A modulator and a modulation method

Abstract

The present application discloses a modulator and a modulation method, wherein the modulator comprises: a beam splitter, a first gradient waveguide, an electro-optic modulator, a second gradient waveguide, an adjustable optical attenuator, a phase shifter and a beam combiner; the input end of the beam splitter is connected to a light source, the first output end of the beam splitter is connected to the input end of the first gradient waveguide, the output end of the first gradient waveguide is connected to the input end of the electro-optic modulator, the output end of the electro-optic modulator is connected to the input end of the second gradient waveguide, the output end of the second gradient waveguide is connected to the first input end of the beam combiner; the second output end of the beam splitter is connected to the input end of the adjustable optical attenuator, the output end of the adjustable optical attenuator is connected to the input end of the phase shifter, the output end of the phase shifter is connected to the second input end of the beam combiner, and the output end of the beam combiner outputs interference light.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of optical communication devices, and relate to but are not limited to a modulator and a modulation method. Background Art

[0002] Since silicon-based modulators are compatible with mature complementary metal oxide semiconductor (CMOS) processes, they can be processed and manufactured on a large scale, reducing the manufacturing cost of the devices.

[0003] Mach-Zehnder silicon-based modulator is a common silicon-based modulator. Traditional Mach-Zehnder silicon-based modulators have problems such as large structure size and high power consumption. In addition, for traditional Mach-Zehnder silicon-based modulators, the bit error rate is high due to the low extinction. Summary of the invention

[0004] In view of this, embodiments of the present application provide a modulator and a modulation method.

[0005] On the one hand, an embodiment of the present application provides a modulator, the modulator comprising: a beam splitter, a first gradient waveguide, an electro-optic modulator, a second gradient waveguide, an adjustable optical attenuator, a phase shifter and a beam combiner;

[0006] The input end of the beam splitter is connected to a light source, the first output end of the beam splitter is connected to the input end of the first gradient waveguide, the output end of the first gradient waveguide is connected to the input end of the electro-optic modulator, the output end of the electro-optic modulator is connected to the input end of the second gradient waveguide, and the output end of the second gradient waveguide is connected to the first input end of the beam combiner;

[0007] The second output end of the beam splitter is connected to the input end of the adjustable optical attenuator, the output end of the adjustable optical attenuator is connected to the input end of the phase shifter, the output end of the phase shifter is connected to the second input end of the beam combiner, and the output end of the beam combiner outputs interference light.

[0008] On the other hand, an embodiment of the present application provides a modulation method, the method comprising:

[0009] The beam splitter splits the incident light into a first beam of light and a second beam of light; wherein the first beam of light enters the electro-optical modulator via a first gradient waveguide, and the second beam of light enters the adjustable optical attenuator; the electro-optical modulator modulates the first beam of light entering the electro-optical modulator via the first gradient waveguide to obtain a first coherent light, and the first coherent light enters a beam combiner via the second gradient waveguide; the adjustable optical attenuator attenuates the intensity of the second beam of light, and the phase shifter shifts the phase of the second beam of light after the intensity attenuation to form a second coherent light; the second coherent light enters the beam combiner; the first coherent light and the second coherent light interfere in the beam combiner to form interference light.

[0010] In a traditional Mach-Zehnder silicon-based modulator, when two beams of light pass through two modulation arms respectively, the two modulation arms have different absorption losses on light, and the intensities of the two beams of light are no longer the same when they are combined, and the interference efficiency is reduced, resulting in a relatively low extinction ratio of the modulator. In contrast, in an embodiment of the present application, a beam splitter divides the incident light into a first beam of light and a second beam of light, and the first beam of light passes through a first gradient waveguide, an electro-optic modulator, and a second gradient waveguide in sequence. The intensity and phase of the first beam of light modulated by the electro-optic modulator change, and therefore, based on the intensity information of the first beam of light, an adjustable optical attenuator is used to attenuate the light intensity of the second beam of light, and based on the phase information of the first beam of light, a phase shifter is used to adjust the phase of the second beam of light, so that when the two beams of light enter the beam combiner, the light intensities of the two beams of light are the same and the phase difference is constant. Therefore, the extinction ratio of the modulator is relatively high, resulting in a low bit error rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The drawings herein are incorporated into the specification and constitute a part of the specification. These drawings illustrate embodiments consistent with the present application and are used together with the specification to illustrate the technical solution of the present application.

[0012] Figure 1 A schematic diagram of the structure of a modulator provided in an embodiment of the present application;

[0013] Figure 2 A schematic diagram of light splitting performed by a beam splitter provided in an embodiment of the present application;

[0014] Figure 3 A schematic diagram of the composition structure of the optical fiber provided in the embodiment of the present application;

[0015] Figure 4 A schematic diagram of the composition structure of a photonic crystal modulator provided in an embodiment of the present application;

[0016] Figure 5 A schematic diagram of a beam combiner for photosynthesis provided in an embodiment of the present application;

[0017] Fig. 6A A schematic diagram of the structure of a first tapered waveguide provided in an embodiment of the present application;

[0018] Figure 6B A schematic diagram of the structure of a second gradient waveguide provided in an embodiment of the present application;

[0019] Figure 7 A schematic diagram of a flow chart of a modulation method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0020] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0021] It should be understood that the embodiments provided herein are only used to explain the present application and are not intended to limit the present application. In addition, the embodiments provided below are partial embodiments for implementing the present application, rather than providing all embodiments for implementing the present application. In the absence of conflict, the technical solutions recorded in the embodiments of the present application can be implemented in any combination.

[0022] In the following description, the terms "first\second\..." are merely used to distinguish different objects, and do not imply that the objects are identical or related.

[0023] It should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element. The term "connected" includes both direct and indirect connections unless otherwise specified.

[0024] The technical solution of the present application is further described in detail below with reference to the accompanying drawings and embodiments.

[0025] Traditional Mach-Zehnder silicon-based modulators have the following two problems:

[0026] On the one hand, the traditional Mach-Zehnder silicon-based modulator is composed of an ordinary strip waveguide. Since the change of the light wave propagation constant in an ordinary strip waveguide is small, in order to obtain sufficient phase shift of the light, the length of the waveguide is very long, resulting in the Mach-Zehnder silicon-based modulator having problems such as large structural size and high power consumption.

[0027] On the other hand, the traditional Mach-Zehnder silicon-based modulator includes a beam splitter, two modulation arms and a beam combiner. The light source is divided into two beams of equal intensity after passing through the beam splitter. When the two beams enter the two modulation arms for modulation, the two modulation arms have different absorption losses of light due to the different paths and media of the modulation arms through which the two beams pass. When the beams are combined, the intensities of the two beams are no longer the same, which makes the extinction of the modulator relatively low, resulting in problems such as high bit error rate.

[0028] In order to solve this problem, an embodiment of the present application provides a modulator, including: a beam splitter, a first gradient waveguide, an electro-optical modulator, a second gradient waveguide, an adjustable optical attenuator, a phase shifter and a beam combiner; the input end of the beam splitter is connected to a light source, the first output end of the beam splitter is connected to the input end of the first gradient waveguide, the output end of the first gradient waveguide is connected to the input end of the electro-optical modulator, the output end of the electro-optical modulator is connected to the input end of the second gradient waveguide, and the output end of the second gradient waveguide is connected to the first input end of the beam combiner; the second output end of the beam splitter is connected to the input end of the adjustable optical attenuator, the output end of the adjustable optical attenuator is connected to the input end of the phase shifter, the output end of the phase shifter is connected to the second input end of the beam combiner, and the output end of the beam combiner outputs interference light.

[0029] In a traditional Mach-Zehnder silicon-based modulator, when two beams of light pass through two modulation arms respectively, the two modulation arms have different absorption losses on light, and the intensities of the two beams of light are no longer the same when they are combined, and the interference efficiency is reduced, resulting in a relatively low extinction ratio of the modulator. In contrast, in an embodiment of the present application, a beam splitter divides the incident light into a first beam of light and a second beam of light, and the first beam of light passes through a first gradient waveguide, an electro-optic modulator, and a second gradient waveguide in sequence. The intensity and phase of the first beam of light modulated by the electro-optic modulator change, and therefore, based on the intensity information of the first beam of light, an adjustable optical attenuator is used to attenuate the light intensity of the second beam of light, and based on the phase information of the first beam of light, a phase shifter is used to adjust the phase of the second beam of light, so that when the two beams of light enter the beam combiner, the light intensities of the two beams of light are the same and the phase difference is constant. Therefore, the extinction ratio of the modulator is relatively high, resulting in a low bit error rate.

[0030] In some embodiments, a beam splitter is an optical device that can split a beam of light into two or more beams of light. It is a key part of most interferometers. The beam splitter can be a directional coupler or a multi-mode interferometer.

[0031] In some embodiments, a waveguide refers to a structure for directionally guiding light waves. Waveguide structures include planar dielectric optical waveguides and optical fibers. The first gradient waveguide in the embodiment of the present application refers to a waveguide that can convert the waveguide mode field in order to reduce the coupling loss between waveguides. During implementation, the first gradient waveguide can adopt a tapered waveguide. The tapered waveguide can achieve mode field conversion in two ways: Method 1, mode field conversion is achieved by slowly changing the width or thickness of the tapered waveguide; Method 2, mode field conversion is achieved by adopting a tapered waveguide with a tapered refractive index structure. When a tapered waveguide with a tapered refractive index structure is adopted, the physical size of the waveguide can remain unchanged, and the mode field conversion in the width and thickness directions of the tapered waveguide is achieved by slowly changing the refractive index.

[0032] In some embodiments, an electro-optic modulator refers to a modulator made of some electro-optic crystals. When a voltage is applied to the electro-optic crystal, the refractive index of the electro-optic crystal will change, resulting in changes in the characteristics of the light wave passing through the crystal, thereby modulating the phase, amplitude, intensity and polarization state of the optical signal. The electro-optic modulator includes an electrical structure and an optical structure. The type of electrical structure and the doping method affect the driving voltage and modulation rate of the modulator; the optical structure parameters, such as the lattice constant, waveguide width and resonant cavity parameters, can affect the extinction ratio, insertion loss and quality factor of the modulator.

[0033] The electro-optic modulator in the embodiment of the present application can be an electro-optic modulator based on lithium niobate (LiNbO3), an electro-optic modulator based on group III-V materials, and a silicon-based electro-optic modulator. In comparison, the modulation efficiency of the lithium niobate modulator is low and the device structure is large; the production cost of the electro-optic modulator based on group III-V materials is very high; and the silicon-based modulator is compatible with the currently mature CMOS process, so it can be processed and prepared on a large scale, reducing the preparation cost of the device. In implementation, the electro-optic modulator in the embodiment of the present application adopts a silicon-based modulator.

[0034] In some embodiments, the second tapered waveguide may be the same as or different from the first tapered waveguide.

[0035] In some embodiments, a variable optical attenuator (VOA) is an electronic component in optical fiber communication that implements real-time control of signals by attenuating the transmission optical power.

[0036] In some embodiments, a phase shifter is a component used to change the phase of a transmission wave. The function of the phase shifter is to adjust the phase of the wave.

[0037] In some embodiments, a beam combiner is an optical device that can combine two or more light beams into one light beam.

[0038] The present application also provides a modulator, referring to Figure 1 , the modulator comprises:

[0039] A beam splitter 20, a first gradient waveguide 30, an electro-optic modulator 40, a second gradient waveguide 50, an adjustable optical attenuator 60, a phase shifter 70 and a beam combiner 80, wherein:

[0040] The input end of the beam splitter 20 is connected to a light source, the first output end of the beam splitter 20 is connected to the input end of the first gradient waveguide 30, the output end of the first gradient waveguide 30 is connected to the input end of the electro-optic modulator 40, the output end of the electro-optic modulator 40 is connected to the input end of the second gradient waveguide 50, and the output end of the second gradient waveguide 50 is connected to the first input end of the beam combiner 80;

[0041] The second output end of the beam splitter 20 is connected to the input end of the adjustable optical attenuator 60, the output end of the adjustable optical attenuator 60 is connected to the input end of the phase shifter 70, the output end of the phase shifter 70 is connected to the second input end of the beam combiner 80, and the output end of the beam combiner 80 outputs interference light.

[0042] In some embodiments, the input end of the beam splitter 20 is connected to the light input end 10 , through which the light source is connected, and the output end of the beam combiner 80 is connected to the light output end 90 , through which the interference light is output.

[0043] In the embodiment of the present application, the beam splitter 20 splits the incident light into a first beam and a second beam. The first beam enters the electro-optic modulator 40 after mode field conversion by the first gradient waveguide 30, enters the second gradient waveguide 50 after modulation by the electro-optic modulator 40, enters the beam combiner 80 after mode field conversion again by the second gradient waveguide 50, and forms a first coherent light. The second beam enters the phase shifter 70 after intensity attenuation by the adjustable optical attenuator 60, enters the beam combiner 80 after phase shifting by the phase shifter 70, and forms a second coherent light. The first coherent light and the second coherent light interfere in the beam combiner 80 to form interference light. Since the first coherent light and the second coherent light have the same light intensity and a constant phase difference, when the two beams interfere, there will be a high coherence, resulting in a relatively high extinction of the modulator, thereby reducing the bit error rate of the modulator.

[0044] In some embodiments, the beam splitter 20 is used to split the incident light into a first beam of light and a second beam of light, wherein the first beam of light enters the electro-optic modulator 40 through the first gradient waveguide 30 , and the second beam of light enters the adjustable optical attenuator 60 .

[0045] Here, reference Figure 2, the incident light 100 enters the beam splitter 20 through the input end of the beam splitter 20, and the beam splitter 20 splits the incident light 100 into a first beam 1001 and a second beam 1002, and the first beam 1001 and the second beam 1002 have the same intensity. The first beam 1001 is output from the waveguide 201 at the first output end of the beam splitter 20, and the second beam 1002 is output from the waveguide 202 at the second output end of the beam splitter 20.

[0046] During implementation, the waveguides at the first and second output ends of the beam splitter may be parallel twin-conductor waveguides, coaxial line waveguides, parallel slab waveguides, rectangular waveguides, circular waveguides, slab dielectric optical waveguides and / or optical fibers.

[0047] In the embodiment of the present application, the waveguides at the first and second output ends of the beam splitter are single-mode optical fibers (Single Mode Fiber). Single-mode optical fibers refer to optical fibers with a very thin central glass core (core diameter is generally 8 to 10 μm) that can only transmit one mode. Single-mode optical fibers are used in the wavelength region of 1.3 μm to 1.6 μm. By properly designing the refractive index distribution of the optical fiber and selecting a very pure material to prepare a cladding that is 7 times larger than the core, the lowest loss and the lowest dispersion can be achieved in this band.

[0048] In the embodiment of the present application, the waveguides at the first and second output ends of the beam splitter use single-mode optical fibers. Compared with multi-mode optical fibers, single-mode optical fibers have a thinner core diameter because they only propagate light waves in one mode. Therefore, single-mode optical fibers have no inter-mode dispersion, small total dispersion, and wide bandwidth, and can support longer transmission distances, making them suitable for long-distance communications.

[0049] In some embodiments, the first gradient waveguide 30 is used to perform a first mode field conversion on the waveguide at the first output end of the beam splitter;

[0050] Here, because the waveguide at the first output end of the beam splitter is different from the waveguide at the input end of the electro-optic modulator, the mode field at the first output end of the beam splitter is also different from the mode field at the input end of the electro-optic modulator. The mode field diameter is often used to quantitatively describe the size of the mode field. The mode field diameter (MFD) refers to the time when the light intensity is reduced to 1 / (e 2 ) is the maximum distance between two points.

[0051] In some embodiments, optical fiber is used as an example to illustrate the mode field diameter. Figure 3 The optical fiber includes a cladding 301 and a core 302 . The light energy is not completely concentrated in the core 302 , and part of the energy is transmitted in the cladding 301 . The diameter of the core 302 is 303 , and the diameter of the mode field is 304 . The mode field diameter 304 is larger than the core diameter 303 .

[0052] In an embodiment of the present application, since the mode field diameter of the first light beam in the waveguide at the first output end of the beam splitter is different from the mode field diameter in the waveguide of the electro-optic modulator, a first gradient waveguide is required to perform mode field conversion so that the mode field of the first light beam in the waveguide at the first output end of the beam splitter matches the mode field of the first light beam in the waveguide of the electro-optic modulator.

[0053] In the embodiment of the present application, the first gradient waveguide is used for mode field conversion, so that the mode field in the waveguide at the first output end of the beam splitter matches the mode field in the waveguide of the electro-optic modulator, thereby reducing the coupling loss between the waveguide at the first output end of the beam splitter and the waveguide of the electro-optic modulator, and realizing a low-loss connection. In some embodiments, the electro-optic modulator is used to modulate the first beam of light entering the electro-optic modulator through the first gradient waveguide to obtain a first coherent light, and the first coherent light enters the beam combiner through the second gradient waveguide;

[0054] In the embodiment of the present application, the electro-optic modulator adopts a photonic crystal modulator among silicon-based modulators.

[0055] Here, photonic crystal refers to an artificial periodic dielectric structure with photonic band gap (PBG) characteristics. Photonic band gap means that waves within a certain frequency range cannot propagate in this periodic structure. In other words, photonic crystal has a "bandgap" structure.

[0056] In some embodiments, low refractive index materials (such as artificially created air holes) will periodically appear at certain locations of high refractive index materials in the photonic crystal structure, where high and low refractive index materials are alternately arranged to form a periodic structure to form a photonic band gap. Since the distances between the periodically arranged low refractive index sites are the same, photonic crystals of a certain distance only produce an energy band effect for light waves of a certain frequency, that is, only light of a certain frequency will be completely prohibited from propagating in a photonic crystal with a certain periodic distance. By introducing defects to destroy the periodic structural characteristics of the photonic crystal, corresponding defect energy levels can be formed in the photonic band gap, allowing only light of a specific frequency to pass through this defect energy level, thereby forming an optical path, so that light can propagate smoothly along the optical path. Photonic crystal modulators are electro-optical modulators made using this characteristic of photonic crystals.

[0057] In some embodiments, the photonic crystal modulator includes a base, a substrate, a silicon waveguide, a photonic crystal waveguide, and an electrode. The material of the base may be silicon; a deposition process is used to form a substrate on the upper surface of the base, and the material of the substrate may be silicon dioxide; a silicon flat waveguide is formed on the upper surface of the substrate by a deposition process, and further, an N-type doping region and a P-type doping region are formed in the silicon flat waveguide by a mask process; a layer of high refractive index material is deposited on the upper surface of the silicon flat waveguide, and then an etching process is used to form a photonic crystal waveguide, and the material of the photonic crystal waveguide may be silicon, silicon nitride, etc.; at the same time, two electrodes are formed on the upper surface of the silicon flat waveguide, and the electrode materials may be aluminum (Al), copper (Cu) and / or tungsten (Wu), etc.

[0058] In some embodiments, the N-type doping region may include a heavily doped N-type region, a medium doped N-type region, and a low doped N-type region. Similarly, the P-type doping region may include a heavily doped P-type region, a medium doped P-type region, and a low doped P-type region.

[0059] Reference below Figure 4 The photonic crystal modulator provided in the embodiment of the present application is described. Figure 4 In the figure, the photonic crystal modulator includes a silicon substrate 401; a silicon dioxide substrate 402 located on the upper surface of the silicon substrate 401, a silicon waveguide 403 formed by depositing silicon material on the silicon dioxide substrate 402 through a deposition process; a photonic crystal waveguide 404 located on the upper surface of the silicon waveguide 403, formed by depositing a layer of high refractive index material and etching; and an electrode 405 and an electrode 406 located on the upper surface of the silicon waveguide 403 and parallel to the photonic crystal waveguide 404.

[0060] Furthermore, a P-type doping region and an N-type doping region are formed on the silicon waveguide 403 by a mask process, wherein the P-type doping region includes a low-doping concentration P-type region 407, a medium-doping concentration P-type region 408 and a heavy-doping concentration P-type region 409, and the N-type doping region includes a low-doping concentration N-type region 410, a medium-doping concentration N-type region 411 and a heavy-doping concentration N-type region 412, wherein the low-doping concentration P-type region 407 and the low-doping concentration N-type region 410 form a PN junction, an ohmic contact is formed between the heavy-doping concentration P-type region 409 and the electrode 405, and an ohmic contact is formed between the heavy-doping concentration N-type region 412 and the electrode 406.

[0061] In the embodiment of the present application, a photonic crystal modulator is used as an electro-optical modulator, and the effective refractive index of the waveguide can be changed by changing the concentration of carriers, thereby limiting the first beam of light to a very small range, increasing the action time of the first beam of light with the doped region in the photonic crystal modulator, and thus improving the modulation efficiency of the photonic crystal modulator. In addition, since the structure size of the photonic crystal modulator is very small, the size of the Mach-Zehnder modulator can be reduced, thereby reducing the power consumption loss of the modulator.

[0062] In some embodiments, the second gradient waveguide 50 is used to perform a second mode field conversion on the waveguide of the electro-optic modulator;

[0063] In some embodiments, since the mode field diameter in the electro-optic modulator waveguide is different from the mode field diameter in the waveguide at the input end of the combiner, a second gradient waveguide is required to perform mode field conversion so that the mode field diameter in the waveguide at the input end of the combiner matches the mode field in the electro-optic modulator waveguide.

[0064] In some embodiments, the adjustable optical attenuator 60 is used to attenuate the intensity of the second light beam so that the difference between the light intensity of the first coherent light and the attenuated second light beam is within a preset range;

[0065] Here, the first beam of light will generate light intensity loss after passing through the first gradient waveguide, the photonic crystal modulator and the second gradient modulator. The sources of light intensity loss include: 1) light intensity loss caused by waveguide coupling between the first gradient waveguide and the photonic crystal modulator waveguide; 2) absorption loss caused by carrier concentration change when the photonic crystal modulator modulates the first beam of light; 3) light intensity loss caused by waveguide coupling between the photonic crystal modulator waveguide and the second gradient waveguide. Therefore, when the first beam of light enters the input end of the beam combiner, the light intensity will decrease.

[0066] Here, the calculation of the extinction ratio ER follows formula (1):

[0067]

[0068] Wherein, ER is the extinction ratio, P1 is the maximum light intensity output from the output end of the combiner, P2 is the minimum light intensity output from the output end of the combiner, and lg(.) is the logarithm with base 10.

[0069] Therefore, in order to make the extinction ratio of the modulator higher, the first beam of light and the second beam of light must completely interfere when they meet in the beam combiner. When the interference is constructive, the light intensity output at the output end of the beam combiner is P1, and when the interference is destructive, the light intensity output at the output end of the beam combiner is P2. Moreover, if the value of the light intensity P2 is smaller, even close to 0, the extinction ratio of the modulator will be higher.

[0070] During implementation, first, the attenuation button of the adjustable optical attenuator is set to "0" (no attenuation); secondly, the light source is divided into a first light beam and a second light beam through a beam splitter, wherein the first light beam generates a first coherent light after passing through the first gradient waveguide, the photonic crystal modulator and the second gradient waveguide, and at the same time, the second light beam passes through the adjustable optical attenuator and the phase shifter, and the phase shifter is adjusted so that the phase difference between the second light beam output from the adjustable optical attenuator and the first coherent light is an odd multiple of π, thereby generating a second coherent light; then, the first coherent light and the second coherent light interfere in the beam combiner to generate interference light, the interference light is output from the output end of the beam combiner, and a spectrometer is used to measure the minimum light intensity P2 of the interference light; finally, the adjustable optical attenuator and the thermal phase shifter are adjusted simultaneously, and a spectrometer is used to continuously measure the minimum light intensity P2 of the interference light, so that the minimum light intensity P2 of the interference light formed after the interference is finally close to 0, at which time, the difference in light intensity between the first coherent light and the attenuated second light beam is within a preset range, and the first coherent light and the second coherent light are close to complete interference.

[0071] In the embodiment of the present application, an adjustable optical attenuator is used to accurately control the intensity of the optical signal and provide a stable attenuation amount to ensure that the minimum light intensity of the interference light formed after interference is close to 0, so that the extinction ratio of the modulator is relatively high.

[0072] In some embodiments, the phase shifter 70 is used to shift the phase of the attenuated second light beam to obtain a second coherent light beam, and the second coherent light beam enters the beam combiner;

[0073] Here, when the first beam of light passes through the photonic crystal modulator, a change in the carrier concentration in the photonic crystal modulator causes a change in the phase of the first beam of light.

[0074] Therefore, in order to generate interference light, it is necessary to shift the phase of the attenuated second light beam based on the phase of the first light beam at the input end of the beam combiner so that the phase difference between the first coherent light and the second coherent light is constant. When destructive interference occurs, the phase difference between the first coherent light and the second coherent light is an odd multiple of π, and when constructive interference occurs, the phase difference between the first coherent light and the second coherent light is an integer multiple of 2π.

[0075] In the embodiment of the present application, the phase shifter is a thermal phase shifter (TPS). The thermal phase shifter may include a thermal phase shifter using titanium nitride as a heat source and a thermal phase shifter using lightly doped silicon as a heat source. For the thermal phase shifter using titanium nitride as a heat source, when titanium nitride transfers heat to the outside, the temperature distribution near the silicon waveguide can be increased, thereby affecting the mode field distribution in the silicon waveguide and achieving phase adjustment of light. For the thermal phase shifter using lightly doped silicon as a heat source, since the resistivity of intrinsic silicon is relatively large, the resistivity is reduced after light doping. When a voltage is applied to both ends of the thermal phase shifter, heat can be generated, thereby changing the phase of light.

[0076] In some embodiments, the beam combiner 80 is used to cause the first coherent light and the second coherent light to interfere with each other to form interference light.

[0077] Here, reference Figure 5 , the first light beam 1001 passes through the first gradient waveguide, the electro-optic modulator and the second gradient waveguide to form the first coherent light 1003, and the first coherent light 1003 passes through the first input waveguide 801 of the combiner and enters the combiner 80; the second light beam 1002 passes through the adjustable optical attenuator and the phase shifter to form the second coherent light 1004, and the second coherent light 1004 passes through the second input waveguide 802 of the combiner and enters the combiner 80, and the first coherent light 1003 and the second coherent light 1004 interfere in the combiner 80 to form interference light 110, which is output from the output waveguide 90 of the combiner.

[0078] An embodiment of the present application also provides a modulator which is a Mach-Zehnder interferometer modulator, wherein the first interference arm of the Mach-Zehnder interferometer modulator includes a first gradient waveguide, a photonic crystal modulator, and a second gradient waveguide; the second interference arm of the Mach-Zehnder interferometer modulator includes an adjustable optical attenuator and a thermal phase shifter.

[0079] In some embodiments, the first gradient waveguide is used to convert the waveguide mode field of the first output end of the beam splitter into the waveguide mode field of the electro-optical modulator; and the second gradient waveguide is used to convert the waveguide mode field of the electro-optical modulator into the waveguide mode field of the first input end of the combiner.

[0080] In some embodiments, reference Fig. 6A and 6B The first gradient waveguide and the second gradient waveguide are tapered in shape, wherein the width of the first gradient waveguide changes from narrow to wide along the light transmission direction; and the width of the second gradient waveguide changes from wide to narrow along the light transmission direction.

[0081] Here, because the shape of the first tapered waveguide is tapered, the cross section of the first tapered waveguide Fig. 6A It can be seen that the cross-section of the first gradient waveguide is trapezoidal, and when the transmission direction of light is from left to right, the width of the first gradient waveguide changes from narrow to wide from left to right, which is used to convert the waveguide mode field at the first output end of the beam splitter into the waveguide mode field of the electro-optical modulator.

[0082] Figure 6B This is a schematic diagram of the structure of the second gradient waveguide provided in the embodiment of the present application, refer to Figure 6BIt can be seen that when the transmission direction of light is from left to right, the width of the second gradient waveguide gradually narrows from left to right, which is used to convert the waveguide mode field of the electro-optic modulator into the waveguide mode field of the first input end of the combiner.

[0083] In some embodiments, the photonic crystal modulator is used to change the phase and intensity of the first light beam.

[0084] In some embodiments, the adjustable optical attenuator is used to attenuate the intensity of the second light beam based on the light intensity of the first coherent light, so that the light intensities of the first coherent light and the attenuated second light beam are the same.

[0085] In some embodiments, a thermal phase shifter is used to adjust the phase of the second light beam after intensity attenuation based on the phase of the first coherent light, so that the phase difference between the first coherent light and the second coherent light is constant, thereby achieving interference.

[0086] In an embodiment of the present application, an adjustable optical attenuator is used to attenuate the intensity of the second light beam based on the light intensity of the first coherent light, so that the light intensity of the first coherent light and the attenuated second light beam is the same, and the light intensity of the attenuated second light beam is also the same as the light intensity of the second coherent light. A thermal phase shifter is used to adjust the phase of the second light beam after intensity attenuation based on the phase of the first coherent light, so that the phase difference between the first coherent light and the second coherent light is constant. In this way, when the first coherent light and the second coherent light interfere to form interference light, the light intensity of the peak of the interference light is the superposition of the light intensities of the first coherent light and the second coherent light, and the light intensity of the trough of the interference light is the cancellation of the light intensities of the first coherent light and the second coherent light. Since the light intensities of the first coherent light and the second coherent light are the same, the light intensity of the trough of the interference light is almost close to zero, so the extinction ratio of the modulator will be greatly increased.

[0087] The embodiment of the present application also provides a modulation method, which is applied to the above modulator, including: a beam splitter, a first gradient waveguide, an electro-optic modulator, a second gradient waveguide, an adjustable optical attenuator, a phase shifter and a beam combiner; Figure 7 , the method comprising:

[0088] Step S701: The beam splitter splits the incident light into a first beam of light and a second beam of light; wherein the first beam of light enters the electro-optic modulator through a first gradient waveguide, and the second beam of light enters the adjustable optical attenuator;

[0089] Here, the first light beam and the second light beam have the same intensity.

[0090] Step S702: the electro-optic modulator modulates the first light beam entering the electro-optic modulator through the first gradient waveguide to obtain a first coherent light beam, and the first coherent light beam enters the beam combiner through the second gradient waveguide;

[0091] Step S703: the adjustable optical attenuator attenuates the intensity of the second light beam, the phase shifter shifts the phase of the second light beam after the intensity attenuation to obtain a second coherent light, and the second coherent light enters the beam combiner;

[0092] Step S704: The first coherent light and the second coherent light interfere with each other in the beam combiner to form interference light.

[0093] In some embodiments, the adjustable optical attenuator attenuates the intensity of the second light beam based on the light intensity of the first coherent light, so that the light intensities of the first coherent light and the attenuated second light beam are the same.

[0094] In some embodiments, the phase shifter adjusts the phase of the second light beam after intensity attenuation based on the phase of the first coherent light, so that the phase difference between the first coherent light and the second coherent light is constant, thereby achieving interference.

[0095] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A modulator, characterized in that: include: A beam splitter, a first gradient waveguide, an electro-optic modulator, a second gradient waveguide, an adjustable optical attenuator, a phase shifter and a beam combiner; The input end of the beam splitter is connected to a light source, the first output end of the beam splitter is connected to the input end of the first gradient waveguide, the output end of the first gradient waveguide is connected to the input end of the electro-optic modulator, the output end of the electro-optic modulator is connected to the input end of the second gradient waveguide, and the output end of the second gradient waveguide is connected to the first input end of the beam combiner; The first gradient waveguide is used to convert the waveguide mode field at the first output end of the beam splitter into the waveguide mode field of the electro-optic modulator; The second gradient waveguide is used to convert the waveguide mode field of the electro-optic modulator into the waveguide mode field of the first input end of the beam combiner; The second output end of the beam splitter is connected to the input end of the adjustable optical attenuator, the output end of the adjustable optical attenuator is connected to the input end of the phase shifter, the output end of the phase shifter is connected to the second input end of the beam combiner, and the output end of the beam combiner outputs interference light.

2. The modulator according to claim 1, characterized in that The beam splitter is used to split the incident light into a first beam of light and a second beam of light; wherein the first beam of light enters the electro-optical modulator through a first gradient waveguide, and the second beam of light enters the adjustable optical attenuator; The electro-optic modulator is used to modulate the first beam of light entering the electro-optic modulator through the first gradient waveguide to obtain a first coherent light, and the first coherent light enters the beam combiner through the second gradient waveguide; The adjustable optical attenuator is used to attenuate the intensity of the second light beam so that the difference between the light intensity of the first coherent light and the attenuated second light beam is within a preset range; The phase shifter is used to shift the phase of the attenuated second light beam to obtain a second coherent light beam, and the second coherent light beam enters the beam combiner; The beam combiner is used to cause the first coherent light and the second coherent light to interfere with each other to form interference light.

3. The modulator according to claim 1, characterized in that The modulator is a Mach-Zehnder interferometer type modulator; The first interference arm of the Mach-Zehnder interferometer modulator comprises the first gradient waveguide, the electro-optic modulator and the second gradient waveguide; The second interferometer arm of the Mach-Zehnder interferometer modulator includes the adjustable optical attenuator and the phase shifter.

4. The modulator according to claim 2, characterized in that The adjustable optical attenuator is used to attenuate the intensity of the second light beam based on the light intensity of the first coherent light, so that the light intensities of the first coherent light and the attenuated second light beam are the same.

5. The modulator according to any one of claims 1 to 4, characterized in that The first tapered waveguide and the second tapered waveguide are tapered in shape; The width of the first gradient waveguide changes from narrow to wide along the light transmission direction; The width of the second gradient waveguide changes from wide to narrow along the light transmission direction.

6. The modulator according to any one of claims 1 to 4, characterized in that The electro-optic modulator is a photonic crystal modulator.

7. The modulator according to any one of claims 1 to 4, characterized in that: The phase shifter is a thermal phase shifter.

8. A modulation method, characterized in that: Applied to the modulator according to any one of claims 1 to 7, the method comprising: The beam splitter splits the incident light into a first beam of light and a second beam of light; wherein the first beam of light enters the electro-optic modulator through a first gradient waveguide, and the second beam of light enters the adjustable optical attenuator; The electro-optic modulator modulates the first beam of light entering the electro-optic modulator through the first gradient waveguide to obtain a first coherent light, and the first coherent light enters the beam combiner through the second gradient waveguide; The adjustable optical attenuator attenuates the intensity of the second light beam, and the phase shifter shifts the phase of the second light beam after the intensity attenuation to obtain a second coherent light, and the second coherent light enters the beam combiner; The first coherent light and the second coherent light interfere in the beam combiner to form interference light.

9. The modulation method according to claim 8, characterized in that: The adjustable optical attenuator attenuates the intensity of the second light beam based on the light intensity of the first coherent light beam, so that the light intensities of the first coherent light beam and the attenuated second light beam are the same.

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