Silicon-based electro-optic modulator based on micro-ring structure and modulation method thereof

Abstract

A silicon-based electro-optical modulator based on a micro-ring structure and a modulation method thereof, the silicon-based micro-ring modulator comprising a straight waveguide and a ring waveguide adjacent to the straight waveguide, the ring waveguide comprising multiple modulation sections, the modulation sections adopting a depletion-type PN diode structure, and the P-type doped regions of two adjacent modulation sections being respectively located on the inner and outer sides of the micro-ring, and the N-type doped regions being opposite. Specifically, if the P-type doped region of the modulation section is located on the inner side of the micro-ring and the N-type doped region is located on the outer side of the micro-ring, then the P-type doped region of the PN junction of the adjacent modulation section is located on the outer side of the micro-ring and the N-type doped region is located on the inner side of the micro-ring. The two adjacent modulation sections are connected in series through a metal electrode distributed above the heavily doped region. The silicon-based micro-ring electro-optical modulator provided by the application reduces the junction capacitance through the segmented series connection of the PN junction, improves the bandwidth of the silicon-based micro-ring modulator, and is conducive to realizing higher-rate signal modulation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of integrated optoelectronics, and in particular to a silicon-based electro-optical modulator based on a micro-ring structure and a modulation method thereof. BACKGROUND

[0002] Silicon-based optoelectronic technology is a low-cost, high-speed, low-power optical communication device implementation technology based on silicon as the main material. With the rapid development of optical communication technology, optical communication chips and pluggable modules are rapidly developing towards 800 Gbit / s in the current complex optical communication system and modulation format. Silicon-based optoelectronic technology has the advantages of high bandwidth, ultra-fast rate, high anti-interference characteristics of light and microelectronic technology in large-scale integration, low power consumption, low cost, etc., and can meet the application of future high-speed optical communication systems and high-capacity optical interconnection systems.

[0003] As a core component in optical communication systems, electro-optical modulators have always been a research hotspot in the field of optical communications. Silicon optical modulators are mainly divided into resonant and interferometric types. Interferometric modulators such as Mach-Zehnder modulators are mainly based on Mach-Zehnder interference structures, and the phase difference between the interference lights is changed to change the intensity of the interference light. Resonant modulators such as micro-ring modulators are mainly based on micro-ring resonant structures, and the output light intensity is changed by adjusting the resonant wavelength. Interferometric modulators are easier to achieve high modulation rates, and have good process stability and thermal stability, but the size of the interferometric modulator is generally larger; while the size of the resonant modulator is smaller, and it is easier to achieve higher density integration. SUMMARY

[0004] The present application provides a method for improving the bandwidth of a silicon-based micro-ring modulator. The silicon-based micro-ring modulator divides the modulation region into several segments, and the several segments of the modulation region are connected in series through electrodes located above the heavily doped region of each segment of the modulation region, and the total capacitance is reduced by dividing the series connection through the junction capacitance. Although the resistance also increases when the series connection is divided, the overall RC response time of the system will decrease because the internal resistance of the driving electrical signal source is usually 50 ohms, and the electro-optical (EO) response bandwidth of the modulator is inversely proportional to the RC response time, so the modulation electrical-optical (EO) response bandwidth will increase.

[0005] The present application can be implemented by the following technical solutions:

[0006] A silicon-based micro-ring modulator based on a micro-ring structure, characterized in that it comprises a straight waveguide and a ring waveguide, and the ring waveguide has multiple modulation regions.

[0007] Further, the modulation region adopts a depletion type PN structure.

[0008] Further, the P-type doped region of the 2n-1th modulation region is located outside the ring waveguide, and the N-type doped region is located inside the ring waveguide; the P-type doped region of the 2nth modulation region is located inside the ring waveguide, and the N-type doped region is located outside the ring waveguide, where n is a positive integer.

[0009] Further, the through holes and the metal electrodes are connected above the heavily doped regions on both sides of the ring waveguide.

[0010] Further, the metal electrodes above the heavily doped regions inside the 2n-1th modulation region and the 2nth modulation region are directly connected. The metal electrodes above the heavily doped regions outside the 2nth modulation region and the 2n+1th modulation region are directly connected.

[0011] The application also provides a method for loading a modulation signal to the silicon-based micro-ring modulator, comprising

[0012] For the ring waveguide with an even number of modulation regions, the modulation signal is loaded to the electrodes above the heavily doped regions outside the first and last modulation regions. For the ring waveguide with an odd number of modulation regions, the modulation signal is loaded to the electrodes above the heavily doped regions outside the first modulation region and the electrodes above the heavily doped regions inside the last modulation region.

[0013] Compared with the prior art, the application has the following advantages:

[0014] Based on the prior art, the application divides the modulation region of the micro-ring modulator into several segments, and forms a series connection structure through the electrodes above the heavily doped regions in the modulation region. By using the series connection of the PN junction capacitor, the total capacitance is reduced, thereby improving the bandwidth of the silicon-based micro-ring electro-optical modulator. Based on the conventional micro-ring modulator, the design of the segmented series electrodes can further improve the bandwidth, which can reach more than 85GHz. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Fig. 1 is a schematic diagram of the overall structure of a micro-ring modulator based on a 1-segment modulation region.

[0016] Figure 2 Fig. 2 is a schematic diagram of the overall structure of a micro-ring modulator based on a 2-segment modulation region.

[0017] Figure 3 Fig. 3 is a schematic diagram of the overall structure of a micro-ring modulator based on an even number of segments of modulation regions.

[0018] Figure 4 Fig. 4 is a schematic diagram of the overall structure of a micro-ring modulator based on an odd number of segments of modulation regions.

[0019] Figure 5 Fig. 5 is a simulation of the EO response bandwidth of a silicon-based micro-ring modulator based on 1-3 segments of modulation regions. DETAILED DESCRIPTION

[0020] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention should not be limited thereto.

[0021] Figure 1 This is a silicon-based microring modulator with a modulation region, comprising a straight waveguide 100 and a ring waveguide 200, wherein the ring waveguide 200 includes a modulation region 201. The modulation signal is applied to an electrode located outside the microring at the start of the modulation region and an electrode located inside the microring at the end of the modulation region.

[0022] When light wave is input from the input end of the straight waveguide 100 and is transmitted to the coupling region with the ring waveguide, the resonance condition (mλ=n eff L, where m is 1, 2, ..., λ is the wavelength of light, n eff The light energy (where L is the effective refractive index of the ring waveguide and the length of the ring waveguide) is coupled into the microring resonator. The ratio of the light field output from the straight waveguide output end to the input light field is determined by the following formula: Among them E t1 is the output light field, E i1 is the input light field, t is the transmission coefficient of the straight waveguide at the coupling point, α is the loss coefficient of the light going around the ring waveguide, is the phase change of light as it travels one circle in the ring waveguide.

[0023] The effective refractive index n of the waveguide can be changed by controlling the voltage applied to the modulation region. eff , thereby changing the output light field amplitude, thereby achieving the purpose of light intensity modulation.

[0024] like Figure 2 As shown, the present invention achieves the goal of reducing capacitance by segmenting the modulation zone of a microring modulator and connecting the two modulation zones in series via electrodes. Specifically, the present invention comprises a straight waveguide 100 and a ring waveguide 200, wherein the ring waveguide includes a first modulation zone 201 and a second modulation zone 202. The first modulation zone 201 and the second modulation zone 202 are directly connected via electrodes located on the inner side of the ring waveguide. The modulation drive electrical signal is applied to the electrodes located on the outer side of the ring waveguide in the first modulation zone 201 and the second modulation zone 202.

[0025] Figure 3 、 Figure 4 The diagrams are schematic diagrams of the micro-ring modulator structures based on even-segment modulation regions and odd-segment modulation regions, respectively, including a straight waveguide 100 and a ring waveguide 200, wherein the ring waveguide includes multiple modulation regions. For the ring waveguide with even-segment modulation regions, the modulated electrical signal is loaded onto the electrodes above the heavily doped regions outside the first and last modulation regions; for the ring waveguide with odd-segment modulation regions, the modulated electrical signal is loaded onto the electrodes above the heavily doped regions outside the first modulation region and the electrodes above the heavily doped regions inside the last modulation region.

[0026] Figure 5 The small signal electro-optical response curves of the segmented and non-segmented silicon-based micro-ring modulator are given, and the micro-ring resonant optical bandwidth is taken as 52.5 GHz (corresponding to the quality factor Q=3686). From the figure, we can see that the electro-optical bandwidth can be effectively improved by segmenting the modulation region in series. The electro-optical 3dB modulation bandwidth corresponding to the non-segmented modulation region is 72 GHz, and after the modulation region is divided into two segments, the bandwidth is improved to 83 GHz. With the increase of the segmentation of the modulation region, the increase of the electro-optical bandwidth gradually slows down. As can be seen, by the way of segmenting the PN junction in series, the junction capacitance is reduced, and the bandwidth of the silicon-based micro-ring modulator is effectively improved, which is conducive to realizing higher code rate signal modulation.

[0027] The present application is not limited to the above-mentioned embodiments, and for those skilled in the art, improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements are also considered within the scope of protection of the present application.

Claims

1. A silicon-based micro-ring modulator based on a micro-ring structure, comprising at least one straight waveguide and a ring waveguide coupled thereto, characterized in that, The ring waveguide is composed of at least one modulation zone, the modulation zone adopts a depletion PN junction type structure, and a metal electrode is distributed above a heavily doped region; The modulation zone is multiple, and the P-type doped region of the adjacent two modulation zones is respectively on the inner and outer sides of the ring waveguide, and the N-type doped region is opposite.

2. The silicon-based micro-ring modulator of claim 1, wherein, The modulation zone is multiple, the P-type doped region of the 2n-1th modulation zone is located on the outer side of the ring waveguide, and the N-type doped region is located on the inner side of the ring waveguide, wherein n is a positive integer (n=1, 2, 3…); the P-type doped region of the 2nth modulation zone is located on the inner side of the ring waveguide, and the N-type doped region is located on the outer side of the ring waveguide.

3. The silicon-based micro-ring modulator of claim 2, wherein, The 2n-1th modulation zone and the 2nth modulation zone are directly connected through the metal electrode above the heavily doped region on the inner side of the ring waveguide; and / or The 2nth modulation zone and the 2n+1th modulation zone are directly connected through the metal electrode above the heavily doped region on the outer side of the ring waveguide.

4. A modulation signal loading method of the micro-ring structure-based silicon-based micro-ring modulator according to claim 3, characterized in that: when the number of the modulation zone is odd, the modulation signal is loaded on the metal electrode outside the first modulation zone and the metal electrode inside the last modulation zone; when the number of the modulation zone is even, the modulation signal is loaded on the metal electrode outside the first modulation zone and the metal electrode outside the last modulation zone; by controlling the voltage loaded on the metal electrode of the modulation zone, the effective refractive index of the ring waveguide is changed, and then the output light field amplitude of the straight waveguide is changed, and then the light intensity modulation is realized.

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