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

Abstract

The invention provides an electro-optical modulation waveguide, which comprises an optical waveguide, the optical waveguide comprises a ridge region and a flat plate region, the ridge region is arranged in the middle of the flat plate region and is higher than the flat plate region, P-type doping and N-type doping are alternately carried out on the ridge region and the flat plate region along the transverse direction of the ridge region, and at least two PN junctions are formed on the ridge region; and the two metal contact electrodes are respectively in ohmic contact with the flat plate regions on the two sides of the ridge-shaped region. The electro-optical modulation waveguide can improve the bandwidth of the silicon modulator and reduce the optical insertion loss of the silicon modulator.

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, including high speed, low loss, and high-density integration.

[0003] The operating principle of silicon optical modulators is based on the plasma dispersion effect. By charging and discharging carriers in a silicon optical waveguide, the carrier concentration changes, causing a change in the effective refractive index of the optical waveguide, ultimately achieving electro-optical phase modulation and intensity modulation. However, the performance of silicon optical modulators is limited by the RC time constant, and large series resistance and series capacitance significantly restrict their bandwidth improvement. Summary of the Invention

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

[0005] One aspect of the present disclosure provides an electro-optical modulation waveguide, comprising: an optical waveguide, the optical waveguide including a ridge region and a slab region, the ridge region being located in the middle of the slab region and higher than the slab region, the ridge region and the slab region being alternately P-type doped and N-type doped laterally along the ridge region, forming at least two PN junctions on the ridge region; and two metal contact electrodes forming ohmic contacts with the slab regions on either side of the ridge region, respectively.

[0006] According to an embodiment of the present disclosure, the widths of the P-type doping region and the N-type doping region in the ridge region are 30 nm-300 nm.

[0007] According to an embodiment of the present disclosure, the doping concentration of the P-type doping region and the N-type doping region in the ridge region is 1×10 16 cm -3 - 1×10 20 cm -3 .

[0008] According to an embodiment of the present disclosure, the number of the PN junctions is 2-10.

[0009] According to an embodiment of the present disclosure, the optical waveguide is a single-mode waveguide or a multi-mode waveguide.

[0010] According to an embodiment of the present disclosure, the optical waveguide is a TE mode waveguide and / or a TM mode waveguide.

[0011] 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.

[0012] Another 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 the electro-optical modulation waveguide described in the first aspect, one of the two modulation arms being used to perform phase modulation on one of the two signals, and the other of the two modulation arms being used to transmit the other of the two signals; a beam combiner connected to the two modulation arms and being used to interfere with the two light beams having a phase difference transmitted by the two modulation arms; and a traveling wave electrode for applying a radio frequency signal to the electro-optical modulation waveguide to drive phase modulation.

[0013] According to the embodiments of the present disclosure, the total series capacitance of the multiple PN junctions cascaded in the ridge region of the electro-optical modulation waveguide is inversely proportional to the number of PN junctions, resulting in a proportional reduction in RC time, improving response speed and modulation bandwidth. Furthermore, the depletion region of the multiple PN junctions reduces the carrier concentration within the ridge region of the optical waveguide, thereby reducing optical transmission losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] 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:

[0015] Figure 1 Schematically shows a cross-sectional view of an electro-optical modulation waveguide according to an embodiment of the present disclosure;

[0016] Figure 2 FIG2 schematically shows a top view of a Mach-Zehnder interferometer electro-optic modulator according to an embodiment of the present disclosure.

[0017] Description of reference numerals:

[0018] 103 - P-type doped region in the ridge region; 104 - N-type doped region in the ridge region; 105 - buried oxide layer; 106 - silicon substrate; 107 - insulating dielectric layer; 121 - first metal contact electrode; 122 - second metal contact electrode; 131 - PN junction; 132 - optical waveguide; 201 - beam splitter; 202 - beam combiner; 210 - traveling wave electrode; 213 - DC electrode; 220 - electro-optical modulation waveguide. DETAILED DESCRIPTION

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] The present disclosure provides an electro-optical modulation waveguide, comprising an optical waveguide 132 and a metal contact electrode. The optical waveguide 132 comprises a ridge region and a slab region, with the ridge region being located in the middle of the slab region. The ridge region and the slab region are alternately doped with P-type and N-type doping laterally along the ridge region. At least two PN junctions 131 are formed on the ridge region, with the PN junctions 131 being formed by the intersection of a P-type doped region 103 and an N-type doped region 104. Two metal contact electrodes form ohmic contacts with the slab regions on both sides of the ridge region, respectively. The electro-optical modulation waveguide further comprises a buried oxide layer 105, a silicon substrate 106, and an insulating dielectric layer 107. The silicon substrate 106 is located at the bottom of the electro-optical modulation waveguide; the buried oxide layer 105 is located between the bottom of the electro-optical modulation waveguide and the silicon substrate 106; and the insulating dielectric layer 107 covers the upper surface of the electro-optical modulation waveguide and is provided with a connection channel between the metal contact electrode and the electro-optical modulation waveguide. In the embodiment of the present disclosure, the widths of the P-type doping region 103 and the N-type doping region 104 in the ridge region are 30 nm-300 nm.

[0024] In the embodiment of the present disclosure, the doping concentration of the P-type doping region 103 and the N-type doping region 104 in the ridge region is 1×10 16 cm -3 - 1×10 20 cm -3 .

[0025] In the embodiment of the present disclosure, the number of the PN junctions 131 is 2-10.

[0026] In the embodiment of the present disclosure, the optical waveguide 132 is a single-mode waveguide or a multi-mode waveguide, wherein the optical waveguide 132 can be a TE mode waveguide and / or a TM mode waveguide.

[0027] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0028] like Figure 1 As shown, in this embodiment, the electro-optical modulation waveguide is formed on a buried oxide layer 105 and a silicon substrate 106. The electro-optical modulation waveguide includes an optical waveguide 132, which includes a ridge region and a slab region. The ridge region of the optical waveguide 132 also includes at least two PN junctions 131, each formed by the intersection of a P-type doped region 103 and an N-type doped region 104; and metal contact electrodes 121 and 122, which are disposed on the slab region of the optical waveguide 132, one on each side of the ridge region of the optical waveguide 132, forming ohmic contacts with the slab region of the optical waveguide 132.

[0029] In this embodiment, the PN junctions 131 are arranged in a horizontal cascade pattern. The number of PN junctions 131 is 7. The width of the ridge region is 480 nm, and the widths of the P-type doping region 103 and the N-type doping region 104 in the ridge region are both 80 nm. The concentrations of the P-type doping region 103 and the N-type doping region 104 are 1×10 18 cm -3 In the slab region of the optical waveguide 132, the slab region on the left side of the ridge region is doped with P-type, and the slab region on the right side of the ridge region is doped with N-type. The concentration of the P-type doping region and the N-type doping region in the metal contact electrode region is 1×10 20 cm -3 The heavy doping is conducive to the formation of carrier tunneling ohmic contact. The medium doping concentration of 3×10 18 cm -3 , in order to balance carrier light absorption and series resistance.

[0030] PN junction 131 has a depletion region when no external driving voltage is applied. When an external voltage is applied, the depletion region of reverse-biased PN junction 131 increases, while the depletion region of forward-biased PN junction 131 decreases. Because the voltage divider is concentrated on reverse-biased PN junction 131, the decrease in the depletion region of forward-biased PN junction 131 is negligible relative to that of reverse-biased PN junction 131. Due to the plasma dispersion effect, the depletion region in the ridge region of optical waveguide 132 widens when a bias voltage is applied, reducing the carrier concentration and causing the refractive index of optical waveguide 132 to change, achieving electro-optical modulation.

[0031] Compared to conventional single-PN junction optical waveguide structures, where the junction capacitance is Cpn, when an external voltage V is applied, the carrier concentration decreases by dQ = Cpn*V. In this embodiment, seven PN junctions 131 are connected in series, with three reverse-biased and four forward-biased. The capacitance of the reverse-biased PN junctions is smaller, so the voltage divider is concentrated on the capacitance of the reverse-biased PN junctions 131. Under high DC operating point bias conditions, the series capacitance of the multiple PN junctions 131 in this embodiment can be reasonably considered to be primarily composed of three reverse-biased PN junctions 131 connected in series, with a capacitance of Cpn / 3, where the junction capacitance of each reverse-biased PN junction 131 is Cpn. The voltage divider for each reverse-biased PN junction 131 is V / 3, resulting in a carrier concentration reduction of dQ = Cpn*V / 3*3 = Cpn*V for the three PN junctions 131, which is the same as the carrier concentration reduction for a conventional single PN junction, resulting in similar modulation efficiency. In both cases, the series resistance is close, so the RC time is reduced to 1 / 3 of that of a traditional single PN junction, significantly improving the bandwidth. At the same time, the carriers in the depletion region of the seven PN junctions are depleted, reducing free carrier absorption losses and improving the optical transmission loss of the electro-optical modulation waveguide.

[0032] It should be noted that the number and doping concentration of the PN junctions 131 in this embodiment are a special case of the present invention. In actual electro-optical modulation waveguides, the number of PN junctions 131 can be adjusted between 2 and 10, and the doping concentration can be adjusted between 1×10 16 cm -3 - 1×10 20 cm -3 At the same time, the width of each P-type doping region and N-type doping region is adjusted between 30nm-300nm.

[0033] Another aspect of the present disclosure provides a Mach-Zehnder interferometer electro-optic modulator.

[0034] like Figure 2 As shown, the Mach-Zehnder interferometer electro-optical modulator includes: a beam splitter 201 for dividing an optical signal into two identical signals; two modulation arms connected to the beam splitter 201, and both modulation arms include Figure 1 In the electro-optical modulation waveguide 220 shown, one of the two modulation arms is used to phase modulate one of the two signals, and the other of the two modulation arms is used to transmit the other of the two signals; the combiner 202 is connected to the two modulation arms and is used to interfere with the two light beams with phase difference transmitted by the two modulation arms.

[0035] The Mach-Zehnder interferometer electro-optic modulator also includes two traveling-wave electrodes 210 and a direct current electrode 213. The two traveling-wave electrodes 210 are respectively connected to the first metal contact electrodes 121 of the electro-optic modulation waveguides 220 on the two modulation arms. The traveling-wave electrodes 210 connected to the electro-optic modulation waveguides 220 performing phase modulation are used to apply radio frequency signals to drive phase modulation. The direct current electrode 213 is connected to the second metal contact electrodes 122 of the electro-optic modulation waveguides 220 on the two modulation arms to control the operating point.

[0036] Since the optical waveguide with multiple PN junctions cascaded has a lower RC time, the modulator bandwidth is significantly improved.

[0037] In the embodiment of the present disclosure, the electrode adopts a CPS traveling wave electrode. The actual electro-optical modulator may also adopt 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 may adopt back-to-back or PN same-direction methods according to the direction of the electrode signal.

[0038] 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), the optical waveguide (132) comprising a ridge region and a slab region, the ridge region being located in the middle of the slab region and higher than the slab region; The ridge region and the flat plate region are alternately doped with P-type and N-type doping along the lateral direction of the ridge region, forming at least two PN junctions (131) on the ridge region; Two metal contact electrodes form ohmic contacts with the flat plate areas on both sides of the ridge area respectively.

2. The electro-optical modulation waveguide according to claim 1, wherein: The widths of the P-type doping region (103) and the N-type doping region (104) in the ridge region are 30 nm to 300 nm.

3. The electro-optical modulation waveguide according to claim 1, wherein: The doping concentration of the P-type doping region (103) and the N-type doping region (104) in the ridge region is 1×10 16 cm -3 - 1×10 20 cm -3 .

4. The electro-optical modulation waveguide according to claim 1, wherein: The number of the PN junctions (131) is 2-10.

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

6. 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.

7. 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 (220); A buried oxide layer (105) is provided between the bottom of the electro-optical modulation waveguide (220) and the silicon substrate (106); An insulating dielectric layer (107) covers the upper surface of the electro-optical modulation waveguide (220) and is provided with a connection channel between the metal contact electrode and the electro-optical modulation waveguide (220).

8. A Mach-Zehnder interferometer electro-optic modulator, comprising: A beam splitter (201), used for splitting an optical signal into two identical signals; Two modulation arms connected to the beam splitter (201), the two modulation arms each comprising the electro-optical modulation waveguide (220) as described in any one of claims 1 to 7, one of the two modulation arms being used to perform phase modulation on one of the two signals, and the other of the two modulation arms being used to transmit the other of the two signals; A beam combiner (202) is connected to the two modulation arms and is used to interfere the two light beams with phase difference transmitted by the two modulation arms; The traveling wave electrode (210) is used for applying a radio frequency signal to the electro-optical modulation waveguide (220) to drive phase modulation.

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