CN115755439A - Strip carrier pilot modulation structure, modulation method and modulation system - Google Patents

Abstract

The strip carrier pilot modulation structure, the modulation method and the modulation system provided by the present disclosure, the modulation structure includes: the modulation structure comprises a thin film made of a material capable of generating corresponding physical property response to an externally applied electric signal, a strip carrier waveguide formed on the thin film and having a refractive index lower than that of the thin film, wherein the strip carrier waveguide and the thin film are jointly used for guiding the advancing direction of an input optical signal in a TE mode in the modulation structure and modulating the input optical signal, and a first electrode and a second electrode which are formed on two sides of the strip carrier waveguide on the thin film, have refractive indexes lower than that of the strip carrier waveguide and are used for bearing an externally applied electric signal so as to generate an electric field which is synchronously changed along with the externally applied electric signal in the thin film between the two electrodes and the strip carrier waveguide. The method can solve the problems of high barrier and poor electro-optic modulation performance of the existing integrated electro-optic modulator processing technology, and has the advantages of simple preparation process and high electro-optic modulation performance.

Description

Strip carrier pilot modulation structure, modulation method and modulation system

Technical Field

The disclosure belongs to the technical field of integrated optics and optical communication, and particularly relates to a strip carrier waveguide modulation structure, a modulation method and a modulation system.

Background

The integrated optical communication device has the advantages of miniaturization, high speed and low power consumption, and is gradually replacing the traditional crystal optical communication device to become a core switching component of a data center. The integrated electro-optical modulator is used for converting an electric signal used by a data processing system into an optical signal used by data transmission, and is a core component in a large-scale data center optical network and an optical communication system. The integrated electro-optical modulator utilizes a material which can generate certain physical property response to an external electrical signal to convert the characteristics of frequency, intensity, phase and the like of the external electrical signal into an input optical signal in real time, so that the optical signal can carry the information of the external electrical signal.

In the field of integrated electro-optic modulators, the material that produces a physical response to an electrical signal may be lithium niobate, which response is typically an electro-optic effect. The lithium niobate electro-optic modulator which is currently in large-scale commercial use is made of lithium niobate crystal and titanium diffusion waveguide technology, and is generally large in size (the packaging length is about 10 cm), and low in modulation rate (the common modulation rate is 10GHz,20GHz or 40 GHz). The modulator adopting the thin-film lithium niobate waveguide structure can reduce the volume (the packaging length is about 3 cm), improve the modulation rate (the advanced level can reach 100 GHz), but has a barrier in the processing technology. Specifically, referring to fig. 1A and 1B, schematic structural diagrams of an electro-optical modulation region of a conventional thin-film lithium niobate modulator are shown. Fig. 1A is a schematic top-view structure diagram of an electro-optical modulation region of a thin-film lithium niobate modulator, and fig. 1B is a schematic cross-sectional structure diagram of the electro-optical modulation region of the thin-film lithium niobate modulator. The electro-optic modulation region of the existing thin-film lithium niobate modulator is formed by processing a lithium niobate thin film with a thickness of usually hundreds of nanometers through a processing method including but not limited to etching and the like, and the lithium niobate waveguide 101 has a physical material boundary, and electrodes 102 which are arranged on two sides of the lithium niobate waveguide 101 and are formed through a material growth and peeling method and the like. A protective material such as silicon dioxide may also be disposed over or under the lithium niobate waveguide 101 and the electrode 102. The width of the lithium niobate waveguide 101 shown in fig. 1A is about 700 nm to 5 μm, and the etching depth of the lithium niobate waveguide 101 shown in fig. 1B is about 180 nm to 400 nm. The etching processing of the thin film lithium niobate to form the thin film lithium niobate waveguide meeting the performance requirements of devices requires a series of expensive micro-nano processing instruments and complex preparation processes, the yield is very low under the condition that special materials of the micro-nano processing instruments cannot be guaranteed (the micro-nano processing instruments for etching the lithium niobate are only used for etching the lithium niobate and are not used for etching any other materials), only a few units and scientific research institutions complete the technical attack at present internationally, and the commercial scale processing has challenges.

Fig. 2A and 2B show a thin film lithium niobate modulator structure with simplified processing techniques, hereinafter referred to as a high index stripe carrier waveguide structure. Fig. 2A is a schematic top view of a high refractive index strip carrier waveguide modulator, and fig. 2B is a schematic cross-sectional view of the high refractive index strip carrier waveguide modulator. In this structure, the film 201 is a film made of a material that can generate a certain physical property response to an applied electric signal and has a thickness of several hundred nanometers to several micrometers (the material is usually lithium niobate, but may be other materials such as doped silicon); the strip waveguide 202 is a strip structure which is made of materials with the refractive index similar to that of the film 201 and easy to process micro-nano patterns and is used for controlling the propagation direction of input optical signals through the refractive index guide effect; the structure, processing method and function of the electrode 203 are similar to those of the electrode 102 in the structure shown in fig. 1A and 1B; the substrate 204 and the cover layer 205 are mainly used to protect the structure and to improve the modulation performance. The structures shown in fig. 2A and 2B avoid etching lithium niobate, which lowers the technical barrier for device processing and production, but because the refractive indexes of the strip waveguide 202 and the thin film 201 are similar, the input optical signal will be distributed in the thin film 201 and the strip waveguide 202 at the same time. Because the strip waveguide 202 does not generally have the property similar to the thin film 201 that can generate a certain physical property response to an external electrical signal, although the structure is easy to process, the electro-optic modulation performance is poor, and the performance indexes such as the electro-optic modulation bandwidth and the half-wave voltage length product are generally inferior to those of the structures shown in fig. 1A and 1B. According to the approximate condition of Ma Kati (marcatil), in order to ensure excellent optical field locality, conventional modulators based on the structures shown in fig. 2A and 2B all use a high-refractive-index strip waveguide with a refractive index close to that of the thin film 201, and the prior example of using a material with a refractive index lower than that of the thin film 201 as a strip waveguide material is rare.

In 2019, yu et al, university of chinese in hong kong, reported that an organic polymer material with a refractive index lower than that of the thin film 201 served as an integrated lithium niobate electro-optical modulator for the material of the strip waveguide 202, but the theory of "bound state in continuum" used in the design thereof resulted in the structure only supporting TM mode propagation, which is not matched with the designed and processed electrode suitable for TE mode, resulting in the modulation voltage-length product of the structure being about 4 times that of the above-mentioned conventional structure, contrary to the low power consumption property required for practical application.

Disclosure of Invention

The present disclosure is directed to solving, at least in part, one of the technical problems in the related art.

Therefore, the strip carrier waveguide modulation structure provided by the embodiment of the first aspect of the disclosure can solve the problems of high barrier and poor electro-optic modulation performance of the existing integrated electro-optic modulator processing technology, and has the advantages of simple preparation process, high electro-optic modulation performance and the like.

The technical scheme adopted by the disclosure for achieving the purpose is as follows:

the strip carrier pilot modulation structure provided in the embodiment of the first aspect of the present disclosure includes:

the thin film is made of a material which can generate corresponding physical property response to an external power-on signal;

the strip carrier waveguide is formed on the thin film layer, the refractive index of the strip carrier waveguide is lower than that of the thin film layer but higher than that of a medium above the strip carrier waveguide, the strip carrier waveguide and the thin film are jointly used for guiding the traveling direction of an input optical signal in the strip carrier waveguide modulation structure and modulating the input optical signal, and the mode of the input optical signal is a TE mode; and

the first electrode and the second electrode are formed on two sides of the strip carrier waveguide on the thin film, and the refractive indexes of the first electrode and the second electrode are lower than that of the strip carrier waveguide and are used for bearing an external electric signal so as to generate an electric field which is synchronously changed with the external electric signal in the thin film and the strip carrier waveguide between the first electrode and the second electrode.

In some embodiments, the principal direction of the electric field generated by the applied electric signal, the principal direction of the change in the physical properties of the thin film, and the principal direction of the polarization of the input optical signal are the same.

In some embodiments, the input optical signal is localized primarily in the film directly below the strip carrier waveguides in the y and z directions, the input optical signal propagating along the strip carrier waveguides in the x direction, and the x, y, and z directions running along the axial direction, the height direction, and the width direction of the strip carrier waveguides, respectively.

In some embodiments, the thin film is made of lithium niobate, aluminum nitride, lithium titanate, potassium dihydrogen phosphate, barium titanate, or zinc telluride.

In some embodiments, the thin film has a thickness of hundreds of nanometers to several micrometers.

In some embodiments, the index of refraction of the strip waveguide is more than 20% less than the index of refraction of the thin film.

In some embodiments, the width and height of the on-strip waveguide is from hundreds of nanometers to several micrometers.

In some embodiments, the strip carrier waveguide modulation structure further comprises a cladding layer formed over the thin film, the strip carrier waveguide, the first electrode, and the second electrode, the cladding layer having a refractive index lower than a refractive index of the strip carrier waveguide.

The strip carrier waveguide modulation structure provided by the embodiment of the first aspect of the disclosure has the following characteristics and beneficial effects:

the strip carrier pilot modulation structure provided in the embodiment of the first aspect of the present disclosure includes: a film (hereinafter referred to as a film) which is made of a material (such as lithium niobate, aluminum nitride, lithium titanate, potassium dihydrogen phosphate, barium titanate, zinc telluride and the like) capable of generating a certain physical property response to an external electric signal and has a thickness of hundreds of nanometers to several micrometers; the refractive index of the strip carrier wave guide which is manufactured on the film in the modes of film growth, etching and the like is higher than that of air but is greatly lower than that of the film; and a signal electrode and a grounding electrode formed by deposition on the surface of the chip; an alternative structure is a cladding layer over the film, strip carrier, electrodes with a refractive index higher than air but substantially lower than the strip waveguide material. Because the refractive index of the strip line waveguide above the film is higher than that of air or the optional cover layer structure and is far lower than that of the film, the input optical field is localized in the film below the strip line waveguide according to the maca yli (Marcatili) approximation condition and can be transmitted in the same path in the film according to the shape of the strip line waveguide. Compared with the etched waveguide type modulator shown in fig. 1A and 1B, the embodiment of the disclosure ensures similar optical signal local area capability while eliminating the processing technology barrier, and provides similar electro-optic modulation performance; compared with the high-refractive-index strip carrier waveguide structure shown in fig. 2A and 2B, the embodiment of the disclosure optimizes material properties based on the approximate condition in Ma Kati, greatly improves the overlapping proportion of the optical field and the thin film, and improves the electro-optical modulation performance, thereby reducing the device size, and/or reducing the microwave power required by modulation, and/or improving the electro-optical modulation rate.

The modulation method provided by the embodiment of the second aspect of the present disclosure is applied to the strip carrier pilot modulation structure according to any embodiment of the first aspect of the present disclosure, and includes the following steps:

a1, receiving an input optical signal in a TE mode;

step A2, inputting the input optical signal into the thin film region directly below the strip carrier guide, where the input optical signal propagates in the thin film directly below the strip carrier guide according to the geometry of the strip carrier guide;

and A3, modulating the received input optical signal by using an external electric signal, wherein the physical property of the input optical signal is changed under the influence of the physical effect of the thin film.

The modulation system provided by the embodiment of the third aspect of the present disclosure includes a laser, a polarization controller, and an optical modulator; the optical modulator is a strip carrier waveguide modulation structure according to any embodiment of the first aspect of the present disclosure.

Drawings

FIG. 1A is a schematic top view of a prior art thin film etched waveguide modulator;

FIG. 1B is a schematic cross-sectional view of a prior art thin film etched waveguide modulator;

FIG. 2A is a schematic top view of a prior art high index strip carrier waveguide modulator;

FIG. 2B is a schematic cross-sectional view of a prior art high index strip carrier waveguide modulator;

fig. 3 is a schematic top view of a strip carrier modulation structure provided in an exemplary embodiment of the present disclosure;

fig. 4 is a schematic cross-sectional view of a strip carrier modulation structure according to an exemplary embodiment of the disclosure;

fig. 5 is a schematic diagram of the physical principles of a strip-carrier pilot modulation structure provided by an exemplary embodiment of the present disclosure;

FIG. 6 is a schematic diagram of an optical waveguide mode in a conventional high index strip carrier waveguide structure;

fig. 7 is a schematic top view of an intensity modulator formed by a strip carrier guided modulation structure according to an exemplary embodiment of the disclosure;

FIG. 8 is a flow chart of a method of fabricating an optical modulator provided by an exemplary embodiment of the present disclosure;

fig. 9 is a block diagram of a light modulation system provided by an exemplary embodiment of the present disclosure.

Detailed Description

In order to make the objects, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the disclosure and do not delimit the disclosure.

On the contrary, the present disclosure covers any alternatives, modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims. Furthermore, in the following detailed description of the present disclosure, certain specific details are set forth in order to provide a better understanding of the present disclosure. It will be apparent to those skilled in the art that the present disclosure may be practiced without these specific details.

Referring to fig. 3, fig. 3 is a block diagram of an electro-optical modulation structure provided by an exemplary embodiment of the present disclosure, the optical modulator includes: a substrate 400, a film 300, a strip carrier conductor 301, and a first electrode 302 and a second electrode 303 arranged in parallel on both sides of the strip carrier conductor 301. Substrate 400, membrane 300, strip carrier conductor 301, first electrode 302, and second electrode 303 may be located on the same die. Illustratively, the lower surface of the film 300 and the upper surface of the substrate 400 are the same surface, and the upper surface of the film 300 and the lower surfaces of the strip carrier conductor 301, the first electrode 302, and the second electrode 303 may be the same surface. In the embodiment shown in fig. 3, the strip carrier conductors 301 are arranged in parallel with the first electrode 302 and the second electrode 303 at intervals, and for other arrangement relations, for example, the strip carrier conductors 301 are in contact with the first electrode 302 and the second electrode 303, or other electrodes with microstructures are used to be in contact with the strip carrier conductors 301, or the bottom surfaces of the strip carrier conductors 301 and the first electrode 302 and/or the second electrode 303 are not located on the same horizontal plane, the present disclosure is applicable. The present disclosure is applicable to an electro-optical phase modulator, an electro-optical intensity modulator, an electro-optical quadrature modulator (IQ modulator), an electro-optical mach-zehnder modulator (MZI modulator), and the like, which are formed by cascade connection or parallel connection of the strip carrier conductive optical modulation structures shown in fig. 3. In the modulator formed by cascading or connecting the strip carrier modulation structures in parallel, two first electrodes 302 and/or two second electrodes 303 of two adjacent strip carrier modulation structures may be merged into the same first electrode or the same second electrode, which is applicable to the present disclosure. For the structure shown in fig. 3, a cover layer film is added on the upper surface of the film 300, for example, the refractive index of the cover layer film is higher than that of air but lower than that of the strip carrier waveguide 301, which is suitable for the present disclosure.

Referring to fig. 4, fig. 4 is a schematic cross-sectional view of an exemplary embodiment of the present disclosure. Substrate 400 is used in this disclosure to support the various structural layers thereon. The film 300 and the strip carrier waveguide 301 are used together in this disclosure to guide the direction of travel of the input optical signal in the present structure and to allow the input optical signal to be properly modulated. The strip carrier conductors 301 are located directly above the film 300, and the lower surfaces of the strip carrier conductors 301 are in close contact with the upper surface of the film 300. The material used for manufacturing the thin film 300 may be a material (including but not limited to lithium niobate, aluminum nitride, lithium titanate, potassium dihydrogen phosphate, barium titanate, zinc telluride, etc.) which has a high refractive index and can generate a certain physical property response to an external electrical signal. The film thickness of thin film 300 (the y-direction thickness shown in fig. 4) may be several hundred nanometers. For example, the film 300 may be a lithium niobate film with a thickness of 300 nm, and the property that can generate a certain physical property response to an applied electric signal is an electro-optic effect, and the physical property response is that the refractive index of the film material changes with the intensity of a space electric field formed by the applied electric signal. The refractive index of the material used to form strip carrier conductor 301 should be 80% or less of that of film 300, but higher than the ambient environment on both sides and above it. In the disclosed embodiment, there is no requirement for the on-strip waveguide 301 to respond to physical properties of an applied electrical signal (1, the greatest advantage of using a strip carrier waveguide from the viewpoint of design, processing, and testing is that it is easy to process, so the strip carrier waveguide material is usually made of a material that is well-processed in the industry, such as silicon dioxide, which is a material that is completely compatible with the current industrial micro-nano processing flow, but is not responsive to an applied electrical signal.2, the greatest advantage of using a low-index strip carrier waveguide structure is that it is able to localize light to a greater extent in the film under the strip carrier waveguide than a conventional high-index strip carrier waveguide structure, and the film is able to respond to an applied electrical signal, so the low-index strip carrier waveguide can be modulated effectively in the film while ensuring that light can be "carried" in the direction of the strip carrier waveguide structure, and thus the process of "carrying" light "mainly" in the direction of the strip carrier waveguide structure ", and the process of" modulating "mainly" 3 "with the electrical signal" has a physical properties, and the half-wave modulation voltage should be achieved by the above-wave modulation method, which should not reduce the voltage by the applied electrical signal. Illustratively, when the material of the thin film 300 is lithium niobate (having a refractive index of about 2.14 to 2.21 at a wavelength of 1550 nm), the material of the strip carrier waveguide 301 may be silicon dioxide (having a refractive index of about 1.44 at a wavelength of 1550 nm), but is not preferably titanium dioxide (having a refractive index of about 2.06 at a wavelength of 1550 nm). The cross-sectional shape of the strip carrier waveguide 301 may be rectangular or trapezoidal. The width (i.e., the geometry of the side of the cross-section that meets the film 300, or the geometry in the z-direction in fig. 4) and height (i.e., the geometry of the side of the cross-section that is perpendicular to the film 300, or the geometry in the y-direction in fig. 4) of the strip carrier waveguide 301 may range from several hundred nanometers to several micrometers. Illustratively, the strip carrier conductor 301 may have a width of 2 microns and a height of 500 nanometers. The larger width can reduce the light propagation loss, but also can increase the electric signal power required by the electric light modulation; the larger height can reduce the light transmission loss, but also can make the structure difficult to process and produce.

According to maxwell's equations and the approximation principle in Ma Kati, for a strip-carrier waveguide structure, the mode of the input optical signal will be localized mainly in the high-index material, but will propagate under the guidance of the material with the relatively high index of refraction in the outer boundary conditions of the high-index material. Referring to fig. 5, fig. 5 is a schematic diagram illustrating the physical principle of the electro-optical modulation structure according to the embodiment of the disclosure. For further explanation, the space of the structural profile of the embodiment of the present disclosure is schematically divided into nine regions 501 to 509. If the refractive index of the material in the regions 504, 505 and 506 is the highest, the refractive index of the material in other regions is lower than that in the regions 504, 505 and 506; meanwhile, if the refractive index of the region 502 is higher than that of the regions 501 and 503 and higher than or equal to that of the regions 507, 508 and 509, the input light mode will be mainly localized in the region 505 in the y and z directions according to the maca ladder approximation principle, and will propagate in the same direction in the x direction according to the waveguide route design of the region 502. For the exemplary embodiments of the present disclosure, the 507, 508, 509 regions may correspond to the substrate 400, 504, 505, 506 regions may correspond to the membrane 300, and the 502 regions may correspond to the strip carrier conductors 301. In the conventional strip carrier waveguide structures (such as the structures shown in fig. 2A and 2B), the refractive index of the region 502 is selected to be close to or higher than that of the region 505, so that the optical field local capability is maximally improved in both the horizontal and vertical directions in the drawing; the present disclosure innovatively proposes that when the refractive index of the material used in the region 502 is much lower than that of the region 505, the optical field local capability in the horizontal direction can still be ensured by the approximation principle in Ma Kati, while the optical field local capability in the vertical direction can be naturally ensured by the slab waveguide theory. The change of the strip carrier waveguide structure greatly changes the inherent design scheme of the strip carrier waveguide structure, so that the strip carrier waveguide structure can realize better applicability in the field of electro-optical modulators.

In the electro-optic modulation structure designed by the present disclosure, the polarization of the mode of the input optical signal needs to be a Transverse Electric (TE) mode. For TE mode optical signals, the electric field component of the optical wave is nearly perpendicular to the propagation direction of the optical wave, i.e., the electric field component of the optical wave in the propagation direction of the optical wave (x direction) is almost 0; and the main electric field component of the light wave is the z-direction component. Input light mode 401 will be primarily localized within film 300, but will propagate in the x-z plane according to the design of strip carrier waveguide 301, subject to the geometric relationship and refractive index difference between film 300 and strip carrier waveguide 301. Fig. 6 is a schematic diagram of an optical waveguide mode in a conventional high refractive index strip carrier waveguide structure (hereinafter simply referred to as "conventional structure"). In the conventional structure, the refractive index of high index strip carrier waveguide 602 is similar to or higher than that of film 300, so the optical waveguide mode 601 in the conventional structure will be distributed in both film 300 and high index strip carrier waveguide 602 according to maxwell's equations and the approximation principle in Ma Kati. Since the material of the high index strip carrier waveguide 602 generally does not have the property of producing some physical response to an applied electrical signal, the electro-optic modulation performance of the conventional structure is weaker than that of the strip carrier waveguide modulation structure provided by the embodiments of the present disclosure.

In the embodiment of the present disclosure, the first electrode 302 and the second electrode 303 are symmetrically disposed on both sides of the strip carrier conductor 301 to implement electro-optical modulation. The material of the first electrode 302 and the second electrode 303 may be a metal material such as gold, copper, aluminum, and/or various non-metal conductive materials such as Transparent Conductive Oxide (TCO), graphene, and the like. The first electrode 302 and the second electrode 303 are used in the structure described in the present disclosure to receive power from an applied electrical signal and form an electric field varying in synchronization with the applied electrical signal in the thin film 300 and the low refractive index strip carrier waveguide 301 between the first electrode 302 and the second electrode 303. The physical properties of the film 300 will change in response to this applied electric field, resulting in some physical properties of the optical mode 401 propagating in the film 300 being changed during propagation. For example, if the material of the thin film 300 is lithium niobate, the physical property of the thin film 300 that changes with the applied electric field is the refractive index, while the physical property of the optical mode 401 that changes during propagation may be frequency, phase, intensity, etc. depending on the structural properties of the modulation structure. In the using process, one of the first electrode 302 and the second electrode 303 is externally connected with a certain voltage signal, and the voltage signal can be a direct current signal, an alternating current signal, a microwave signal and the like; the other ground, i.e., electro-optically modulated, may be used with the electro-optically modulating structures provided by the exemplary embodiments of the present disclosure. The first electrode 302 and the second electrode 303 have geometric dimensions such that better electro-optic modulation performance can be achieved through the electrical design of the system (which can be achieved by electrical design methods known in the art, such as a coplanar waveguide traveling wave electrode design). Illustratively, if the thickness of the thin film 300 is 300 nm, the height of the strip carrier waveguides 301 is 500 nm, and the width is 2 μm, if the width (the z-direction geometry shown in fig. 4) of the first electrodes 302 and the second electrodes 303 in cross section is about 15 μm to 20 μm, and the spacing (the z-direction spacing shown in fig. 4) is about 7 μm to 9 μm, an electric field with a voltage of 1V can be applied to generate an electric field with a strength of up to about 10KV/cm in the region of the optical mode 401, which changes a physical property of the thin film 300 (e.g., if the material of the thin film 300 is lithium niobate, this physical property is the refractive index), so that the optical mode 401 is modulated during propagation.

The strip carrier waveguide modulation structure provided by the embodiment of the disclosure requires that the main direction of an external electric field, the main direction of the change of the physical properties of the thin film, and the main direction of the polarization of an input optical signal are the same. The main direction of the applied electric field may be defined as the direction of the electric field component having the greatest intensity among the electric fields generated by the applied electric signals, which are generated between the first electrode 302 and the second electrode 302. Illustratively, in the exemplary embodiment of the present disclosure shown in fig. 4, the main direction of the applied electric field is the z-direction. The main direction of the physical property change of the thin film can be defined as the direction of an applied electric field when the change amount of a certain physical property of the thin film is maximum under the condition that the electric fields with the same strength and different directions are applied. For example, if the thin film 300 is a lithium niobate thin film, the physical property of the thin film change is the refractive index, and the main direction of the change in the physical property of the thin film may be referred to in the industry as d ₃₃ In the direction of the beam. The main direction of polarization of the input optical signal refers to the main electric field component of the input optical signal. Illustratively, if the film 300 is a lithium niobate film, the structure described in this disclosure requires that, in the case where the main direction of the applied electric field is the z-direction, the d of the film 300 ₃₃ The direction of the input optical signal needs to be the z direction and the input optical signal polarization needs to be the TE polarization. Different from the structure reported by Yu et al of the university of Chinese in hong Kong in 2019, the structure disclosed by the invention can theoretically allow the main direction of an external electric field, the main direction of the change of the physical property of the film and the main direction of the polarization of an input optical signal to be the same, and in practical use, the three main directions are generally ensured to be the same, so that the support structure realizes the highest electro-optical modulation performance by virtue of the property of the lithium niobate film.

In practical fabrication, a modulator structure is usually adopted, in which a first electrode 302 is in the middle, two second electrodes 303 are at two ends, and two carrier waveguides 301 are sandwiched therebetween, and the modulator can achieve intensity modulation of an optical signal, and is therefore generally called an intensity modulator, and the structure is shown in fig. 7. The principle of operation of such a modulator is exactly the same as described above and the method of changing from the modulator form described in fig. 3 to the intensity modulator form described in fig. 7 is well known to those skilled in the art and is therefore within the scope of the present application.

Another embodiment of the present disclosure further provides a manufacturing method of the strip carrier modulation structure. Referring to fig. 8, fig. 8 is a flowchart of a method for manufacturing a strip carrier pilot modulation structure according to an exemplary embodiment of the present disclosure, where the method is used to manufacture the strip carrier pilot modulation structure shown in fig. 3 and 4, and the method for manufacturing the strip carrier pilot modulation structure may include:

step 701 provides a substrate.

In an embodiment of the present disclosure, the substrate may be a semiconductor substrate whose top layer is made of a material that can generate a certain physical property response to an applied electric signal, and the semiconductor substrate may be an LNOI substrate formed with a lithium niobate thin film (corresponding to structure 300 in fig. 4), a silicon dioxide thin film (corresponding to structure 400 in fig. 4) and a silicon substrate from top to bottom.

Step 702 forms the strip-loaded waveguide 301 by additive manufacturing over a substrate.

For example, a layer of thin film made of silicon dioxide or the like (the thin film is used for subsequently generating the strip waveguide) may be fabricated on the top electro-optical material layer by magnetron sputtering, chemical vapor deposition, plasma enhanced chemical vapor deposition, or the like, then a layer of photoresist is coated on the thin film, the photoresist is exposed through a mask, and the exposed photoresist is developed, so that a photoresist pattern corresponding to the top view surface geometry of the strip waveguide 301 (as shown in fig. 4) may be formed, where the photoresist pattern may include: and etching the film made of materials such as silicon dioxide and the like corresponding to the light-transmitting area in the light-transmitting area and the non-light-transmitting area, and stripping the photoresist pattern after etching. This process is generally referred to as a one-shot patterning process. This step should not involve any subtractive manufacturing flow of the film 300.

Step 703, forming a first electrode 302 and a second electrode 303 at two ends of the strip carrier conductor 301.

Illustratively, a shaped metal layer, which may be gold in its content, may be formed by a process that may include a deposition or a single patterning process, over the top electro-optic material layer.

The method of manufacturing the intensity modulator shown in fig. 7 is identical to that described above.

An embodiment of the present invention further provides an optical modulation system, please refer to fig. 9, where fig. 9 is a block diagram of an optical modulation system according to an exemplary embodiment of the present invention, where the optical modulation system may include: a laser 801, a polarization controller 802, and an optical modulator 803, wherein the optical modulator 803 may be a strip carrier waveguide modulation structure as shown in fig. 3 and 4.

Wherein the laser 801 is used for emitting light waves; the polarization controller 802 is configured to convert an optical wave emitted from the laser 801 into an optical wave in a TE mode, and input an input optical signal in the TE mode to the optical modulator 803.

The embodiment of the present invention further provides a modulation method, which is applied to an optical modulator, where the optical modulator may be a strip carrier waveguide modulation structure shown in fig. 3, fig. 4, and fig. 7. The modulation method may include:

step A1, receiving an input optical signal in a TE mode.

In step A2, the input optical signal is input to the region of the film 300 directly below the strip carrier waveguide 301 (i.e., the region indicated by the optical wave 401). The input optical signal in TE mode is an optical wave 401, and propagates in the thin film 300 under the strip carrier waveguide 301 according to the geometry of the strip carrier waveguide 301.

Step A3, modulating the received input optical signal by using the external electrical signal, wherein the physical properties (such as phase and intensity) of the input optical signal are changed under the influence of the physical effect of the thin film 300.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

While embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the application, the scope of which is defined by the claims and their equivalents.

Claims (10)

1. A strip-carrier pilot modulation architecture, comprising:

the thin film is made of a material which can generate corresponding physical property response to an external power-on signal;

the strip carrier waveguide is formed on the thin film layer, the refractive index of the strip carrier waveguide is lower than that of the thin film layer but higher than that of a medium above the strip carrier waveguide, the strip carrier waveguide and the thin film are jointly used for guiding the traveling direction of an input optical signal in the strip carrier waveguide modulation structure and modulating the input optical signal, and the mode of the input optical signal is a TE mode; and

the first electrode and the second electrode are formed on two sides of the strip carrier waveguide on the thin film, and the refractive indexes of the first electrode and the second electrode are lower than that of the strip carrier waveguide and are used for bearing an external electric signal so as to generate an electric field which is synchronously changed along with the external electric signal in the thin film between the first electrode and the second electrode and the strip carrier waveguide.

2. The strip carrier waveguide modulation structure of claim 1 wherein the principal direction of the electric field generated by the applied electrical signal, the principal direction of the change in the physical properties of the thin film, and the principal direction of the polarization of the input optical signal are the same.

3. The strip carrier waveguide modulation structure of claim 1 wherein the input optical signal is localized primarily in the thin film directly below the strip carrier waveguide in the y and z directions, the input optical signal propagating along the strip carrier waveguide in the x direction, the x, y, and z directions running along the axial direction, the height direction, and the width direction of the strip carrier waveguide, respectively.

4. The strip carrier waveguide modulation structure according to claim 1, wherein the thin film is made of lithium niobate, aluminum nitride, lithium titanate, potassium dihydrogen phosphate, barium titanate, or zinc telluride.

5. The strip carrier waveguide modulation structure of claim 1 wherein the thin film has a thickness of hundreds of nanometers to microns.

6. The strip-carrier waveguide modulation structure of claim 1 wherein the refractive index of the strip-carrier waveguide is 20% or more less than the refractive index of the thin film.

7. The strip-carrier waveguide modulation structure of claim 1 wherein the strip-carrier waveguide has a width and height of several hundred nanometers to several micrometers.

8. The strip carrier waveguide modulation structure according to any one of claims 1 to 7, further comprising a cover layer formed over the thin film, the strip carrier waveguide, the first electrode, and the second electrode, the cover layer having a refractive index lower than that of the strip carrier waveguide.

9. A modulation method applied to the strip carrier pilot modulation structure according to any one of claims 1 to 8, the modulation method comprising the steps of:

a1, receiving an input optical signal in a TE mode;

step A2, inputting the input optical signal into the thin film region directly below the strip carrier waveguide, wherein the input optical signal propagates in the thin film directly below the strip carrier waveguide according to the geometric shape of the strip carrier waveguide;

and A3, modulating the received input optical signal by using an external electric signal, wherein the physical property of the input optical signal is changed under the influence of the physical effect of the thin film.

10. A modulation system comprising a laser, a polarization controller, and an optical modulator; the optical modulator is a strip carrier waveguide modulation structure according to any one of claims 1 to 8.

Images