Electric absorption modulator and method for improving EAM modulation efficiency

Abstract

The invention belongs to the technical field of semiconductor optoelectronic devices, and particularly relates to an electro-absorption modulator and a method for improving EAM modulation efficiency. The modulator comprises a silicon substrate and an insulating layer deposited on the silicon substrate; a waveguide layer is arranged on the insulating layer; a germanium absorption layer is embedded in the waveguide layer; the first depth of the germanium absorption layer embedded into the waveguide layer is smaller than the thickness of the waveguide layer, or the second depth of the germanium absorption layer embedded into the waveguide layer is larger than or equal to the thickness of the waveguide layer; the germanium absorption layer is provided with a heating unit, and compared with a traditional thought that the absorption coefficient is improved by depending on high electric field intensity, a thermal compensation mechanism aiming at the end-point effect and real-time feedback is provided, so that the light absorption coefficient of the germanium absorption layer is ensured, and meanwhile, the working voltage requirement of the electro-absorption modulator is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor optoelectronic devices, and particularly relates to an electro-absorption modulator and a method for improving the modulation efficiency of an EAM. Background Art

[0002] As a core device in optical communication systems, an electro-absorption modulator (EAM) realizes intensity modulation of optical signals by regulating the optical absorption characteristics of materials through an electric field. Traditional EAMs mostly use III-V compound semiconductors (such as InGaAsP / InP) and utilize the quantum-confined Stark effect (QCSE) or the Franz-Keldysh effect to achieve efficient modulation. However, such materials have poor compatibility with silicon-based CMOS processes, high manufacturing costs, and are difficult to achieve large-scale integration.

[0003] In recent years, pure germanium (Ge) has been regarded as an ideal candidate material for silicon-based optoelectronic integration due to its high compatibility with silicon processes, wide-band response (especially suitable for the 1550 nm communication window), and high carrier mobility. The electro-absorption effect of pure Ge mainly depends on the Franz-Keldysh effect, that is, under the action of an external electric field, the absorption edge of the material redshifts, allowing photons originally below the bandgap energy to excite electrons to jump from the valence band to the conduction band, thereby realizing intensity modulation. However, currently, the internal electric field of pure germanium modulators is generally weak. To achieve effective modulation, a high reverse bias voltage needs to be applied, and there are also problems such as insufficient thermal stability.

[0004] To overcome the above problems, various improvement schemes have been proposed in the prior art. For example: 1. Adopting a doping process: increasing the built-in electric field through high-concentration doping. However, the free carrier absorption (FCA) caused by doping will increase optical losses, limit the modulation depth, and increase the wafer cost.

[0005] 2. Optimizing the waveguide structure: adopting a ridge waveguide or a tapered coupling design to improve the optical field overlap efficiency, but the improvement of the inherent defects of the absorption coefficient is limited.

[0006] The Chinese patent application CN113050304A in the prior art discloses an electro-absorption modulator with improved optoelectronic uniformity, which is constructed and / or operated to improve the uniformity of the photocurrent density along the active region. In various embodiments, this improvement is achieved by increasing the optical absorption at the rear of the EAM, for example, by heating the rear region, increasing the bias voltage applied across the EAM towards the rear, or changing the material composition of the intrinsic layer towards the rear. In another embodiment, this improvement is achieved by continuously coupling light from the waveguide to the EAM active region along the length of the EAM through the overlap between the tapered section of the waveguide and the EAM.

[0007] That is to say, this solution locally increases the temperature of the active region by integrating a micro-heater (such as a resistive heater) at the rear of the active region, thereby enhancing the light absorption coefficient of the rear region and balancing the front and rear photocurrent densities. However, the above solution also fails to fundamentally solve the contradiction between the high operating voltage and low light absorption caused by the low internal electric field in pure Ge. Summary of the Invention

[0008] The object of the present invention is to provide an electro-absorption modulator and a method for improving the modulation efficiency of the EAM to partially alleviate or solve the above deficiencies, while ensuring the light absorption coefficient of the germanium absorption layer and reducing the operating voltage of the electro-absorption modulator.

[0009] To solve the above-mentioned technical problems, the present invention specifically adopts the following technical solutions: An electro-absorption modulator includes: a silicon substrate and an insulating layer deposited on the silicon substrate; a waveguide layer is provided on the insulating layer; a germanium absorption layer is embedded in the waveguide layer; the first depth at which the germanium absorption layer is embedded in the waveguide layer is less than the thickness of the waveguide layer, or the second depth at which the germanium absorption layer is embedded in the waveguide layer is equal to the thickness of the waveguide layer; A heating unit is provided at the top and / or bottom of the germanium absorption layer, and the heating unit extends along the length direction of the germanium absorption layer; or, Heating units are respectively provided on both sides of the germanium absorption layer, and the heating units extend along the length direction of the germanium absorption layer; or, Heating unit groups are respectively provided on both sides of the germanium absorption layer, and each heating unit group on each side includes a plurality of heating units uniformly spaced along the length direction of the germanium absorption layer, wherein the heating levels of two adjacent heating units on the same side are primary heating and secondary heating respectively.

[0010] As an improvement, the electro-modulator further includes: A temperature monitoring module for real-time monitoring of the actual temperature value of the germanium absorption layer; A first judgment module for judging whether the actual temperature value monitored by the temperature monitoring module is greater than a first preset temperature threshold, If the actual temperature value is greater than the first preset temperature threshold, generate and send a first control signal indicating to stop heating to the heating unit / heating unit group; If the actual temperature value is less than the first preset temperature threshold, generate and send a second control signal indicating to continue monitoring to the temperature monitoring module; and / or, A temperature monitoring module for real-time monitoring of the actual temperature value of the germanium absorption layer after being heated by the heating unit with a heating level of primary heating and in a heating state; A second determination module, configured to determine whether the actual temperature value monitored by the temperature monitoring module reaches a preset target temperature threshold after a preset time duration. If not, a third control signal is generated and sent to activate a heating unit with a second-level heating level and in a dormant state, so that the actual temperature of the germanium absorption layer reaches the preset target temperature threshold.

[0011] As an improvement, the germanium absorption layer includes a gradient region and a constant region arranged in sequence along the light propagation direction. The cross-sectional area of the gradient region gradually increases from the incident end along the direction approaching the constant region; the cross-sectional area of the constant region is the same along the direction away from the constant region from the end connected to the gradient region.

[0012] As an improvement, the width of the gradient region gradually increases from the incident end along the direction approaching the constant region; and the longitudinal section of the gradient region is a right trapezoid, and the hypotenuse of the right trapezoid corresponds to the interface between the gradient region and the waveguide layer, and the angle between it and the bottom side is 86° - 89°; the longitudinal section of the constant region is a rectangle; or, the interface between the gradient region and the waveguide layer is fan-shaped.

[0013] As an improvement, the width and length of the heating unit located at the top and / or bottom of the germanium absorption layer are both smaller than the width and length of the germanium absorption layer.

[0014] Another aspect of the present invention is to provide a method for improving the modulation efficiency of an EAM, including the steps of: S101, depositing an insulating layer on the surface of a silicon substrate, and depositing a waveguide layer on the surface of the insulating layer; S102, etching two grooves in parallel on the waveguide layer, and the depth of the grooves is less than the thickness of the waveguide layer; S103, using a mask to deposit a silicon oxide layer on the surface of the waveguide layer to cover the regions on the waveguide layer that do not need to be etched; S104, etching the waveguide layer along the outer walls of the two grooves outward and between the two grooves, so as to form a ridge optical waveguide and a first etching groove for depositing a germanium absorption layer on the silicon ridge of the ridge optical waveguide; the depth of the first etching groove is a first depth or a second depth; the first depth is less than the thickness of the waveguide layer, and the second depth is equal to the thickness of the waveguide layer; S105, depositing germanium in the first etching groove to form a germanium absorption layer; S106, removing the mask, and depositing an insulating layer on the germanium absorption layer and the waveguide layer; S107, etch a second etching groove on the insulating layer and at the top of the germanium absorption layer, bury a heating unit in the second etching groove, and deposit an insulating layer again to cover the heating unit; the distance between the second etching groove and the top of the germanium absorption layer is less than or equal to 3um; Alternatively, on the insulating layer, etch third etching grooves on both sides of the germanium absorption layer respectively, bury a heating unit in the third etching groove, and deposit an insulating layer again to cover the heating unit; the distance between the heating unit and both sides of the germanium absorption layer is less than or equal to 3um; Alternatively, on the insulating layer, etch a plurality of fourth etching grooves at intervals on both sides of the germanium absorption layer respectively, bury a heating unit in each fourth etching groove, and deposit an insulating layer again to cover all the heating units; the distance between the heating unit and both sides of the germanium absorption layer is less than or equal to 3um, and the distance between two adjacent heating units is greater than 1um.

[0015] As an improvement, before depositing the waveguide layer on the insulating layer in step S101, it further includes the step of: Etch a fifth etching groove on the insulating layer, bury a heating unit in the fifth etching groove, and deposit an insulating layer again to cover the heating unit.

[0016] As an improvement, the first etching groove with a second depth etched on the waveguide layer in step S104 includes a gradient region and a constant region arranged in sequence along the light propagation direction, where The width of the gradient region gradually increases from one end close to the waveguide layer to the other end close to the constant region.

[0017] As an improvement, it further includes the step of: Real-time monitor the actual temperature value of the germanium absorption layer; Judge whether the actual temperature value is greater than a first preset temperature threshold, If the actual temperature value is greater than the first preset temperature threshold, control the heating unit or the heating group to stop heating; otherwise, continue to monitor.

[0018] As an improvement, it further includes the step of: Real-time monitor the actual temperature value of the germanium absorption layer heated by the heating unit with a heating level of first-level heating and in a heating state; Judge whether the actual temperature value reaches a preset target temperature threshold after a preset time. If not, start the heating unit with a heating level of second-level heating and in a dormant state; Or, Real-time monitor the actual temperature values of the gradient region and the constant region in the germanium absorption layer; Determine whether the temperature difference between the actual temperature value of the gradient region and the actual temperature value of the constant region is less than or equal to a preset difference threshold; If it is less than or equal to the preset difference threshold, continue to monitor; If it is greater than the preset difference threshold, control the heating power of the multiple heating units corresponding to the region with the larger actual temperature value to decrease, or control the heating power of the multiple heating units corresponding to the region with the smaller actual temperature value to increase, so that the temperature difference between the actual temperature values of the constant regions is less than or equal to the preset difference threshold.

[0019] The principle and beneficial technical effects of the present invention are as follows: Contrary to the traditional idea of relying on a high electric field strength to increase the absorption coefficient, the present invention provides a thermal compensation mechanism for the end effect and real-time feedback, which can reduce the working voltage requirement of the electro-absorption modulator while ensuring the light absorption coefficient of the germanium absorption layer.

[0020] Specifically, in this application, by arranging heating units on at least one side (bottom and / or top, or front and back sides) of the germanium absorption layer, the heating units act on the germanium absorption layer along the length direction of the germanium absorption layer, ensuring the consistency and uniformity of the temperature of the entire germanium absorption layer, thereby increasing the number of valence band electrons that can transition, and further changing the light absorption coefficient of the germanium absorption layer while reducing the working voltage of the electro-absorption modulator; moreover, in this process, only the final light absorption rate (i.e., the ratio of the input light to the output light / the input light) needs to be ensured, without considering other non-essential factors, such as the uniformity of the light absorption coefficient of the germanium absorption layer.

[0021] Furthermore, the present invention regulates the temperature of the germanium absorption layer through a real-time feedback mechanism. On the one hand, it can make the number of valence band electrons that can transition in the germanium absorption layer tend to be maximized as much as possible. On the other hand, it can improve the stability of the temperature of the germanium absorption layer and prevent the problem that the light signal emitted by the germanium absorption layer is unstable due to frequent temperature changes.

[0022] Furthermore, through the partition design (gradient region and constant region) of the germanium absorption layer, a gradient interface formed by gradually changing the height and width of the gradient region is used to guide the optical signal transmitted from the optical waveguide, which can greatly reduce the reflection at the incident end, that is, it can ensure that the light is conducted from the waveguide layer to the germanium absorption layer as much as possible. Description of the Drawings

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the attached drawings required for the description of the embodiments or the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts do not necessarily draw according to the actual scale. Obviously, the following described drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings.

[0024] Figure 1 It is an exemplary side view of the modulator in the first embodiment of the present invention; Figure 2 It is another exemplary side view of the modulator in the first embodiment of the present invention; Figure 3 It is another exemplary side view of the modulator in the first embodiment of the present invention; Figure 4 It is a top view of the modulator in the first embodiment of the present invention; Figure 5 It is a front view of the germanium absorption layer in the first embodiment of the present invention; Figure 6 It is a top view of the germanium absorption layer in the first embodiment of the present invention; Figure 7 It is a flowchart of steps S101 - S106 in the second embodiment of the present invention; Figure 8 It is a flowchart of step S107 in the second embodiment of the present invention.

[0025] Markings in the figure: 1, silicon substrate; 2, waveguide layer; 3, heating unit; 4, insulating layer; 5, germanium absorption layer; 51, gradient region; 52, constant region; 6, electrode; 7, silicon strip. Detailed implementation manners

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the attached drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0027] In this document, suffixes such as "module", "component", or "unit" used to represent elements are only for the convenience of explaining the present invention and have no specific meaning in themselves. Therefore, "module", "component", or "unit" can be used interchangeably. In this document, terms such as "upper", "lower", "inner", "outer", "front", "rear", "one end", "the other end", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation on the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0028] In this document, unless otherwise clearly defined and limited, terms such as "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, and can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In this document, "a plurality of" means two or more, that is, it includes two, three, four, five, etc.

[0029] Embodiment 1 Refer to Figures 1-4 , the present invention provides an electro-absorption modulator, including a silicon substrate 1 and an insulating layer 4 deposited on the silicon substrate 1; a waveguide layer 2 is provided on the insulating layer 4; a germanium absorption layer 5 is embedded in the waveguide layer 2; the first depth at which the germanium absorption layer 5 is embedded in the waveguide layer 2 is less than the thickness of the waveguide layer 2, or the second depth at which the germanium absorption layer 5 is embedded in the waveguide layer 2 is greater than or equal to the thickness of the waveguide layer 2.

[0030] Among them, when the second depth is equal to the thickness of the waveguide layer 2, it means that the bottom of the germanium absorption layer 5 is flush with the upper surface of the insulating layer 4; when the second depth is greater than the thickness of the waveguide layer 2, it means that the germanium absorption layer 5 is embedded in the insulating layer 4.

[0031] In the above embodiments, when the second depth is equal to the thickness of the waveguide layer 2, that is, with the insulating layer 4 as the etching end point, on the one hand, the germanium absorption layer 5 can have a larger cross-section, so that the coincidence time between the modulation region and the optical field is the longest. At the same length, the responsivity is higher; at the same responsivity, the size is the smallest. On the other hand, the etching depth is easy to control, which can ensure the consistency of the etching groove depth between different modulators. In the traditional shallow etching process, due to the relatively shallow etching depth and difficult to accurately control, it is easily affected by factors such as uneven silicon layer thickness, resulting in inconsistent etching depths, and then affecting the performance uniformity of the modulator. The etching groove process reaching the insulating layer 4 has better stability, which is beneficial to the large-scale production of high-quality modulators.

[0032] In some embodiments, a heating unit 3 is provided at the top and / or bottom of the germanium absorption layer 5, and the heating unit 3 extends along the length direction of the germanium absorption layer 5; alternatively, heating units 3 are respectively provided on both sides of the germanium absorption layer 5, and the heating units 3 extend along the length direction of the germanium absorption layer 5; alternatively, heating unit groups 3 are respectively provided on both sides of the germanium absorption layer 5, and each heating unit group 3 on each side includes a plurality of heating units 3 evenly spaced along the length direction of the germanium absorption layer 5, wherein the heating levels of two adjacent heating units 3 on the same side are the first-level heating and the second-level heating respectively.

[0033] Contrary to the traditional idea of relying on high electric field strength to increase the absorption coefficient to ensure the uniformity of photocurrent density, the present invention provides a thermal compensation mechanism only for the end point effect. Specifically, by providing a heating unit 3 on at least one side (bottom and / or top, or front and back sides) of the germanium absorption layer 5, the heating unit 3 acts on the germanium absorption layer 5 along the length direction of the germanium absorption layer, ensuring the consistency and uniformity of the temperature of the entire germanium absorption layer 5, thereby increasing the valence band electrons that can transition, and then changing the light absorption coefficient of the germanium absorption layer 5 while reducing the operating voltage of the electro-absorption modulator. In this process, only the final light absorption rate (that is, the ratio of input light to output light / input light) needs to be ensured, without considering the uniformity of the light absorption coefficient of the germanium absorption layer 5.

[0034] In some embodiments, the electro-absorption modulator further includes: A temperature monitoring module for real-time monitoring of the actual temperature value of the germanium absorption layer 5.

[0035] A first judgment module for judging whether the actual temperature value monitored by the temperature monitoring module is greater than a first preset temperature threshold. If the actual temperature value is greater than the first preset temperature threshold, a first control signal indicating to stop heating is generated and sent to the heating unit 3 / the heating unit group; if the actual temperature value is less than the first preset temperature threshold, a second control signal indicating to continue monitoring is generated and sent to the temperature monitoring module; and / or, A temperature monitoring module is used to monitor in real time the actual temperature value of the germanium absorption layer 5 after being heated by the heating unit 3 with a heating level of primary heating and in a heating state.

[0036] A second judgment module is used to judge whether the actual temperature value monitored by the temperature monitoring module reaches a preset target temperature threshold after a preset time. If not, a third control signal is generated and sent to activate the heating unit 3 with a heating level of secondary heating and in a dormant state, so that the actual temperature of the germanium absorption layer 5 reaches the preset target temperature threshold.

[0037] Among them, the first temperature threshold can be obtained through a large number of experiments in advance, or preset by the user according to experience. When the actual temperature is near the first preset temperature threshold, the number of valence band electrons that can transition tends to be maximized, but at the same time, it will not cause too many adverse effects on the material itself.

[0038] The division of heating levels (primary and secondary) is only for distinguishing between the two, and cannot limit their heating power or other characteristics. In the case of only primary heating being turned on, the heating power is small, while when both primary heating and secondary heating are turned on, the heating power increases, and the temperature of the germanium absorption layer 5 can also be correspondingly increased.

[0039] The present invention regulates the temperature of the germanium absorption layer 5 through a real-time feedback mechanism. On the one hand, it can make the number of valence band electrons that can transition tend to be maximized as much as possible. On the other hand, it can improve the stability of the temperature of the germanium absorption layer 5 and prevent the problem that the optical signal emitted by the germanium absorption layer 5 becomes unstable due to frequent temperature changes.

[0040] In some embodiments, the germanium absorption layer 5 includes a gradient region 51 and a constant region 52 arranged in sequence along the light propagation direction, and the cross-sectional area of the gradient region 51 gradually increases from the incident end along the direction close to the constant region 52.

[0041] In some embodiments, the width of the gradient region 51 gradually increases from the incident end along the direction close to the constant region 52; and the longitudinal section of the gradient region 51 is a right trapezoid, and the hypotenuse of the right trapezoid corresponds to the interface between the gradient region 51 and the waveguide layer 2, and the angle α between it and the bottom edge is 86° - 89°; the longitudinal section of the constant region 52 is a rectangle; or, the interface between the gradient region 51 and the waveguide layer 2 is a sector. Among them, the longitudinal section refers to a vertical plane parallel to the length direction of the germanium absorption layer.

[0042] In some embodiments, silicon strips 7 are connected to both ends of the germanium absorption layer 5.

[0043] The purpose of the above settings is to achieve a smooth transition of the refractive index. Since the refractive index of silicon is approximately 3.4 and that of germanium is approximately 4.4, a relatively large amount of light is reflected at the interface between the optical waveguide and the germanium absorption layer. Through this gradual structural change, the refractive index can gradually transition from the waveguide layer 2 (silicon waveguide) to germanium, reducing the reflection of light at the incident end. When light propagates at the interface of media with different refractive indices, the greater the difference in refractive indices, the more severe the reflection. This gradual transition structure enables light to be more smoothly guided from the silicon waveguide into the germanium absorption layer 5, improving the light coupling efficiency and thereby enhancing the light absorption ability of the modulator.

[0044] Ideally, the tapered region is conical with a smaller front and a larger rear. The conical structure can achieve a more perfect refractive index gradient, minimizing the reflection of light when it enters the germanium absorption layer 5, and theoretically maximizing the light coupling efficiency.

[0045] Due to process limitations, a conical tapered region incurs high costs. Therefore, in this embodiment, to reduce the process difficulty, it is only necessary to make the cross-sectional area of the tapered region gradually increase from the incident end along the direction towards the constant region 52. For example, the tapered region is triangular with a narrow front and a wide rear when viewed from above; and trapezoidal with a larger upper part and a smaller lower part when viewed from the front. Although it differs from the ideal conical shape, the trapezoidal structure can still achieve a refractive index gradient to a certain extent, reducing light reflection, and is a feasible solution under the existing process conditions.

[0046] That is to say, by restricting the shape of the tapered region in the present invention, the cross-sectional area of the tapered region gradually increases both in height and length directions from the incident end, and a gradually changing tapered interface is formed to guide the optical signal transmitted from the optical waveguide, which can significantly reduce the reflection of light at the incident end and improve the light absorption rate of the modulator.

[0047] In some embodiments, the width and length of the heating unit 3 located at the top and / or bottom of the germanium absorption layer 5 are both smaller than the width and length of the germanium absorption layer 5. In this way, while ensuring the heating effect, unnecessary heat waste is avoided. In this embodiment, since the germanium absorption layer with the above structure is additionally adopted, the light absorption efficiency is improved. However, at the same time, once there is an abnormality in the data, such as data distortion, it will be correspondingly amplified, making it easier to detect data abnormalities in the subsequent process. There are various factors causing data abnormalities, and the specific judgment and recognition mechanism can adopt existing technologies for recognition, which will not be elaborated here. Once it is recognized that the data distortion and other abnormalities are caused by temperature, temperature compensation can be correspondingly performed through this heating unit.

[0048] Embodiment Two The present invention also provides a method for improving the modulation efficiency of an EAM, including the steps: S101, deposit an insulating layer on the surface of a silicon substrate and deposit a waveguide layer on the surface of the insulating layer; In this embodiment, the thickness of the silicon waveguide layer is 220 nm, providing a material basis for etching a ridge waveguide. The ridge waveguide structure formed on the silicon waveguide layer includes a flat layer and a silicon ridge. The ridge waveguide utilizes the propagation characteristics of light in media with different refractive indices. The refractive index of the silicon ridge is higher than that of the surrounding environment (such as air or the insulating layer), which can confine and guide light, reducing light scattering and loss, enabling light to propagate along a specific path. Precise control of the thickness of the silicon waveguide layer is crucial for forming a ridge waveguide with precise dimensions and stable performance, directly affecting the propagation effect of light therein.

[0049] S102, etch two grooves in parallel on the waveguide layer, and the depth of the grooves is less than the thickness of the waveguide layer; By etching two grooves with a depth less than that of the silicon waveguide layer in parallel on the silicon waveguide layer, the outer contour of the ridge waveguide is clearly defined. The silicon ridge will be formed in the area between the two grooves. The position of the grooves directly determines the position of the silicon ridge, while the width between the grooves affects the width of the flat layer. Precise control of the positions of these two grooves can ensure that the silicon ridge is in a proper position in the waveguide layer, guaranteeing that the propagation path of light in the waveguide meets the design requirements. At the same time, an appropriate width of the flat layer is also crucial for maintaining the optical performance and structural stability of the waveguide, which affects the distribution of the light field in the waveguide and the coupling effect with the germanium absorption layer.

[0050] S103, use a mask to deposit a silicon oxide layer on the surface of the waveguide layer to cover the areas on the waveguide layer that do not need to be etched; Deposit a silicon oxide layer on the surface of the silicon waveguide layer using a mask. The pattern of the mask determines the area covered by the silicon oxide layer. The areas covered by the silicon oxide layer will not be etched during the subsequent etching process, playing a protective role. This can ensure that only the designed areas are etched during the subsequent etching, avoiding unnecessary damage to other areas and guaranteeing the integrity and accuracy of the modulator structure.

[0051] S104, etch the waveguide layer along the outer sidewalls of the two grooves outward and between the two grooves, thereby forming a ridge optical waveguide and a first etching groove on the silicon ridge of the ridge optical waveguide for depositing a germanium absorption layer; the depth of the first etching groove is a first depth or a second depth; the first depth is less than the thickness of the waveguide layer, and the second depth is equal to the thickness of the waveguide layer; S105, deposit germanium in the first etching groove to form a germanium absorption layer; S106, remove the mask and deposit an insulating layer on the germanium absorption layer and the waveguide; S107. Etch a second etching groove on the insulating layer and on top of the germanium absorption layer, embed a heating unit in the second etching groove, and deposit an insulating layer again to cover the heating unit; the distance between the second etching groove and the top of the germanium absorption layer is less than or equal to 3 μm.

[0052] Alternatively, on the insulating layer, etch third etching grooves on both sides of the germanium absorption layer respectively, embed a heating unit in the third etching groove, and deposit an insulating layer again to cover the heating unit; the distance between the heating unit and both sides of the germanium absorption layer is less than or equal to 3 μm; Alternatively, on the insulating layer, etch a plurality of fourth etching grooves at intervals on both sides of the germanium absorption layer respectively, embed a heating unit in each fourth etching groove, and deposit an insulating layer again to cover all the heating units; the distance between the heating unit and both sides of the germanium absorption layer is less than or equal to 3 μm, and the distance between two adjacent heating units is greater than 1 μm.

[0053] This solution provides at least three different installation schemes for the heating unit. For different application scenarios, different installation schemes can be selected. For example, in the scenario where large-scale integration is required, the heating unit can be installed only on the top of the germanium absorption layer; in the scenario where high requirements are placed on power consumption and device thermal uniformity, the heating unit can be installed on both the bottom and the top of the germanium absorption layer; and in the case where high requirements are placed on thermal efficiency but low requirements are placed on the chip volume, the heating unit can be installed on both sides of the germanium absorption layer.

[0054] In some embodiments, before depositing the silicon waveguide layer on the insulating layer in step S101, the following steps are further included: Etch a fifth etching groove on the insulating layer, embed a heating unit in the fifth etching groove, and deposit an insulating layer again to cover the heating unit.

[0055] In some embodiments, the first etching groove with the second depth etched on the waveguide layer in step S104 includes a gradient region and a constant region arranged in sequence along the light propagation direction, wherein the width of the gradient region gradually increases from one end close to the waveguide layer to the other end close to the constant region.

[0056] In some embodiments, the following steps are further included: Monitor the actual temperature value of the germanium absorption layer in real time; Judge whether the actual temperature value is greater than a first preset temperature threshold, If the actual temperature value is greater than the first preset temperature threshold, control the heating unit or the heating group to stop heating; otherwise, continue to monitor.

[0057] In some embodiments, the following steps are further included: Monitor in real time the actual temperature value of the germanium absorption layer after being heated by the heating unit with the heating level of primary heating and in the heating state; Determine whether the actual temperature value reaches a preset target temperature threshold after a preset time duration. If not, start the heating unit with the heating level of secondary heating and in the dormant state; Alternatively, monitor in real time the actual temperature values of the gradient region and the constant region in the germanium absorption layer; Determine whether the temperature difference between the actual temperature value of the gradient region and the actual temperature value of the constant region is less than or equal to a preset difference threshold; If it is less than or equal to the preset difference threshold, continue the monitoring; If it is greater than the preset difference threshold, control the heating power of the multiple heating units corresponding to the region with the larger actual temperature value to decrease, or control the heating power of the multiple heating units corresponding to the region with the smaller actual temperature value to increase, so that the temperature difference between the actual temperature values of the constant regions is less than or equal to the preset difference threshold.

[0058] In some embodiments, after S107, the following steps are further included: S108, set electrodes on both sides of the silicon ridge. S108 specifically includes: S81, deposit insulating materials on both sides of the ridge-type optical waveguide.

[0059] Depositing insulating materials on both sides of the ridge-type optical waveguide electrically isolates the electrodes from the waveguide layer, preventing short circuits between the electrodes and the waveguide layer and ensuring the stability of the electrical performance of the modulator. At the same time, the insulating materials can also protect the waveguide layer and the germanium strip, avoiding damage to them during the subsequent electrode preparation process.

[0060] S82, etch electrode grooves on the insulating materials above the flat layer on both sides of the silicon ridge.

[0061] Etching electrode grooves on the insulating materials above the flat layer on both sides of the silicon ridge determines the position and shape of the electrodes. Precise etching of the electrode grooves can ensure good contact between the electrodes, the germanium strip, and the external circuit, facilitating the extraction and transmission of photo-generated carriers.

[0062] S83, deposit electrodes in the electrode grooves.

[0063] Depositing electrodes in the electrode grooves, the electrodes are used to collect photo-generated carriers and transmit them to the external circuit. By selecting a suitable electrode material (such as copper or aluminum) and precisely controlling the deposition process, it can be ensured that the electrodes have good conductivity and stability, improving the response speed and efficiency of the modulator.

[0064] It should be noted that in this text, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also other elements not explicitly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the existence of additional identical elements in the process, method, article or device comprising such element.

[0065] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the spirit of the present invention and the scope protected by the claims. All of these fall within the protection scope of the present invention.

Claims

1. An electroabsorption modulator, characterized in that: include: A silicon substrate and an insulating layer deposited on the silicon substrate; a waveguide layer is arranged on the insulating layer; a germanium absorption layer is embedded on the waveguide layer; The first depth to which the germanium absorption layer is embedded in the waveguide layer is less than the thickness of the waveguide layer, or the second depth to which the germanium absorption layer is embedded in the waveguide layer is equal to the thickness of the waveguide layer; A heating unit is disposed on the top and / or bottom of the germanium absorption layer, and the heating unit extends along the length direction of the germanium absorption layer; or, Heating units are respectively arranged on both sides of the germanium absorption layer, and the heating units extend along the length direction of the germanium absorption layer; or, Heating unit groups are respectively arranged on both sides of the germanium absorption layer, and the heating unit group on each side includes a plurality of heating units evenly spaced along the length direction of the germanium absorption layer, wherein the heating levels of two adjacent heating units on the same side are primary heating and secondary heating, respectively.

2. An electroabsorption modulator according to claim 1, characterized in that: Also includes: A temperature monitoring module, used for real-time monitoring of the actual temperature value of the germanium absorption layer; A first judgment module is used to judge whether the actual temperature value monitored by the temperature monitoring module is greater than a first preset temperature threshold value, If the actual temperature value is greater than the first preset temperature threshold, generating and sending a first control signal indicating stopping heating to the heating unit / the heating unit group; If the actual temperature value is less than the first preset temperature threshold, generating and sending a second control signal indicating continued monitoring to the temperature monitoring module; and / or, A temperature monitoring module, used for real-time monitoring of the actual temperature value of the germanium absorption layer after being heated by the heating unit with a heating level of first level and in a heating state; The second judgment module is used to judge whether the actual temperature value monitored by the temperature monitoring module reaches the preset target temperature threshold after a preset period of time. If not, a third control signal is generated and sent to indicate that the heating unit has started the heating level of the second-level heating and is in a dormant state, so that the actual temperature of the germanium absorption layer reaches the preset target temperature threshold.

3. The electroabsorption modulator according to claim 1, characterized in that: The germanium absorption layer includes a gradient zone and a constant zone arranged in sequence along the light propagation direction, and the cross-sectional area of ​​the gradient zone gradually increases from the incident end in the direction close to the constant zone; the cross-sectional area of ​​the constant zone is the same from the end connected to the gradient zone in the direction away from the constant zone.

4. An electroabsorption modulator according to claim 3, characterized in that: The width of the gradient zone gradually increases from the incident end in the direction close to the constant zone; the longitudinal section of the gradient zone is a right-angled trapezoid, and the hypotenuse of the right-angled trapezoid corresponds to the interface between the gradient zone and the waveguide layer, and the angle between the hypotenuse and the bottom side is 86°-89°; the longitudinal section of the constant zone is a rectangle; or, The interface between the gradient zone and the waveguide layer is fan-shaped.

5. The electroabsorption modulator according to claim 1, characterized in that: The width and length of the heating unit located at the top and / or bottom of the germanium absorption layer are both smaller than the width and length of the germanium absorption layer.

6. A method for improving EAM modulation efficiency, characterized in that: Includes steps: S101, depositing an insulating layer on a surface of a silicon substrate, and depositing a waveguide layer on a surface of the insulating layer; S102, etching two grooves in parallel on the waveguide layer, wherein the depth of the grooves is less than the thickness of the waveguide layer; S103, using a mask to deposit a silicon oxide layer on the surface of the waveguide layer to cover the area of ​​the waveguide layer that does not need to be etched; S104, etching the waveguide layer outward along the outer side walls of the two grooves and between the two grooves, so as to form a ridge-type optical waveguide and a first etched groove located on the silicon ridge of the ridge-type optical waveguide for depositing a germanium absorption layer; the depth of the first etched groove is a first depth or a second depth; the first depth is less than the thickness of the waveguide layer, and the second depth is equal to the thickness of the waveguide layer; S105, depositing germanium in the first etching groove to form a germanium absorption layer; S106, removing the mask, and depositing an insulating layer on the germanium absorption layer and the waveguide layer; S107, etching a second etching groove on the insulating layer and located on the top of the germanium absorption layer, burying a heating unit in the second etching groove, and depositing an insulating layer again to cover the heating unit; the distance between the second etching groove and the top of the germanium absorption layer is less than or equal to 3 um; Alternatively, on the insulating layer, third etching grooves are respectively etched on both sides of the germanium absorption layer, and a heating unit is buried in the third etching grooves, and an insulating layer is deposited again to cover the heating unit; the distance between the heating unit and both sides of the germanium absorption layer is less than or equal to 3 um; Alternatively, on the insulating layer, a plurality of fourth etching grooves are etched at intervals on both sides of the germanium absorption layer, and a heating unit is buried in each fourth etching groove, and an insulating layer is deposited again to cover all the heating units; the distance between the heating unit and both sides of the germanium absorption layer is less than or equal to 3um, and the distance between two adjacent heating units is greater than 1um.

7. A method for improving EAM modulation efficiency according to claim 1, characterized in that: Before depositing the waveguide layer on the insulating layer in step S101, the method further includes the following steps: A fifth etching groove is etched on the insulating layer, a heating unit is buried in the fifth etching groove, and an insulating layer is deposited again to cover the heating unit.

8. A method for improving EAM modulation efficiency according to claim 6, characterized in that: The first etched groove of the second depth etched on the waveguide layer in step S104 includes a gradual change area and a constant area sequentially arranged along the light propagation direction, wherein: The width of the gradient zone increases gradually from one end close to the waveguide layer to the other end close to the constant zone.

9. A method for improving EAM modulation efficiency according to claim 6, characterized in that: Also includes the steps: Real-time monitoring of the actual temperature value of the germanium absorption layer; Determine whether the actual temperature value is greater than a first preset temperature threshold, If the actual temperature value is greater than the first preset temperature threshold, the heating unit or the heating group is controlled to stop heating; otherwise, monitoring continues.

10. The method for improving EAM modulation efficiency according to claim 6, characterized in that: Also includes the steps: Real-time monitoring of the actual temperature value of the germanium absorption layer after being heated by the heating unit having a first-level heating level and being in a heating state; Determine whether the actual temperature value reaches a preset target temperature threshold after a preset time period, and if not, start a heating unit whose heating level is secondary heating and is in a dormant state; or, Real-time monitoring of actual temperature values ​​of the gradient zone and the constant zone in the germanium absorption layer; Determine whether a temperature difference between an actual temperature value of the gradual change zone and an actual temperature value of the constant zone is less than or equal to a preset difference threshold; If it is less than or equal to the preset difference threshold, continue monitoring; If it is greater than the preset difference threshold, multiple heating units corresponding to an area with a larger actual temperature value are controlled to reduce the heating power, or multiple heating units corresponding to an area with a smaller actual temperature value are controlled to increase the heating power, so that the temperature difference between the actual temperature values ​​of the constant zone is less than or equal to the preset difference threshold.

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