Laser chip and preparation method therefor

Abstract

A laser chip (900) and a preparation method therefor. The laser chip (900) comprises a light-emitting region (910) and an electro-absorption modulation region (920). The electro-absorption modulation region (920) comprises a substrate (922), an active layer (923), a waveguide layer (924), and a modulation electrode (926). The waveguide layer (924) comprises a ridge structure (900a), and a first ridge groove (900a1) and a second ridge groove (900a2) located on two sides of the ridge structure. A first filling medium (940) is provided in the first ridge groove (900a1), and a second filling medium (950) is provided in the second ridge groove (900a2). The first filling medium (940) and the second filling medium (950) are both low dielectric constant media. An end of the modulation electrode (926) is disposed on the surface of the ridge structure (900a), and another end thereof is disposed on the surface of the first filling medium (940), that is, the first filling medium (940) is located between the modulation electrode (926) and the surface of the laser chip (900).

Description

Laser chip and preparation method thereof

[0001] This application claims priority to the application filed on May 29, 2024 in the China Patent Office, application number 202410681147.5; the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates to the field of optical communication technology, in particular to a laser chip and a preparation method thereof. BACKGROUND

[0003] An EML laser chip includes a distributed feedback laser (DFB) and an electro absorption modulator (EAM). With the rapid development of application markets such as big data, cloud computing, and artificial intelligence, the demand for optical modules is also rapidly increasing. The optical device industry is continuously developing in the direction of meeting higher rates and lower power consumption, and therefore the EML laser chip should also have a higher modulation rate.

[0004] SUMMARY

[0005] In a first aspect, the laser chip provided by the embodiments of the present disclosure includes:

[0006] a light emitting region configured to generate light;

[0007] an electro absorption modulation region configured to modulate the light generated by the light emitting region, the electro absorption modulation region including:

[0008] a substrate;

[0009] an active layer configured to modulate the light generated by the light emitting region according to a modulation current signal;

[0010] a waveguide layer including a ridge structure, a first ridge groove and a second ridge groove located on both sides of the ridge structure;

[0011] a first filling medium having a dielectric constant lower than that of the substrate, the first filling medium including a first connecting portion and a second connecting portion, the first connecting portion being embedded in the first ridge groove, and the second connecting portion having one end disposed on the surface of the first connecting portion and the other end disposed on the surface of the laser chip;

[0012] a second filling medium having a dielectric constant lower than that of the substrate, the second filling medium including a fourth connecting portion and a fifth connecting portion, the fourth connecting portion being embedded in the second ridge groove, and the fifth connecting portion having one end disposed on the surface of the fourth connecting portion and the other end disposed on the surface of the laser chip;

[0013] A modulation electrode is arranged on one surface of the ridge structure and another surface of the second connecting part, and is used to transmit a modulation current signal to the active layer.

[0014] In a second aspect, the disclosure provides a preparation method of a laser chip, including:

[0015] A first electrode layer, a substrate, and an active layer of the laser chip are sequentially epitaxially grown.

[0016] An InP epitaxial region is grown along a surface of the active layer.

[0017] A shallow etching is performed on the InP epitaxial region corresponding to the light emitting region to form a ridge waveguide layer of the light emitting region, and a deep etching is performed on the InP epitaxial region corresponding to the electro-absorption modulation region to form a ridge waveguide layer of the electro-absorption modulation region, and the ridge waveguide layer includes a ridge structure, a first ridge groove, and a second ridge groove arranged on two sides of the ridge structure.

[0018] A dielectric film is deposited along the ridge waveguide layer of the electro-absorption modulation region.

[0019] The dielectric film on the surface of the ridge structure of the electro-absorption modulation region is etched away through photolithography.

[0020] A low dielectric constant medium is uniformly coated along the current surface of the laser chip, so that the low dielectric constant medium is filled in the first ridge groove and the second ridge groove corresponding to the electro-absorption modulation region, and the low dielectric constant medium is uniformly coated along the surface of the laser chip.

[0021] Through two times of photolithography, part of the low dielectric constant medium on the surface of the laser chip and the low dielectric constant medium on two sides of the ridge structure are etched away, so as to respectively achieve that the low dielectric constant medium has a preset distance to the edge of the chip after etching, and the surface of the ridge structure is exposed.

[0022] The current low dielectric constant medium is heated and reflowed to supplement the low dielectric constant medium on two sides of the ridge structure upwards, until the first filling medium and the second filling medium located on two sides of the ridge structure are obtained. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the disclosure, the following will briefly introduce the drawings used in some embodiments of the disclosure. Obviously, the drawings in the following description are only some drawings of the embodiments of the disclosure, and other drawings can also be obtained by those skilled in the art according to these drawings. In addition, the drawings in the following description can be regarded as schematic diagrams, and are not limited to the actual size of the product, the actual flow of the method, the actual time sequence of the signal, etc. involved in the embodiments of the disclosure.

[0024] Figure 1 is a partial architecture diagram of an optical communication system according to some embodiments of the present disclosure;

[0025] Figure 2 is a partial structure diagram of a host computer according to some embodiments of the present disclosure;

[0026] Figure 3 is a structure diagram of an optical module according to some embodiments of the present disclosure;

[0027] Figure 4 is an exploded view of an optical module according to some embodiments of the present disclosure;

[0028] Figure 5 is a structure diagram of an optical transmitting component according to some embodiments of the present disclosure;

[0029] Figure 6 is an exploded view of an optical transmitting component according to some embodiments of the present disclosure;

[0030] Figure 7 is a structure diagram of a laser chip according to some embodiments of the present disclosure;

[0031] Figure 8 is an exploded diagram of a laser chip according to some embodiments of the present disclosure;

[0032] Figure 9 is a structure diagram of a laser chip according to some embodiments of the present disclosure;

[0033] Figure 10 is a cross-sectional structure diagram of a laser chip according to some embodiments of the present disclosure;

[0034] Figure 11 is a cross-sectional structure diagram of a laser chip according to some embodiments of the present disclosure;

[0035] Figure 12 is a cross-sectional structure diagram of a laser chip according to some embodiments of the present disclosure;

[0036] Figure 13 is a cross-sectional structure diagram of a laser chip according to some embodiments of the present disclosure;

[0037] Figure 14 is a structure diagram of a laser chip according to some embodiments of the present disclosure;

[0038] Figure 15 is an exploded diagram of a laser chip according to some embodiments of the present disclosure;

[0039] Figure 16 is an exploded diagram of a laser chip according to some embodiments of the present disclosure;

[0040] Figure 17 is a side structure diagram of a laser chip according to some embodiments of the present disclosure;

[0041] Figure 18 is a flowchart of a method for manufacturing a laser chip according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0042] Some embodiments of the present disclosure will be described in detail below with reference to the drawings. However, the described embodiments are only some embodiments of the present disclosure, not all embodiments. Based on the embodiments provided in the present disclosure, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present disclosure.

[0043] Unless otherwise required by the context, throughout the specification and claims, the term "comprising" is to be interpreted as open, inclusive, meaning "including, but not limited to"; the terms "first", "second" are not to be interpreted as indicating or implying relative importance or indicating the upper limit of the number; the term "multiple" means two or more; the term "connected" should be broadly interpreted, for example, "connected" can be fixed connection, or detachable connection, or integrated, can be directly connected, or indirectly connected through an intermediate medium; The use of the terms "suitable for" or "configured to" means open and inclusive language, which does not exclude devices suitable for or configured to perform additional tasks or steps; The terms "parallel", "vertical", "same", "consistent", "flush" and the like are not limited to absolute mathematical relationships, but also include acceptable error ranges generated in practice, and also include differences based on the same design concept but due to manufacturing reasons.

[0044] In optical communication technology, in order to establish information transmission between information processing devices, information needs to be loaded onto light, and the transmission of information is realized by the propagation of light. Here, the light loaded with information is an optical signal. The optical signal can reduce the loss of optical power when transmitted in the information transmission device, so as to realize high-speed, long-distance and low-cost information transmission. The signal that the information processing device can recognize and process is an electrical signal. Information processing devices usually include optical network units (ONUs), gateways, routers, switches, mobile phones, computers, servers, tablets, televisions, etc., and information transmission devices usually include optical fibers and optical waveguides, etc.

[0045] The optical module can realize mutual conversion between optical signals and electrical signals between the information processing device and the information transmission device. For example, at least one of the optical signal input end or the optical signal output end of the optical module is connected with an optical fiber, and at least one of the electrical signal input end or the electrical signal output end of the optical module is connected with an optical network terminal; a first optical signal from the optical fiber is transmitted to the optical module, the optical module converts the first optical signal into a first electrical signal, and transmits the first electrical signal to the optical network terminal; a second electrical signal from the optical network terminal is transmitted to the optical module, the optical module converts the second electrical signal into a second optical signal, and transmits the second optical signal to the optical fiber. Since information transmission can be performed between multiple information processing devices through electrical signals, at least one of the multiple information processing devices needs to be directly connected with the optical module, without the need for all the information processing devices to be directly connected with the optical module. Here, the information processing device directly connected with the optical module is referred to as a host computer of the optical module. In addition, the optical signal input end or the optical signal output end of the optical module can be referred to as an optical port, and the electrical signal input end or the electrical signal output end of the optical module can be referred to as an electrical port.

[0046] FIG. 1 is a partial structure diagram of an optical communication system according to some embodiments. As shown in FIG. 1, the optical communication system mainly includes a remote information processing device 1000, a local information processing device 2000, a host computer 100, an optical module 200, an optical fiber 101, and a network cable 103.

[0047] One end of the optical fiber 101 extends towards the remote information processing device 1000, and the other end of the optical fiber 101 is connected with the optical module 200 through the optical port of the optical module 200. The optical signal can be totally reflected in the optical fiber 101, and the propagation of the optical signal in the totally reflected direction can almost maintain the original optical power. The optical signal is totally reflected multiple times in the optical fiber 101 to transmit the optical signal from the remote information processing device 1000 to the optical module 200, or to transmit the optical signal from the optical module 200 to the remote information processing device 1000, thereby realizing long-distance and low-power-loss information transmission.

[0048] The optical communication system can include one or more optical fibers 101, and the optical fiber 101 can be detachably connected with the optical module 200 or fixedly connected. The host computer 100 is configured to provide a data signal to the optical module 200, or receive a data signal from the optical module 200, or monitor or control the working state of the optical module 200.

[0049] The host computer 100 includes a housing substantially in the shape of a rectangular cuboid, and an optical module interface 102 disposed on the housing. The optical module interface 102 is configured to access the optical module 200, so as to establish a unidirectional or bidirectional electrical signal connection between the host computer 100 and the optical module 200.

[0050] The host computer 100 further comprises an external electrical interface configured to access an electrical signal network. For example, the external electrical interface comprises a Universal Serial Bus (USB) interface or a network cable interface 104 configured to access a network cable 103 to establish a unidirectional or bidirectional electrical signal connection between the host computer 100 and the network cable 103. One end of the network cable 103 is connected to the local information processing device 2000, and the other end of the network cable 103 is connected to the host computer 100 to establish an electrical signal connection between the local information processing device 2000 and the host computer 100 through the network cable 103. For example, a third electrical signal emitted by the local information processing device 2000 is transmitted to the host computer 100 through the network cable 103, and the host computer 100 generates a second electrical signal according to the third electrical signal. The second electrical signal from the host computer 100 is transmitted to the optical module 200, and the optical module 200 converts the second electrical signal into a second optical signal and transmits the second optical signal to the optical fiber 101. The second optical signal is transmitted in the optical fiber 101 to the remote information processing device 1000. For example, the first optical signal from the remote information processing device 1000 is transmitted through the optical fiber 101, the first optical signal from the optical fiber 101 is transmitted to the optical module 200, the optical module 200 converts the first optical signal into a first electrical signal, the optical module 200 transmits the first electrical signal to the host computer 100, the host computer 100 generates a fourth electrical signal according to the first electrical signal, and the fourth electrical signal is transmitted to the local information processing device 2000. It should be noted that the optical module is a tool for converting optical signals and electrical signals, and the information does not change in the conversion process of the optical signals and the electrical signals, and the encoding and decoding mode of the information can change.

[0051] In addition to the optical network terminal, the host computer 100 further comprises an optical line terminal (OLT), an optical network terminal (ONT), or a data center server, etc.

[0052] Figure 2 is a partial structure diagram of a host computer according to some embodiments. In order to clearly show the connection relationship between the optical module 200 and the host computer 100, Figure 2 only shows the structure of the host computer 100 related to the optical module 200. As shown in Figure 2, the host computer 100 further comprises a PCB circuit board 105 arranged in the shell, a cage 106 arranged on the surface of the PCB circuit board 105, a heat sink 107 arranged on the cage 106, and an electrical connector arranged inside the cage 106. The electrical connector is configured to access the electrical port of the optical module 200; the heat sink 107 has a fin or other protruding structure to increase the heat dissipation area.

[0053] The optical module 200 is inserted into the cage 106 of the host computer 100, and the optical module 200 is fixed by the cage 106. The heat generated by the optical module 200 is conducted to the cage 106, and then diffused through the heat sink 107. After the optical module 200 is inserted into the cage 106, the electrical port of the optical module 200 is connected with the electrical connector inside the cage 106, so that the optical module 200 and the host computer 100 establish a bidirectional electrical signal connection. In addition, the optical port of the optical module 200 is connected with the optical fiber 101, so that the optical module 200 and the optical fiber 101 establish a bidirectional optical signal connection.

[0054] FIG. 3 is a structural diagram of an optical module according to some embodiments of the present disclosure, and FIG. 4 is an exploded view of an optical module according to some embodiments of the present disclosure. As shown in FIGS. 3 and 4, the optical module 200 includes a shell, a circuit board 300 arranged in the shell, an optical transmitting component 400, and an optical receiving component 500. However, the present disclosure is not limited thereto, and in some embodiments, the optical module 200 includes one of the optical transmitting component 400 and the optical receiving component 500.

[0055] The shell includes an upper shell 201 and a lower shell 202. The upper shell 201 is covered on the lower shell 202 to form the above-mentioned shell having two openings 204 and 205. The outer contour of the shell generally presents a square body.

[0056] In some embodiments, the lower shell 202 includes a bottom plate 2021 and two lower side plates 2022 arranged perpendicularly to the bottom plate 2021 on both sides of the bottom plate 2021. The upper shell 201 includes a cover plate 2011, and the cover plate 2011 is covered on the two lower side plates 2022 of the lower shell 202 to form the above-mentioned shell.

[0057] In some embodiments, the lower shell 202 includes a bottom plate 2021 and two lower side plates 2022 arranged perpendicularly to the bottom plate 2021 on both sides of the bottom plate 2021. The upper shell 201 includes a cover plate 2011 and two upper side plates arranged perpendicularly to the cover plate 2011 on both sides of the cover plate 2011. The two upper side plates are combined with the two lower side plates 2022 to realize that the upper shell 201 is covered on the lower shell 202.

[0058] The direction of the line connecting the two openings 204 and 205 can be consistent with the length direction of the optical module 200, or can be inconsistent with the length direction of the optical module 200. For example, the opening 204 is located at the end of the optical module 200 (the right end of FIG. 3), and the opening 205 is also located at the end of the optical module 200 (the left end of FIG. 3). Alternatively, the opening 204 is located at the end of the optical module 200, and the opening 205 is located at the side of the optical module 200. The opening 204 is an electrical port, and the gold fingers 301 of the circuit board 300 extend from the opening 204 and are inserted into the electrical connector of the host computer 100. The opening 205 is an optical port configured to access the external optical fiber 101, so that the optical fiber 101 connects the optical transmitting component 400 and the optical receiving component 500 in the optical module 200.

[0059] The assembly of the upper shell 201 and the lower shell 202 facilitates the installation of the circuit board 300, the optical transmitting component 400, the optical receiving component 500, etc. in the shells, and the shells can protect the above-mentioned devices. In addition, when assembling the circuit board 300, the optical transmitting component 400, and the optical receiving component 500, etc., the positioning components, heat dissipation components, and electromagnetic shielding components of these devices can be easily deployed, which facilitates automated production.

[0060] In some embodiments, the upper shell 201 and the lower shell 202 are made of metal materials, which facilitates electromagnetic shielding and heat dissipation.

[0061] In some embodiments, the optical module 200 further includes an unlocking component 600 located outside the shell of the optical module 200. The unlocking component 600 is configured to achieve fixed connection between the optical module 200 and the host computer, or to release the fixed connection between the optical module 200 and the host computer.

[0062] For example, the unlocking component 600 is located outside the two lower side plates 2022 of the lower shell 202, and includes a clamping component matched with the cage 106 of the host computer 100. When the optical module 200 is inserted into the cage 106, the clamping component of the unlocking component 600 fixes the optical module 200 in the cage 106. When the unlocking component 600 is pulled, the clamping component of the unlocking component 600 moves, thereby changing the connection relationship between the clamping component and the host computer, to release the fixation between the optical module 200 and the host computer, so that the optical module 200 can be pulled out of the cage 106.

[0063] The circuit board 300 includes circuit traces, electronic components, and chips, etc. The electronic components and chips are connected according to circuit design through the circuit traces to realize power supply, electrical signal transmission, and grounding, etc. The electronic components may, for example, include capacitors, resistors, transistors, and Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs). The chips may, for example, include Microcontroller Units (MCUs), laser drive chips, Transimpedance Amplifiers (TIAs), limiting amplifiers, Clock and Data Recovery (CDR) chips, power management chips, and Digital Signal Processing (DSP) chips.

[0064] The circuit board 300 is generally a rigid circuit board. Due to its relatively hard material, the rigid circuit board can also realize a bearing function, such as stably bearing the above-mentioned electronic components and chips. The rigid circuit board can also be inserted into the electrical connector in the cage 106 of the host computer 100.

[0065] The circuit board 300 also includes a gold finger 301 formed on the surface of the end thereof. The gold finger 301 is composed of a plurality of pins independent of each other. The circuit board 300 is inserted into the cage 106, and the gold finger 301 is in conduction with the electrical connector in the cage 106. The gold finger 301 can be provided only on the surface (e.g., the upper surface shown in FIG. 4) of one side of the circuit board 300, or can be provided on the surfaces of both upper and lower sides of the circuit board 300 to provide a larger number of pins to adapt to occasions requiring a large number of pins. The gold finger 301 is configured to establish electrical connection with the host computer to realize power supply, grounding, Inter-Integrated Circuit (I2C) signal transmission, data signal transmission, etc. Of course, flexible circuit boards are also used in some optical modules. The flexible circuit board is generally used in cooperation with the rigid circuit board to supplement the rigid circuit board.

[0066] At least one of the light emitting component 400 or the light receiving component 500 is located on the side of the circuit board 300 away from the gold finger 301.

[0067] In some embodiments, the light emitting component 400 and the light receiving component 500 are physically separated from the circuit board 300, and then are electrically connected to the circuit board 300 through corresponding flexible circuit boards or electrical connectors, respectively.

[0068] In some embodiments, at least one of the light emitting component or the light receiving component may be directly disposed on the circuit board 300. For example, at least one of the light emitting component or the light receiving component may be disposed on the surface of the circuit board 300 or on the side of the circuit board 300.

[0069] As shown in Figure 4, in the optical module provided in this embodiment, the optical emitting component 400 and the optical receiving component 500 are both disposed on a circular-square tube. The optical emitting component 400 is used to generate and output signal light, and the optical receiving component 500 is used to receive signal light from outside the optical module. An optical fiber adapter is disposed on the circular-square tube to connect the optical module to an external optical fiber. A lens assembly is typically disposed within the circular-square tube to change the propagation direction of the signal light output by the optical emitting component 400 or the signal light input from the external optical fiber. The optical emitting component 400 and the optical receiving component 500 are physically separated from the circuit board 300. Therefore, it is difficult to directly connect the optical emitting component 400 and the optical receiving component 500 to the circuit board 300. Thus, in this embodiment, the optical emitting component 400 and the optical receiving component 500 are electrically connected via flexible circuit boards. However, in this embodiment, the assembly structure of the light emitting component 400 and the light receiving component 500 is not limited to the structure shown in Figures 3 and 4. Other assembly structures are also possible, such as the light emitting component 400 and the light receiving component 500 being disposed on different tubes. This embodiment only uses the structure shown in Figures 3 and 4 as an example.

[0070] Figure 5 is a structural diagram of a light emitting component provided according to some embodiments of the present disclosure. As shown in Figure 5, the light emitting component 400 provided in this embodiment includes a tube base 490, a tube cap 480, and other devices disposed within the tube cap 480 and the tube base 490. The tube cap 480 covers one end of the tube base 490, and the tube base 490 includes a plurality of pins. The pins are used to realize the electrical connection between the flexible circuit board and other electrical devices within the light emitting component 400, thereby realizing the electrical connection between the light emitting component 400 and the circuit board 300. This embodiment only uses the structure shown in Figure 5 as an example.

[0071] Figure 6 is an exploded view of a light emitting component provided according to some embodiments of the present disclosure. As shown in Figure 6, the light emitting component 400 includes a laser component 410, which generates signal light that passes through a cap 480.

[0072] In some embodiments, the laser assembly 410 includes a laser chip 900 and a substrate, an upper surface of the substrate is paved with circuits, and the laser chip 900 is connected to the corresponding circuits on the substrate by wire bonding. For example, the laser chip 900 can be an electro-absorption modulated laser (EML) chip, which is a monolithic integration of a DFB laser and an EAM modulator. The EML laser chip avoids the interaction between photons and electrons in the laser during high-speed modulation by using an external modulation technique, reduces the large chirp caused by direct modulation, and thus can achieve a higher transmission rate.

[0073] FIG. 7 is a structural schematic diagram of a laser chip according to some embodiments of the present disclosure; and FIG. 8 is an exploded schematic diagram of a laser chip according to some embodiments of the present disclosure. As shown in FIGS. 7 and 8, in some embodiments, the laser chip 900 can be an EML laser chip.

[0074] In some embodiments, the laser chip 900 can include a light emitting region 910. The light emitting region 910 is configured to emit light that does not carry a signal.

[0075] In some examples, the light emitting region 910 can be provided with a light emitting electrode 919. The light emitting electrode 919 can be located on a surface of the light emitting region 910.

[0076] In some embodiments, the laser chip 900 can include an electro-absorption modulation region 920. The electro-absorption modulation region 920 is configured to modulate the light emitted by the light emitting region 910 to generate an optical signal.

[0077] In some examples, the electro-absorption modulation region 920 can be located on one side of the light emitting region 910.

[0078] In some examples, the electro-absorption modulation region 920 includes a modulation electrode 926. The modulation electrode 926 is located on a surface of the electro-absorption modulation region 920.

[0079] In some embodiments, the modulation electrode 926 includes an electrode region 9261, a pad region 9263, and a connection region 9262 between the electrode region 9261 and the pad region 9263. The electrode region 9261 is used to electrically connect to the surface of the ridge structure 900a; and the connection region 9262 is used to connect the electrode region 9261 and the pad region 9263.

[0080] In some examples, the laser chip 900 is disposed on a substrate surface, and the laser chip 900 is electrically connected to a high-frequency signal line on the substrate surface to receive an electrical signal transmitted by the high-frequency signal line. For example, the pad region 9263 is electrically connected to the high-frequency signal line on the substrate surface. The pad region 9263 has a larger size than the electrode region 9261, which facilitates wire bonding between the pad region 9263 and the high-frequency signal line on the substrate surface.

[0081] In some embodiments, the light emitting region 910 and the electro-absorption modulation region 920 are disposed along the light field transmission direction.

[0082] In some embodiments, the optical waveguide of the laser chip 900 adopts a ridge structure. The ridge waveguide structure has low power loss.

[0083] In some embodiments, the ridge waveguide structure includes a ridge structure 900a and first and second ridge grooves 900a1 and 900a2 on both sides of the ridge structure 900a.

[0084] The ridge grooves on both sides of the ridge structure can be formed by an etching process. According to the etching depth of the ridge grooves, the ridge waveguide is divided into a shallow etching ridge waveguide structure and a deep etching ridge waveguide structure. The shallow etching ridge waveguide structure refers to the etching depth of the ridge groove being less than the depth of the corresponding active layer. The deep etching ridge waveguide structure refers to the etching depth of the ridge groove being greater than the depth of the corresponding active layer.

[0085] In some embodiments, the etching depth of the ridge grooves of the light emitting region 910 and the electro-absorption modulation region 920 is the same. For example, both are shallow etching ridge waveguide structures to protect the integrity of the active layer of the light emitting region 910.

[0086] In some embodiments, the etching depth of the ridge grooves of the light emitting region 910 and the electro-absorption modulation region 920 is different. For example, the light emitting region 910 adopts a shallow etching ridge waveguide structure, and the electro-absorption modulation region 920 adopts a deep etching ridge waveguide structure.

[0087] The light emitting region 910 adopts a shallow etching ridge waveguide structure to protect the integrity of the active layer of the light emitting region 910.

[0088] The electro-absorption modulation region 920 adopts a deep etching ridge waveguide structure to improve the modulation rate and modulation efficiency. When the etching depth is greater, the effective refractive index difference provided by the ridge is greater, and the modulation rate and modulation efficiency are higher.

[0089] In some embodiments, the light emitting region 910 adopts a shallow etching ridge waveguide structure, and the electro-absorption modulation region 920 adopts a deep etching ridge waveguide structure. The light field mode spot transmitted in the light emitting region 910 is larger, and the light field mode spot transmitted in the electro-absorption modulation region 930 is smaller, so the light field modes between the light emitting region 910 and the electro-absorption modulation region 930 are not matched, and there is a light field mode abrupt interface.

[0090] FIG. 9 is a schematic diagram of a structure of a laser chip according to some embodiments of the present disclosure. As shown in FIG. 9, in some embodiments, a transition region 930 is provided between the light emitting region 910 and the electro-absorption modulation region 920 to match the light field patterns of the light emitting region 910 and the electro-absorption modulation region 930.

[0091] In some embodiments, the transition region 930 includes a shallow ridge portion 931 and a deep ridge portion 932 along the light field transmission direction. The shallow ridge portion 931 is provided adjacent to the light emitting region 910, and the deep ridge portion 932 is provided adjacent to the electro-absorption modulation region 920.

[0092] In some embodiments, the shallow ridge portion 931 adopts a shallow etched ridge waveguide structure, i.e., the ridge grooves on both sides of the shallow ridge portion 931 are etched downward to a depth that does not exceed the active layer. Exemplarily, the etching depth of the ridge grooves in the shallow ridge portion 931 is the same as the etching depth of the ridge grooves in the light emitting region 910.

[0093] In some examples, the etching depth of the ridge grooves in the shallow ridge portion 931 can be greater than the etching depth of the ridge grooves in the light emitting region 910.

[0094] In some embodiments, the deep ridge portion 932 adopts a deep etched ridge waveguide structure, i.e., the ridge grooves on both sides of the deep ridge portion 932 are etched downward to a depth that exceeds the active layer. Exemplarily, the etching depth of the ridge grooves in the deep ridge portion 932 is the same as the etching depth of the ridge grooves in the electro-absorption modulation region 920.

[0095] In some examples, the etching depth of the ridge grooves in the deep ridge portion 932 can be less than the etching depth of the ridge grooves in the electro-absorption modulation region 920.

[0096] In some examples, the etching depth gradually increases from the shallow ridge portion 931 to the deep ridge portion 932.

[0097] The transition region 930 can achieve a transition in etching depth, avoid a large mutation interface in etching depth, and thus avoid light field loss and reflection.

[0098] In some embodiments, in the deep ridge portion 932, the two sides of the ridge are respectively formed with a first sub-region 933 and a second sub-region 934. Exemplarily, the first sub-region 933 and the second sub-region 934 are symmetrically arranged on both sides of the ridge. The first sub-region 933 is exemplarily described below.

[0099] In some embodiments, the first sub-region 933 is formed with a gradient portion 935 at one end facing the light emitting region 910.

[0100] Exemplarily, the width of the gradual change section 935 gradually increases along the light field transmission direction. Exemplarily, the first gradual change section 935 presents a taper shape, with the taper tip pointing to the light emitting region 910 and the taper tail pointing to the electro-absorption modulation region 920.

[0101] In some embodiments, the first sub-region 933 is formed with a non-gradual change section 936 at one end of the electro-absorption modulation region 920.

[0102] Exemplarily, the width of the non-gradual change section 936 can remain unchanged along the light field transmission direction.

[0103] In some embodiments, the surface height of the enclosed area formed by the gradual change section 935 and the non-gradual change section 936 is lower than the surface height of the ridge groove in the first sub-region 933, i.e. the enclosed area is hollowed out relative to the surface of the ridge groove.

[0104] The light field spot size output by the light emitting region 910 is large enough for the light field to be transmitted along the ridge structure 900a and the area on both sides of the ridge structure 900a. When the light field is transmitted to the deep ridge section 932, the medium in the enclosed area is air and the medium outside the enclosed area is semiconductor material, so at this time the light field spot is transmitted along the semiconductor material with a larger refractive index.

[0105] That is, the surface height of the gradual change section 935 is lower than the surface height of the first ridge groove 900a1. When the light field is transmitted to the deep ridge section 932, the medium in the gradual change section 935 is air and the medium in the area on both sides of the gradual change section 935 is semiconductor material, so at this time the light field spot is transmitted along the semiconductor area with a larger refractive index.

[0106] In some embodiments, along the direction from the shallow ridge section 931 to the deep ridge section 932, the sidewall of the gradual change section 935 close to the ridge structure 900a gradually approaches the ridge structure 900a. Then the width of the semiconductor area enclosed by the sidewall and the ridge structure 900a gradually decreases, and the light field spot emitted by the light emitting region 910 gradually decreases, so that the light field transmitted in the semiconductor area on both sides of the ridge structure 900a is gradually squeezed into the ridge structure 900a, realizing smooth transition of the light field mode between the light emitting region 910 and the electro-absorption modulation region 920, matching the light field mode of the light emitting region 910 and the electro-absorption modulation region 920, solving the problem of abrupt interface of light field mode between the shallow etched ridge waveguide structure and the deep etched ridge waveguide structure, thus avoiding light field loss and reflection, and further improving the coupling efficiency between the light emitting region 910 and the electro-absorption modulation region 920.

[0107] By setting the transition region 930 between the light emitting region 910 and the electro-absorption modulation region 920, the smooth transition of the light field mode between the light emitting region 910 and the electro-absorption modulation region 920 can be realized, and then the light field mode between the light emitting region 910 and the electro-absorption modulation region 920 is matched, and then the coupling efficiency between the light emitting region 910 and the electro-absorption modulation region 920 is improved.

[0108] FIG. 10 is a schematic diagram of a cross-sectional structure of a laser chip according to some embodiments of the present disclosure. FIG. 10 is a cross-sectional structure diagram of the laser chip 900 corresponding to the position of the light emitting region 910 along the light field transmission direction. As shown in FIG. 10, in some embodiments, the laser chip 900 includes, from bottom to top, at the position of the light emitting region 910:

[0109] a first electrode layer 911;

[0110] a substrate 912;

[0111] a lower confinement layer 913;

[0112] an active layer 914;

[0113] an upper confinement layer 915;

[0114] a grating layer 916;

[0115] a waveguide layer 917, that is, the layer where the ridge structure 900a is located;

[0116] a passivation layer 918;

[0117] a light emitting electrode 919.

[0118] The first electrode layer 911 can be an N-type electrode layer configured to inject N-type carriers into the active layer 914.

[0119] The light emitting electrode 919 can be a P-type electrode layer configured to inject P-type carriers into the active layer 914.

[0120] In some embodiments, when the light emitting electrode 919 and the first electrode layer 911 form a PN junction, the concentration difference of the carriers causes diffusion motion, and the result of the carrier diffusion motion is that the light emitting electrode 919 injects holes into the active layer 914, and the holes are the above-mentioned P-type carriers; the first electrode layer 911 is used to inject electrons into the active layer 914, and the electrons are the above-mentioned N-type carriers. In the active layer 914, the stimulated radiation makes the discrete electron-hole pairs recombine to generate photons, thereby effectively converting the electrically injected carriers into photons and generating gain light.

[0121] The lower confinement layer 913 and the upper confinement layer 915 are respectively arranged on two sides of the active layer 914. The lower confinement layer 913 and the upper confinement layer 915 can confine the injected electrons and holes in the quantum well of the active layer 914, so as to ensure the carrier concentration.

[0122] The active layer 914 adopts an Al-containing quantum well, such as an AlInGaAs quantum well. The valence band of the Al-containing quantum well has a band gap of about 0.1 eV larger than that of the InGaAsP quantum well, which can better bind electrons. Therefore, the AlInGaAs quantum well enables the laser chip to work in a wide temperature range, thereby eliminating the semiconductor cooler with high energy consumption, and facilitating the reduction of the power consumption of the laser chip.

[0123] In the active layer 914, the stimulated radiation makes the discrete electron-hole pairs recombine to generate photons, thereby effectively converting the electrically injected carriers into photons and generating gain light. The gain light is reflected by the resonant cavity or the distributed feedback grating to form positive feedback, thereby generating lasing light. The grating layer 916 includes a distributed feedback grating or a Bragg grating. The grating layer 916 is usually arranged on the surface of the waveguide layer, and the gain light is feedback coupled in the grating layer 916. Since only the light satisfying the Bragg condition can form stable oscillation, the Bragg grating has good frequency selection characteristics.

[0124] The waveguide layer 917 can be an InP waveguide layer, which is arranged in a ridge waveguide structure, and the grating layer 916 is arranged on the bottom surface of the waveguide layer 917. The waveguide layer 917 includes a ridge structure 900a and first and second ridge grooves 900a1 and 900a2 arranged on two sides of the ridge structure 900a. The ridge structure 900a protrudes relative to the first and second ridge grooves 900a1 and 900a2.

[0125] The first and second ridge grooves 900a1 and 900a2 are formed by etching downward to a certain depth. In the present disclosure, the etching depth of the first and second ridge grooves 900a1 and 900a2 corresponding to the light emitting region 910 is the depth H1 indicated in FIG. 10.

[0126] The etching depth of the first and second ridge grooves 900a1 and 900a2 does not exceed the depth of the active layer 914. The deepest etching of the first and second ridge grooves 900a1 and 900a2 is located above the active layer 914. The active layer 914 is completely arranged below the first and second ridge grooves 900a1 and 900a2, that is, the active layer 914 has a preset distance from the first and second ridge grooves 900a1 and 900a2. Therefore, the active layer 914 is protected and isolated from the air, thereby avoiding the problem of oxidation failure of the Al-containing quantum well directly exposed to the air. It can be seen that, in the present disclosure, the waveguide layer 917 of the light emitting region adopts a shallow etching ridge waveguide structure.

[0127] A passivation layer 918 is grown above the waveguide layer 917. The passivation layer 918 is made of SiO2, and functions to prevent oxidation and water, thereby protecting the laser chip 900.

[0128] FIG. 11 is a schematic diagram of a cross-sectional structure of a laser chip according to some embodiments of the present disclosure. FIG. 11 is a cross-sectional structure diagram of the laser chip 900 corresponding to a position of a shallow ridge 931 in the transition region 930 along the light field transmission direction. As shown in FIG. 11, in some embodiments, the laser chip 900 from bottom to top at the position of the shallow ridge 931 in the transition region 930 includes:

[0129] a first electrode layer 9311;

[0130] a substrate 9312;

[0131] an active layer 9313;

[0132] a waveguide layer 9314, i.e., the layer where the ridge structure 900a is located;

[0133] a passivation layer 9315.

[0134] In some embodiments, the shallow ridge 931 can adopt a shallow etched ridge waveguide structure to maintain continuity with the light emitting region 910 in etching depth.

[0135] FIG. 12 is a schematic diagram of a cross-sectional structure of a laser chip according to some embodiments of the present disclosure. FIG. 12 is a cross-sectional structure diagram of the laser chip 900 corresponding to a position of a deep ridge 932 in the transition region 930 along the light field transmission direction. As shown in FIG. 12, in some embodiments, the laser chip 900 from bottom to top at the position of the deep ridge 932 in the transition region 930 includes:

[0136] a first electrode layer 9321;

[0137] a substrate 9322;

[0138] an active layer 9323;

[0139] a waveguide layer 9324, i.e., the layer where the ridge structure 900a is located;

[0140] a passivation layer 9325.

[0141] In some embodiments, the surface height of the gradual change region 935 is lower than the surface height of the first ridge groove 900a1. When the light field is transmitted to the deep ridge 932, the medium in the gradual change region 935 is air, and the medium on both sides of the gradual change region 935 is semiconductor material, so at this time the light field mode spot is transmitted along the semiconductor region with a larger refractive index.

[0142] In the direction of the shallow ridge portion 931 pointing to the deep ridge portion 932, the sidewall in the gradual change portion 935 close to the ridge structure 900a gradually approaches the ridge structure 900a. Then the semiconductor region width surrounded by the sidewall and the ridge structure 900a gradually decreases, and the light field mode spot emitted by the light emitting region 910 gradually decreases, so that the light field transmitted in the semiconductor region on both sides of the ridge structure 900a is gradually squeezed into the ridge structure 900a, realizing the smooth transition of the light field mode between the light emitting region 910 and the electro-absorption modulation region 920.

[0143] FIG. 13 is a schematic diagram of a cross-sectional structure of a laser chip according to some embodiments of the present disclosure. FIG. 13 is a cross-sectional structure diagram of the laser chip 900 corresponding to the position of the electro-absorption modulation region 920 in the direction of light field transmission. As shown in FIG. 13, in some embodiments, at the position of the electro-absorption modulation region 920, the laser chip 900 includes, from bottom to top:

[0144] a first electrode layer 921;

[0145] a substrate 922;

[0146] an active layer 923;

[0147] a waveguide layer 924, that is, the layer where the ridge structure 900a is located;

[0148] a passivation layer 925;

[0149] a modulation electrode 926.

[0150] In some embodiments, the first electrode layer 921 can be an N-type electrode layer. The modulation electrode 926 can be a P-type electrode layer. Through the first electrode layer 921 and the modulation electrode 926, a reverse bias voltage and a modulation current signal can be input to the active layer 923, and the light emitted by the light emitting region 910 has parameters such as phase, intensity, and frequency. Under the action of the reverse bias voltage, one of these parameters changes with the law of the modulation current signal, so that this parameter is modulated, such as intensity modulation, and finally the light emitted by the light emitting region 910 without carrying a signal is modulated into an optical modulation signal.

[0151] In some embodiments, when the first ridge groove 900a1 and the second ridge groove 900a2 on both sides of the ridge structure 900a have a large etching depth, the effective refractive index difference provided by the ridge is larger, so that the light can be better confined in the center of the waveguide, and the power loss is reduced. For example, the etching depth of the first ridge groove 900a1 and the second ridge groove 900a2 corresponding to the electro-absorption modulation region 920 is H2 indicated in FIG. 13.

[0152] In some embodiments, the modulating current signal is injected through the pad region 9263 of the modulating electrode 926, and then through the connecting region 9262 and the electrode region 9261, and thus into the corresponding ridge structure 900a of the electro-absorption modulation region 920, to modulate the light generated by the light emitting region 910. A portion of the modulating current signal injected into the electro-absorption modulation region 920 is lost through the parasitic network, thus limiting the further increase of the modulation bandwidth and affecting the modulation bandwidth. The parasitic network includes parasitic capacitance.

[0153] In some embodiments, the modulating electrode 926 covers the first ridge trench 900a1.

[0154] In some embodiments, when the ridge structure 900a and the first ridge trench 900a1 and the second ridge trench 900a2 on both sides are fabricated by photolithography, the alignment tolerance required for overlaying during the fabrication of the modulating electrode 926 causes the width of the electrode region 9261 to exceed the ridge structure 900a and cover a portion of the surface of the second ridge trench 900a2.

[0155] The covering of the modulating electrode 926 along the ridge structure 900a on both sides introduces a large parasitic capacitance, thus affecting the modulation bandwidth of the laser chip 900.

[0156] FIG. 14 is a structural schematic diagram III of a laser chip according to some embodiments of the present disclosure, and FIG. 15 is an exploded schematic diagram II of a laser chip according to some embodiments of the present disclosure. As shown in FIG. 14 and FIG. 15, in some embodiments, the first ridge trench 900a1 in the electro-absorption modulation region 920 is filled with a first filling medium 940, and the second ridge trench 900a2 is filled with a second filling medium 950. The first filling medium 940 and the second filling medium 950 are respectively located on both sides of the ridge structure 900a.

[0157] In some embodiments, the first filling medium 940 and the second filling medium 950 are both low dielectric constant mediums. The first filling medium 940 and the second filling medium 950 have a small dielectric constant and low dielectric loss.

[0158] In some embodiments, the dielectric constant of the first filling medium 940 and the second filling medium 950 is lower than that of the substrate 912 or the substrate 922. Exemplarily, the substrate 912 and the substrate 922 are the same substrate.

[0159] When the first ridge trench 900a1 and the second ridge trench 900a2 on both sides of the ridge structure 900a are filled with low dielectric constant mediums, the introduced parasitic capacitance is reduced, the dielectric loss is reduced, and thus the influence of the parasitic parameters on the modulation bandwidth of the laser chip 900 is reduced, and the modulation bandwidth is improved.

[0160] In some embodiments, the first filling medium 940 and the second filling medium 950 can be the same low dielectric constant medium or different low dielectric constant mediums.

[0161] Exemplarily, the low dielectric constant medium can be polyimide (PI). PI refers to a kind of high molecular material containing imide ring in the main chain. PI has stable imide ring in the main chain, and most of them are aromatic polymers, thereby having aromatic heterocyclic conjugation effect. In addition, the charge transfer complex is easily formed in the molecular chain and between the molecular chains of polyimide due to charge transfer. These structures make it have excellent dielectric properties and lower dielectric constant.

[0162] Exemplarily, the low dielectric constant medium can be polybenzoxazole (PBO). Compared with PI, PBO has a lower dielectric constant because there is no carbonyl group in the main chain of PBO.

[0163] In some embodiments, the surface of the first filling medium 940 and the surface of the second filling medium 950 are respectively higher than the surface of the ridge structure 900a.

[0164] In some embodiments, the first filling medium 940 extends upward from the first ridge groove 900a1 to the surface of the laser chip to support the modulation electrode 926. That is, the first filling medium 940 is under the modulation electrode 926.

[0165] In some embodiments, the first filling medium 940 includes a first connecting part 941 and a second connecting part 942. Exemplarily, the second connecting part 942 is arranged above the first connecting part 941.

[0166] In some embodiments, the first connecting part 941 is embedded in the first ridge groove 900a1.

[0167] The second connecting part 942 is located outside the first ridge groove 900a1 and is arranged below the pad area 9263. The second connecting part 942 is located between the pad area 9263 and the surface of the laser chip 900.

[0168] Exemplarily, the first connecting part 941 extends along the bottom end of the first ridge groove 900a1 towards the top end; and the second connecting part 942 extends along the ridge structure 900a towards an edge of the laser chip.

[0169] In some embodiments, one end of the second connecting part 942 is arranged on the surface of the first connecting part 941, and the other end is arranged on the surface of the laser chip 900.

[0170] In some embodiments, the electrode region 9261 of the modulation electrode 926 is disposed on the surface of the ridge structure 900a, the pad region 9263 is disposed on the surface of the second connecting portion 942, and the connecting region 9262 is disposed on the side of the second connecting portion 942. The second connecting portion 942 is disposed between the pad region 9263 and the surface of the laser chip 900.

[0171] In some embodiments, the side of the second connecting portion 942 for supporting the connecting region 9262 is arc-shaped.

[0172] In some embodiments, the second filling medium 950 extends upward from the second ridge groove 900a2 to the surface of the laser chip 900.

[0173] In some embodiments, the second filling medium 950 includes a fourth connecting portion 951 and a fifth connecting portion 952 connected to each other. The fourth connecting portion 951 is disposed inside the second ridge groove 900a2, and the fifth connecting portion 952 is disposed outside the second ridge groove 900a2.

[0174] In some embodiments, the fourth connecting portion 951 extends from the bottom end of the first ridge groove 900a1 to the top end of the first ridge groove 900a1, and the fifth connecting portion 952 extends from the ridge structure 900a to the other edge of the chip.

[0175] In some embodiments, one end of the fifth connecting portion 952 is connected to the surface of the fourth connecting portion 951, and the other end is disposed on the surface of the laser chip 900.

[0176] In some embodiments, the second connecting portion 942 has a gap from the edge of the laser chip 900. Since the edge of the chip needs to be scribed, the filling medium is amorphous, which will affect the scribing effect, and therefore the second connecting portion 942 does not extend to the edge of the laser chip 900. Similarly, the fifth connecting portion 952 also has a gap from the edge of the laser chip 900.

[0177] In some embodiments, the second connecting portion 942 extends to the edge of the chip with a length greater than the fifth connecting portion 952 extending to the other edge of the chip. The larger area of the second connecting portion 942 can better support the modulation electrode 926. The size of the laser chip 900 is limited, and therefore the fifth connecting portion 952 has a smaller extension length than the second connecting portion 942.

[0178] In some embodiments, the surfaces of the first connecting portion 941 and the fourth connecting portion 951 are higher than the surface of the ridge structure 900a. That is, the first connecting portion 941 and the fourth connecting portion 951 have a certain thickness.

[0179] The parasitic capacitance is related to the epitaxial structure parameters, such as the distance between the upper and lower electrodes. When the first filling medium 940 and the second filling medium 950 have a certain thickness, the larger the thickness, the parasitic capacitance can be further reduced, and the modulation bandwidth can be improved.

[0180] In some embodiments, when the laser chip 900 is grabbed by the chip suction device, in order to avoid damage to the laser chip 900 by the suction nozzle, the surface of the laser chip 900 is provided with respective protrusions protruding relative to the surface of the laser chip 900. The suction nozzle acts on the surface of the protrusion, thereby grabbing the surface of the laser chip 900, so as to avoid damage to the laser chip 900. The protrusion surface can be the highest point of the laser chip 900, and the thickness of the first connecting portion 941 and the fourth connecting portion 951 should ensure that the surface of the modulation electrode 926 is lower than the height of the protrusion surface, that is, cannot exceed the height of the highest point of the laser chip 900.

[0181] FIG. 16 is an exploded schematic view III of a laser chip according to some embodiments of the present disclosure. As shown in FIG. 16, in some embodiments, the ridge trenches corresponding to the light emitting region 910 and the electro-absorption modulation region 920 in the laser chip 900 are arranged in a stepped manner.

[0182] In some embodiments, in order to facilitate distinction and description, the two ridge trenches on both sides of the ridge structure in the electro-absorption modulation region 920 are described as a first ridge trench 961 and a second ridge trench 962. The two ridge trenches in the light emitting region 910 are described as a third ridge trench 963 and a fourth ridge trench 964.

[0183] In some embodiments, the first filling medium 940 includes a first connecting portion 941, a second connecting portion 942, and a third connecting portion 943.

[0184] In some embodiments, the third connecting portion 943 is arranged in the space formed by the first connecting portion 941 and the second connecting portion 942.

[0185] In some embodiments, the first connecting portion 941 is located inside the first ridge trench 961.

[0186] The third connecting portion 943 is located on one side of the first connecting portion 941 and below the pad region 9263.

[0187] The second connecting portion 942 is located above the first connecting portion 941 and the third connecting portion 943.

[0188] The arrangement of the third connecting portion 943 can increase the thickness of the first filling medium 940 between the pad region 9263 and the surface of the laser chip, further reduce the parasitic capacitance, and improve the modulation bandwidth.

[0189] In some embodiments, the second filling medium 950 includes a fourth connecting portion 951, a fifth connecting portion 952, and a sixth connecting portion 953.

[0190] In some embodiments, the sixth connecting portion 953 is arranged in a space formed by the fourth connecting portion 951 and the fifth connecting portion 952.

[0191] In some embodiments, the fourth connecting portion 951 is located inside the second ridge groove 962.

[0192] The sixth connecting portion 953 is located on one side of the fourth connecting portion 951.

[0193] The fifth connecting portion 952 is located above the fourth connecting portion 951 and the sixth connecting portion 953.

[0194] The arrangement of the sixth connecting portion 953 can increase the thickness of the first filling medium 940, further reduce the parasitic capacitance, and improve the modulation bandwidth.

[0195] In some embodiments, in order to prevent the surface of the first filling medium 940 from exceeding the highest point of the laser chip 900, i.e., the convex surface of the laser chip 900 arranged to prevent suction nozzle damage to the chip, the first ridge groove 961 is arranged in a sunken manner relative to the third ridge groove 963. Similarly, the second ridge groove 962 is arranged in a sunken manner relative to the fourth ridge groove 964.

[0196] In some embodiments, the first ridge groove 961 includes a first sunken portion 9611 and a second sunken portion 9612.

[0197] The first sunken portion 9611 is used for embedding the first connecting portion 941; and the second sunken portion 9612 is used for embedding the third connecting portion 943.

[0198] In some embodiments, the second ridge groove 962 includes a third sunken portion 9621 and a fourth sunken portion 9622.

[0199] The third sunken portion 9621 is used for embedding the fourth connecting portion 951; and the fourth sunken portion 9622 is used for embedding the sixth connecting portion 953.

[0200] In some embodiments, the first sunken portion 9611 is arranged on one side of the ridge structure 900a, and the second sunken portion 9612 extends along the sidewall of the first sunken portion 9611 towards an edge of the laser chip 900.

[0201] In some embodiments, the width of the first sunken portion 9611 is the same as the width of the third ridge groove 963. The second sunken portion 9612 is formed by extending along the sidewall of the first sunken portion 9611 towards an edge of the chip.

[0202] In some embodiments, the first sunken portion 9611 is sunken relative to the surface of the third ridge groove 963 to sink the first connecting portion 941, further increase the depth of the first connecting portion 941 extending downward, further reduce the parasitic capacitance, and improve the modulation bandwidth. Exemplarily, a step is formed between the first sunken portion 9611 and the third ridge groove 963.

[0203] In some embodiments, the second sunken portion 9612 is sunken relative to the surface of the third ridge groove 963 to sink the third connecting portion 943, increase the thickness of the first filling medium 940 between the pad area 9263 and the surface of the laser chip, further reduce the parasitic capacitance, and improve the modulation bandwidth.

[0204] The arrangement of the first sunken portion 9611 and the second sunken portion 9612 can ensure that the surface of the modulation electrode 926 does not exceed the highest point of the laser chip 900, further increase the thickness of the first filling medium 940, further reduce the parasitic capacitance, and improve the modulation bandwidth. The highest point of the chip refers to the position of the aforementioned convex surface for preventing damage to the chip by the suction nozzle.

[0205] In some embodiments, the third sunken portion 9621 is arranged on the other side of the ridge structure 900a, and the fourth sunken portion 9622 extends along the sidewall of the third sunken portion 9621 towards the other edge of the laser chip 900.

[0206] In some embodiments, the third sunken portion 9621 has the same width as the fourth ridge groove 964, and the fourth sunken portion 9622 is formed by extending along the sidewall of the third sunken portion 9621 towards the other edge of the chip.

[0207] The third sunken portion 9621 is sunken relative to the surface of the fourth ridge groove 964 to sink the fourth connecting portion 951, further increase the depth of the fourth connecting portion 951 extending downward, further reduce the parasitic capacitance, and improve the modulation bandwidth. Exemplarily, a step is formed between the third sunken portion 9621 and the fourth ridge groove 964.

[0208] The fourth sunken portion 9622 is sunken relative to the surface of the fourth ridge groove 964 to sink the sixth connecting portion 953, further increase the thickness of the second filling medium 950, further reduce the parasitic capacitance, and improve the modulation bandwidth.

[0209] The arrangement of the third sunken portion 9621 and the fourth sunken portion 9622 can increase the thickness of the second filling medium 950. The highest point of the chip refers to the position of the aforementioned convex surface.

[0210] In some embodiments, the second sunken portion 9612 extends towards the edge of the chip with a length greater than the fourth sunken portion 9622 extending towards the other edge of the chip, to match the size relationship between the second connecting portion 942 and the fifth connecting portion 952.

[0211] FIG. 17 is a schematic diagram of a side structure of a laser chip according to some embodiments of the present disclosure. As shown in FIG. 17, in some embodiments, in the electro-absorption modulation region 920, the first ridge groove 961 and the second ridge groove 962 are respectively filled with the first filling medium 940 and the second filling medium 950.

[0212] In some embodiments, the first filling medium 940 is spaced apart from the light emitting region 910 to avoid affecting the heat dissipation of the light emitting region 910. For example, the first connecting portion 941 is spaced apart from the sidewall of the third ridge groove 963.

[0213] In some embodiments, the second filling medium 950 is spaced apart from the light emitting region 910 to avoid affecting the heat dissipation of the light emitting region 910. For example, the fourth connecting portion 951 is spaced apart from the sidewall of the fourth ridge groove 964.

[0214] Based on the laser chip provided in the above embodiments, the present disclosure provides a preparation method of a laser chip for preparing the laser chip. FIG. 18 is a flowchart of a preparation method of a laser chip according to some embodiments of the present disclosure. FIG. 18 shows the cross-sectional structure corresponding to each step in the preparation of the laser chip. The left side of the dashed line is the light emitting region 910, and the right side is the electro-absorption modulation region 920. The present disclosure provides a preparation method of a laser chip, which comprises:

[0215] S110: epitaxially growing a first electrode layer, a substrate, and an active layer of the laser chip in sequence. The laser chip comprises a light emitting region and an electro-absorption modulation region along the light field transmission direction.

[0216] In some embodiments, the first electrode layer, the substrate, and the active layer of the light emitting region and the electro-absorption modulation region are epitaxially grown in sequence.

[0217] In some embodiments, at the position of the light emitting region 910, the laser chip 900 comprises, from bottom to top, a first electrode layer 911, a substrate 912, a lower limiting layer 913, and an active layer 914. For example, the substrate 912 is an InP substrate.

[0218] In some embodiments, at the position of the electro-absorption modulation region 920, the laser chip 900 comprises, from bottom to top, a first electrode layer 921, a substrate 9222, and an active layer 923. For example, the substrate 9222 is an InP substrate.

[0219] It can be understood that the first electrode layer 911 and the first electrode layer 921 are actually the same layer, which are only divided according to the light emitting region 910 and the electro-absorption modulation region 920.

[0220] It can be understood that the active layer 914 and the active layer 923 are actually the same layer, which is only divided into two parts according to the light emitting area 910 and the electro-absorption modulation area 920.

[0221] S120: growing an InP epitaxial area along the surface of the active layer.

[0222] In some embodiments, the InP epitaxial area is a precursor material of the etched waveguide layer.

[0223] S130: shallow etching the InP epitaxial area corresponding to the light emitting area to form a ridge waveguide layer of the light emitting area; deep etching the InP epitaxial area corresponding to the electro-absorption modulation area to form a ridge waveguide layer of the electro-absorption modulation area.

[0224] In some embodiments, the laser chip 900 from bottom to top at the position of the light emitting area 910 includes: a first electrode layer 911, a substrate 912, a lower limiting layer 913, an active layer 914, an upper limiting layer 915, a grating layer 916, and a waveguide layer 917.

[0225] In some embodiments, in the light emitting area 910, the upper limiting layer 915 and the grating layer 916 are grown along the surface of the active layer 914, respectively, and then shallow etching is performed to form the waveguide layer 917 of the light emitting area.

[0226] In some embodiments, in the electro-absorption modulation area 920, the waveguide layer 924 is grown along the surface of the active layer 923.

[0227] In some embodiments, the waveguide layer 917 of the light emitting area 910 adopts a shallow etching ridge waveguide structure to protect the integrity of the active layer of the light emitting area 910. The waveguide layer 917 of the light emitting area 910 is a ridge waveguide layer.

[0228] In some embodiments, the waveguide layer 924 of the electro-absorption modulation area 920 adopts a deep etching ridge waveguide structure to improve the modulation rate and modulation efficiency. The waveguide layer 924 of the electro-absorption modulation area 920 is a ridge waveguide layer.

[0229] In some embodiments, the waveguide layer of the light emitting area 910 includes: a ridge structure 900a, a third ridge groove 963 and a fourth ridge groove 964 located on both sides of the ridge structure 900a.

[0230] In some embodiments, the waveguide layer of the electro-absorption modulation area 920 includes: a ridge structure 900a, a first ridge groove 961 and a second ridge groove 962 located on both sides of the ridge structure 900a.

[0231] S140: depositing a dielectric film along the ridge waveguide layer of the electro-absorption modulation area.

[0232] In some embodiments, after the ridge waveguide etching is completed, a dielectric film is formed on the surface of the substrate. Exemplarily, the dielectric film is SiO2.

[0233] In order to increase the adhesion of the low dielectric constant medium to be filled later on the InP substrate, a dielectric layer can be grown between the low dielectric constant medium and the InP substrate.

[0234] S150: The dielectric film on the surface of the ridge structure of the electro-absorption modulation region is etched away by lithography.

[0235] Lithography refers to a process of transferring a pattern on a mask to a substrate by using photochemical reaction principles.

[0236] In some embodiments, the lithography process includes uniform coating of photoresist, exposure, development, etching, etc.

[0237] Photoresist refers to a thin film material that, after irradiation by light of a certain wavelength, undergoes a photochemical reaction in the exposed area, so that its solubility in the developing solution changes. Photoresist has photochemical sensitivity, and after processes such as spin coating, pre-baking, exposure, and development, the pattern on the mask is transferred to the substrate to obtain the desired circuit pattern.

[0238] According to the change in solubility before and after exposure, photoresist is divided into positive photoresist and negative photoresist. Among them, the solubility of positive photoresist in the developing solution increases after exposure and is dissolved away, and the non-exposed area left after development is the pattern to be drawn. The solubility of negative photoresist in the developing solution decreases after exposure and remains on the substrate, and the non-exposed area can be dissolved in the developing solution, and the obtained pattern is complementary to the pattern on the mask.

[0239] In some embodiments, after the substrate dielectric film, the dielectric film on the surface of the ridge structure of the electro-absorption modulation region is etched away by spin coating photoresist and using underexposure, that is, opening the electrical injection window.

[0240] S160: Uniformly coat a low dielectric constant medium along the current surface of the laser chip, so that the low dielectric constant medium fills in the first ridge groove 961 and the second ridge groove 962 and extends along the surface of the laser chip.

[0241] In some embodiments, when filling the low dielectric constant medium in the first ridge groove 900a1 and the second ridge groove 900a2 on both sides of the ridge structure 900a, the introduced parasitic capacitance is reduced, the dielectric loss is reduced, and thus the influence of the parasitic parameters on the modulation bandwidth of the laser chip 900 is reduced, and the modulation bandwidth is improved.

[0242] In some embodiments, the low dielectric constant medium can be spin-coated along the current surface of the laser chip.

[0243] Exemplarily, the low dielectric constant medium can be polyimide (PI). PI has excellent dielectric properties and has a lower dielectric constant.

[0244] Exemplarily, the low dielectric constant medium can be polybenzoxazole (PBO). Compared with PI, PBO has a lower dielectric constant because there is no carbonyl group on the PBO main chain.

[0245] S170: By twice photolithography, the low dielectric constant medium on the surface of the laser chip and the low dielectric constant medium on both sides of the ridge structure are etched away respectively to respectively achieve that the low dielectric constant material after etching has a preset distance to the chip edge and the surface of the ridge structure is exposed.

[0246] In some embodiments, because the chip edge needs to be scribed, the filling medium is amorphous, which will affect the scribing effect, so the low dielectric constant medium has a preset distance to the chip edge. Exemplarily, part of the low dielectric constant medium can be removed by once photolithography to achieve the above effect.

[0247] In some embodiments, the low dielectric constant medium on both sides of the ridge structure in a certain height can be removed by re-photolithography, so that the surface on both sides of the ridge structure is exposed to facilitate the growth of the subsequent modulation electrode 926. Exemplarily, the electrode area 9261 in the modulation electrode 926 is electrically connected with the surface of the ridge structure.

[0248] By photolithography on both sides, the low dielectric constant medium on the position where the low dielectric constant medium is not needed is removed, and the ridge waveguide is exposed at the same time.

[0249] In some embodiments, the light-sensitive low dielectric constant medium can be used as a photoresist. Therefore, the present disclosure selects a light-sensitive low dielectric constant medium, such as light-sensitive PBO. In step S160, the low dielectric constant medium with light sensitivity is uniformly coated along the current surface of the laser chip, so that no additional photoresist needs to be uniformly coated in the photolithography process, simplifying the photolithography process.

[0250] In some embodiments, when the low dielectric constant medium with light sensitivity is filled, it can not only play the role of photoresist, but also can reduce the introduced parasitic capacitance, reduce dielectric loss, and thus reduce the influence of parasitic parameters on the modulation bandwidth of the laser chip 900, and improve the modulation bandwidth.

[0251] Exemplarily, the light-sensitive PBO is a positive photoresist.

[0252] S180: The current low dielectric constant medium is heated and reflowed to supplement the low dielectric constant medium on both sides of the ridge structure upwards until the first filling medium and the second filling medium located on both sides of the ridge structure are obtained.

[0253] In some embodiments, the sidewall of the low dielectric constant medium on both sides of the ridge structure after developing in step S170 is steep, which is not conducive to the electrical connection of the modulation electrode 926 on the sidewall. For example, when the connection area 9262 of the modulation electrode 926 overlaps on the steep sidewall, the transmission of high-frequency signals is not conducive. At the same time, when the sidewall is steep, stress accumulation of the medium film is prone to occur.

[0254] In some embodiments, the current low dielectric constant medium is heated and reflowed. When the low dielectric constant medium is heated and reflowed, the low dielectric constant medium on both sides of the ridge structure is thin and is replenished after reflowing, so that the sidewall of the first filling medium and the second filling medium is gentle, the stress accumulation of the medium film on the sidewall is reduced, and the high-frequency signal transmission performance of the modulation electrode 926 is increased. At the same time, the low dielectric constant medium can be filled higher by reflowing, further reducing dielectric loss and reducing the introduced parasitic capacitance.

[0255] In some embodiments, after reflowing, solidification is performed. After solidification, the following preparation process can be performed. For example, after solidification, the modulation electrode 926 is prepared. In some embodiments, while the modulation electrode 926 is prepared, the light-emitting electrode 919 of the light-emitting region 910 can also be prepared.

[0256] In the laser chip preparation method provided by the embodiments of the present disclosure, the low dielectric constant medium is heated and reflowed before the filling medium is solidified. When the low dielectric constant medium is heated and reflowed, the low dielectric constant medium on both sides of the ridge structure is thin and is replenished after reflowing, so that the sidewall of the first filling medium and the second filling medium is gentle, the stress accumulation of the medium film on the sidewall is reduced, and the high-frequency signal transmission performance of the modulation electrode 926 is increased. At the same time, the low dielectric constant medium can be filled higher by reflowing, further reducing dielectric loss and reducing the introduced parasitic capacitance.

[0257] The above merely provides a specific implementation of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art can think of changes or replacements within the technical range disclosed by the present disclosure, which should be covered by the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.

Claims

1. A laser chip, comprising: a light emitting region configured to generate light; an electro-absorption modulation region configured to modulate the light generated by the light emitting region, the electro-absorption modulation region comprising: a substrate; an active layer configured to modulate the light generated by the light emitting region according to a modulation current signal; a waveguide layer, the waveguide layer comprising a ridge structure, a first ridge trench and a second ridge trench located on both sides of the ridge structure; a first filling medium having a dielectric constant lower than that of the substrate, the first filling medium comprising a first connecting portion and a second connecting portion, the first connecting portion being embedded in the first ridge trench, and the second connecting portion having one end on the surface of the first connecting portion and the other end on the surface of the laser chip; a second filling medium having a dielectric constant lower than that of the substrate, the second filling medium comprising a fourth connecting portion and a fifth connecting portion, the fourth connecting portion being embedded in the second ridge trench, and the fifth connecting portion having one end on the surface of the fourth connecting portion and the other end on the surface of the laser chip; a modulation electrode having one end on the surface of the ridge structure and the other end on the surface of the second connecting portion, and configured to transmit the modulation current signal to the active layer.

2. The laser chip of claim 1, wherein, the light emitting region comprises a waveguide layer, the waveguide layer comprising a ridge structure, a third ridge trench and a fourth ridge trench located on both sides of the ridge structure; the first filling medium comprises a third connecting portion, the third connecting portion being located in a space formed by the first connecting portion and the second connecting portion; the first ridge trench comprises a first sunken portion and a second sunken portion, the surfaces of the first sunken portion and the second sunken portion are lower than the surface of the third ridge trench; the first sunken portion is configured to embed the first connecting portion, and the second sunken portion is configured to embed the third connecting portion.

3. The laser chip of claim 1, wherein, the light emitting region comprises a waveguide layer, the waveguide layer comprising a ridge structure, a third ridge trench and a fourth ridge trench located on both sides of the ridge structure; the second filling medium comprises a sixth connecting portion, the sixth connecting portion being located in a space formed by the fourth connecting portion and the fifth connecting portion; the second ridge trench comprises a third sunken portion and a fourth sunken portion, the surfaces of the third sunken portion and the fourth sunken portion are lower than the surface of the fourth ridge trench; the third sunken portion is configured to embed the fourth connecting portion, and the fourth sunken portion is configured to embed the sixth connecting portion.

4. The laser chip of claim 1, wherein, the first filling medium has a spacing from the light emitting region, and the second filling medium has a spacing from the light emitting region.

5. The laser chip of claim 1, wherein, the modulation electrode comprises an electrode region, a pad region, and a connecting region connecting the electrode region and the pad region; the electrode region is located on the surface of the ridge structure; the pad region is located on the surface of the second connecting portion; the connecting region is located on the sidewall of the first filling medium. 6.A method for manufacturing a laser chip, comprising: sequentially epitaxially growing a first electrode layer, a substrate layer, and an active layer of the laser chip, wherein the laser chip comprises a light emitting region and an electro-absorption modulation region along an optical field transmission direction; growing an InP epitaxial region along the surface of the active layer; The InP epitaxial region corresponding to the light emitting region is shallowly etched to form a ridge waveguide layer of the light emitting region; the InP epitaxial region corresponding to the electro-absorption modulation region is deeply etched to form a ridge waveguide layer of the electro-absorption modulation region; the ridge waveguide layer comprises a ridge structure, a first ridge groove and a second ridge groove arranged on both sides of the ridge structure; A dielectric film is deposited along the ridge waveguide layer of the electro-absorption modulation region; The dielectric film on the surface of the ridge structure of the electro-absorption modulation region is etched by lithography; A low dielectric constant medium is uniformly coated along the current surface of the laser chip, so that the low dielectric constant medium fills the first ridge groove and the second ridge groove corresponding to the electro-absorption modulation region, and the low dielectric constant medium is uniformly coated along the surface of the laser chip; By twice lithography, part of the low dielectric constant medium on the surface of the laser chip and the low dielectric constant medium on both sides of the ridge structure are etched to respectively achieve that the low dielectric constant medium after etching has a preset distance to the edge of the chip and the surface of the ridge structure is exposed; The current low dielectric constant medium is heated and reflowed to supplement the low dielectric constant medium on both sides of the ridge structure upwards until the first filling medium and the second filling medium on both sides of the ridge structure are obtained.

7. The method of fabricating a laser chip according to claim 6, wherein After the first filling medium and the second filling medium are obtained, a modulation electrode is formed on the surface of the first filling medium, wherein the modulation electrode comprises an electrode region, a pad region and a connection region connecting the electrode region and the pad region; the electrode region is arranged on the surface of the ridge structure; the pad region is arranged on the surface of the first filling medium; and the connection region is arranged on the sidewall of the first filling medium.

8. The method of fabricating a laser chip according to claim 6, wherein, The first filling medium has a gap to one edge of the laser chip, and the second filling medium has a gap to the other edge of the laser chip.

9. The method of fabricating a laser chip according to claim 6, wherein, The first filling medium has a spacing from the light emitting region, and the second filling medium has a spacing from the light emitting region.

10. The method of fabricating a laser chip according to claim 6, wherein, The low dielectric constant medium has photosensitivity.

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