguide, one side of the ridge is etched, and the number of ridge layers is one.

As shown in FIG. 10 , the upper cladding layer 100 and the lower cladding layer 102 are made of different materials, at least one of which is an electro-optical material. The core layer 101 is a ridge waveguide on both sides. Both sides of the ridge are etched, and the etching depth is the same on both sides. The number of ridge layers is one, and the number of ridge layers on both sides is the same.

As shown in FIG. 11 , the upper cladding layer 100 and the lower cladding layer 102 are made of different materials, at least one of which is an electro-optical material. The core layer 101 is a ridge waveguide on both sides. Both sides of the ridge are etched with different etching depths. The number of ridge layers is one, and the number of ridge layers on both sides is the same.

As shown in FIG. 12 , the upper cladding layer 100 and the lower cladding layer 102 are made of different materials, at least one of which is an electro-optical material. The core layer 101 is a ridge waveguide on both sides. Both sides of the ridge are etched. The etching depths on both sides are different, and the number of layers of the ridges on both sides is different.

As shown in FIG. 13 , the upper cladding layer 100 and the lower cladding layer 102 are made of different materials, at least one of which is an electro-optical material. The core layer 101 is a ridge waveguide on both sides. Both sides of the ridge are etched. The etching depths on both sides are different, and the number of layers of the ridges on both sides is different.

As shown in FIG. 14 , the upper cladding layer 100 and the lower cladding layer 102 are made of different materials, at least one of which is an electro-optical material. The core layer 101 is a ridge waveguide on both sides. One side of the ridge is etched with different etching depths on both sides. The number of layers of the ridges on both sides is the same. The modulation electrode 103 is located above the waveguide core layer 101 and contacts it.

As shown in FIGS. 15 and 14 , the upper cladding layer 100 and the lower cladding layer 102 are made of different materials, at least one of which is an electro-optical material. The core layer 101 is a ridge waveguide on both sides. Both sides of the ridge are etched with different etching depths. The number of layers of the ridges on both sides is the same. The modulation electrode 103 is located on one side of the waveguide core layer 101 in contact with it.

As shown in FIGS. 16 and 14 , the upper cladding layer 100 and the lower cladding layer 102 are made of different materials, at least one of which is an electro-optical material. The core layer 101 is a ridge waveguide on both sides. The two sides of the ridge are etched with different etching depths. The number of layers of the ridges on both sides is the same. The modulation electrode 103 is located at the lower part of the waveguide core layer 101 and is in contact with it.

As shown in FIGS. 17 and 14 , the upper cladding layer 100 and the lower cladding layer 102 are made of different materials, at least one of which is an electro-optical material. The core layer 101 is a ridge waveguide on both sides. Both sides of the ridge are etched with different etching depths. The number of layers of the ridges on both sides is the same. The modulation electrode 103 is in contact with the waveguide core layer 101 through other conductive materials 104.

As shown in FIG. 18 , the upper cladding layer 100 and the lower cladding layer 102 are made of different materials, at least one of which is an electro-optical material. The core layer 101 is a fully etched waveguide, and the modulation electrode 103 is in contact with the waveguide core layer 101 through other conductive materials 104 .

As shown in Figure 19, the upper cladding layer 100 is an electro-optical material, and the core layer 101 is a periodic waveguide structure with a constant period.

As shown in Figure 20, the upper cladding layer 100 is an electro-optical material, and the core layer 101 is a periodic waveguide structure that changes periodically.

As shown in Figure 22, it is the working principle of the electro-optical phase modulator of the present invention. The electro-optic modulation waveguide is located in the cladding of the electro-optic material, and is connected to a positive and a negative modulation electrode on both sides. A certain voltage is applied between them. Due to the conductivity of the waveguide material, an electric field distribution is formed between the two adjacent periodic waveguide structures from the positive electrode to the negative electrode. According to the electro-optical effect, the refractive index of the electro-optical material in the electric field will change with the intensity of the electric field. changes with the change; therefore, by changing the voltage applied between the two electrodes, the refractive index of the electro-optical material in the electric field between the two electrodes can be changed, thereby also changing the phase of the electro-optical modulated waveguide light passing through this section, achieving Electro-optical phase modulation function. The working principle of the electro-optical intensity modulator of the micro-ring resonant cavity of the present invention is similar to that of the electro-optical phase modulator. The electro-optical modulation waveguide in the micro-ring resonant cavity performs phase modulation to further realize the change of the resonant wavelength of the micro-ring resonant cavity. When the input light When the wavelength of the wavelength changes in the resonance state in the microring resonator (from resonance to disresonance or from non-resonance to resonance), the intensity of the output light also changes accordingly. The output light intensity is very small when resonant and not resonant. When the output light intensity is very large, it is about the input optical power.

As shown in Figure 26, it is the Mach-Zehnder electro-optical intensity modulation principle of the present invention. It is similar to the principle of the above-mentioned electro-optical phase modulator. When an electric field is applied to the electro-optical modulation waveguide, the phase of the light passing through the waveguide changes. Due to the Mach-Zehnder two The electric fields applied by the two interference arms are in opposite directions, so the light phase changes have opposite signs. The two beams of light that have undergone different phase changes interfere in the power combiner. According to the different phase differences, the intensity of the interference output light is also different. Therefore, by changing the applied Modulating the voltage between the electrodes changes the phase difference between the two beams of light to achieve modulation of light intensity.

Specific implementation examples and implementation processes of the present invention are:

Example 1

As shown in Figure 1, a high-speed electro-optic phase modulator using an electro-optic modulation waveguide has the left side of the input waveguide 1 as the input port and the right side of the output waveguide 8 as the output port. The voltage applied between the first modulation electrode 5a and the second modulation electrode 5b is The two types of V _Off and V _on make the device in this embodiment correspond to two working states: Off and On.

In this embodiment, the cladding structure is as shown in Figure 5, the modulation electrode arrangement is as shown in Figure 14, and the upper cladding layer is made of an electro-optical material with an electro-optical coefficient of 192pm/V.

Light is input from the left side of input waveguide 1 and enters electro-optical modulation waveguide 4 from the left side:

When the working state is Off, the voltage between the first modulation electrode 5a and the second modulation electrode 5b is V _Off , the equivalent refractive index of the electro-optical modulation waveguide 4 is n _eff , and the length is L, then the phase of the light passing through the electro-optical modulation waveguide 4 is Increase k is the wave number in vacuum, and L is the length of the electro-optical modulation band 4.

When the working state is On, the voltage between the first modulation electrode 5a and the second modulation electrode 5b is V _On . At this time, an electric field distribution as shown in Figure 22 is generated between adjacent finger-shaped periodic waveguides of the electro-optical modulation waveguide. Due to the electro-optical properties of the electro-optical material, Effect, the refractive index of the electro-optic material located between adjacent periodic structures of the electro-optic modulation waveguide changes under the action of the electric field:

Among them, n is the original refractive index of the electro-optical material, r ₃₃ is the electro-optical coefficient of the electro-optical material, and d is the spacing in the middle of the periodic structure. Due to the change in the refractive index of the electro-optic material, the equivalent refractive index of the mode in the electro-optic modulation waveguide also changes, and the relationship between them can be expressed as:

△n _eff =S△n

Among them, △n represents the refractive index change of the electro-optical material, △n _eff represents the equivalent refractive index change of the mode in the electro-optical modulated waveguide, and S is the coefficient of the mode equivalent refractive index change with the refractive index of the electro-optical material. In ordinary waveguides , generally S = 0.5. In the electro-optical modulated waveguide of the present invention, the mode field distribution is shown in Figure 21. There are more light fields distributed in the electro-optical material, and the change in the equivalent refractive index is enhanced. According to Figure 25, etc. The effective refractive index changes with the refractive index of the electro-optical material, and S = 1.145, which is much higher than the ordinary waveguide structure. Therefore, the phase of the light passing through the electro-optical modulation waveguide 4 also changes, which can be expressed as:

Among them, k is the wave number in vacuum, and L is the length of the periodic structure. Therefore, the half-wave voltage-length of the electro-optical phase modulator based on the electro-optical modulation waveguide of the present invention can be expressed as:

Among them, _Vπ represents the half-wave voltage of the electro-optical phase modulator, and λ is the operating wavelength. Here, a set of typical parameters of the electro-optical modulated waveguide electro-optical phase modulator used in the present invention are given: d=150nm, λ=1.55μm, S=1.145, n=1.66, r ₃₃ =192pm/V. After calculation, it can be obtained that, The half-wave voltage-length V _π L = 0.23V·mm is much smaller than the reported integrated all-silicon modulators based on plasma dispersion effects and silicon-based modulators based on electro-optical materials.

As shown in Figure 23, it is a schematic circuit diagram of an electro-optical phase modulator based on an electro-optical modulation waveguide. Its form can be equivalent to the equivalent circuit diagram in Figure 24. After calculation, the electro-optical phase modulator of the present invention is loaded on the electro-optic material. The relationship between the voltage V _eff at both ends and the input voltage V _in can be expressed as:

Among them, j represents an imaginary number, C is the capacitance between two adjacent periodic waveguide structures, ω represents the angular frequency of the modulation signal, R represents the resistance of the periodic waveguide structure, and R _S represents the resistance of the modulation signal source, generally 50Ω. , N represents the number of periodic structures contained in the modulated waveguide.

As shown in Figure 26, the relationship between V _eff /V _in and the modulation signal frequency f is shown. Therefore, the present invention uses an electro-optical phase modulator using an electro-optical modulation waveguide. Its 3dB bandwidth due to the limitation of the circuit RC constant is 176GHz, which is much higher. Most of the existing modulators use silicon plasma dispersion effect and electro-optical effect, and the 3dB bandwidth of the latter is generally tens of GHz.

According to the calculation formula of energy consumption E:

Among them, V _pp is the peak-to-peak value of the modulation voltage, and C is the total capacitance of the modulator. Calculated according to the above formula, the energy consumption of the electro-optical phase modulator of the present invention is 1 fJ/bit, which is better than the reported tens to hundreds of fJ/bit. bit power consumption.

Example 2

As shown in Figure 2, a Mach-Zehnder electro-optical intensity modulator using an electro-optical modulation waveguide has the input port on the left side of the input waveguide 1 and the output port on the right side of the output waveguide 8. There are two voltages V _Off1 and V _on1 applied between the first modulation electrode 5a and the second modulation electrode 5b, so that the device in this embodiment corresponds to two working states: Off and On. There are two voltages V _Off2 and V _on2 applied between the third modulation electrode 5c and the second modulation electrode 5b, so that the device in this embodiment corresponds to two working states: Off and On.

In this embodiment, the cladding structure is as shown in Figure 5, the modulation electrode arrangement is as shown in Figure 14, and the upper cladding layer is made of an electro-optical material with an electro-optical coefficient of 192pm/V.

Light is input from the left side of input waveguide 1 and enters power divider 2. The light is divided into two beams with the same energy, beam A and beam B, which enter the first connection waveguide 3a and the second connection waveguide 3b respectively:

When the working state is Off, the voltage between the first modulation electrode 5a and the second modulation electrode 5b is V _Off1 , the voltage between the third modulation electrode 5c and the second modulation electrode 5b is V _Off2 , and the light beam A passes through the first electro-optical modulation waveguide 4a, The phase increases to Beam B passes through the second electro-optical modulation waveguide 4b, and the phase increases to/> Beam A and beam B enter the power combiner 7 through the third connecting waveguide 6a and the fourth connecting waveguide 6b respectively. When beam A and beam B are combined, the phase difference is/>

When the working state is On, the voltage between the first modulation electrode 5a and the second modulation electrode 5b is V _On1 , and the voltage between the third modulation electrode 5c and the second modulation electrode 5b is V _On2 . According to the electro-optic phase of the electro-optic modulation waveguide used above The working principle of the modulator is that beam A passes through the first electro-optical modulation waveguide 4a, and the phase increase changes as Beam B passes through the second electro-optical modulation waveguide 4b, and the phase increase changes to/> Beam A and beam B enter the power combiner 7 through the third connecting waveguide 6a and the fourth connecting waveguide 6b respectively. When beam A and beam B are combined, the phase difference is/>

According to the working principle of the Mach-Zehnder interferometer, the relationship between the optical power entering the output waveguide 8 from the power combiner 7 and the phase difference between beam A and beam B is:

Among them, I _in is the optical power input from the input port, and I _out is the optical power output from the output port. When Pick and/> At different values, the optical power I _out output by the output port is also different (under the best modulation effect, ).

According to the working principle of the phase modulator in the above-mentioned Embodiment 1, the phase difference generated by beam A and beam B passing through the electro-optical modulation waveguide in the On state and the Off state can be expressed as:

As shown in FIG. 26, when a voltage is applied to the first electrode between the first modulation electrode 5a and the second modulation electrode 5b and between the second modulation electrode 5b and the third modulation electrode 5c, the first modulation electrode 5a and the second modulation electrode 5c The direction of the electric field between the electrodes 5b is opposite to the direction of the electric field between the second modulation electrode 5b and the third modulation electrode 5c, so Therefore, the half-wave voltage-length of the Mach-Zehnder electro-optic intensity modulator using electro-optic modulation waveguide can be expressed as:

Here, a set of typical parameters of the electro-optical modulated waveguide Mach-Zehnder type electro-optical intensity modulator used in the present invention are given: d=2μm, λ=1.55μm, S=1, n=1.66, r ₃₃ =192pm/V, It can be calculated that the half-wave voltage-length V _π L = 0.12V·mm, which is much smaller than the reported integrated all-silicon modulator based on the plasma dispersion effect.

As shown in Figure 27, it is a circuit diagram of a Mach-Zehnder type electro-optical intensity modulator using an electro-optical modulation waveguide. Its form can be equivalent to the circuit diagram in Figure 28. Since its half-wave voltage-length V _π L = 0.12V·mm , is only 1/2 of the electro-optical phase modulator using electro-optical modulated waveguide. Under the same operating voltage, the same modulation effect is achieved, and its modulation length is only 1/2 of the electro-optical modulated waveguide. At the same time, the Mach-Zen of the electro-optical modulated waveguide is The German-type electro-optical intensity modulator adopts a pull-push structure, and the circuits of the first electro-optical modulation waveguide 4a and the second electro-optical modulation waveguide 4b are in parallel structure, so its equivalent circuit is the same as that of the electro-optical phase modulator in Embodiment 1. The effective circuit is the same, so its 3dB bandwidth and energy consumption are also the same as those of the electro-optical phase modulator. The 3dB bandwidth caused by the RC constant limitation is 176GHz and the energy consumption is 1fj/bit. Both parameters are far beyond those reported or commercial silicon based electro-optical modulator.

Example 3

As shown in Figure 3, an electro-optical modulated waveguide microring resonant cavity electro-optical intensity modulator is used. The left side of the input waveguide 1 is the input port, the right side of the output band 5 is the input port, and the input light is a single-wavelength light with a wavelength of λ. There are two voltages V _Off and V _on applied between the first modulation electrode 5a and the second modulation electrode 5b, so that the device in this embodiment corresponds to the two working states Off and On.

In this embodiment, the cladding structure is as shown in Figure 5, the modulation electrode arrangement is as shown in Figure 14, and the upper cladding layer is made of an electro-optical material with an electro-optical coefficient of 192pm/V.

Light is input from the left side of the input waveguide 1 and passes through the coupling area composed of the first coupling waveguide 9a and the second coupling waveguide 9b:

When working in the Off state, the voltage between the first modulation electrode 5a and the second modulation electrode 5b is V _Off . At this time, the resonant wavelength λ _Off of the microring resonant cavity is equal to the input light wavelength λ, so the input light is in the microring resonant cavity. In medium resonance, there is no light output from the right end of input waveguide 5.

When working in the On state, the voltage between the first modulation electrode 5a and the second modulation electrode 5b is V _On . According to the working principle of the electro-optical phase modulator using the electro-optic modulation waveguide mentioned above, it is located in the adjacent finger period of the electro-optic modulation waveguide. The refractive index of the electro-optical material between the waveguides changes under the action of the electric field, and the phase of the light in the microring resonant cavity increases and changes, causing the resonant wavelength λ _On of the microring resonant cavity to change, and is not equal to the input light wavelength λ, so the input The light does not resonate in the microring resonant cavity and will be output from the right end of the output waveguide 8 . In summary, by changing the voltage between the first modulation electrode 5a and the second modulation electrode 5b from V _Off to V _On , the light intensity is modulated.

In this embodiment, the microring resonant cavity electro-optic intensity modulator using electro-optic modulation waveguide has a modulation structure similar to that of the electro-optic phase modulator using electro-optic modulation waveguide in Embodiment 1. Therefore, its half-wave voltage-length and modulation rate are 3dB. The calculation of bandwidth and energy consumption is similar to that in Embodiment 1 and will not be described again.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention. should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (6)

1. A low bias large bandwidth electro-optic modulator, characterized by: the electro-optic modulator is a phase modulator with an electro-optic modulation waveguide, a Mach-Zehnder type electro-optic intensity modulator or a micro-ring resonant cavity type electro-optic intensity modulator, an electric field is applied to the electro-optic modulation waveguide by using a modulation electrode to realize the modulation of light intensity or phase, and the modulation electrode is electrically connected with the electro-optic modulation waveguide;

the electro-optical modulation waveguide is a waveguide structure formed by alternately arranging a plurality of waveguide units in the same period or in an interdigital mode with a changing period along the transmission direction, and the gaps among the waveguide units and the dimensions of the waveguide units can be the same or different;

the phase modulator with the electro-optic modulation waveguide comprises a cladding structure, an input waveguide (1), an electro-optic modulation waveguide (4), a first modulation electrode (5 a), a second modulation electrode (5 b) and an output waveguide (8), wherein the input waveguide (1), the electro-optic modulation waveguide (4), the first modulation electrode (5 b) and the output waveguide are coated in the cladding structure; the input waveguide (1), the electro-optic modulation waveguide (4) and the output waveguide (8) are sequentially connected, and the first modulation electrode (5 a) and the second modulation electrode (5 b) are respectively positioned at two sides near the electro-optic modulation waveguide (4) and are respectively and electrically connected with the electro-optic modulation waveguide (4);

the Mach-Zehnder type electro-optic intensity modulator with the electro-optic modulation waveguide comprises a cladding structure, an input waveguide (1), a power divider (2), a first connecting waveguide (3 a), a second connecting waveguide (3 b), a first electro-optic modulation waveguide (4 a), a second electro-optic modulation waveguide (4 b), a first modulation electrode (5 a), a second modulation electrode (5 b), a third modulation electrode (5 c), a third connecting waveguide (6 a), a fourth connecting waveguide (6 b), a power combiner (7) and an output waveguide (8), wherein the input waveguide (1), the power divider (2), the first connecting waveguide (3 a), the second connecting waveguide (3 b), the first electro-optic modulation waveguide (4 a), the second electro-optic modulation waveguide (4 b), the first modulation electrode (5 a), the second modulation electrode (5 b), the third modulation electrode (5 c), the third connecting waveguide (6 a), the fourth connecting waveguide (6 b) and the power combiner (8) are coated in the cladding structure; the input waveguide (1) is connected with an input port of the power divider (2), two output ports of the power divider (2) are respectively connected with two input ports of the first connecting waveguide (3 a) and the second connecting waveguide (3 b), an output end of the first connecting waveguide (3 a) is connected with an input end of the third connecting waveguide (6 a) through the first electro-optical modulation waveguide (4 a), an output end of the second connecting waveguide (3 b) is connected with an input end of the fourth connecting waveguide (6 b) through the second electro-optical modulation waveguide (4 b), an output end of the third connecting waveguide (6 a) and an output end of the fourth connecting waveguide (6 b) are respectively connected with two input ports of the power combiner (7), and an output port of the power combiner (7) is connected with the output waveguide (8); the first modulation electrode (5 a) and the second modulation electrode (5 b) are respectively positioned at two sides near the first electro-optic modulation waveguide (4 a) and are respectively electrically connected with the first electro-optic modulation waveguide (4 a); simultaneously, the second modulation electrode (5 b) and the third modulation electrode (5 c) are respectively positioned at two sides near the second electro-optic modulation waveguide (4 b) and are respectively electrically connected with the second electro-optic modulation waveguide (4 b);

the micro-ring resonant cavity type electro-optic intensity modulator with the electro-optic modulation waveguide comprises a cladding structure, an input waveguide (1), a first coupling waveguide (9 a), a second coupling waveguide (9 b), an electro-optic modulation waveguide (4), a first modulation electrode (5 a), a second modulation electrode (5 b) and an output waveguide (8), wherein the input waveguide (1), the first coupling waveguide (9 a), the second coupling waveguide (9 b), the electro-optic modulation waveguide (4) are coated in the cladding structure; the input waveguide (1), the first coupling waveguide (9 a) and the output waveguide (8) are sequentially connected, the first coupling waveguide (9 a) and the second coupling waveguide (9 b) are in coupling arrangement, and the second coupling waveguide (9 b) and the electro-optic modulation waveguide (4) are connected end to form a micro-ring resonant cavity; the first modulation electrode (5 a) and the second modulation electrode (5 b) are respectively arranged on both sides near the electro-optical modulation waveguide (4) and are respectively electrically connected with the electro-optical modulation waveguide (4).

2. A low bias large bandwidth electro-optic modulator as claimed in claim 1, wherein: the cladding structure is a cladding structure with a symmetrical or asymmetrical waveguide section.

3. A low bias large bandwidth electro-optic modulator as claimed in claim 2, wherein: the cladding structure mainly comprises an upper cladding layer (100) and a lower cladding layer (102), wherein the refractive indexes of the upper cladding layer (100) and the lower cladding layer (102) are equal.

4. A low bias large bandwidth electro-optic modulator as claimed in claim 1, wherein: the cladding structure is asymmetric up and down or left and right on a section perpendicular to the transmission direction by taking the core layer (101) as a center, wherein the asymmetry means that the refractive indexes are different or at least one of the thickness and the width is different.

5. A low bias large bandwidth electro-optic modulator according to any of claims 1-2, wherein: each waveguide is used as a core layer (101) and is a full-etched waveguide or a single-side ridge waveguide or a double-side ridge waveguide; in the case of a double-sided ridge waveguide, the number of layers, height, or length of the two-sided ridge may be equal or unequal.

6. A low bias large bandwidth electro-optic modulator according to any of claims 1-2, wherein: the cladding structure mainly comprises an upper cladding (100) covered on the core layer (101) and a lower cladding (102) positioned below the core layer (101), and the waveguide is used as the core layer (101); each of the modulation electrodes is simultaneously located at a plurality of different positions in an upper portion of the upper cladding layer (100), an inside of the lower cladding layer (102), or between the upper cladding layer (100) and the lower cladding layer (102), or each of the modulation electrodes is respectively located at a plurality of different positions in the upper portion of the upper cladding layer (100), an inside of the lower cladding layer (102), or between the upper cladding layer (100) and the lower cladding layer (102).