A laser and optical module

Abstract

The laser and the optical module provided in the application, the laser comprises a grating waveguide and a filter waveguide. The width of the grating waveguide is greater than the width of a single-mode waveguide. A grating structure is arranged in the grating waveguide. High-order mode light waves and base mode light waves are generated in the grating waveguide. Compared with the single-mode waveguide, the grating waveguide increases the charge-carrying area, so that the current density is reduced, and the reliability of the laser is improved. One end of the filter waveguide is provided with a high-reflection film, and the other end is connected with the grating waveguide. The filter waveguide comprises a filter straight waveguide and a filter tapered waveguide. The width of the filter straight waveguide is less than or equal to the width of the single-mode waveguide, and the one end of the filter straight waveguide is provided with the high-reflection film. The width of the grating waveguide is greater than the width of the single-mode waveguide, which leads to the formation of high-order mode light waves. The filter straight waveguide makes the transmittance of the high-order mode light waves lower than a preset value. The high-order mode light waves are lost in the filter straight waveguide, so that the far field of the light emitted by the laser is consistent, and the optical coupling efficiency is improved.

Description

Technical Field

[0001] This application relates to the field of optical communication technology, and in particular to a laser and an optical module. Background Technology

[0002] Using silicon photonics chips to achieve photoelectric conversion has become a mainstream solution for high-speed optical modules. Since silicon is not an ideal material for laser chips, the light-emitting unit cannot be integrated into the silicon photonics chip manufacturing process. Therefore, silicon photonics chips need to be provided with light by an external light source, usually an external laser.

[0003] High-power distributed feedback Bragg grating lasers for silicon photonics circuits, operating under DC current, generate continuous, strong interference light, providing a light source for subsequent optical signal modulation in silicon waveguides. Currently, the most important market requirement for this type of laser is sufficiently high output power across the entire temperature range. At 85°C, the power of the laser to be driven needs to reach 75mW, 130mW, or even higher, corresponding to higher input currents. Current market demand for this product's input current has reached the 400mA to 600mA range, placing even higher demands on the laser's reliability under such conditions.

[0004] Current technology for feedback Bragg grating lasers mainly involves fabricating devices using indium gallium arsenide phosphide or indium aluminum gallium arsenide material systems. Reducing current density and improving reliability are urgent problems to be solved. Summary of the Invention

[0005] This application provides a laser and an optical module that improves device reliability while reducing laser current density by employing a non-uniform waveguide structure.

[0006] On one hand, this application provides a laser, comprising: a grating waveguide with a width greater than that of a single-mode waveguide, the grating waveguide being used to allow light of a specific wavelength to be amplified and emitted; a grating structure disposed within the grating waveguide; and light generating higher-order mode light waves and a fundamental mode light wave in the grating waveguide.

[0007] A filter waveguide, one end of which is provided with a high-reflectivity film, and the other end is connected to the grating waveguide, wherein the filter waveguide comprises:

[0008] A filtered straight waveguide has a width less than or equal to the width of a single-mode waveguide, and a high-reflectivity film is disposed at one end of the filtered straight waveguide; light passes through the filtered straight waveguide to reach the high-reflectivity film, is reflected by the high-reflectivity film, and then passes through the filtered straight waveguide again, resulting in loss of higher-order mode light waves;

[0009] A filtered tapered waveguide is located between the filtered straight waveguide and the grating waveguide; the width of the filtered tapered waveguide gradually increases along the direction from the filtered straight waveguide to the grating waveguide.

[0010] On the other hand, this application provides a laser, including: an output waveguide, wherein the width of the output waveguide is less than or equal to the width of a single-mode waveguide;

[0011] A grating waveguide, wider than the output waveguide, contains a grating structure. Light is generated in the grating waveguide to produce higher-order mode and fundamental mode light waves.

[0012] A filter waveguide, one end of which is provided with a high-reflectivity film, and the other end is connected to the grating waveguide, wherein the filter waveguide comprises:

[0013] A filtered straight waveguide has a width less than or equal to the width of a single-mode waveguide, and a high-reflectivity film is disposed at one end of the filtered straight waveguide; light passes through the filtered straight waveguide to reach the high-reflectivity film, is reflected by the high-reflectivity film, and then passes through the filtered straight waveguide again, after which the higher-order mode light wave suffers loss;

[0014] A filtered tapered waveguide is located between the filtered straight waveguide and the grating waveguide; the width of the filtered tapered waveguide gradually increases along the direction from the filtered straight waveguide to the grating waveguide.

[0015] The optical module provided in this application includes the aforementioned laser.

[0016] The laser and optical module provided in this application include a grating waveguide and a filter waveguide. The grating waveguide has a width greater than that of a single-mode waveguide; it allows light of a specific wavelength to be amplified and emitted. The wider grating waveguide increases the charge-carrying area compared to a single-mode waveguide, reducing current density and improving laser reliability. A high-reflectivity film is provided at one end of the filter waveguide, and the other end is connected to the grating waveguide. The filter waveguide includes a straight filter waveguide and a graded filter waveguide. The width of the straight filter waveguide is less than or equal to that of the single-mode waveguide, and a high-reflectivity film is provided at one end. The wider grating waveguide leads to the formation of higher-order mode light waves. The straight filter waveguide causes the transmittance of these higher-order mode light waves to be lower than a preset value, resulting in loss of the higher-order mode light waves within the straight filter waveguide. This ensures a consistent far-field output from the laser and improves optical coupling efficiency. The filtered tapered waveguide is located between the filtered straight waveguide and the grating waveguide. Along the direction from the filtered straight waveguide to the grating waveguide, the width of the filtered tapered waveguide gradually increases, thereby increasing the transmittance of single-mode light waves in the filtered tapered waveguide and improving optical coupling efficiency. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this disclosure, the accompanying drawings used in some embodiments of this disclosure will be briefly described below. Obviously, the drawings described below are only drawings of some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings. In addition, the drawings described below can be regarded as schematic diagrams and are not intended to limit the actual size of the product, the actual flow of the method, the actual timing of the signals, etc. involved in the embodiments of this disclosure.

[0018] Figure 1 This is a connection diagram of an optical communication system according to some embodiments;

[0019] Figure 2 This is a structural diagram of an optical network terminal according to some embodiments;

[0020] Figure 3 This is a structural diagram of an optical module according to some embodiments;

[0021] Figure 4 An exploded view of an optical module according to some embodiments;

[0022] Figure 5 This is a structural diagram of a laser according to some embodiments;

[0023] Figure 6 This is a schematic cross-sectional structure of a laser according to some embodiments. Figure 1 ;

[0024] Figure 7 This is a schematic cross-sectional structure of a laser according to some embodiments. Figure 2 ;

[0025] Figure 8 This is a schematic cross-sectional structure of a laser according to some embodiments. Figure 3 ;

[0026] Figure 9 This is a schematic diagram of the active layer structure of a laser according to some embodiments;

[0027] Figure 10 This is a schematic diagram illustrating the existence of waveguide modes under different waveguide width conditions according to some embodiments;

[0028] Figure 11 This is a graph showing the relationship between the transmittance of a higher-order mode and the length of a filtered trapezoidal straight waveguide, according to some embodiments.

[0029] Figure 12 This is a graph showing the relationship between the transmittance of a fundamental mode and the length of a filtered graded waveguide, according to some embodiments. Detailed Implementation

[0030] In optical communication systems, optical signals carry the information to be transmitted and are transmitted through information transmission equipment such as optical fibers or waveguides to information processing equipment such as computers to complete the information transmission. Because light has passive transmission characteristics when transmitted through optical fibers or waveguides, low-cost, low-loss information transmission can be achieved. However, the signals transmitted by information transmission equipment such as optical fibers or waveguides are optical signals, while the signals that information processing equipment such as computers can recognize and process are electrical signals. Therefore, in order to establish an information connection between information transmission equipment such as optical fibers or waveguides and information processing equipment such as computers, it is necessary to achieve mutual conversion between electrical and optical signals.

[0031] In the field of optical communication technology, optical modules realize the mutual conversion function between optical signals and electrical signals. An optical module includes an optical port and an electrical port. The optical port enables optical communication with information transmission devices such as optical fibers or optical waveguides, while the electrical port enables electrical connection with optical network terminals (e.g., optical modems). The electrical connection is mainly used for power supply, I2C signal transmission, data transmission, and grounding. The optical network terminal transmits electrical signals to information processing devices such as computers via network cables or Wi-Fi.

[0032] Figure 1 This is a diagram showing the connection relationships within an optical communication system. (Example:) Figure 1 As shown, the optical communication system includes a remote server 1000, a local information processing device 2000, an optical network terminal 100, an optical module 200, an optical fiber 101, and a network cable 103.

[0033] One end of optical fiber 101 is connected to the remote server 1000, and the other end is connected to the optical network terminal 100 via optical module 200. Optical fiber itself can support long-distance signal transmission, such as signal transmission over several kilometers (6 to 8 kilometers). Theoretically, unlimited distance transmission can be achieved by using repeaters. Therefore, in typical optical communication systems, the distance between the remote server 1000 and the optical network terminal 100 can typically reach several kilometers, tens of kilometers, or hundreds of kilometers.

[0034] One end of the network cable 103 is connected to the local information processing device 2000, and the other end is connected to the optical network terminal 100. The local information processing device 2000 can be any one or more of the following devices: router, switch, computer, mobile phone, tablet computer, television, etc.

[0035] The physical distance between the remote server 1000 and the optical network terminal 100 is greater than the physical distance between the local information processing device 2000 and the optical network terminal 100. The connection between the local information processing device 2000 and the remote server 1000 is completed by optical fiber 101 and network cable 103; while the connection between optical fiber 101 and network cable 103 is completed by optical module 200 and optical network terminal 100.

[0036] The optical module 200 includes an optical port and an electrical port. The optical port is configured to connect to the optical fiber 101, thereby establishing a bidirectional optical signal connection between the optical module 200 and the optical fiber 101. The electrical port is configured to connect to the optical network terminal 100, thereby establishing a bidirectional electrical signal connection between the optical module 200 and the optical network terminal 100. The optical module 200 performs mutual conversion between optical and electrical signals, thereby establishing an information connection between the optical fiber 101 and the optical network terminal 100. For example, the optical signal from the optical fiber 101 is converted into an electrical signal by the optical module 200 and then input to the optical network terminal 100, and the electrical signal from the optical network terminal 100 is converted into an optical signal by the optical module 200 and then input to the optical fiber 101. Since the optical module 200 is a tool for mutual conversion between optical and electrical signals and does not have the function of data processing, the information does not change during the above photoelectric conversion process.

[0037] The optical network terminal 100 includes a generally cuboid housing, and an optical module interface 102 and a network cable interface 104 disposed on the housing. The optical module interface 102 is configured to connect to an optical module 200, thereby establishing a bidirectional electrical signal connection between the optical network terminal 100 and the optical module 200; the network cable interface 104 is configured to connect to a network cable 103, thereby establishing a bidirectional electrical signal connection between the optical network terminal 100 and the network cable 103. The optical module 200 and the network cable 103 are connected through the optical network terminal 100. For example, the optical network terminal 100 transmits electrical signals from the optical module 200 to the network cable 103, and vice versa, thus the optical network terminal 100 acts as a host computer for the optical module 200, monitoring its operation. Besides the optical network terminal 100, the host computer for the optical module 200 may also include an optical line terminal (OLT), etc.

[0038] The remote server 1000 establishes a bidirectional signal transmission channel with the local information processing equipment 2000 through optical fiber 101, optical module 200, optical network terminal 100 and network cable 103.

[0039] Figure 2 This is a structural diagram of an optical network terminal. To clearly show the connection relationship between the optical module 200 and the optical network terminal 100... Figure 2Only the structure of the optical network terminal 100 related to the optical module 200 is shown. For example... Figure 2 As shown, the optical network terminal 100 also includes a circuit board 300 disposed within a housing, a cage 106 disposed on the surface of the circuit board 300, a heat sink 107 disposed on the cage 106, and an electrical connector disposed inside the cage 106. The electrical connector is configured to connect to the electrical port of the optical module 200; the heat sink 107 has protrusions such as fins to increase the heat dissipation area.

[0040] The optical module 200 is inserted into the cage 106 of the optical network terminal 100, where it is secured. Heat generated by the optical module 200 is conducted to the cage 106 and then dissipated through the heat sink 107. After insertion into the cage 106, the optical module 200's electrical port connects to an electrical connector inside the cage 106, establishing a bidirectional electrical signal connection between the optical module 200 and the optical network terminal 100. Furthermore, the optical port of the optical module 200 connects to the optical fiber 101, establishing a bidirectional optical signal connection between the optical module 200 and the optical fiber 101.

[0041] Figure 3 This is a structural diagram of an optical module according to some embodiments; Figure 4 Here is an exploded view of an optical module according to some embodiments; the following is in conjunction with... Figure 3 and Figure 4 The optical module in the optical communication terminal of the foregoing embodiments will be described. For example... Figure 3 , Figure 4 As shown, the optical module 200 provided in this application embodiment includes an upper housing 201, a lower housing 202, an unlocking component 203, an opening 204, an opening 205, a circuit board 300, a silicon photonic chip 400, a light source 500, a first optical fiber ribbon 600, a second optical fiber ribbon 700, and an optical fiber interface 800, wherein the silicon photonic chip 400 and the light source 500 are disposed on the same side surface of the circuit board 300.

[0042] The housing includes an upper housing 201 and a lower housing 202, with the upper housing 201 covering the lower housing 202 to form the aforementioned housing with two openings; the outer contour of the housing is generally square.

[0043] In some embodiments of this disclosure, the lower housing 202 includes a base plate 2021 and two lower side plates 2022 located on both sides of the base plate 2021 and perpendicular to the base plate 2021; the upper housing 201 includes a cover plate 2011, which covers the two lower side plates 2022 of the lower housing 202 to form the aforementioned housing.

[0044] In some embodiments, the lower housing 202 includes a base plate 2021 and two lower side plates 2022 located on both sides of the base plate 2021 and perpendicular to the base plate 2021; the upper housing 201 includes a cover plate 2011 and two upper side plates located on both sides of the cover plate 2011 and perpendicular to the cover plate 2011. The two upper side plates and the two lower side plates 2022 are combined to realize that the upper housing 201 covers the lower housing 202.

[0045] The direction of the line connecting the two openings 204 and 205 can be consistent with or inconsistent with the length direction of the optical module 200. For example, opening 204 is located at the end of the optical module 200. Figure 3 The opening 205 is also located at the end of the optical module 200 (right end). Figure 3 (Left end). Alternatively, opening 204 is located at the end of optical module 200, while opening 205 is located on the side of optical module 200. Opening 204 is an electrical port, through which the gold fingers of circuit board 300 extend and are inserted into a host computer (e.g., optical network terminal 100); opening 205 is an optical port, configured to connect to external optical fiber 101 so that external optical fiber 101 can connect to the optical transceiver assembly inside optical module 200.

[0046] The assembly method using an upper housing 201 and a lower housing 202 facilitates the installation of components such as the circuit board 300 and optical transceiver assemblies into the housing, with the upper housing 201 and lower housing 202 providing encapsulation and protection for these components. Furthermore, the assembly of the circuit board 300 and optical transceiver assemblies facilitates the deployment of positioning components, heat dissipation components, and electromagnetic shielding components, which is beneficial for automated production.

[0047] In some embodiments, the upper housing 201 and the lower housing 202 are generally made of metal materials, which facilitates electromagnetic shielding and heat dissipation.

[0048] In some embodiments, the optical module 200 further includes an unlocking component 203 located outside its housing, the unlocking component 203 being configured to establish a 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.

[0049] For example, the unlocking component 203 is located on the outer wall of the two lower side plates 2022 of the lower housing 202, and has a locking component that matches the host computer cage (e.g., the cage 106 of the optical network terminal 100). When the optical module 200 is inserted into the host computer cage, the locking component of the unlocking component fixes the optical module 200 in the host computer cage; when the unlocking component is pulled, the locking component of the unlocking component moves accordingly, thereby changing the connection relationship between the locking component and the host computer, so as to release the locking relationship between the optical module 200 and the host computer, thereby allowing the optical module 200 to be pulled out of the host computer cage.

[0050] Circuit board 300 includes circuit traces, electronic components, and chips. The circuit traces connect the electronic components and chips according to the circuit design to achieve functions such as power supply, electrical signal transmission, and grounding. Electronic components include, for example, capacitors, resistors, transistors, and metal-oxide-semiconductor field-effect transistors (MOSFETs). Chips include, for example, microcontroller units (MCUs), laser driver chips, limiting amplifiers, clock and data recovery (CDR) chips, power management chips, and digital signal processing (DSP) chips.

[0051] Circuit board 300 is generally a rigid circuit board. Due to its relatively rigid material, the rigid circuit board can also perform a load-bearing function. For example, the rigid circuit board can stably support the aforementioned electronic components and chips. When the optical transceiver assembly is located on the circuit board, the rigid circuit board can also provide stable support. The rigid circuit board can also be inserted into the electrical connector in the host computer cage.

[0052] The circuit board 300 also includes gold fingers formed on its end surfaces, each gold finger consisting of a plurality of independent pins. The circuit board 300 is inserted into a cage 106 and electrically connected to an electrical connector within the cage 106 by the gold fingers. The gold fingers may be located only on one side of the surface of the circuit board 300 (e.g., ...). Figure 4 The gold fingers (shown on the upper surface) can also be placed on the upper and lower surfaces of the circuit board 300 to accommodate applications with a large number of pins. The gold fingers are configured to establish an electrical connection with the host computer to enable power supply, grounding, I2C signal transmission, and data signal transmission.

[0053] Of course, flexible circuit boards are also used in some optical modules. Flexible circuit boards are generally used in conjunction with rigid circuit boards as a supplement to rigid circuit boards. For example, flexible circuit boards can be used to connect rigid circuit boards to optical transceiver components.

[0054] The silicon photonic chip 400 itself has no light source; the light source 500 serves as an external light source for the silicon photonic chip 400. The light source 500 can be a laser box, which encapsulates a laser. The laser emits light to generate a laser beam, and the light source 500 provides the emitted laser to the silicon photonic chip 400. Lasers, with their superior single-wavelength characteristics and excellent wavelength tuning characteristics, are the preferred light source for optical modules and even fiber optic transmission. Other types of light, such as LED light, are generally not used in common optical communication systems. Even if such light sources are used in special optical communication systems, their characteristics and chip components differ significantly from those of lasers. This results in a significant technical difference between optical modules using lasers and those using other light sources. Those skilled in the art generally do not believe that these two types of optical modules can mutually provide technical inspiration.

[0055] Light source 500 emits light from the side, and the emitted light enters the silicon photonics chip 400. The silicon photonics chip uses silicon as its main substrate. However, silicon is not an ideal light-emitting material, and a light source cannot be integrated within the silicon photonics chip 400; therefore, an external light source 500 is required. The light provided by light source 500 to the silicon photonics chip is a single-wavelength, stable-power emitted light that does not carry any data. The silicon photonics chip 400 modulates this emitted light to load data into it.

[0056] The light source 500 provides emitted laser light to the silicon photonic chip 400 through a laser. There are many types of lasers. In recent years, high-power distributed feedback Bragg grating lasers of silicon photonic circuits are commonly used, and the devices are mainly fabricated in the indium gallium arsenide phosphide material system.

[0057] In conventional indium gallium arsenide phosphorus lasers, a phase-shifted silicon grating structure is used to achieve single-wavelength output of the laser, and a waveguide of uniform width is used to couple the laser into the silicon waveguide, providing a specific wavelength light source for devices such as silicon modulators on silicon photonic integrated chips.

[0058] The laser 900 provided in this application features a non-uniform waveguide structure where the width of the grating waveguide is greater than that of the single-mode waveguide, increasing the charge-carrying area and reducing the current density. The filtered straight waveguide improves the loss of higher-order mode optical waves, while the filtered tapered waveguide improves the transmittance of single-mode optical waves. This achieves single-ended, high-power, single-wavelength output of the laser while reducing current density and improving the reliability of the optical module.

[0059] Figure 5 This is a structural diagram of a laser according to some embodiments; such as Figure 5 As shown, the arrow of the dashed line Aa points in the direction of the laser beam output. For ease of description, this application will use... Figure 5 The X direction shown is called the laser length direction; the Y direction is called the laser width direction; and the Z direction is called the laser thickness direction.

[0060] Figure 6 This is a schematic cross-sectional structure of a laser according to some embodiments. Figure 1 . Figure 7 This is a schematic cross-sectional structure of a laser according to some embodiments. Figure 2 . Figure 8 This is a schematic cross-sectional structure of a laser according to some embodiments. Figure 3 .in, Figure 6 for Figure 5 The diagram shows the cross-sectional view of section Aa. Figure 7 for Figure 5 The diagram shows a cross-sectional view of Bb.

[0061] Figure 8 for Figure 5 The diagram shows a cross-sectional view of section Cc. Figure 6 , Figure 7 and Figure 8 As shown, the laser includes, in sequence along its length, a reflection region, an active region, and a light-emitting region. Along its thickness, from bottom to top, it comprises a lower electrode layer 920, a lower substrate layer 960, an active layer 950, a passive waveguide layer 940, an upper substrate layer 930, and an upper electrode layer 910. Along its width, it includes, in sequence, a first protective zone 911, a gain region 912, and a second protective zone 913.

[0062] In some embodiments, the lower electrode layer 920 is an N-type electrode metal layer used to inject N-type carriers into the active region 932; the upper electrode layer 910 is a P-type electrode metal layer used to inject P-type carriers into the active region 932.

[0063] Figure 9 This is a schematic diagram of the active layer structure of a laser according to some embodiments. Figure 9 As shown, the active layer 950 includes a lower confinement layer 953, a quantum well layer 952, and an upper confinement layer 951 arranged sequentially from bottom to top.

[0064] For example, the confinement layer is a split-confinement heterojunction layer with a material thickness of 0.02 micrometers and an optical refractive index of 3.3144. The quantum well layer is a multilayer quantum well layer, whose unfolded layered structure consists of alternating layers of 5 well materials (each 0.0075 micrometers thick, with an optical refractive index of 3.5391) and 6 barrier materials (each 0.01 micrometers thick, with an optical refractive index of 3.3324). The grating layer has a thickness of 0.014 micrometers and an optical refractive index of 3.3832. A passive waveguide layer is provided between the grating and the split-confinement heterojunction layer, with a distance of 0.38 micrometers between the grating and the split-confinement heterojunction layer.

[0065] In some embodiments, the quantum well is made of indium gallium arsenide phosphide and the substrate is made of indium phosphide.

[0066] Figure 7 The middle arrow indicates the direction of the current. When current is injected into the active layer of the active region, it provides energy to excite electrons, resulting in population inversion. This condition allows stimulated emission, where incident photons stimulate stimulated electrons to release more photons of the same wavelength. The photons then enter the passive waveguide layer upwards. The waveguide width mentioned in the embodiments of this application is the width of the gain region. Figure 8 This is a schematic diagram of the passive waveguide layer. Figure 8 As shown, along the light-emitting direction, the passive waveguide layer includes a filter waveguide, a grating waveguide, and a light-emitting waveguide. The width of the grating waveguide is greater than that of the filter waveguide, and the width of the grating waveguide is greater than that of the light-emitting waveguide. Increasing the width of the grating waveguide increases the charge-carrying area and decreases the current density.

[0067] High-power distributed feedback Bragg grating lasers used in silicon photonics circuits require the devices to operate under single-mode conditions, which imposes a maximum requirement on the width of the waveguide. Figure 10 This is a schematic diagram illustrating the existence of waveguide modes under different waveguide widths according to some embodiments. For example... Figure 10 As shown, the horizontal axis represents the waveguide width, and the vertical axis, Neff, represents the equivalent refractive index, which is a parameter characterizing each mode. Neff0 is the equivalent refractive index of the fundamental mode, and Neff1 is the equivalent refractive index of higher-order modes.

[0068] Taking a laser with a target wavelength of 1310nm as an example. From Figure 10 As can be seen, when the waveguide width is greater than 2.8 μm, Neff0 and Neff1 exist simultaneously, indicating that the 0th-order mode (or fundamental mode) and the 1st-order mode coexist. When the waveguide width is less than 2.8 μm, only the fundamental mode exists, and the waveguide operates under single-mode conditions. Figure 10 It can be concluded that, under existing parameters, the maximum waveguide width of a traditional uniform waveguide design is 2.8 μm. In practical manufacturing processes, considering waveguide etching tolerances and single-mode yield, a certain safety margin is usually left even under extreme single-mode conditions. If a waveguide width of 2 μm is used, under a typical operating current of 480 mA, the minimum current density is 24 kA / cm², far exceeding the traditional 10–15 kA / cm². This current density increases material stress and negatively impacts reliability.

[0069] In some embodiments of this application, the single-mode waveguide width is the waveguide width in which light is only excited to produce the fundamental mode light wave. When the waveguide width is greater than the single-mode waveguide width, higher-order mode light waves and the fundamental mode light waves will be generated, so that the light in the waveguide has multiple media mode forms.

[0070] To reduce current density, the width of the grating waveguide is larger than that of the filter waveguide, and the width of the grating waveguide is larger than that of the output waveguide. Increasing the width of the grating waveguide increases the charge-carrying area, thereby reducing the current density.

[0071] Taking a laser with a target wavelength of 1310nm as an example, the width of the grating waveguide is larger than the width of the single-mode waveguide, and the width of the grating waveguide is 3μm-6μm. For example, the width of the grating waveguide can be 5μm. (This is repeated three times in the original text.)

[0072] In some embodiments, the width of the grating waveguide in this application is greater than the width of the single-mode waveguide, meaning that the width of the grating waveguide allows light to be excited to generate higher-order modes in the grating waveguide region. Light generates higher-order mode light waves and fundamental mode light waves within the grating waveguide; the generation of higher-order mode light waves will cause the far-field distribution of light to be inconsistent with the far-field distribution of single-order mode, which is not conducive to light coupling.

[0073] The laser provided in this application embodiment has, from left to right, a high-reflectivity film, a filter waveguide, a grating waveguide, an output waveguide, and a high-transmittance film.

[0074] A grating waveguide contains a grating, which consists of periodic variations in the refractive index of a semiconductor material. This grating acts as a diffraction grating, allowing only specific wavelengths of light to be amplified and emitted.

[0075] From the high-reflectivity film to the corresponding active layer of the grating waveguide, photons can be generated spontaneously. The photons enter the passive waveguide layer and can travel in either the high-reflectivity (HR) or low-reflectivity (AR) direction. The photons are reflected back and forth between the high-reflectivity film and the grating waveguide until light of a specific wavelength is selected and enters the output waveguide.

[0076] The width of the grating waveguide is a crucial factor. Mode mismatch and significant loss occur during light propagation between the filter and grating waveguides. To minimize this loss, the width difference at the junction of the filter and grating waveguides should be as small as possible.

[0077] For example, the filtering waveguide includes a filtered straight waveguide 914 and a filtered tapered waveguide 915. The width of the filtered straight waveguide 914 is the fundamental mode waveguide, that is, the width of the filtered straight waveguide is less than or equal to 2.8 μm. In some embodiments, the width of the filtered straight waveguide 914 may be 2.0 μm or 1.8 μm.

[0078] In some embodiments, the edge of the filtered tapered waveguide 915 can be a straight line or a curve. That is, the filtered tapered waveguide 915 can be a trapezoidal waveguide or an arc-shaped waveguide.

[0079] A high-reflectivity film is provided at one end of the filter straight waveguide 914, where light waves are completely reflected and directed towards the output waveguide. One end of the filter tapered waveguide 915 is connected to the filter straight waveguide 914, and the other end of the filter tapered waveguide 915 is connected to the grating waveguide. The width of the filter tapered waveguide 915 gradually increases along the direction from the filter straight waveguide to the grating waveguide.

[0080] In some embodiments, the lengths of the filter waveguide and the grating waveguide are set so that the higher-order mode light wave is lost in the filter waveguide and the grating waveguide, thereby ensuring that the device as a whole operates in single mode.

[0081] Figure 11 This is a graph showing the relationship between the transmittance of a higher-order mode and the length of a filtered trapezoidal straight waveguide, according to some embodiments. Figure 11 As shown in the figure, W1 represents the width of the filtered straight waveguide, W2 represents the width of the grating waveguide, the horizontal axis L1 represents the length of the filtered straight waveguide, and the vertical axis represents the transmittance of higher-order modes. Figure 11 As can be seen, when the width of the grating waveguide is fixed at 5 μm, as the width of the filtered straight waveguide increases (from 1.8 μm to 2.2 μm), the transmittance curve of the higher-order modes has a minimum value, which is below 0.01%. If the width of the filtered straight waveguide is fixed at 2 μm, and the width of the grating waveguide 916 increases from 3 μm to 5 μm, the position of the minimum value does not change much, but the minimum value decreases.

[0082] In some embodiments, if the width of the filtered straight waveguide is 2 μm and the width of the grating waveguide 916 is 5 μm, the length of the filtered straight waveguide 914 with a higher-order mode transmittance of less than 0.1% (or a preset value) corresponds to a range of 160 μm to 230 μm.

[0083] In some embodiments, the width of the filtered straight waveguide can be 1.8 μm or 2.0 μm. The width of the filtered straight waveguide is 1.8 μm-2 μm.

[0084] Taking a laser with a target wavelength of 1310nm as an example, when the width of the grating waveguide is 5μm, in order to maximize the loss of higher-order modes while minimizing the loss of the fundamental mode, the length of the filter gradient waveguide is set to make the fundamental mode transmittance greater than 95%.

[0085] One end of the filtered tapered waveguide 915 is connected to the filtered straight waveguide 914, and the other end of the filtered tapered waveguide 915 is connected to the grating waveguide. The width of the filtered tapered waveguide 915 gradually increases along the direction from the filtered straight waveguide 914 to the grating waveguide.

[0086] Figure 12 This is a graph showing the relationship between the transmittance of a fundamental mode and the length of a filtered graded waveguide, according to some embodiments. Figure 12The horizontal axis represents the length of the filtered graded waveguide, and the vertical axis represents the transmittance of the fundamental mode. (Through...) Figure 12 It can be seen that when the length of the filtered graded waveguide 915 is greater than or equal to 75 μm, the fundamental mode transmittance is greater than 95%.

[0087] The laser provided in this application has a non-uniform waveguide structure, including a filter waveguide and a grating waveguide, wherein the width of the grating waveguide is larger than that of the filter waveguide, and the width of the grating waveguide is larger than that of the single-mode waveguide. The filter waveguide is used to reduce the loss of higher-order mode light waves, so that the light emitted by the laser remains single-mode, thereby improving the coupling efficiency between the laser and external optical devices. The filter waveguide includes a straight filter waveguide and a tapered filter waveguide, wherein the straight filter waveguide is a single-mode waveguide, and the transmittance of higher-order mode light waves in the straight filter waveguide is less than a preset value. The tapered filter waveguide is located between the straight filter waveguide and the grating waveguide, and the width of the tapered filter waveguide gradually increases along the direction from the straight filter waveguide to the grating waveguide. The tapered filter waveguide makes the transmittance of single-mode light waves greater than 95%, thereby improving the optical coupling efficiency.

[0088] In some embodiments, along the light emission direction, the grating waveguide sequentially includes: a first blank area 9162, a grating area 9161, and a second blank area 9163. The first blank area 9162 and the second blank area 9163 are located at opposite ends of the grating area 9161, ensuring that the grating structure exists only in a uniform waveguide region, rather than in a region where the waveguide width varies. This guarantees a uniform grating structure and better filtering performance.

[0089] The first blank area 9162 is located between the filtered graded waveguide 915 and the grating area 9161 to prevent the grating structure from entering the filtered graded waveguide 915 and causing wavelength inconsistency. The second blank area 9163 is located between the output waveguide and the grating area 9161 to prevent the grating structure from entering the output waveguide and causing grating structure non-uniformity.

[0090] In some embodiments, to ensure consistency with the original output beam spot and far-field distribution, the output waveguide is a single-mode waveguide. While keeping the laser length constant, the length of the output waveguide is minimized as much as possible to increase the length of the grating waveguide 916, increase the charge-carrying area, reduce the current density, and improve the stability of the laser.

[0091] The width of the grating waveguide is greater than the width of the output waveguide, thus causing light loss when light enters the output waveguide from the grating waveguide. In some embodiments, to reduce optical loss, the output waveguide includes an output straight waveguide 918 and an output tapered waveguide 917, wherein the output tapered waveguide 917 is located between the output straight waveguide 918 and the grating waveguide 916. The width of the output tapered waveguide 917 gradually decreases along the direction from the grating waveguide 916 to the output straight waveguide 918. The output tapered waveguide 917 ensures that the transmittance of single-mode light is greater than 95%, improving optical coupling efficiency. Therefore, the length of the output tapered waveguide is greater than or equal to 75 μm.

[0092] In some embodiments, the edge of the output gradient waveguide can be a straight line or an arc. Therefore, the output gradient waveguide can be a trapezoidal waveguide or a fan-shaped waveguide.

[0093] In some embodiments, the width of the output straight waveguide 918 is smaller than the width of the grating waveguide. For example, the width of the output straight waveguide 918 is less than or equal to the width of the single-mode waveguide. Taking a laser target wavelength of 1310 nm as an example, the width of the output straight waveguide 918 is 2.0 μm or 1.8 μm.

[0094] The length of the 918 straight waveguide can be 50 μm.

[0095] In some embodiments, the width of the filtered straight waveguide is less than or equal to the width of the output waveguide.

[0096] As described above, the laser provided in this application exhibits an asymmetric waveguide structure, with the grating waveguide width being greater than the single-mode waveguide width, increasing the charge-carrying area and reducing the current density. The filtered straight waveguide improves the loss of higher-order mode optical waves, while the filtered tapered waveguide improves the transmittance of single-mode optical waves. This achieves single-ended, high-power, single-wavelength output of the laser while reducing current density and improving the reliability of the optical module.

[0097] In some embodiments, a laser growth process includes: growing a waveguide layer on the surface of a top silicon layer of a wafer; etching the waveguide layer to form a grating; filling the grating region with outer-edge fabrication; and etching the waveguide layer to form waveguide structures of different widths.

[0098] It should be noted that, in this description, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that an optical path structure, related device, or device that comprises a list of elements includes not only those elements but also other elements not expressly listed. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the optical path structure, related device, or device that includes said element.

[0099] The embodiments described above do not constitute a limitation on the scope of protection of this application.

Claims

1. A laser, characterized in that, include: A grating waveguide, the width of which is greater than the width of a single-mode waveguide; a grating structure is disposed within the grating waveguide; light is generated in the grating waveguide to produce higher-order mode light waves and a fundamental mode light wave; A filter waveguide, one end of which is provided with a high-reflectivity film, and the other end is connected to the grating waveguide, wherein the filter waveguide comprises: A filter straight waveguide has a width less than or equal to the width of a single-mode waveguide, and a high-reflectivity film is disposed at one end of the filter straight waveguide; light is reflected multiple times between the high-reflectivity film and the grating waveguide, and the light reaches the high-reflectivity film through the filter straight waveguide. During the process of the light being reflected by the high-reflectivity film and then passing through the filter straight waveguide, the higher-order mode light wave is lost. A filtered gradient waveguide is located between the filtered straight waveguide and the grating waveguide; the width of the filtered gradient waveguide gradually increases along the direction from the filtered straight waveguide to the grating waveguide. An optical waveguide is provided, with one end connected to the other end of the grating waveguide and the other end having a high-transmittance film.

2. The laser according to claim 1, characterized in that, The grating waveguide includes: a first blank area, a grating area, and a second blank area; The first blank area and the second blank area are located on both sides of the grating area, respectively; A grating structure is provided within the grating region to allow light of a specific wavelength to be amplified and emitted. No grating structure is set in the first blank area and the second blank area.

3. The laser according to claim 1, characterized in that, The filtered gradient waveguide is a trapezoidal waveguide, the first end of the filtered gradient waveguide is connected to the filtered straight waveguide, and the second end of the filtered gradient waveguide is connected to the grating waveguide; The width of the first end of the filtered tapered waveguide is the same as the width of the filtered straight waveguide; The width of the second end of the filtered gradient waveguide is the same as the width of the grating waveguide.

4. The laser according to claim 1 or 2, characterized in that, The width of the output waveguide is smaller than that of the grating waveguide; The light-emitting waveguide includes: a straight light-emitting waveguide and a graded light-emitting waveguide; The light-emitting gradient waveguide is located between the light-emitting straight waveguide and the grating waveguide, and the width of the light-emitting gradient waveguide gradually decreases along the direction from the light-emitting straight waveguide to the grating waveguide.

5. The laser according to claim 4, characterized in that, The width of the output waveguide is less than or equal to the width of the single-mode waveguide.

6. The laser according to claim 1, characterized in that, The width of the filter straight waveguide is 1.8-2.0 μm; the width of the grating waveguide is 3-5 μm; and the length of the filter straight waveguide is greater than or equal to 75 μm.

7. The laser according to claim 1, characterized in that, It includes, in sequence: a lower electrode layer, a lower substrate layer, an active layer, a passive waveguide layer, an upper substrate layer, and an upper electrode layer; The passive waveguide layer includes the grating waveguide, the filter waveguide, and the output waveguide connected in sequence. The width of the grating waveguide is greater than that of the filter waveguide.

8. A laser, characterized in that, include: An output waveguide, wherein the width of the output waveguide is less than or equal to the width of a single-mode waveguide; A grating waveguide, the width of which is greater than that of the output waveguide, is provided with a grating structure, and light generates higher-order mode light waves and fundamental mode light waves in the grating waveguide. One end of the grating waveguide is connected to the output waveguide. A filter waveguide, one end of which is provided with a high-reflectivity film, and the other end is connected to the grating waveguide, wherein the filter waveguide comprises: A filter straight waveguide has a width less than or equal to that of the output waveguide, and a high-reflectivity film is disposed at one end of the filter straight waveguide; light is reflected multiple times between the high-reflectivity film and the grating waveguide, and the light reaches the high-reflectivity film through the filter straight waveguide. After being reflected by the high-reflectivity film and then passing through the filter straight waveguide again, the higher-order mode light wave is lost. A filtered gradient waveguide is located between the filtered straight waveguide and the grating waveguide; the width of the filtered gradient waveguide gradually increases along the direction from the filtered straight waveguide to the grating waveguide, thereby reducing the loss of the fundamental mode light wave.

9. The laser according to claim 8, characterized in that, The grating waveguide includes: a first blank area, a grating area, and a second blank area; The first blank area and the second blank area are located on both sides of the grating area, respectively; A grating structure is provided within the grating region to allow light of a specific wavelength to be amplified and emitted. No grating structure is set in the first blank area and the second blank area.

10. An optical module, characterized in that, Includes the laser as described in any one of claims 1 to 9.

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