Thermo-optic phase modulation apparatus and optical phase modulator

Abstract

The present disclosure provides a thermo-optic phase modulation apparatus and an optical phase modulator. The thermo-optic phase modulation apparatus comprises: a substrate; an isolation layer disposed on the substrate; an integrated waveguide structure disposed on a side of the isolation layer facing away from the substrate, and comprising a first waveguide and a second waveguide, the first waveguide being disposed on the side of the isolation layer facing away from the substrate, the second waveguide being disposed on a side of the first waveguide facing away from the substrate, and a projection of the second waveguide in a first direction Z being located above the first waveguide; and a cladding layer disposed on a side of the first waveguide facing away from the isolation layer and covering the integrated waveguide structure. The first waveguide has a first refractive index, the second waveguide has a second refractive index, and the first refractive index is different from the second refractive index. The technical solution of the embodiments of the present disclosure enables an optimized configuration of thermo-optic phase modulation apparatus functions, and in particular improves thermal modulation efficiency of thermo-optic phase modulation apparatuses.

Description

Thermo-optical phase modulation device and optical phase modulator Cross-reference to related applications

[0001] This application incorporates Chinese Patent Application No. 202411857820.2, filed on December 17, 2024, entitled “Thermo-optical phase modulation device and optical phase modulator”, which is incorporated herein by reference in its entirety. Technical Field

[0002] This disclosure relates to the field of optical communication technology, and in particular to a thermo-optical phase modulation device and an optical phase modulator. Background Technology

[0003] The thermo-optic coefficient is an important parameter describing the change of refractive index with temperature in the optical properties of materials. It is defined as the change in refractive index of a material caused by a unit change in temperature. Optical phase modulators based on the thermo-optic effect can use the change in refractive index caused by temperature to modulate the phase of the propagating optical signal by integrating a micro-heater near the waveguide structure, thereby achieving precise control of optical performance.

[0004] However, some materials have low thermo-optic coefficients, resulting in low modulation efficiency when used to fabricate thermo-optic phase modulators.

[0005] Therefore, the problem to be solved is: how to improve the thermal modulation efficiency of optical phase modulators. Summary of the Invention

[0006] In view of the above problems, this disclosure provides a thermo-optical phase modulation device and an optical phase modulator.

[0007] According to a first aspect of this disclosure, a thermo-optical phase modulation device is provided, comprising: a substrate; an isolation layer disposed on the substrate; an integrated waveguide structure disposed on the side of the isolation layer away from the substrate, including a first waveguide and a second waveguide, wherein the first waveguide is disposed on the side of the isolation layer away from the substrate, the second waveguide is disposed on the side of the first waveguide away from the substrate, and the projection of the second waveguide along a first direction Z is located above the first waveguide; and a cover layer disposed on the side of the first waveguide away from the isolation layer and covering the integrated waveguide structure. The first waveguide has a first refractive index, the second waveguide has a second refractive index, and the first refractive index is different from the second refractive index.

[0008] In the technical solution of this disclosure embodiment, the integrated waveguide structure includes a first waveguide (main waveguide) and a second waveguide (auxiliary waveguide). The main waveguide and the auxiliary waveguide have different refractive indices: the main waveguide is used to realize the core function of the modulator and can be made of materials suitable for electro-optic modulation, high-speed modulation, or other functions; the auxiliary waveguide is made of materials with different thermo-optic coefficients than the main waveguide. This differentiated waveguide material design allows optical signals to be efficiently coupled between the main waveguide and the auxiliary waveguide as needed, while also improving the thermal modulation efficiency of the modulator. Such a thermo-optic phase modulation device can fully utilize the functional characteristics of different materials to achieve optimized configuration of the modulator's functions, especially improving the thermal modulation efficiency of the modulator.

[0009] In some embodiments, the first refractive index is less than the second refractive index. In such a design, the second waveguide (auxiliary waveguide) is made of a material with a higher thermo-optic coefficient, allowing light to couple from the first waveguide with a relatively lower refractive index into the second waveguide with a relatively higher refractive index.

[0010] In some embodiments, the first waveguide includes: a planar layer disposed on the side of the isolation layer opposite to the substrate; and a ridge layer disposed on the side of the planar layer opposite to the isolation layer. In such a design, the first waveguide can be configured as a ridge waveguide, which can provide lower transmission loss.

[0011] In some embodiments, the first waveguide is in direct contact with the second waveguide, and the covering layer covers the portion of the second waveguide that is not in direct contact with the first waveguide.

[0012] In some embodiments, the first waveguide and the second waveguide are spaced apart, and the cladding layer fills the gap between the second waveguide and the first waveguide.

[0013] In some embodiments, the thermo-optical phase modulation device further includes a resistive layer disposed on the side of the cover layer away from the integrated waveguide structure.

[0014] In some embodiments, the projection of the second waveguide above the first waveguide gradually narrows from the middle region of the second waveguide toward its two ends.

[0015] In some embodiments, the first waveguide is made of lithium niobate or lithium tantalate.

[0016] In some embodiments, the second waveguide is made of silicon or silicon carbide.

[0017] According to a second aspect of this disclosure, an optical phase modulator is provided, including the thermo-optical phase modulation device described in the above embodiments. Such an optical phase modulator can provide the advantages described above regarding the thermo-optical phase modulation device, which will not be repeated for the sake of brevity.

[0018] It should be understood that the above description is only an overview of the technical solution of this disclosure. In order to better understand the technical means of this disclosure and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of this disclosure more obvious and understandable, specific embodiments of this disclosure are given below. Attached Figure Description

[0019] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this disclosure. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0020] Figure 1 shows a cross-sectional view of a thermo-optical phase modulation device according to some embodiments of the present disclosure;

[0021] Figure 2 shows a cross-sectional view of a thermo-optical phase modulation device according to some other embodiments of the present disclosure;

[0022] Figure 3 shows the projection of the second waveguide above the first waveguide along the first direction Z in some embodiments of the present disclosure. Detailed Implementation

[0023] The embodiments of the technical solutions disclosed herein will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solutions disclosed herein and are therefore intended to limit the scope of protection of this disclosure.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure; the terms “comprising” and “having”, and any variations thereof, in the specification, claims and foregoing description of the drawings of this disclosure are intended to cover non-exclusive inclusion.

[0025] In the description of the embodiments of this disclosure, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary or secondary relationship of the indicated technical features. In the description of the embodiments of this disclosure, "a plurality of" means two or more, unless otherwise explicitly defined.

[0026] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this disclosure. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0027] In the description of the embodiments of this disclosure, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0028] In the description of the embodiments of this disclosure, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this disclosure.

[0029] In the description of the embodiments of this disclosure, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this disclosure according to the specific circumstances.

[0030] This disclosure relates to a thermo-optical phase modulation device that can optimize the functional configuration of a modulator, and in particular, improve the thermal modulation efficiency of the modulator. The thermo-optical phase modulation device of this disclosure can be used in optical phase modulators.

[0031] For ease of explanation, the thermo-optical phase modulation device of some embodiments of the present disclosure is used as an example for description. Figure 1 shows a schematic diagram of the structure of a thermo-optical phase modulation device of some embodiments of the present disclosure; Figure 2 shows a schematic diagram of the structure of a thermo-optical phase modulation device of other embodiments of the present disclosure; Figure 3 shows the projection of the second waveguide above the first waveguide of some embodiments of the present disclosure.

[0032] In this disclosure, the first direction Z refers to the thickness extension direction or height direction of the waveguide structure. In Figures 1 and 2, the first direction Z is parallel to the image plane. In Figure 3, the first direction Z is perpendicular to the illustrated light transmission direction.

[0033] Referring first to Figures 1 and 2, the thermo-optical phase modulation device 10 includes: a substrate 60, an isolation layer 50, an integrated waveguide structure 30, and a cover layer 40. The isolation layer 50 is disposed on the substrate 60. The integrated waveguide structure 30 is disposed on the side of the isolation layer 50 facing away from the substrate 60. The integrated waveguide structure 30 includes a first waveguide 31 and a second waveguide 32. The first waveguide 31 is disposed on the side of the isolation layer 50 facing away from the substrate 60, and the second waveguide 32 is disposed on the side of the first waveguide 31 facing away from the substrate 60, with the projection of the second waveguide 32 along the first direction Z located above the first waveguide 31. The cover layer 40 is disposed on the side of the first waveguide 31 facing away from the isolation layer 50 and covers the integrated waveguide structure 30. The first waveguide 31 has a first refractive index, and the second waveguide 32 has a second refractive index. The first refractive index is different from the second refractive index.

[0034] In the embodiments shown in Figures 1 and 2, the substrate 60 is a lithium niobate substrate, a quartz substrate, or a silicon substrate, and may also be implemented using other suitable materials as needed. The isolation layer 50 may be implemented using silicon dioxide or other insulating materials to provide electrical insulation for other components disposed on the isolation layer 50. The capping layer 40 may be formed using silicon oxide, aluminum oxide, silicon nitride, silicon oxynitride, titanium oxide, or other materials with good thermal conductivity to conduct heat and protect the integrated waveguide structure 30.

[0035] In the embodiments shown in Figures 1 and 2, the integrated waveguide structure 30 includes a first waveguide 31 and a second waveguide 32. The first waveguide 31 and the second waveguide 32 can have different refractive indices by selecting different materials. In some embodiments, the first waveguide 31 is configured to implement the core function of the modulator, for example, it can be made of an electro-optic material with a high electro-optic coefficient. In some embodiments, the second waveguide 32 is configured to improve the thermal modulation efficiency of the modulator, for example, it can be implemented using a material with a different thermo-optic coefficient than the first waveguide 31. Through the differentiated design of the first waveguide 31 and the second waveguide 32, optical signals can be efficiently coupled between them as needed. For example, when an optical signal is transmitted in the first waveguide 31, due to the difference in refractive index, the optical signal can be partially or completely coupled into the second waveguide 32.

[0036] In some embodiments, the first refractive index is less than the second refractive index. This design allows the second waveguide 32 to be made of a material with a higher thermo-optic coefficient, thereby ensuring that the optical signal entering the thermo-optic phase modulation device 10 is completely coupled from the first waveguide 31 to the second waveguide 32. Furthermore, during heating, the optical signal remains entirely within the second waveguide 32. Due to the higher thermo-optic coefficient of the second waveguide 32, the modulation efficiency of the thermo-optic phase modulation device 10 is significantly improved.

[0037] In some embodiments, referring to Figures 1 and 2, the first waveguide 31 may be configured to include a planar layer 311 and a ridge layer 312. The planar layer 311 is disposed on the side of the isolation layer 50 facing away from the substrate 60. The ridge layer 312 is disposed on the side of the planar layer 311 facing away from the isolation layer 50. In such a design, the first waveguide 31 is a ridge waveguide, which can provide lower transmission loss. The specific shape of the first waveguide 31 is not limited to the convex symmetrical shape shown in Figures 1 and 2. Depending on the modulation requirements in the actual application, it can also be designed as other shapes. For example, at least a portion of the planar layer 311 may have a shape with increasing or decreasing width along its extension direction, or for example, at least a portion of the ridge layer 312 may have a semi-circular cross-section.

[0038] In some embodiments, the projection of the second waveguide 32 along the first direction Z is located above the first waveguide 31. It should be understood that the second waveguide 32 can have various configurations, and this disclosure does not limit this. For example, the second waveguide 32 can be arranged closely above the first waveguide 31, or it can be arranged with a gap above the first waveguide 31; the second waveguide 32 can be arranged directly above the first waveguide 31, or it can be arranged offset above the first waveguide 31. To aid better understanding, Figures 1 and 2 illustrate two exemplary configurations of the second waveguide 32.

[0039] In the exemplary configuration of Figure 1, the second waveguide 32 is configured to directly contact the first waveguide 31, and the cladding layer 40 covers the portion of the second waveguide 32 that is not in direct contact with the first waveguide 31. In this design, the second waveguide 32 is directly disposed on the first waveguide 31, and the second waveguide 32 is completely surrounded and covered by the cladding layer 40 and the first waveguide 31. This arrangement enables tighter coupling of the optical signal between the first waveguide 31 and the second waveguide 32. For example, in thermo-optical modulation, this arrangement can improve the thermal response speed and modulation efficiency of the system, and reduce optical signal attenuation and transmission loss.

[0040] In the exemplary configuration of Figure 2, the first waveguide 31 and the second waveguide 32 are spaced apart, and the cladding layer 40 fills the gap between the second waveguide 32 and the first waveguide 31. For example, the second waveguide 32 can be formed in the cladding layer 40 first, and then the cladding layer 40 can be placed on the first waveguide 31. This design can effectively reduce the mutual influence between the first waveguide 31 and the second waveguide 32, optimize the coupling efficiency of the optical signal between the first waveguide 31 and the second waveguide 32, avoid excessive attenuation or reflection, and ensure the transmission quality of the optical signal. At the same time, since the cladding layer 40 completely surrounds and covers the second waveguide 32, it can prevent the second waveguide 32 from having uneven temperature during thermal modulation, thereby improving the stability of the modulator. This arrangement can be used, for example, in scenarios with high requirements for thermal management.

[0041] In some embodiments, referring to Figures 1 and 2, the thermo-optical phase modulation device 10 may further include a resistive layer 20 disposed on the side of the capping layer 40 opposite to the integrated waveguide structure 30. The resistive layer 20 includes a resistor suitable for electrical heating, such as a resistor made of metals like molybdenum, aluminum, or tungsten, or other high-resistivity alloy materials. The resistive layer 20 is electrically connected to an external power source (not shown), and by converting electrical energy into heat energy, it can provide the desired temperature change. The resistive layer 20 is in direct contact with the capping layer 40, which acts as a heat conduction medium, transmitting the temperature change caused by the resistive layer 20 to the integrated waveguide structure 30, thereby achieving thermal phase modulation of the optical signal.

[0042] In other embodiments of this disclosure, the resistive layer 20 may also be provided with a temperature sensor, a heat insulation layer and a heat dissipation element to achieve more sensitive temperature control or maintain a more stable operating temperature.

[0043] In some embodiments, referring to FIG3, the projection of the second waveguide 32 above the first waveguide 31 gradually tapers from the middle region of the second waveguide 32 towards its two end regions 321, 322. As shown in FIG3, the optical signal is conducted from the first waveguide 31 to the first end 321 of the second waveguide 32 along the optical transmission direction, and coupled into the second waveguide 32 from the first end 321; furthermore, when the optical signal is conducted to the second end 322 of the second waveguide 32, it is recoupled back into the first waveguide 31. This design can optimize the coupling efficiency of the optical signal between the first waveguide 31 and the second waveguide 32, especially reducing the reflection and loss of the optical signal at the interface of the two materials. The first end 321 and the second end 322 of the tip structure help the optical signal to be smoothly transmitted between the two materials, improving the transmission quality of the optical signal.

[0044] In some embodiments, the first waveguide 31 is made of lithium niobate or lithium tantalate. In other embodiments of this disclosure, the first waveguide 31 may also be made of electro-optic materials with high electro-optic coefficients, such as aluminum magnesium silicate or sodium niobate. Such a first waveguide 31 can provide high electro-optic modulation efficiency.

[0045] In some embodiments, the second waveguide 32 is made of silicon or silicon carbide. In other embodiments of this disclosure, the second waveguide 32 may also be made of electro-optic materials with high thermo-optic coefficients, such as silicon nitride or germanium. Such a second waveguide 32 can improve the modulation response of the modulator to temperature changes.

[0046] This disclosure also provides an optical phase modulator, including the thermo-optical phase modulation device 10 of any of the foregoing embodiments. The specific product type of the optical phase modulator is not limited. The thermo-optical phase modulation device 10 of this disclosure can be used as a core modulation component in the optical phase modulator to achieve phase modulation of optical signals, thereby realizing high-speed, low-loss transmission and high-precision modulation of optical signals, meeting the diverse application needs of optical communication and photonics integration fields.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this disclosure, and not to limit them. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this disclosure, and they should all be covered within the scope of the claims and specification of this disclosure. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. This disclosure is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0048] The attached icons are numbered as follows:

[0049] Thermo-optical phase modulation device 10;

[0050] Resistive layer 20, integrated waveguide structure 30;

[0051] First waveguide 31, flat plate layer 311, ridge layer 312;

[0052] Second waveguide 32, first end 321 of second waveguide, second end 322 of second waveguide;

[0053] Cover layer 40, isolation layer 50, substrate 60.

Claims

1. A thermo-optic phase modulation device, comprising: a substrate; an isolation layer disposed on the substrate; an integrated waveguide structure disposed on a side of the isolation layer facing away from the substrate, comprising: a first waveguide disposed on a side of the isolation layer facing away from the substrate; and a second waveguide disposed on a side of the first waveguide facing away from the substrate, and a projection of the second waveguide along a first direction Z is located above the first waveguide; a cover layer disposed on a side of the first waveguide facing away from the isolation layer and covering the integrated waveguide structure; wherein the first waveguide has a first refractive index, and the second waveguide has a second refractive index, the first refractive index being different from the second refractive index.

2. The thermo-optic phase modulation device of claim 1, wherein, the first refractive index is smaller than the second refractive index.

3. The thermo-optic phase modulation device of claim 1, wherein, the first waveguide comprises: a slab layer disposed on a side of the isolation layer facing away from the substrate; and a ridge layer disposed on a side of the slab layer facing away from the isolation layer.

4. The thermo-optic phase modulation device of claim 3, wherein, the first waveguide is in direct contact with the second waveguide, and the cover layer covers a portion of the second waveguide that is not in direct contact with the first waveguide.

5. The thermo-optic phase modulation device of claim 3, wherein, the first waveguide is spaced apart from the second waveguide, and the cover layer fills a gap between the second waveguide and the first waveguide. 6.The thermo-optic phase modulation device according to any one of claims 1 to 5, further comprising: a resistive layer disposed on a side of the cover layer facing away from the integrated waveguide structure.

7. The thermo-optic phase modulation device of any one of claims 1 to 5, wherein, a projection of the second waveguide above the first waveguide gradually narrows from a middle region of the second waveguide to both end regions thereof.

8. The thermo-optic phase modulation device of any one of claims 1 to 5, wherein, the first waveguide is made of lithium niobate or lithium tantalate.

9. The thermo-optic phase modulation device of any one of claims 1 to 5, wherein, the second waveguide is made of silicon or silicon carbide.

10. An optical phase modulator comprising: the thermo-optic phase modulation device according to any one of claims 1 to 9.

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