Novel Mach-Zehnder electro-optical modulator based on two-dimensional black phosphorus

Abstract

The invention discloses a novel Mach-Zehnder electro-optical modulator based on two-dimensional black phosphorus. The novel Mach-Zehnder electro-optical modulator comprises a two-dimensional black phosphorus modulation structure (4), a modulator (7) and a silicon dioxide substrate (12), the Mach-Zehnder modulator is characterized in that the Mach-Zehnder modulator (7) comprises an input waveguide (1), a beam splitter (2), two interference arms (3), a beam combiner (5) and an output waveguide (6); the two-dimensional black phosphorus modulation structure (4) is composed of a silicon waveguide (11), a lower coated aluminum oxide layer (9), a black phosphorus modulation layer (10) and an upper coated aluminum oxide layer (8), wherein the lower coated aluminum oxide layer (9) and the black phosphorus modulation layer (10) are arranged on the silicon waveguide (11), and the upper coated aluminum oxide layer (8) plays an insulating role. The black phosphorus modulation layer (10) and the lower coating aluminum oxide layer (9) form a two-dimensional black phosphorus modulation structure for phase modulation; and the two-dimensional black phosphorus modulation structure (4) regulates and controls the refraction characteristic of the black phosphorus layer through the gold electrode (13) under the action of an externally applied voltage, so that the dynamic modulation of the output light intensity of the modulator (7) is realized. Electro-optical modulation can be realized by adjusting the optical phase change of the black phosphorus layer.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optoelectronics, in particular to an electro-optic modulator, and more particularly to a novel Mach-Zehnder electro-optic modulator based on two-dimensional black phosphorus. BACKGROUND

[0002] Mid-infrared electro-optic modulators have important applications in fiber-optic communication, optical sensing, and environmental monitoring. Modulators in the mid-infrared band (2-5 μm) play a key role in many modern optoelectronic systems, especially in gas sensing and imaging technologies. However, existing mid-infrared electro-optic modulators mostly rely on lithium niobate (LiNbO3) or other traditional materials, which usually have large volume, high cost, and poor compatibility with silicon-based processes, limiting their application in on-chip integrated systems.

[0003] In recent years, two-dimensional materials have attracted widespread attention in optoelectronic device design due to their excellent electronic, optical, and electro-optic properties. Among them, graphene and black phosphorus, as representatives of two-dimensional materials, have shown great potential in the study of mid-infrared electro-optic modulators due to their superior bandgap adjustment and electro-optic response characteristics. Compared with graphene, black phosphorus has a smaller bandgap (about 0.3 eV, depending on thickness), which can better adapt to the application of the mid-infrared band (2-5 μm), and black phosphorus material exhibits significant anisotropic optical absorption and electro-optic effect.

[0004] The electro-optic properties of black phosphorus, including high carrier mobility (more than 2000 cm 2 / V·s) and adjustable bandgap, make it an ideal candidate material for mid-infrared electro-optic modulators. Through an external voltage, the optical absorption characteristics and dielectric constant of black phosphorus can be adjusted, which provides new opportunities for achieving high-efficiency modulation. However, black phosphorus-based mid-infrared electro-optic modulators still face challenges in modulation efficiency, bandwidth, and integration.

[0005] Mach-Zehnder modulators (MZMs) as a mature electro-optic modulator architecture have been widely used in mid-infrared optical communication systems due to their high modulation efficiency and good temperature stability. Compared with micro-ring resonant structures, MZM structures can provide a wider operating wavelength band and stronger modulation bandwidth, especially suitable for high-speed optical communication systems. However, existing MZM structures are mostly based on lithium niobate or graphene materials, and have not fully utilized the two-dimensional black phosphorus material with better electro-optic response characteristics.

[0006] Therefore, developing a high-efficiency, low-power, and silicon-compatible black phosphorus-based Mach-Zehnder electro-optic modulator that can both improve modulation efficiency and expand its application in the mid-infrared band has become an important research topic in the field of optoelectronics. SUMMARY

[0007] The purpose of the present application is to design a two-dimensional black phosphorus phase modulation type electro-optical modulator based on a silicon waveguide Mach-Zehnder interference structure to overcome the deficiencies of existing two-dimensional material electro-optical modulators in terms of modulation efficiency, bandwidth and energy consumption. The modulator combines the excellent electro-optical response characteristics of black phosphorus material in the mid-infrared waveband and the structural advantages of high bandwidth and high stability of the Mach-Zehnder modulator, while realizing low-voltage driving and silicon-based platform integration, and has the advantages of high modulation depth, low insertion loss and low energy consumption.

[0008] To achieve the above purpose, the present application adopts the following technical scheme:

[0009] A novel Mach-Zehnder electro-optical modulator based on two-dimensional black phosphorus, comprising: a two-dimensional black phosphorus modulation structure 4, a Mach-Zehnder modulator 7 based on a silicon waveguide, and a silicon dioxide substrate 12, the modulator 7 is arranged on the silicon dioxide substrate 12, and the two-dimensional black phosphorus modulation structure 4 is loaded on the modulator 7; characterized in that the Mach-Zehnder modulator 7 comprises an input waveguide 1, a beam splitter 2, two interference arms 3, a beam combiner 5 and an output waveguide 6; the two-dimensional black phosphorus modulation structure 4 is composed of a silicon waveguide 11, a lower alumina cladding layer 9 arranged on the silicon waveguide 11, a black phosphorus modulation layer 10 and an upper alumina cladding layer 8 serving as insulation; the black phosphorus modulation layer 10 and the lower alumina cladding layer 9 form a two-dimensional black phosphorus modulation structure for phase modulation; the two-dimensional black phosphorus modulation structure 4 controls the refractive properties of the black phosphorus layer through a gold electrode 13 under the action of an external applied voltage, thereby realizing dynamic modulation of the output light intensity of the modulator 7.

[0010] The thickness of the black phosphorus layer is preferably 10 nanometers, and the thickness of the upper and lower alumina insulation layers is 7 nanometers and 10 nanometers respectively, for providing a symmetric electric field and environmental stability.

[0011] The cross-sectional size of the silicon waveguide is 1.3 microns in width and 600 nanometers in thickness; the black phosphorus length is 400 microns.

[0012] The working principle of the present application is that the real part of the refractive index of the black phosphorus phase modulation structure changes controllably under the action of an external applied electric field, mainly due to the Burstein-Moss effect and the Franz-Keldysh modulation effect. By adjusting the effective optical path length difference in the interference arm through voltage, the intensity of the output interference signal is controlled, and the phase modulation of the mid-infrared light signal is realized. This method has the characteristics of fast modulation response and low energy consumption.

[0013] The Mach-Zehnder modulator of the application is a typical phase modulation type, and light intensity modulation is realized through interference phase difference without relying on absorption loss, so that lower insertion loss and wider working bandwidth are achieved, and the Mach-Zehnder modulator is especially suitable for high-speed on-chip communication systems in the mid-infrared wave band.

[0014] Compared with the prior art, the application has the following beneficial effects:

[0015] High modulation efficiency: an extinction ratio of more than 37.5dB can be achieved, and a V π L=0.96V·mm.

[0016] Wide bandwidth: the modulation bandwidth can reach 26.8GHz, which is much better than that of a conventional electro-optic modulator.

[0017] Low energy consumption: the typical bit energy consumption is only 47.48fJ / bit, which meets the low-power communication demand.

[0018] Strong compatibility: the design is based on a silicon waveguide platform, and the structure and process are completely compatible with standard CMOS optoelectronic processes.

[0019] Flexible structure: single-arm or double-arm modulation structure design is supported, which is convenient for various topology configurations and system-level integration.

[0020] The application adjusts the light phase of black phosphorus by applying a driving voltage on the black phosphorus material layer. When the voltage changes, the carrier concentration of black phosphorus changes, thereby adjusting the refractive index, causing an asymmetric change in the light intensity in the interference arm, and then changing the light power at the interference output end, thereby realizing intensity modulation of light.

[0021] The Mach-Zehnder modulator of the application does not rely on resonance effect, has a wider working wave band and better temperature stability. The structure is simple, and the process is compatible with CMOS technology, which is suitable for large-scale integration. Test results show that the structure can realize an extinction ratio of 37.52dB in the mid-infrared wave band, the operating voltage is as low as ±2V, the device bandwidth is 26.8GHz, the energy consumption is about 47.48fJ / bit, and excellent low-power modulation performance is exhibited.

[0022] The application can be widely applied to the fields of on-chip integrated mid-infrared communication, optical interconnection, environmental monitoring and the like, and provides key support for constructing high-performance and high-integration optical electronic systems. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a schematic diagram of a two-dimensional black phosphorus electro-optic modulator.

[0024] Figure 2 It is a structural diagram of a two-dimensional black phosphorus electro-optic modulator.

[0025] Figure 3Circuit diagram of Mach-Zehnder modulator (MZM) of the present application.

[0026] Figure 4 Total performance chart of two-dimensional black phosphorus electro-optical modulator of the present application.

[0027] Figure 5 Optical phase and applied voltage relationship curve schematic diagram of the present application DETAILED DESCRIPTION

[0028] The present application is further described in detail below in conjunction with the accompanying drawings and examples.

[0029] As Figures 1-5 shown.

[0030] A novel Mach-Zehnder electro-optical modulator based on two-dimensional black phosphorus, the structure of which is based on the classic Mach-Zehnder interferometer (MZI) framework, black phosphorus is deposited on the two arms, and a voltage is applied (circuit diagram as Figure 3 shown), the principle as Figure 1 shown, and the structure as Figure 2 shown. In combination with the adjustable refractive index characteristics of two-dimensional black phosphorus material, high-efficiency electro-optical modulation in the mid-infrared band is realized, and the comprehensive performance is as Figure 4 shown. The specific structure of the present application includes: a two-dimensional black phosphorus modulation structure 4, a Mach-Zehnder modulator 7 based on a silicon waveguide, and a silicon dioxide substrate 12, the modulator 7 is arranged on the silicon dioxide substrate 12, and the two-dimensional black phosphorus modulation structure 4 is loaded on the modulator 7; the Mach-Zehnder modulator 7 includes an input waveguide 1, a beam splitter 2, two interference arms 3, a beam combiner 5, and an output waveguide 6; the two-dimensional black phosphorus modulation structure 4 is composed of a silicon waveguide 11, a lower cladding aluminum oxide layer 9 arranged on the silicon waveguide 11, a black phosphorus modulation layer 10, and an upper cladding aluminum oxide layer 8 serving as insulation; the black phosphorus modulation layer 10 and the lower cladding aluminum oxide layer 9 form a two-dimensional black phosphorus modulation structure for phase modulation; the two-dimensional black phosphorus modulation structure 4 controls the refractive characteristics of the black phosphorus layer through a gold electrode 13 under the action of an external applied voltage, thereby realizing dynamic modulation of the output light intensity of the modulator 7.

[0031] The details are as follows:

[0032] As Figure 2As shown, the modulator structure comprises: a silicon dioxide substrate 12, an embedded silicon waveguide modulator 7, upper and lower aluminum oxide cladding layers 8, 9 and an intermediate black phosphorus modulation layer 10. On a surface portion area of the silicon waveguide, a 10 nm thick lower aluminum oxide cladding layer 9, a 10 nm thick black phosphorus absorption layer 10 (BP) and a 10 nm upper aluminum oxide cladding layer 9 are sequentially deposited to form a BP-Al2O3 composite modulation unit. The area is a modulation arm, and the remaining BP-uncovered area (beam splitter, combiner, input waveguide, output waveguide) is covered with aluminum oxide to maintain symmetry and stability.

[0033] As shown in the simulation platform, a complete MZM modulation system model is constructed, including a laser source (CWL, λ=3.5μm), two-stage DC bias electrodes, a modulation driver, a PIN detector and a spectrum / eye diagram analysis module. Two interference arms are connected to independent voltage sources to achieve modulation offset and differential driving. Figure 3

[0034] As shown in the simulation platform, a complete MZM modulation system model is constructed, including a laser source (CWL, λ=3.5μm), two-stage DC bias electrodes, a modulation driver, a PIN detector and a spectrum / eye diagram analysis module. Two interference arms are connected to independent voltage sources to achieve modulation offset and differential driving. Figure 4

[0035] · The maximum and minimum output powers are 6.31mW and 1.12μW, respectively, and the extinction ratio (ER) is 37.52dB;

[0036] · The insertion loss (IL) is 2dB;

[0037] · The voltage-length product required for π phase shift is V π L=0.96V·mm

[0038] · The bit energy E=47.48fJ / bit

[0039] · The -3dB modulation bandwidth reaches 26.8GHz, which can support high-speed (>25Gbps) mid-infrared communication.

[0040] As shown in the simulation platform, a complete MZM modulation system model is constructed, including a laser source (CWL, λ=3.5μm), two-stage DC bias electrodes, a modulation driver, a PIN detector and a spectrum / eye diagram analysis module. Two interference arms are connected to independent voltage sources to achieve modulation offset and differential driving. Figure 5 As shown in the simulation platform, a complete MZM modulation system model is constructed, including a laser source (CWL, λ=3.5μm), two-stage DC bias electrodes, a modulation driver, a PIN detector and a spectrum / eye diagram analysis module. Two interference arms are connected to independent voltage sources to achieve modulation offset and differential driving.

[0041] The position and structure position relationship of each layer of the application is: in the Mach-Zehnder modulator, the interference arm adopts a vertically stacked silicon-aluminum oxide-black phosphorus-aluminum oxide structure: the bottom is a silicon waveguide, a thin layer of aluminum oxide is sandwiched in the middle as an insulator and gate dielectric, the upper layer is a black phosphorus layer with modulation activity, and the uppermost layer is covered with a layer of aluminum oxide to provide electrical insulation and protection. After applying voltage to the black phosphorus, the vertical electric field passes through the aluminum oxide and acts on the black phosphorus, adjusting the carrier concentration and changing the refractive index, thereby achieving phase modulation. ​​

[0042] exist Figure 2 In the figure, the leftmost part is the input waveguide, which guides the light in; the Y-shaped structure at the bifurcation point is the beam splitter, which divides the light into two paths, upper and lower; the two horizontal lines in the middle are interference arms, which are straight waveguides and can be covered with the modulation material black phosphorus on the top to modulate the phase; the converging area on the right is the beam combiner, which has a structure similar to the beam splitter and is used to interfere and merge the two light paths again; the rightmost line is the output waveguide, which outputs the modulated light.

[0043] In summary, the black phosphorus-MZM phase modulator described in the present invention has a compact structure, fast response, and the advantages of CMOS compatibility and low power consumption. It has broad application prospects in mid-infrared high-speed optical communications and on-chip integrated optical systems.

[0044] The parts not involved in the present invention are the same as the existing technology or can be implemented by using the existing technology.

Claims

1. A novel Mach-Zehnder electro-optical modulator based on two-dimensional black phosphorus, comprising: A two-dimensional black phosphorus modulation structure (4), a Mach-Zehnder modulator (7) based on a silicon waveguide, and a silicon dioxide substrate (12), wherein the modulator (7) is arranged on the silicon dioxide substrate (12), and the two-dimensional black phosphorus modulation structure (4) is loaded on the modulator (7); the Mach-Zehnder modulator (7) comprises an input waveguide (1), a beam splitter (2), two interference arms (3), a beam combiner (5), and an output waveguide (6); the two-dimensional black phosphorus modulation structure (4) is composed of a silicon waveguide ( 11) and a lower cladding aluminum oxide layer (9), a black phosphorus modulation layer (10) and an upper cladding aluminum oxide layer (8) arranged on the silicon waveguide (11); the black phosphorus modulation layer (10) and the lower cladding aluminum oxide layer (9) form a two-dimensional black phosphorus modulation structure for phase modulation; the two-dimensional black phosphorus modulation structure (4) controls the refractive properties of the black phosphorus layer through the gold electrode (13) under the action of an external voltage, thereby realizing dynamic modulation of the output light intensity of the modulator (7); and electro-optical modulation is realized by adjusting the optical phase change of the black phosphorus layer.

2. The electro-optic modulator according to claim 1, wherein The thickness of the black phosphorus absorption layer (10) is 10 nanometers, and the thickness of the aluminum oxide insulation layer (8) is 10 nanometers.

3. The electro-optic modulator according to claim 1, wherein The length of each interference arm in the modulator (7) is 1000 microns, wherein the length of the two-dimensional black phosphorus modulation structure (4) is 400 microns, and the lateral width of the silicon waveguide (11) is 1.3 microns and the thickness is 0.6 microns.

4. The electro-optic modulator according to claim 1, wherein The relative dielectric constants of the silicon waveguide, the silicon dioxide substrate and the aluminum oxide insulating layer are 11.8, 1.56 and 6.5 respectively.

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