Electro-optical modulation waveguide and Mach-Zehnder interference type electro-optical modulator

Abstract

The invention provides an electro-optical modulation waveguide comprising an optical waveguide comprising a ridge region and a flat plate region; the ridge-shaped region is higher than the flat plate region and is arranged in the middle of the flat plate region; the optical waveguide is divided into a P-type doped region and an N-type doped region, the P-type doped region and the N-type doped region are located at the junction of the ridge-type region and form a PN junction at the junction, and the first current expansion layer is located above the P-type doped region, is parallel to the flat plate region and extends downwards at the position close to the ridge-type region to make contact with the ridge-type region and the flat plate region; the second current expansion layer is positioned above the N-type doped region, is parallel to the flat plate region, and extends downwards at a position close to the ridge-type region to be in contact with the ridge-type region and the flat plate region; the first current expansion layer and the second current expansion layer are not in contact, and isolation dielectric layers are arranged between the first current expansion layer and the flat plate area; and the two metal contact electrodes are respectively contacted with the first current expansion layer and the second current expansion layer. The invention further provides a Mach-Zehnder interference type electro-optical modulator comprising the electro-optical modulation waveguide.

Description

Technical Field

[0001] The present disclosure relates to the technical field of integrated optoelectronic devices, and more particularly, to an electro-optical modulation waveguide and a Mach-Zehnder interferometer electro-optical modulator. Background Art

[0002] Silicon photonic modulators are core components in fiber-optic communication systems, primarily used for high-speed conversion of electrical signals into optical signals. They are widely used in data center interconnects, telecommunications networks, and computing chip interconnects. As a foundational component in the silicon-based optoelectronics platform, silicon photonic modulators inherit the advantages of silicon-based optoelectronics technology, such as high speed, low loss, and high-density integration, making them a key optoelectronic platform.

[0003] Its operating principle is based on the plasma dispersion effect: by charging and discharging carriers in a silicon optical waveguide, the carrier concentration is changed, thereby regulating the effective refractive index of the optical waveguide, ultimately achieving electro-optical phase modulation and intensity modulation. However, the silicon optical slab region suffers from high resistance and large light absorption losses, which leads to slow charging and discharging of the PN junction, thereby limiting the device's electro-optical bandwidth performance. Summary of the Invention

[0004] In view of this, the present disclosure provides an electro-optic modulation waveguide and a Mach-Zehnder interferometer electro-optic modulator to improve the bandwidth of a silicon modulator.

[0005] A first aspect of the present disclosure provides an electro-optical modulation waveguide, comprising: an optical waveguide, comprising a ridge region and a slab region; the ridge region being higher than the slab region and located in the middle of the slab region; the optical waveguide being divided into a P-type doped region and an N-type doped region, the P-type doped region and the N-type doped region intersecting the ridge region and forming a PN junction at the junction; a first current spreading layer, located above the P-type doped region and parallel to the slab region, extending downwardly near the ridge region to contact the ridge region and the slab region; a second current spreading layer, located above the N-type doped region and parallel to the slab region, extending downwardly near the ridge region to contact the ridge region and the slab region; the first current spreading layer and the second current spreading layer not contacting each other, and both having an isolation dielectric layer between them and the slab region; a first metal contact electrode and a second metal contact electrode, contacting the first current spreading layer and the second current spreading layer, respectively.

[0006] According to an embodiment of the present disclosure, the materials of the first current spreading layer and the second current spreading layer are transparent conductive materials.

[0007] According to an embodiment of the present disclosure, the distances between the first current spreading layer, the second current spreading layer, and the slab region are greater than 50 nm.

[0008] According to an embodiment of the present disclosure, the contact manner of the first metal contact electrode and the second metal contact electrode includes: the first metal contact electrode contacts the first current spreading layer, and the second metal contact electrode contacts the second current spreading layer; or the first metal contact electrode contacts the first current spreading layer and the P-type doped region of the planar layer, and the second metal contact electrode contacts the second current spreading layer and the N-type doped region of the planar layer.

[0009] According to an embodiment of the present disclosure, surfaces of the first current spreading layer, the second current spreading layer, and the ridge region are covered with an insulating dielectric layer.

[0010] According to an embodiment of the present disclosure, it further includes: a silicon substrate disposed at the bottom of the electro-optical modulation waveguide; and a buried oxide layer disposed between the bottom of the electro-optical modulation waveguide and the silicon substrate.

[0011] According to an embodiment of the present disclosure, the optical waveguide is a single-mode waveguide or a multi-mode waveguide.

[0012] According to an embodiment of the present disclosure, the optical waveguide is a TE mode waveguide and / or a TM mode waveguide.

[0013] A second aspect of the present disclosure provides a Mach-Zehnder interferometer electro-optical modulator, comprising: a beam splitter for splitting an optical signal into two identical signals; two modulation arms connected to the beam splitter, each of the two modulation arms comprising an electro-optical modulation waveguide as described in any one of the first aspects, for phase modulating the two signals; a beam combiner connected to the two modulation arms for interfering the two light beams with a phase difference; and a traveling wave electrode for applying a radio frequency signal to the electro-optical modulation waveguide to drive phase modulation.

[0014] The electro-optical modulated waveguide disclosed herein utilizes a current spreading layer to provide a low-resistance, high-frequency channel for the optical waveguide, resulting in a higher modulator bandwidth. Compared to existing methods that use transparent electrodes to increase bandwidth, the slab region of the current spreading layer provided herein is located away from the slab region of the optical waveguide, minimizing additional optical loss and resulting in superior optoelectronic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0016] Figure 1 Schematically shows a cross-sectional view of an electro-optical modulation waveguide according to an embodiment of the present disclosure;

[0017] Figure 2 Schematically shows a cross-sectional view of an electro-optical modulation waveguide according to another embodiment of the present disclosure;

[0018] Figure 3 Schematically shows a top view of a Mach-Zehnder interferometer electro-optic modulator according to an embodiment of the present disclosure;

[0019] Figure 4 Schematically shows Figure 3 Electro-optic bandwidth of the Mach-Zehnder interferometer electro-optic modulator shown.

[0020] Description of reference numerals:

[0021] 103 - P-type doped region; 104 - N-type doped region; 105 - buried oxide layer; 106 - silicon substrate; 107 - insulating dielectric layer; 111 - first current spreading layer; 112 - second current spreading layer; 121 - first metal contact electrode; 122 - second metal contact electrode; 131 - PN junction; 132 - optical waveguide.

[0022] 201-beam splitter; 202-beam combiner; 210-traveling wave electrode; 213-DC electrode; 220-electro-optical modulation waveguide. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0024] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise," "include," etc. used herein indicate the presence of the features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0025] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0026] When expressions such as “at least one of A, B, and C, etc.” are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art. For example, “a system having at least one of A, B, and C” should include but is not limited to systems having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, and C, etc. When expressions such as “at least one of A, B, or C, etc.” are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art. For example, “a system having at least one of A, B, or C” should include but is not limited to systems having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, and C, etc.

[0027] The present disclosure provides an electro-optic modulation waveguide, including: an optical waveguide 132 , a first current spreading layer 111 , a second current spreading layer 112 , a first metal contact electrode 121 , and a second metal contact electrode 122 .

[0028] Figure 1 A schematic diagram of an electro-optical modulation waveguide according to one embodiment of the present disclosure is shown schematically.

[0029] like Figure 1 As shown, the optical waveguide 132 includes a ridge region and a slab region; the ridge region is higher than the slab region and is located in the middle of the slab region; the optical waveguide 132 is divided into a P-type doped region 103 and an N-type doped region 104, and the P-type doped region 103 and the N-type doped region 104 intersect at the ridge region and form a PN junction 131 at the intersection, that is, one side of the ridge region and the slab region on this side are the P-type doped region 103, and the other side of the ridge region and the slab region on this side are the N-type doped region 104.

[0030] The first current spreading layer 111 is located above the P-type doped region 103 and parallel to the slab region. It extends downward near the ridge region to contact both the ridge and slab regions. The second current spreading layer 112 is located above the N-type doped region 104 and parallel to the slab region. It extends downward near the ridge region to contact both the ridge and slab regions. The first and second current spreading layers 111, 112 do not contact each other, and an insulating dielectric layer 107 is located between each layer and the slab region. The insulating dielectric layer reduces light absorption losses in the first and second current spreading layers 111, 112. The first and second current spreading layers 111, 112 are made of transparent conductive materials. The distance between the first and second current spreading layers 111, 112 and the slab region is greater than 50 nm. The surfaces of the first and second current spreading layers 111, 112, and the ridge region are covered with an insulating dielectric layer 107.

[0031] The first metal contact electrode 121 and the second metal contact electrode 122 are in contact with the first current spreading layer 111 and the second current spreading layer 112, respectively. The contact method of the first metal contact electrode 121 and the second metal contact electrode 122 includes:

[0032] The first metal contact electrode 121 contacts the first current spreading layer 111 , and the second metal contact electrode 122 contacts the second current spreading layer 112 ; or

[0033] The first metal contact electrode 121 contacts the first current spreading layer 111 and the P-type doping region 103 of the slab layer, and the second metal contact electrode 122 contacts the second current spreading layer 112 and the N-type doping region 104 of the slab layer.

[0034] The electro-optical modulation waveguide further includes a buried oxide layer 105 and a silicon substrate 106. The silicon substrate 106 is disposed at the bottom of the electro-optical modulation waveguide; the buried oxide layer 105 is disposed between the bottom of the electro-optical modulation waveguide and the silicon substrate 106.

[0035] In the embodiment of the present disclosure, the refractive index of the first current spreading layer 111 and the second current spreading layer 112 between 1.2 μm and 1.6 μm is 1.0-2.0, and the extinction coefficient is 1×10 -5 ~1×10 -2 , the resistivity is 1×10 -4 Ω.cm~1×10 -2 Ω.cm.

[0036] In this embodiment, the material of the first current spreading layer 111 and the second current spreading layer 112 is a transparent conductive material indium tin oxide (ITO) (other materials with high conductivity, low light absorption coefficient and low refractive index are also optional, such as chromium oxide, zinc oxide, etc.).

[0037] In this embodiment, the first current spreading layer has a width w1 of 10nm-100nm, a width w2 of 50nm-150nm, and a thickness h1 of 100nm-1000nm. The second current spreading layer has a width w3 of 10nm-100nm, and a width w4 of 50nm-150nm.

[0038] In this embodiment, the doping concentration of the P-type doping region 103 and the N-doping region 105 is 5×10 17 cm -3 The PN junction 131 is located in the center of the ridge region of optical waveguide 132. The ridge region of optical waveguide 132 has a thickness between approximately 110 nm and approximately 220 nm, the slab region has a thickness between 50 nm and 150 nm, and the ridge region has a width w1 between approximately 300 nm and approximately 1000 nm. The presence of the ridge region can further concentrate the optical field within optical waveguide 132 below the waveguide 132, reducing light absorption in the current expansion region.

[0039] In this embodiment, the first metal contact electrode 121 is in direct contact with the P-type doped region 103 of the slab region of the ridge waveguide, and the second metal contact electrode 122 is in direct contact with the N-type doped region 104 of the slab region of the ridge waveguide; when an external driving voltage is applied, the PN junction 131 in the optical waveguide 132 is charged and discharged through the metal contact electrodes, thereby changing the width of the depletion region of the PN junction 131, and according to the plasma dispersion effect, changing the effective refractive index and light absorption loss of the optical waveguide 132.

[0040] Optionally, the optical waveguide 132 may be a single-mode waveguide or a multi-mode waveguide; the optical waveguide 132 may be a TE mode waveguide and / or a TM mode waveguide.

[0041] Figure 2 A schematic diagram of an electro-optical modulation waveguide according to another embodiment of the present disclosure is schematically shown.

[0042] like Figure 2 As shown, the overall structure of the electro-optical modulation waveguide is similar to Figure 1 The electro-optical modulation waveguide shown is similar, with the difference being the position of the metal contact electrodes and the doping of the optical waveguide 132. The first metal contact electrode 121 and the second metal contact electrode 122 are both in direct contact with the current spreading layer and the slab area of ​​the optical waveguide 132. The optical waveguide 132 is doped using multi-stage doping. The doping concentration of the P-doped region from the ridge region outward is low doping, medium doping, and heavy doping, and the N-doped region and the P-doped region are symmetrical. Figure 1 Compared to the embodiment shown, the multi-segment doping of the slab region of the optical waveguide 132 introduces additional optical loss, but the benefit is that there are two current channels, which will result in lower series resistance and higher optoelectronic bandwidth.

[0043] Figure 3 FIG2 schematically shows a top view of a Mach-Zehnder interferometer electro-optic modulator according to an embodiment of the present disclosure.

[0044] like Figure 3 As shown, the Mach-Zehnder interferometer electro-optical modulator includes: a beam splitter, two modulation arms and a beam combiner. The beam splitter is used to split the optical signal into two identical signals; the two modulation arms are connected to the beam splitter, and the two modulation arms both contain the electro-optical modulation waveguide proposed in the present disclosure, which is used to phase modulate the two signals; the beam combiner is connected to the two modulation arms, and is used to interfere the two light beams with a phase difference. The Mach-Zehnder interferometer electro-optical modulator also includes at least two traveling wave electrodes, which are respectively connected to the first metal contact electrodes 121 of the electro-optical modulation waveguides on the two modulation arms, and are used to apply radio frequency signals to drive phase modulation. The Mach-Zehnder interferometer electro-optical modulator also includes a DC electrode, which is connected to the second metal contact electrodes 122 of the electro-optical modulation waveguides on the two modulation arms, and is used to control the working point.

[0045] In the disclosed embodiment, the traveling wave electrode 210 adopts a single-ended CPS transmission line structure. The traveling wave electrode 210 is connected to the first metal contact electrode 121 of the electro-optical modulation waveguide 220. The two modulation arms are parallel to each other and the PN junctions 131 are back-to-back (i.e., in opposite directions). When an RF signal is applied, push-pull drive is achieved, and the design of the traveling wave electrode satisfies electro-optical refractive index matching and impedance matching. The DC electrode 213 is connected to the second metal contact electrode 122 of the electro-optical modulation waveguide 220 to control the operating point. Under the premise that the current expansion layer has good contact with the optical waveguide 132, the current expansion layer can achieve a conductivity far lower than that of the flat plate area of ​​the optical waveguide 132, effectively reducing the dielectric loss of the traveling wave electrode and improving the modulator bandwidth.

[0046] The electrodes in this embodiment use CPS traveling wave electrodes. The actual electro-optical modulator may also use other types of electrodes, including differential GSGSG, GSSG, SS and other electrodes, depending on factors such as the driving signal and electrode crosstalk. The position and direction of the PN junction 131 may be back-to-back or PN in the same direction according to the direction of the electrode signal.

[0047] Figure 4 yes Figure 3 The electro-optic bandwidth of the electro-optic modulator shown in FIG. 1 is shown. The contact between the current spreading layer and the optical waveguide 132 is in ohmic contact. The P-type doping concentration and the N-type doping concentration of the ridge region of the optical waveguide 132 are both 5×10 17 cm -3 Due to the lower resistivity of the current spreading layer, about 3×10 -4 Ω.cm, the electro-optic bandwidth is significantly improved compared to traditional silicon electro-optic modulators, and the theoretical value can be increased from 40 GHz to over 160 GHz.

[0048] The above describes the embodiments of the present disclosure. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be advantageously used in combination. Without departing from the scope of the present disclosure, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. An electro-optical modulation waveguide, comprising: An optical waveguide (132) comprising a ridge region and a slab region; The ridge region is higher than the flat plate region and is located in the middle of the flat plate region; The optical waveguide (132) is divided into a P-type doping region (103) and an N-type doping region (104), wherein the P-type doping region (103) and the N-type doping region (104) intersect at the ridge region and form a PN junction (131) at the intersection; A first current spreading layer (111), located above the P-type doped region (103) and parallel to the flat plate region, extending downward near the ridge region to contact the ridge region and the flat plate region; A second current spreading layer (112) is located above the N-type doped region (104) and parallel to the flat plate region, and extends downward near the ridge region to contact the ridge region and the flat plate region; The first current spreading layer (111) and the second current spreading layer (112) are not in contact with each other, and both have an insulating dielectric layer (107) between them and the flat plate area; A first metal contact electrode (121) and a second metal contact electrode (122) are in contact with the first current spreading layer (111) and the second current spreading layer (112), respectively.

2. The electro-optical modulation waveguide according to claim 1, wherein: The materials of the first current spreading layer (111) and the second current spreading layer (112) are transparent conductive materials.

3. The electro-optical modulation waveguide according to claim 1, wherein: The distance between the first current spreading layer (111) and the second current spreading layer (112) and the flat plate region is greater than 50 nm.

4. The electro-optical modulation waveguide according to claim 1, wherein the contact method of the first metal contact electrode (121) and the second metal contact electrode (122) comprises: The first metal contact electrode (121) contacts the first current spreading layer (111), and the second metal contact electrode (122) contacts the second current spreading layer (112); or The first metal contact electrode (121) contacts the first current spreading layer (111) and the P-type doping region (103) of the flat layer, and the second metal contact electrode (122) contacts the second current spreading layer (112) and the N-type doping region (104) of the flat layer.

5. The electro-optical modulation waveguide according to claim 1, wherein: Also includes: A silicon substrate (106) is provided at the bottom of the electro-optical modulation waveguide; A buried oxide layer (105) is provided between the bottom of the electro-optical modulation waveguide and the silicon substrate (106).

6. The electro-optical modulation waveguide according to claim 1, wherein: The optical waveguide (132) is a single-mode waveguide or a multi-mode waveguide.

7. The electro-optical modulation waveguide according to claim 1, wherein: The optical waveguide (132) is a TE mode waveguide and / or a TM mode waveguide.

8. A Mach-Zehnder interferometer electro-optic modulator, comprising: A beam splitter is used to split the optical signal into two identical signals; Two modulation arms connected to the beam splitter, each of the two modulation arms comprising the electro-optical modulation waveguide according to any one of claims 1 to 7, for phase modulating the two signals; a beam combiner connected to the two modulation arms, and configured to interfere the two light beams having a phase difference; The traveling wave electrode is used to apply a radio frequency signal to the electro-optical modulation waveguide to drive phase modulation.

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