Upload and download type electro-optical modulator based on winding type doped micro-ring structure

Abstract

The invention discloses an upload and download type electro-optical modulator based on a winding type doped micro-ring structure, and belongs to the technical field of integrated photoelectronics. The electro-optical modulator comprises a silicon substrate, a silicon dioxide layer, a strip-shaped ridge waveguide, an annular ridge waveguide and a metal electrode, according to the electro-optical modulator, simultaneous modulation of a transverse PN junction and a longitudinal PN junction is achieved through winding type doping, the overlapping factor of a depletion region and a light field region is increased under the condition that junction capacitance is not affected, and the modulation efficiency of the micro-ring modulator is improved; by adjusting the gaps between the two strip-shaped ridge waveguides and the middle annular ridge waveguide respectively, the optical quality factor of the micro-ring modulator can be controlled, the extinction ratio can be improved, the working bandwidth of the micro-ring modulator is improved, and therefore high modulation efficiency and high electro-optical modulation bandwidth of the micro-ring electro-optical modulator can be achieved at the same time.

Description

Technical Field

[0001] This application relates to the field of integrated optoelectronic technologies, and particularly to an add-drop electro-optic modulator based on a meandering doped micro-ring structure. Background Art

[0002] In the 21st century, silicon photonics has developed rapidly, and various silicon optoelectronic devices have emerged continuously. Among them, optical interconnection, as one of the important application scenarios of silicon optoelectronic devices, is considered to be one of the feasible solutions to replace traditional electrical interconnections. Optical interconnection has the characteristics of low latency, small loss, small propagation crosstalk, and immunity to electromagnetic interference in electronic communication, and can be used to achieve high-speed, high-bandwidth, high-density, and low-power consumption interconnections.

[0003] As one of the core components of an optical interconnection system, an electro-optic modulator directly affects the quality of the entire communication system. Common modulator structures include Mach-Zehnder modulators and micro-ring resonator modulators, etc. Although Mach-Zehnder modulators have good process stability, are insensitive to temperature, and can achieve high-speed modulation, they have disadvantages such as high power consumption and large volume. Micro-ring resonator modulators have smaller sizes, lower power consumption, and higher integration levels. Therefore, they are more suitable for the preparation of high-density integrated systems.

[0004] The modulation efficiency of the micro-ring resonator modulators provided by existing mainstream active process silicon-based device foundries is basically between 15 and 25 pm / V, and the electro-optic modulation bandwidth is less than 56 GHz. Both the modulation efficiency and the electro-optic modulation bandwidth are relatively low. However, in the application of high-speed optical communication systems, electro-optic modulators often require higher modulation efficiency to achieve lower driving voltages, and higher electro-optic modulation bandwidth to achieve higher rate transmissions.

[0005] Therefore, it is urgent to solve technical problems such as low modulation efficiency and low electro-optic modulation bandwidth of micro-ring electro-optic modulators. Summary of the Invention

[0006] In view of the above-mentioned deficiencies and improvement requirements of the prior art, this application provides an add-drop electro-optic modulator based on a meandering doped micro-ring structure. The purpose is to simultaneously modulate the lateral PN junction and the longitudinal PN junction through meandering doping, increase the overlap factor between the depletion region and the optical field region without affecting the junction capacitance, and improve the modulation efficiency of the micro-ring modulator; by respectively adjusting the gaps between the two strip-shaped ridge waveguides and the middle ring-shaped ridge waveguide, the optical quality factor of the micro-ring modulator can be controlled and the extinction ratio can be improved, and the working bandwidth of the micro-ring modulator is increased, so that high modulation efficiency and high electro-optic modulation bandwidth of the micro-ring electro-optic modulator can be achieved simultaneously.

[0007] To achieve the above purpose, this application provides the following technical solutions:

[0008] In a first aspect, this application provides a silicon-based micro-ring electro-optic modulator, including:

[0009] Silicon substrate;

[0010] A silicon dioxide layer disposed on the silicon substrate;

[0011] A strip ridge waveguide disposed in the silicon dioxide layer, the strip ridge waveguide including a first strip ridge waveguide and a second strip ridge waveguide;

[0012] An annular ridge waveguide disposed in the silicon dioxide layer, the annular ridge waveguide being between the first strip ridge waveguide and the second strip ridge waveguide and coupled to the first strip ridge waveguide and the second strip ridge waveguide, the annular ridge waveguide being formed into a meandering structure by a P-type doped layer and an N-type doped layer;

[0013] Metal electrodes, the metal electrodes including a P electrode and an N electrode, the P electrode forming an ohmic contact with the P-type doped layer, the N electrode forming an ohmic contact with the N-type doped layer, and both the P electrode and the N electrode passing through the silicon dioxide layer.

[0014] Further, the P-type doped layer and the N-type doped layer of the annular ridge waveguide are embedded in each other.

[0015] Further, the P-type doped layer and the N-type doped layer form a depletion-type PN structure.

[0016] Preferably, the width W1 of the mutual embedding of the P-type doped layer and the N-type doped layer of the annular ridge waveguide is less than the width W2 of the annular ridge waveguide.

[0017] Further, the meandering structure of the annular ridge waveguide is at least one of a conical shape, an arc shape, and a rectangular shape.

[0018] Further, the metal electrodes are respectively ohmically connected to the P-type heavily doped region and the N-type heavily doped region.

[0019] In a second aspect, the present application provides a preparation method of the foregoing silicon-based micro-ring electro-optic modulator, including the following steps:

[0020] S1. Pattern and etch a strip ridge waveguide and an annular ridge waveguide structure respectively on a SOI wafer, wherein the SOI wafer sequentially includes a silicon waveguide layer, a silicon dioxide layer, and a silicon substrate from top to bottom;

[0021] S2. Perform patterned ion implantation in the silicon waveguide layer of the annular ridge waveguide to form doped regions, wherein the doped regions include a P-doped region, an N-doped region, a P++ doped region, and an N++ doped region;

[0022] S3. Grow a silicon dioxide cladding on the wafer surface using a chemical vapor deposition process;

[0023] S4. Pattern the silica cladding until reaching the waveguide layer, and deposit a metal layer in the cladding pattern using the Lift off process;

[0024] S5. Etch the top silica layer to expose the topmost metal layer as the electrode, obtaining the final electro-optic modulator.

[0025] The technical solution provided by the embodiments of this application, compared with the prior art, has at least the following beneficial effects:

[0026] 1. Based on the existing process, this application realizes the simultaneous modulation of the lateral PN junction and the longitudinal PN junction through the meandering doping method, increasing the overlap factor between the depletion region and the optical field region without affecting the junction capacitance, thereby improving the modulation efficiency of the microring modulator. Compared with the devices prepared by the existing process, its modulation efficiency can be increased by more than 35%.

[0027] 2. By separately adjusting the gaps between the two strip waveguides and the ring ridge waveguide disposed on the strip waveguides, this application can control the optical quality factor of the microring modulator, improve the extinction ratio, and increase the working bandwidth of the microring modulator. By adjusting the gap design, the electro-optic bandwidth of the modulator can be made greater than 67 GHz.

[0028] 3. The idea of using the meandering doping structure to improve the modulation efficiency of the electro-optic modulator provided by this application is universal, and is not only suitable for microring modulators, but can also be applied to other doped devices such as Mach-Zehnder modulators to improve performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The following will further describe this application in detail with reference to the drawings and preferred embodiments. However, those skilled in the art will understand that these drawings are only drawn for the purpose of explaining the preferred embodiments and should not be used to limit the scope of this application. In addition, unless otherwise specified, the drawings only schematically show the composition or structure of the described object and may include exaggerated displays, and the drawings are not necessarily drawn to scale.

[0030] Figure 1 It is a three-dimensional schematic diagram of the up / down load type electro-optic modulator with a meandering doping microring structure provided by the embodiments of this application;

[0031] Figure 2 It is a top view schematic diagram of the up / down load type electro-optic modulator with a meandering doping microring structure provided by the embodiments of this application. Among them, a is the top view of the electro-optic modulator, and b is the sectional view of Figure a along the A-A' direction;

[0032] Figure 3 It is a schematic diagram of the meandering doping structure provided by the embodiments of this application. Among them, a is the top view, and b is the sectional view of Figure a along the A-A' and B-B' directions;

[0033] Figure 4 Measured transmission spectra of a conventional modulator and the microring modulator prepared in the embodiments of the present application;

[0034] Figure 5 It is the measured electro-optic response bandwidth spectrum of a microring modulator shown according to the embodiments of the present disclosure;

[0035] Wherein, 1 is a silicon substrate, 2 is a silicon dioxide layer, 3 is a strip ridge waveguide, 31 is the first strip ridge waveguide, 32 is the second strip ridge waveguide, 4 is a ring ridge waveguide, 41 is the first modulation region, 42 is the second modulation region, 5 is a metal electrode, 51 is the outer electrode, 52 is the inner electrode, and 6 is a silicon waveguide layer. Detailed implementation manners

[0036] Other embodiments obtained by those skilled in the art without creative efforts shall fall within the scope of protection of the present application.

[0037] The electro-optic modulator provided by the embodiments of the present application is composed of a strip ridge waveguide and a microring ridge waveguide. Among them, in the microring ridge waveguide, by arranging a meandering doping structure, a lateral PN junction and a longitudinal PN junction are formed, so as to realize bidirectional modulation in the horizontal and vertical directions. Without affecting the junction capacitance, the overlap factor between the depletion region and the optical field region is increased, and the modulation efficiency of the microring modulator is further improved; by adjusting the gap between the two strip ridge waveguides and the middle microring ridge waveguide, the optical quality factor of the microring modulator can be controlled and the extinction ratio can be improved, and the working bandwidth of the microring modulator can be increased.

[0038] Based on this, the embodiments of the present application provide an add-drop electro-optic modulator based on a meandering doped microring structure, as Figure 1 shown. The electro-optic modulator includes: a silicon substrate 1, a silicon dioxide layer 2, a strip ridge waveguide 3, a ring ridge waveguide 4, and a metal electrode 5; the strip ridge waveguide 3 includes a first strip ridge waveguide 31 and a second strip ridge waveguide 32, and the first strip ridge waveguide 31 and the second strip ridge waveguide 32 are both arranged in the silicon dioxide layer 2; the ring ridge waveguide 4 is arranged in the silicon dioxide layer 2 and is located between the first strip ridge waveguide 31 and the second strip ridge waveguide 32, and the ring ridge waveguide 4 is coupled to the first strip ridge waveguide 31 and the second strip ridge waveguide 32; the ring ridge waveguide 4 is formed by a meandering structure of a P-type doping layer and an N-type doping layer (as Figure 2 shown); the metal electrode 5 includes an outer electrode 51 and an inner electrode 52, and the metal electrode 5 forms an ohmic contact with the corresponding P-type doping layer or N-type doping layer and penetrates through the silicon dioxide layer 2.

[0039] In some embodiments, the strip ridge waveguide 3 and the ring ridge waveguide 4 structures are obtained by etching the silicon waveguide layer 6 of the SOI.

[0040] In some embodiments, as Figure 2 shown, the P-type doped layer and the N-type doped layer of the ring ridge waveguide 4 are obtained by ion implantation and are embedded with each other, and the P-type doped layer and the N-type doped layer form a depletion-type PN structure. The ring ridge waveguide 4 includes a first modulation region 41 and a second modulation region 42 (as Figure 3 shown).

[0041] In some embodiments, the meandering structure of the ring ridge waveguide 4 can be of various geometric shapes, such as one or more combinations of a cone, an arc, and a rectangle, and the meandering structure forms a PN junction.

[0042] In some preferred embodiments, as Figure 2 、 Figure 3 shown, the width W1 of the mutual embedding of the P-type doped layer and the N-type doped layer of the ring ridge waveguide 4 is less than the width W2 of the ring ridge waveguide 4. At this time, the meandering doping structure of the ring ridge waveguide 4 can simultaneously form a lateral PN junction and a longitudinal PN junction. Under the same voltage condition, the overlap factor between the depletion region and the optical field region can be increased, thereby improving the modulation efficiency of the ring modulator.

[0043] In the embodiments of the present application, the positions of the P-type doped layer and the N-type doped layer of the ring ridge waveguide 4 can be set according to actual situations. In some embodiments, as Figure 2 shown, the P-type doped layer of the ring ridge waveguide 4 is located inside, and the N-type doped layer is located outside. At this time, the outer electrode 51 of the metal electrode 5 is an N electrode that forms an ohmic contact with the N-type doped layer, and the inner electrode 52 is a P electrode that forms an ohmic contact with the P-type doped layer. In some embodiments, the P-type doped layer of the ring ridge waveguide 4 is located outside, and the N-type doped layer is located inside. At this time, the outer electrode 51 of the metal electrode 5 is a P electrode that forms an ohmic contact with the P-type doped layer, and the inner electrode 52 is an N electrode that forms an ohmic contact with the N-type doped layer.

[0044] In some embodiments, the P-type doped layer is divided into a P-type doped region and a P-type heavily doped region (P++ doped region); the N-type doped layer is divided into an N-type doped region and an N-type heavily doped region (N++ doped region); the P electrode forms an ohmic contact with the P-type heavily doped region; the N electrode forms an ohmic contact with the N-type heavily doped region.

[0045] In some embodiments, the outer electrode 51 and the inner electrode are both copper electrodes.

[0046] In the embodiment of the present application, the modulation electrical signal is loaded on the inner electrode 52 located inside the ring ridge waveguide 4, and the outer electrode 51 located outside the ring ridge waveguide 4 is used for grounding. The optical wave can be input from any port of the first strip ridge waveguide 31 or the second strip ridge waveguide 32. When the optical wave is transmitted to the coupling region with the ring ridge waveguide 4, the optical wave that satisfies the resonance condition will be coupled into the microring resonator (resonance condition: mλ = 2πRn eff , where R is the radius of the microring, m is an integer, and λ is the wavelength of the optical wave), part of the light is output from the output port of the upload end, and part of the light is output from the port of the download end. Assuming that the second strip ridge waveguide 32 is the upload end waveguide, then the first strip ridge waveguide 31 is the download end waveguide. The optical wave is input from the input end of the second strip ridge waveguide 32. The ratios of the output optical field intensities of the upload end waveguide and the download end waveguide to the input optical field intensity are respectively: Where is the output optical field of the upload end waveguide, is the output optical field of the download end waveguide, a is the loss coefficient of the optical wave around the ring ridge waveguide 4 for one circle, t1 is the transmission coefficient of the upload end waveguide, t2 is the transmission coefficient of the download end waveguide, k1 is the coupling coefficient between the upload end waveguide and the ring ridge waveguide, k2 is the coupling coefficient between the download end waveguide and the ring ridge waveguide 4, is the phase change of the optical wave around the ring ridge waveguide 4 for one circle. By applying voltages on the outer electrode 51 and the inner electrode 52 on the inner and outer sides of the ring ridge waveguide 4, the working state of the PN junction of the ring ridge waveguide 4 is changed to change the effective refractive index n eff of the waveguide, so as to change the phase change of the optical wave around the ring for one circle, realize the change of the output optical field intensities of the upload end waveguide and the download end waveguide, and finally achieve the goal of electrically controlling the modulation change of the optical signal.

[0047] Based on this, the embodiment of the present application provides a preparation method of a silicon-based microring electro-optic modulator, including the following steps: patterning and etching the strip ridge waveguide 3 and the ring ridge waveguide 4 structures on the SOI wafer, where the SOI wafer includes a silicon waveguide layer 6, a silicon dioxide layer 2, and a silicon substrate 1 from top to bottom in sequence; performing patterned ion implantation in the silicon waveguide layer 6 of the ring ridge waveguide 4 to form doping regions, where the doping regions include a P-doped region, an N-doped region, a P++-doped region, and an N++-doped region, as Figure 3 shown; growing a silicon dioxide cladding layer (i.e., the silicon dioxide layer 2 on the upper side of the silicon waveguide layer 6) on the wafer surface using a chemical vapor deposition process; patterning and etching the silicon dioxide cladding layer until the silicon waveguide layer 2, and depositing a metal layer in the cladding pattern using a Lift off process; etching the top silicon dioxide cladding layer to expose the topmost metal layer as an electrode to obtain the final electro-optic modulator.

[0048] In some embodiments, the method for fabricating the structures of the strip ridge waveguide 3 and the ring ridge waveguide 4 is as follows: a mask pattern is formed by any one of electron beam lithography (EBL), step-and-repeat lithography, and laser direct writing, and then dry etching such as inductively coupled plasma etching (ICP), reactive ion etching (RIE), hydrogen bromide (HBr) etching, or wet etching is used for fabrication.

[0049] In some embodiments, the silica cladding can be fabricated by any one of magnetron sputtering, chemical vapor deposition, thermal oxidation, and sol-gel methods.

[0050] In some embodiments, the metal layer can be fabricated by any one of thermal evaporation, magnetron sputtering, electron beam evaporation, electroplating, etc.

[0051] The technical effects of the invention are further described in detail through more specific embodiments below.

[0052] Embodiment

[0053] The embodiment of the present application provides a method for fabricating a silicon-based micro-ring electro-optic modulator, including the following steps: patterning and etching the strip ridge waveguide 3 and the ring ridge waveguide 4 structures respectively on an SOI wafer, where the SOI wafer includes a silicon waveguide layer 6, a silica layer 2, and a silicon substrate 1 from top to bottom; performing patterned ion implantation in the silicon waveguide layer 6 of the ring ridge waveguide 4 to form doping regions, where the doping regions include a P-doped region, an N-doped region, a P++-doped region, and an N++-doped region, as Figure 3 shown; growing a silica cladding (i.e., the silica layer 2 on the upper side of the silicon waveguide layer 6) on the wafer surface using a chemical vapor deposition process; patterning and etching the silica cladding until the silicon waveguide layer 2, and depositing a metal layer in the cladding pattern using a Lift off process; etching the top silica cladding to expose the topmost metal layer as the metal electrode 5 to obtain the final electro-optic modulator.

[0054] In the electro-optic modulator obtained by the above method, the P-type doped region is located inside the ring ridge waveguide 4, the N-type doped region is located outside the ring ridge waveguide 4, the P-doped and N-doped meandering doping regions are in the middle region of the ring ridge waveguide, the meandering doping region structure of the ring ridge waveguide 4 adopts a square structure, the width W1 is less than the width W2 of the ring ridge waveguide 4, and the metal electrodes 5 are all copper electrodes.

[0055] Figure 4 are the measured transmission spectra of an existing ordinary micro-ring modulator and the meandering micro-ring modulator fabricated in the embodiment of the present application. From Figure 4It can be seen that the modulation efficiency of the ordinary micro-ring modulator prepared under the existing process conditions is 24.3 pm / V, while the modulation efficiency of the meandering doping structure micro-ring modulator provided in the embodiments of the present application is 33.5 pm / V. The meandering doping structure can increase the modulation efficiency by more than 35% based on the modulation efficiency of the devices prepared by the existing process.

[0056] Figure 5 This is the measured electro-optic response bandwidth spectrum of the meandering micro-ring modulator prepared in the embodiments of the present application. As Figure 5 shown, the electro-optic bandwidth of the meandering doping up / down load type micro-ring modulator is greater than 67 GHz.

[0057] In summary, the up / down load type electro-optic modulator with a meandering doping micro-ring structure provided in the embodiments of the present application can simultaneously achieve high modulation efficiency and high electro-optic modulation bandwidth.

[0058] The above has introduced the present application in detail. Specific examples are used in the present application to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the present application and its core idea. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A silicon-based micro-ring electro-optic modulator, characterized in that, Comprising: A silicon substrate; A silicon dioxide layer disposed on the silicon substrate; A strip ridge waveguide disposed in the silicon dioxide layer, the strip ridge waveguide comprising a first strip ridge waveguide and a second strip ridge waveguide; A ring ridge waveguide disposed in the silicon dioxide layer, the ring ridge waveguide being between the first strip ridge waveguide and the second strip ridge waveguide and coupled to the first strip ridge waveguide and the second strip ridge waveguide, the coupling spacings being controllable respectively, and the ring ridge waveguide forming a meandering structure by a P-type doped layer and an N-type doped layer; Metal electrodes, the metal electrodes comprising a P electrode and an N electrode, the P electrode forming an ohmic contact with the P-type doped layer, the N electrode forming an ohmic contact with the N-type doped layer, and both the P electrode and the N electrode penetrating through the silicon dioxide layer.

2. The silicon-based microring electro-optic modulator according to claim 1, wherein The P-type doped layer and the N-type doped layer of the ring ridge waveguide are embedded with each other.

3. The silicon-based microring electro-optic modulator according to claim 1, wherein The meandering structure of the ring ridge waveguide is at least one of a conical shape, an arc shape, and a rectangular shape.

4. The silicon-based microring electro-optic modulator according to claim 1, wherein The P-type doped layer and the N-type doped layer form a depletion-type PN structure.

5. The silicon-based microring electro-optic modulator according to claim 2, characterized in that, Preferably, the width W1 of the mutual embedding of the P-type doped layer and the N-type doped layer of the ring ridge waveguide is less than the width W2 of the ring ridge waveguide.

6. The silicon-based microring electro-optic modulator according to claim 1, wherein The P electrode forms an ohmic contact with the heavily doped region of the P-type doped layer, and the N electrode forms an ohmic contact with the heavily doped region of the N-type doped layer.

7. The silicon-based microring electro-optic modulator according to claim 1, wherein, The P-type doped layer of the ring ridge waveguide is located on the outer side of the ring ridge waveguide, and the N-type doped layer is located on the inner side of the ring ridge waveguide.

8. The silicon-based micro-ring electro-optic modulator according to claim 1, characterized in that, The P-type doped layer of the ring ridge waveguide is located on the inner side of the ring ridge waveguide, and the N-type doped layer is located on the outer side of the ring ridge waveguide.

9. A preparation method of a silicon-based microring electro-optic modulator, characterized in that, Comprising the following steps: S1. Pattern and etch respectively the strip ridge waveguide and the ring ridge waveguide structures on a SOI wafer, wherein the SOI wafer sequentially comprises a silicon waveguide layer, a silicon dioxide layer, and a silicon substrate from top to bottom; S2. Perform patterned ion implantation in the silicon waveguide layer of the ring ridge waveguide to form a doped region, wherein the doped region comprises a P-doped region, an N-doped region, a P++ doped region, and an N++ doped region; S3. Grow a silicon dioxide cladding on the wafer surface using a chemical vapor deposition process; S4. Pattern and etch the silicon dioxide cladding until reaching the waveguide layer, and deposit a metal layer in the cladding pattern using a Lift off process; S5. Etch the top silicon dioxide to expose the topmost metal layer as an electrode to obtain the final electro-optic modulator.

10. The preparation method according to claim 9, wherein, The preparation method of the structures of the strip ridge waveguide and the ring ridge waveguide is: forming a mask pattern by any one of electron beam lithography, step-and-repeat lithography, and laser direct writing, and then preparing by any one of dry etching methods such as inductively coupled plasma etching, reactive ion etching, and hydrogen bromide etching or a wet etching method.

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