Novel grating waveguide suitable for Mach-Zehnder electro-optical modulator

Abstract

The invention discloses a novel grating waveguide suitable for a Mach-Zehnder electro-optical modulator. The novel grating waveguide is characterized in that the grating structure of the novel grating waveguide is composed of periodic etching holes processed in the center of the waveguide. Specifically, the novel grating waveguide comprises: adiabatic gratings Taper located at two ends, each adiabatic grating Taper being composed of periodic grating etching holes whose sizes are asymptotically distributed in the width direction; the phase shift Bragg grating is used for connecting the two heat insulation gratings Taper, the phase shift Bragg grating is formed by cascading a plurality of resonance units with the same structure, and each resonance unit is composed of a phase shift area etching hole and a periodic grating etching hole. Optimization of the grating waveguide of the electro-optical modulator is achieved, the size of the device is reduced, the bandwidth of the device is increased, and the electro-optical modulator is suitable for an optoelectronic system in the field of high-speed optical communication and optoelectronic integration.

Description

Technical Field

[0001] The invention relates to the technical field of optoelectronic integration and high-speed optical communication, and in particular to a novel grating waveguide suitable for a Mach-Zehnder electro-optic modulator. Background Art

[0002] At present, the diversity, timeliness and value density of data have been significantly improved, and there is a broad market prospect for realizing high-speed, high-quality transmission and processing of signals. However, microelectronics technology faces severe challenges as it gradually approaches physical limits. As the feature size continues to shrink, the limitations of electrical interconnection make some undesirable physical effects difficult to ignore. In addition, the delay and power consumption problems of interconnection lines also make electrical interconnection chips seem powerless in the context of the big data era. In contrast, optical interconnection technology can effectively improve the transmission bandwidth and transmission energy efficiency of communication systems. Silicon-based optoelectronic technology, which combines optical interconnection technology with electrical interconnection technology, is expected to solve the bottleneck of short-distance electrical interconnection and achieve important applications in the field of communications.

[0003] Electro-optic modulators are important components that convert electrical signals into optical signals for transmission. They are essential in any information technology application, such as data transmission, interconnection, computing and processing. By leveraging the complementary metal oxide semiconductor process compatibility of silicon photonics, silicon-based electro-optic modulators are expected to support wafer-level manufacturing, reduce device costs and achieve high-density integration. According to different structures, silicon modulators can be divided into two categories: Mach-Zehnder modulators and micro-ring resonator modulators. Traditional Mach-Zehnder modulators have advantages such as good thermal stability, small dispersion, large extinction ratio, wide operating wavelength range, large manufacturing tolerance and low temperature sensitivity, but they still have limitations in terms of large size, high driving voltage and high power consumption. Moreover, most device sizes are in the millimeter range, which is still far from the goal of large-scale optoelectronic integration. In contrast, micro-ring resonator modulators are favored for their small size and low power consumption, but they also face problems such as large dispersion, narrow bandwidth, high processing difficulty and high temperature sensitivity. The high temperature sensitivity of micro-ring resonator modulators often requires additional temperature control modules in practical applications, which undoubtedly increases system energy consumption. Obviously, existing modulators still have many performance bottlenecks and shortcomings.

[0004] In recent years, some solutions have been proposed to effectively improve the performance of silicon-based electro-optical modulators. For example, a modulator using time-frequency balanced segmented modulation can achieve a bandwidth of 110 GHz, but it will lead to higher insertion loss and is very sensitive to process errors. There is also a slow light modulator based on Bragg grating. Although the bandwidth is as high as 110 GHz and the size is only 124um, the structure is also very sensitive to process errors and has rate mismatch problems. At present, this device cannot support higher format signal transmission such as PAM4.

[0005] Therefore, providing a new type of grating waveguide suitable for Mach-Zehnder electro-optic modulator to realize an electro-optic modulator with smaller size and higher bandwidth is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0006] The object of the present invention is to provide a novel grating waveguide suitable for a Mach-Zehnder electro-optic modulator, so as to realize an electro-optic modulator with a smaller size and a higher bandwidth.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A novel grating waveguide suitable for Mach-Zehnder electro-optic modulator, characterized in that the grating structure of the novel grating waveguide is composed of periodic etched holes processed in the center of the waveguide. The novel grating waveguide includes adiabatic grating Tapers at both ends and a phase-shifted Bragg grating connected between the two adiabatic grating Tapers.

[0009] Preferably, the adiabatic grating Taper is located at both ends of the grating waveguide, and the grating etched holes constituting its structure are distributed periodically in the length direction and have a progressive size distribution in the width direction.

[0010] Preferably, the phase-shifted Bragg grating is located between the adiabatic grating Tapers at both ends and is formed by cascading a number of resonance units with the same structure, each resonance unit consisting of a phase-shift region etched hole and a periodic grating etched hole.

[0011] Preferably, the resonant unit comprises a phase shift region etched hole and a periodic grating etched hole structure, wherein the phase shift region etched hole has a larger length dimension than the periodic grating etched hole, and the width dimension may be the same as or different from the periodic grating etched hole.

[0012] Preferably, the grating structure of the novel grating waveguide is realized by machining an etched hole at the center of the ridge of the ridge waveguide and using the periodic arrangement of these etched holes. The etched holes are spaced apart from the ridge edge of the ridge waveguide in the width direction and are periodic in the length direction, and the etching depth is less than the thickness of the waveguide layer.

[0013] Preferably, the ridge waveguide is used to etch a grating hole at the center of the ridge, and its waveguide structure can be a ridge structure, or any structure composed of waveguide materials, such as a strip shape, a bend shape, etc.

[0014] Preferably, the etched holes have a fixed period and duty cycle, and can be in the shape of a square structure, a circular structure, an arc structure or a multi-tooth structure, and can be distributed in a uniform distribution, a linear distribution, a parabolic distribution, etc., and can have the same or different etching depths.

[0015] Preferably, the traveling wave electrode of the novel grating waveguide is electrically connected to the grating waveguide structure through a through hole, loads the electrical signal onto the phase-shifted Bragg grating and transmits the electrical signal from the source end to the terminal end.

[0016] Preferably, in the above-mentioned novel grating waveguide, the novel grating waveguide is suitable for a dual-drive push-pull electro-optic modulator, and a similar structure can also be applied to a GSG single-drive push-pull electro-optic modulator.

[0017] Preferably, the novel grating waveguide suitable for a Mach-Zehnder electro-optic modulator may be a silicon-based electro-optic modulator or a lithium niobate electro-optic modulator or other electro-optic modulators capable of realizing electro-optic functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0019] Figure 1 A top view of a novel grating waveguide suitable for a Mach-Zehnder electro-optic modulator provided by the present invention.

[0020] Figure 2 A local enlarged view of a novel grating waveguide suitable for a Mach-Zehnder electro-optic modulator provided by the present invention, the local enlarged position is Figure 1 Solid line frame E.

[0021] Figure 3 The cross-sectional views of a novel grating waveguide suitable for a Mach-Zehnder electro-optic modulator provided by the present invention at the cut planes AA', BB', CC' and DD'.

[0022] Figure 4 This is a schematic diagram of a novel grating waveguide electro-optical modulator with a single-drive push-pull structure, provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The embodiment of the present invention discloses a novel grating waveguide suitable for a Mach-Zehnder electro-optic modulator.

[0025] like Figure 1 The schematic diagram of a novel grating waveguide suitable for a Mach-Zehnder electro-optic modulator is shown. The Mach-Zehnder electro-optic modulator mainly consists of a 1×2 MMI coupler (101), a traveling wave electrode structure (102), a strip-ridge structure (103), an adiabatic grating Taper structure (104) and a phase-shifted Bragg grating structure (105), and can be divided into a waveguide layer (201), a silicon dioxide lower cladding layer (202) and a substrate layer (203) according to the cross section. The novel grating waveguide consists of an adiabatic grating Taper structure (104) and a phase-shifted Bragg grating structure (105).

[0026] Specifically, the traveling wave electrode structure (102) of the Mach-Zehnder electro-optic modulator is designed as a GSGSG type. The grating structure of the novel grating waveguide is composed of periodic etched holes processed in the center of the waveguide. The novel grating waveguide includes adiabatic grating Tapers (104) at both ends and a phase-shifted Bragg grating (105) connected between the two adiabatic grating Tapers (104). Figure 3 Schematic diagram of the cross section of the novel grating waveguide at different positions. Figure 2 As shown in the figure, the size and distribution type of the etched holes in the width direction, the duty cycle, the number of cycles, the cycle length, and the etching depth in the length direction can all be optimized.

[0027] Furthermore, the adiabatic grating taper (104) is located at both ends of the grating waveguide, and the grating etched holes constituting the structure are periodically distributed in the length direction, and the size in the width direction is gradually distributed. The optical mode field propagates along the waveguide layer (201), and according to the design of the adiabatic grating taper (104), the effective refractive index of the optical mode field changes slowly and gradually along the length direction, thereby realizing adiabatic mode field transition.

[0028] Furthermore, the phase-shifted Bragg grating (105) is located between the adiabatic grating Tapers at both ends (104), and is formed by cascading a number of resonant units (106) with the same structure, each resonant unit (106) is composed of a phase-shift region etched hole (107) and a periodic grating etched hole. Its working principle is that by introducing the phase-shift region etched hole (107), the refractive index distribution changes and the Bragg reflection condition is destroyed, which will cause a quarter-wavelength phase shift at a specific wavelength. The interference superposition of the quarter-wavelength phase shift allows part of the wavelength of light to be transmitted into the phase-shift region etched hole (107) to achieve resonance enhancement and finally form an optical transmission window with a lower group velocity in the transmission spectrum band gap, thereby realizing a smaller size and higher bandwidth electro-optical modulator.

[0029] Furthermore, the resonance unit comprises a phase shift region etched hole and a periodic grating etched hole structure. The phase shift region etched hole has a larger dimension in the length direction than the periodic grating etched hole, and the dimension in the width direction can be the same as or different from the periodic grating etched hole. Specifically, the width of the phase shift region etched hole (107) of a single resonance unit (106) is designed to be the ratio of a quarter wavelength to the average effective refractive index, which can be expressed as follows according to the formula: Where ΔΛ represents the length dimension of the phase shift region etched hole (107), λ represents the central wavelength, (n eff1 +n eff2 ) / 2 represents a waveguide with grating-etched holes (n eff1 ) and waveguide without grating etched holes (n eff2 ) is the average effective refractive index near the central wavelength, Λ represents the length dimension of the grating etched hole period in the length direction, C represents the duty ratio of the size of the waveguide with the grating etched holes within the grating period to Λ, Figure 2 The enlarged schematic diagram shown marks the structural design corresponding to the formula parameters.

[0030] Furthermore, the grating structure of the novel grating waveguide is realized by machining an etched hole at the center of the ridge of the ridge waveguide and utilizing the periodic arrangement of the etched holes. The etched holes are spaced apart from the edge of the ridge of the ridge waveguide in the width direction and are periodic in the length direction, and the etching depth is less than the thickness of the waveguide layer (201).

[0031] Furthermore, the ridge waveguide is used to etch a grating hole at the center of the ridge, and its waveguide structure can be a ridge structure, or any structure composed of waveguide materials, such as a strip shape, a bend shape, etc.

[0032] Furthermore, the etched holes have a fixed period and duty cycle, and can be in the shape of a square structure, a circular structure, an arc structure or a multi-tooth structure, and can be distributed in a uniform distribution, a linear distribution, a parabolic distribution, etc., and can have the same or different etching depths.

[0033] Example: Figure 4 As shown, the grating waveguide can be made of a variety of materials such as silicon-based optical waveguide, lithium niobate optical waveguide, etc., and the electrode structure can also be changed to a GSG single-drive push-pull form.

[0034] The specific embodiments described above provide a relatively detailed and specific explanation of the objectives, technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit, ideas and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A novel grating waveguide suitable for Mach-Zehnder electro-optic modulator, characterized in that: The grating structure of the novel grating waveguide is composed of periodic etched holes processed in the center of the waveguide. The novel grating waveguide comprises adiabatic grating Tapers (104) at both ends and a phase-shifted Bragg grating (105) connected between the two adiabatic grating Tapers (104).

2. The novel grating waveguide according to claim 1, characterized in that: The adiabatic grating Taper (104) is located at both ends of the novel grating waveguide, and the grating etched holes constituting the structure are distributed periodically in the length direction and the size in the width direction is distributed gradually.

3. The novel grating waveguide according to claim 1, characterized in that: The phase-shift Bragg grating (105) is located between the adiabatic grating Tapers (104) at both ends and is formed by cascading a number of resonant units (106) with the same structure. Each resonant unit (106) is composed of a phase-shift region etched hole (107) and a periodic grating etched hole.

4. The novel grating waveguide according to claim 3, characterized in that: The resonant unit (106) comprises a phase shift region etched hole (107) and a periodic grating etched hole structure, wherein the phase shift region etched hole (107) is larger in length than the periodic grating etched hole, and can be the same or different in width from the periodic grating etched hole.

5. The novel grating waveguide according to any one of claims 1 to 4, characterized in that: The grating structure of the novel grating waveguide is realized by machining an etched hole at the center of the ridge of the ridge waveguide and utilizing the periodic arrangement of the etched holes. The etched hole is spaced apart from the edge of the ridge of the ridge waveguide in the width direction and is periodic in the length direction, and the etching depth is less than the thickness of the waveguide layer (201).

6. The ridge waveguide according to claim 5, characterized in that: The ridge waveguide is used to etch a grating hole at the center of the ridge, and its waveguide structure can be a ridge structure, or any structure composed of waveguide materials, such as a strip shape, a bend shape, etc.

7. The etched hole according to any one of claims 1 to 6, characterized in that: The etched holes have a fixed period and duty cycle, and can be in the shape of a square structure, a circular structure, an arc structure or a multi-tooth structure, and can be distributed in a uniform distribution, a linear distribution, a parabolic distribution, etc., and can have the same or different etching depths.

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