A heterogeneous integrated tunable laser

Abstract

The present invention relates to the technical field of tunable lasers, specifically providing a heterogeneously integrated tunable laser comprising a silicon nitride photonic chip and a lithium tantalate film bonded to the upper surface of the silicon nitride photonic chip. The lithium tantalate film and the silicon nitride waveguide layer are heterogeneously integrated to form a hybrid waveguide. The silicon nitride photonic chip is sequentially provided with a ring reflector, a gain chip, a vernier microring filter, a phase modulator, and a tunable ring mirror along the waveguide layer. The ring reflector and the tunable ring mirror form a resonant cavity. By adjusting the voltage applied to the electrodes of the vernier microring filter, the refractive index of the hybrid waveguide is changed, thereby achieving rapid switching of the output laser wavelength. By adjusting the voltage applied to the electrodes of the phase modulator, the refractive index of the hybrid waveguide is changed, thereby achieving linear frequency modulation signal output. The present invention overcomes the shortcomings of conventional tunable lasers, such as low tuning speed, narrow linear frequency modulation bandwidth, and small wavelength tunable range, while also simplifying the manufacturing process and achieving low economic cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of tunable lasers, and in particular relates to a heterogeneous integrated tunable laser. Background Art

[0002] As artificial intelligence and big data demand increased information transmission speed and capacity, silicon photonics technology has rapidly developed. Optical chips, leveraging their high light transmission speed and low heat generation, have garnered widespread attention. Silicon waveguide optical chips can be produced using the mature silicon CMOS process used in electronic chip manufacturing. They offer low cost, high yield, and ease of optoelectronic integration and co-packaging with electronic chips, while also delivering excellent performance. These technologies are driving the development of optical communications, optical interconnects, and optical sensing.

[0003] However, due to the two-photon absorption characteristics of the silicon waveguide material itself, the transmission loss of the silicon waveguide chip is large. In addition, silicon is a centrosymmetric crystal and does not have a linear electro-optical effect. It can only modulate light through the free carrier dispersion effect of silicon. The modulation speed is slow and it is easy to be distorted under high-speed signals.

[0004] Because silicon material has excessive transmission loss, researchers have proposed using silicon nitride as the transmission waveguide material for optical chips. Compared to silicon, silicon nitride offers low-loss transmission characteristics. However, as an insulator, silicon nitride lacks the linear Pockels electro-optic effect, exhibiting only a weaker Kerr electro-optic effect. Consequently, light modulation often relies on the thermo-optic effect, which is slow and cannot meet the requirements of high-speed modulation.

[0005] In recent years, research on lithium niobate waveguide materials has been in full swing. Thin-film lithium niobate is hailed as the silicon of photonic chips. It exhibits lower transmission loss than silicon waveguides, a large electro-optic coefficient, and a linear Pockels effect. Because the refractive index of lithium tantalate can be directly altered by voltage, lithium niobate modulation can meet high-speed requirements. Currently, high-speed optical modulators are primarily fabricated based on lithium niobate. However, lithium niobate is difficult to etch, and currently, lithium niobate waveguides can only be ridge waveguides, and the etching angle cannot reach 90°. Consequently, due to the rough sidewall etching, lithium niobate experiences high side scattering losses, failing to achieve the low-loss performance of silicon nitride. This makes fabrication difficult and costly.

[0006] A recent article published in Nature, titled "Lithium tantalate photonic integrated circuits for volume manufacturing," by Chengli Wang, Zihan Li, Johann Riemensberger, Grigory Lihachev, Mikhail Churaev, Wil Kao, Xinru Ji, Junyin Zhang, Terence Blesin, Alisa Davydova, Yang Chen, Kai Huang, Xi Wang, Xin Ou, and Tobias J. Kippenberg, demonstrates the feasibility of fabricating high-performance lithium tantalate photonic chips. Like lithium niobate, lithium tantalate is a noncentrosymmetric crystal with a strong linear electro-optical (Pockels) effect. Under an applied electric field, its refractive index changes, effectively converting electrical signals into optical modulation. These electro-optical properties of lithium tantalate are crucial for its applications in optical communications, optical computing, and lidar. The fabrication process for silicon-based lithium tantalate wafers is similar to that of silicon on insulators, making lithium tantalate thin films feasible for low-cost, scalable manufacturing and promising applications. Furthermore, lithium tantalate thin films exhibit excellent electro-optical conversion properties, temperature stability, good thermal conductivity, and compatibility with silicon, resulting in lower optical losses than wafer-grade lithium niobate. This makes them a highly sought-after material for the development of new devices in the post-Moore era.

[0007] As a new laser solution, heterogeneous integrated high-speed linear frequency modulated lasers have important application potential in intelligent driving and LiDAR technology. The requirements for light sources for linear frequency modulated LiDAR applications require that the light source have the characteristics of high linearity, high speed, narrow linewidth, and high power. Combining the advantages of low loss of silicon nitride materials and high-speed linear electro-optical modulation of lithium tantalate materials, and taking advantage of the high output of heterogeneous integration process technology, compared with the disadvantages of hybrid integration that have high requirements for end-to-end coupling and packaging, it has the advantages of low coupling requirements and low loss. In summary, the use of heterogeneous integration technology combined with the advantages of low transmission loss of silicon nitride and high-speed linear modulation of lithium tantalate meets the requirements of OPA-FMCW LiDAR for integrated frequency modulated lasers with mass production capabilities, small size, narrow linewidth, high linearity, fast frequency modulation speed, and high power.

[0008] An existing proposal involves bonding a lithium niobate film to a silicon waveguide double microring and a toroidal mirror microcavity. This approach utilizes the vernier effect of the two microring filters to create a filtering structure, resulting in a wide tuning range and narrow linewidth laser. Leveraging the advantages of the bonded lithium niobate film, such as low loss, strong linear electro-optical effect, and fast modulation speed, it is possible to further compress the laser linewidth, increase output laser power, and achieve high-speed linear frequency modulation. However, this approach still presents the following challenges:

[0009] First, the gain chip is end-to-end coupled with the heterogeneous integrated lithium silicon nitride niobate chip, which is technically difficult, has a complex manufacturing process, and has poor mass production capabilities.

[0010] Second, lithium niobate thin film wafers are currently rarely used and are expensive.

[0011] Third, the use of silicon waveguides, due to the two-photon absorption effect of silicon, will affect the power output under high-power application requirements, resulting in low tuning speed, small linear frequency modulation bandwidth and small wavelength adjustable range.

[0012] Fourth, when the double microring structure is tuned over a large range, the mode gain is low and the output laser side mode suppression ratio is low. Summary of the Invention

[0013] In view of this, the present invention aims to provide a heterogeneous integrated high-power and high-speed tunable laser, which overcomes the defects of the existing technology such as complex manufacturing process, low tuning speed, small linear frequency modulation bandwidth and small wavelength adjustable range, and has the advantages of wide wavelength tuning range, high linearity, large modulation bandwidth, narrow linewidth and high power.

[0014] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0015] The present invention provides a heterogeneous integrated tunable laser, comprising:

[0016] A silicon nitride photonic chip includes: a gain unit, a vernier micro-ring filter, a phase modulator, and an adjustable ring mirror connected in sequence along a laser emission path;

[0017] and a lithium tantalate film covering the upper surface of the silicon nitride photonic chip, wherein the lithium tantalate film and the silicon nitride waveguide layer of the silicon nitride photonic chip are heterogeneously integrated to form a hybrid waveguide;

[0018] The phase modulator, the vernier microring filter and the adjustable ring mirror are arranged in the hybrid waveguide area, and the first electrode of the vernier microring filter and the second electrode of the phase modulator are arranged on the upper surface of the lithium tantalate film;

[0019] By adjusting the voltage applied to the first electrode, the wavelength of the output laser can be adjusted based on the electro-optical effect of lithium ion battery.

[0020] By adjusting the voltage applied to the second electrode, linear frequency modulation of the output laser is achieved based on the electro-optical effect of lithium ion battery.

[0021] Preferably, a third electrode of an adjustable ring mirror is provided on the upper surface of the lithium tantalate film. By adjusting the voltage applied to the third electrode, the reflection and transmission ratio of the adjustable ring mirror to the laser is changed based on the electro-optical effect of the lithium tantalate film, thereby realizing laser output power adjustment.

[0022] Preferably, the gain unit includes a ring reflector and a gain chip, the ring reflector and the adjustable ring mirror form a Fabry-Perot resonant cavity, and the gain chip is used to provide laser gain.

[0023] Preferably, the gain chip is a Group III-V gain chip, and the Group III-V gain chip is bonded to the silicon nitride waveguide layer of the silicon nitride photonic chip.

[0024] Preferably, the gain unit includes: two gain chips, the two gain chips are designed to be connected in parallel, and the same voltage is applied to the two gain chips at the same time to increase the laser gain.

[0025] Preferably, a spot converter and a Y-shaped input waveguide are sequentially provided between the gain unit and the vernier microring filter, and the spot converter is used to match the gain waveguide optical mode size in the gain unit with the waveguide spot size of the Y-shaped input waveguide.

[0026] Preferably, the vernier microring filter includes three cascaded microrings with different circumferences, wherein the first microring and the second microring realize laser wavelength adjustment based on the vernier effect, and the third microring is used to narrow the linewidth and improve the side mode suppression ratio.

[0027] Preferably, the third microring is an asymmetric AMZ.

[0028] Preferably, the perimeters of the first microring and the second microring are both in the range of 600-800 microns, and the difference in perimeter between the first microring and the second microring is 5-15 microns.

[0029] Preferably, the wavelength switching of the output laser is achieved by applying a square wave voltage to the first electrode of the vernier microring filter; and the linear frequency modulation of the output laser is achieved by applying a triangle wave voltage to the second electrode of the phase modulator.

[0030] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0031] The present invention forms a heterogeneous integrated external cavity tunable laser by bonding a III-V gain chip and a lithium tantalate film on a partial area of ​​a silicon nitride photonic chip. The laser has the advantages of a wide wavelength tuning range, high linearity frequency modulation, a large modulation bandwidth, a narrow linewidth, and high power. In addition, a hybrid waveguide is formed by heterogeneously integrating the lithium tantalate film and the silicon nitride waveguide layer. By applying square wave voltage and triangular wave voltage to electrodes of a vernier microring filter and a phase modulator, the refractive index of the hybrid waveguide of lithium tantalate and silicon nitride is regulated by voltage by utilizing the excellent linear electro-optical effect of lithium tantalate. By adjusting the voltage applied to the electrodes of the vernier microring filter, the refractive index of the hybrid waveguide is changed, thereby achieving rapid switching of the output laser wavelength. By adjusting the voltage applied to the electrodes of the phase modulator, the refractive index of the hybrid waveguide is changed, thereby changing the optical cavity length and the longitudinal mode position, thereby achieving linear frequency modulation signal output. Furthermore, lithium tantalate has stable chemical properties and a high Curie point, maintaining its performance over a wide temperature range, effectively improving device reliability and lifespan. Furthermore, lithium tantalate has low dielectric loss, effectively reducing energy loss during transmission. Compared to lithium niobate wafers, lithium tantalate has been widely used in the RF field, offering the advantage of low wafer costs. Heterogeneous integration of lithium tantalate and silicon nitride can result in chips with superior performance, diverse functionality, low coupling loss, and advantages for packaging and mass production.

[0032] The laser of the present invention is driven by voltage, achieving not only a wide wavelength tuning range and highly linear frequency modulation, but also controlling the laser's reflection and transmission ratios through voltage-controlled adjustable ring mirrors, thereby enabling laser power output control and extending the output power range. Furthermore, by bonding III-V gain chips to silicon nitride, chip integration is improved. A dual-gain chip design, coupled via Y-branching, effectively increases laser gain by applying the same voltage to both gain chips, thereby achieving high-power output.

[0033] The present invention heterogeneously integrates the III-V gain chip and the lithium tantalate thin film on the silicon nitride photonic chip through a bonding process. Compared with the existing end-face coupling process, it effectively reduces complex manufacturing steps, significantly improves production efficiency, and increases structural integration. In addition, the modified structure does not need to rely on complex optical lens systems and mechanical rotation systems, which reduces the difficulty and requirements of coupling packaging and is conducive to product packaging and mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0035] Figure 1 1 is a schematic structural diagram of a heterogeneous integrated tunable laser provided in an embodiment of the present invention;

[0036] Figure 2 is a top view of a heterogeneous integrated tunable laser provided according to an embodiment of the present invention;

[0037] Figure 3 is a cross-sectional view of a hybrid waveguide provided according to an embodiment of the present invention.

[0038] Reference numerals include:

[0039] Ring reflector 1, gain chip 2, spot converter 3, Y-shaped input waveguide 4, lithium tantalate film 5, vernier microring filter 6, first microring 601, second microring 602, third microring 603, phase modulator 7, adjustable ring mirror 8, output waveguide 9;

[0040] Electrode a, first electrode a01, second electrode a02, third electrode a03, silicon nitride waveguide layer b, silicon dioxide cladding layer c, silicon substrate d. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation to the present invention. Similar elements in different embodiments use associated similar element numbers. In the following embodiments, many detailed descriptions are intended to enable the present invention to be better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, or methods. In some cases, some operations related to the present invention are not shown or described in the specification. This is to avoid the core part of the present invention being overwhelmed by too much description. For those skilled in the art, it is not necessary to describe these related operations in detail. They can fully understand the related operations based on the description in the specification and the general technical knowledge in the art.

[0042] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other to form various implementation methods. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various orders in the description and the drawings are only for the purpose of clearly describing a certain embodiment and are not intended to be a required order, unless otherwise specified that a certain order must be followed.

[0043] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0044] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art can understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0045] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0046] See also Figure 1 and Figure 2 In one embodiment of the present invention, a heterogeneous integrated tunable laser is provided, which realizes high-power, high-speed tunable laser output through heterogeneous integration of silicon nitride and lithium tantalate film 5. Specifically, the heterogeneous integrated tunable laser includes a silicon nitride photonic chip and a lithium tantalate film 5. The waveguide layer used for light beam transmission in the silicon nitride photonic chip is a silicon nitride waveguide, and the thickness of the lithium tantalate film 5 is 0.2-0.5 microns. The lithium tantalate film 5 is covered on the silicon nitride waveguide layer of the silicon nitride photonic chip through a bonding or transfer process, and a hybrid waveguide is formed through heterogeneous integration. Figure 3 As shown, the hybrid waveguide includes the following material layers from bottom to top:

[0047] The substrate layer is made of silicon, that is, a silicon substrate d, and the silicon substrate d is used to provide mechanical support.

[0048] The silicon dioxide cladding layer c is provided on the silicon substrate d. The silicon dioxide cladding layer c is an insulating material and is used to protect the waveguide structure and limit light field leakage.

[0049] The silicon nitride waveguide layer b is arranged above the silicon dioxide cladding layer c and mainly serves as a transmission channel for optical signals. Silicon nitride material has a high refractive index and can effectively constrain the transmission of optical signals within it.

[0050] The lithium tantalate film 5 is disposed above the silicon nitride waveguide layer b and together with the silicon nitride waveguide layer b form a hybrid waveguide. The lithium tantalate material has a highly linear electro-optical effect. The lithium tantalate film 5 is bonded to the silicon nitride waveguide layer to form a heterogeneous integrated structure. In this structure, the optical signal is transmitted in the silicon nitride waveguide while being modulated by the lithium tantalate film 5. By changing the voltage applied to the lithium tantalate film 5, its refractive index changes, thereby changing the phase modulation and wavelength tuning of the optical signal. The electro-optical effect of the lithium tantalate film 5 enables the hybrid waveguide to quickly respond to electrical signals, achieving high-speed modulation of the optical signal, meeting the optical signal modulation requirements of applications such as lidar.

[0051] The electrode layer a is arranged on the upper surface of the lithium tantalate film 5. The electrode layer a mainly includes electrodes of various functional units. The electrode material is gold, and the distance between adjacent electrodes is 1-5 microns.

[0052] The silicon nitride photonic chip includes the following elements, connected in sequence along the laser emission path: a gain unit, a spot size converter 3, an input waveguide, a vernier microring filter 6, a phase modulator 7, an adjustable loop mirror 8, and an output waveguide 9. These elements are all located in the silicon nitride waveguide layer of the silicon nitride photonic chip. The gain unit, which provides the gain medium for the laser, specifically includes a loop mirror 1 and a gain chip 2. The loop mirror 1 is located at the front end of the silicon nitride waveguide and serves as one end face of the resonant cavity of the tunable laser. The loop mirror 1 and the adjustable loop mirror 8 at the rear end form a Fabry-Perot resonant cavity. The loop mirror 1 can be a reflector with adjustable reflectivity, a reflector with fixed reflectivity, or a built-in electrically adjustable directional coupler.

[0053] Gain chip 2 utilizes a III-V gain chip, heterogeneously integrated onto the silicon nitride waveguide layer of the silicon nitride photonic chip via bonding or micro-transfer printing. The III-V gain chip provides gain for the laser, effectively amplifying the optical signal. A spot size converter 3 is installed on the silicon nitride waveguide segment at the rear end of gain chip 2 to adjust the optical mode size of the gain waveguide of gain chip 2.

[0054] As an optional embodiment, in order to increase the maximum output power of the laser, the embodiment of the present invention can also set up multiple parallel gain chips 2. Taking the two-way gain design as an example, the gain unit is provided with two annular reflectors 1 and two gain chips 2. In each gain optical path, a annular reflector 1 is connected to a gain chip 2, and the two gain chips 2 are bonded in parallel to form a parallel design. A mode spot converter 3 is respectively provided at the rear end of the two gain chips 2. The two-way gain is coupled through a Y-shaped input waveguide 4 at the rear end of the two mode spot converters 3. At this time, the same voltage is applied to the two gain chips 2 at the same time to increase the laser gain. When multiple parallel gain chips 2 are provided, their principles and structures are the same or similar to the above-mentioned two-way gain. The above-mentioned parallel design increases the laser output power and reduces the laser output laser line width without increasing the equivalent length of the gain chip 2.

[0055] The vernier microring filter 6, phase modulator 7, adjustable loop mirror 8, and output waveguide 9 are all located in the hybrid waveguide region. Specifically, the silicon nitride photonic chip is covered with a lithium tantalate thin film 5 on the upper surface of the vernier microring filter 6, phase modulator 7, adjustable loop mirror 8, and output waveguide 9. After the laser enters the hybrid waveguide through the Y-shaped input waveguide 4, the optical mode exists simultaneously in the silicon nitride and lithium tantalate materials, and the laser is transmitted through the hybrid waveguide of silicon nitride and lithium tantalate. The vernier microring filter 6 employs a three-cascade vernier microring design, comprising a first microring 601, a second microring 602, and a third microring 603. The circumferences of the first and second microrings 601, 602 are similar, both ranging from 600 to 800 microns, with a circumference difference of 5 to 15 microns. The first and second microrings 601, 602 are coupled to each other via the waveguide. A wide wavelength tuning range is achieved through the vernier effect of the perimeter difference between the two. The perimeter of the third microring 603 is significantly different from that of the first microring 601 and the second microring 602, and the perimeter size range is 1000-1500 microns.

[0056] A first electrode a01, made of gold, is provided on the upper surface of the lithium tantalate film 5 above the first microring 601, the second microring 602, and the third microring 603. By applying and adjusting voltage to the corresponding first electrodes a01 of the first and second microrings 601, 602, the lithium tantalate material in the hybrid waveguides corresponding to the first and second microrings 601, 602, experiences an electro-optical effect, changing the refractive index of the lithium tantalate film and, consequently, the refractive index of the hybrid waveguide. Due to the circumference difference between the first and second microrings 601, 602, a vernier effect is generated between them, effectively expanding the tuning range. By applying an adjustable voltage to the first electrodes a01 corresponding to the first microring 601 and the second microring 602, an electro-optical effect is caused in the lithium tantalate waveguide, the resonance peak of the laser is red-shifted, and the laser emits a set wavelength when the transmission peaks of its resonant cavity completely overlap, that is, when the transmittance reaches the maximum value. By adjusting the applied voltage, the position of the overlapping transmission peaks can be electrically and accurately adjusted, and then the lasing wavelength can be tuned to achieve the switching of the laser output wavelength of the laser.

[0057] In addition, since the first microring 601 and the second microring 602 may exhibit dual-wavelength or multi-wavelength lasing during the microring lasing process, resulting in a small tuning range, a large mode gain difference is required to achieve a sufficiently high side mode suppression ratio. The mode transmission difference between the dominant laser mode and the nearest side mode can significantly affect the side mode suppression ratio and the stability of the laser. When the gain difference is too small, the laser wavelength will become unstable, and in some cases, multi-mode oscillation may occur. To address this problem, an embodiment of the present invention adds a third microring 603 to the rear end of the first microring 601 and the second microring 602 to further extend the cavity length, narrow the linewidth, increase the mode gain, and improve the side mode suppression ratio. The third microring 603 works in conjunction with the first microring 601 and the second microring 602 to precisely control the resonant peak position of the microrings, thereby achieving alignment of the transmission peak with the longitudinal mode of the laser. During actual control, by simultaneously applying square wave voltages to the three groups of first electrodes a01 corresponding to the vernier microring filter 6, i.e., the three groups of first electrodes a01 corresponding to the first microring 601, the second microring 602, and the third microring 603, the wavelength switching of the output laser is achieved, while the side mode suppression ratio is improved.

[0058] As an optional embodiment, the third microring 603 can adopt an asymmetric AMZ (Asymmetric Mach-Zehnder Interferometer). The asymmetric AMZ enables the laser to increase the mode gain difference at different wavelengths, improve the side mode suppression ratio, adapt to the needs of wavelength tuning, and achieve single-mode output with high SMSR.

[0059] The rear-end hybrid waveguide of the vernier microring filter 6 is provided with a phase modulator 7. A second electrode a02 is provided on the upper surface of the lithium tantalate film 5 above the phase modulator 7. The second electrode a02 is also a gold electrode. The hybrid waveguide corresponding to the phase modulator 7 is used to guide the transmission of optical signals and is composed of silicon nitride and lithium tantalate. When a voltage is applied to the second electrode a02 corresponding to the phase modulator 7, due to the excellent linear electro-optical effect of lithium tantalate, the voltage change will cause the effective refractive index of the hybrid waveguide to change. The change in refractive index causes the propagation constant of the optical signal in the hybrid waveguide to change, and the optical cavity length to change, thereby achieving modulation of the phase of the optical signal. During actual control, a triangular waveform voltage is applied to the second electrode a02 corresponding to the phase modulator 7 to achieve high-linearity laser output.

[0060] An adjustable loop mirror 8 is provided on the rear-end waveguide of the phase modulator 7. The adjustable loop mirror 8 is the other end face of the laser resonant cavity and forms the Fabry-Perot resonant cavity of the laser together with the loop reflector 1. Since the adjustable loop mirror 8 is also provided on the hybrid waveguide, a third electrode a03 is provided on the upper surface of the lithium tantalate film 5 above the adjustable loop mirror 8. The third electrode a03 is a gold electrode. When a voltage is applied to the third electrode a03, the lithium tantalate in the hybrid waveguide undergoes an electro-optical effect, thereby changing the effective refractive index of the hybrid waveguide. The change in refractive index causes the adjustable loop mirror 8 to change the reflection and transmission ratio of the laser, that is, changes the laser emission conditions. Therefore, by adjusting the voltage applied to the third electrode a03, the laser output power can be changed. The adjustable loop mirror 8 can also be replaced by an electrically adjustable directional coupler with a three-cascade microring.

[0061] After emitting from the adjustable ring mirror 8, the laser enters the output waveguide 9 and is output through the output waveguide 9. By simultaneously changing the voltages applied to the vernier microring filter 6 and the bit modulator 7, a wide range of linear frequency modulation of the laser can be achieved. By changing the voltage applied to the adjustable ring mirror 8, a wide range of laser output power can be achieved.

[0062] In short, the above description is only a preferred embodiment of this specification and is not intended to limit the scope of protection of this specification. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this specification shall be included in the scope of protection of this specification.

[0063] The systems, devices, modules, or units described in one or more of the above embodiments may be implemented by a computer chip or entity, or by a product having a certain function. A typical implementation device is a computer. Specifically, the computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0064] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0065] The various embodiments in this specification are described in a progressive manner. Similar parts between the various embodiments can be referred to in conjunction with each other. Each embodiment focuses on the differences between the other embodiments. In particular, the system embodiments are generally similar to the method embodiments, so the description is relatively simple. For relevant parts, refer to the description of the method embodiments.

[0066] The foregoing description of this specification describes specific embodiments. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims can be performed in an order different from that described in the embodiments and still achieve the desired results. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the specific order shown or the sequential order to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. A heterogeneous integrated tunable laser, characterized in that: include: A silicon nitride photonic chip includes: a gain unit, a vernier micro-ring filter, a phase modulator, and an adjustable ring mirror connected in sequence along a laser emission path; and a lithium tantalate film covering the upper surface of the silicon nitride photonic chip, wherein the lithium tantalate film and the silicon nitride waveguide layer of the silicon nitride photonic chip are heterogeneously integrated to form a hybrid waveguide; The phase modulator, the vernier microring filter and the adjustable ring mirror are arranged in the hybrid waveguide region, and the first electrode of the vernier microring filter and the second electrode of the phase modulator are provided on the upper surface of the lithium tantalate film; By adjusting the voltage applied to the first electrode, the wavelength of the output laser is adjusted based on the electro-optical effect of lithium ion battery; By adjusting the voltage applied to the second electrode, linear frequency modulation of the output laser is achieved based on the electro-optical effect of the lithium ion battery.

2. The heterogeneous integrated tunable laser according to claim 1, characterized in that: A third electrode of the adjustable ring mirror is also provided on the upper surface of the lithium tantalate film. By adjusting the voltage applied to the third electrode, the reflection and transmission ratio of the adjustable ring mirror to the laser is changed based on the electro-optical effect of the lithium tantalate film, thereby realizing the adjustment of the laser output power.

3. The heterogeneous integrated tunable laser according to claim 1, characterized in that: The gain unit includes a ring reflector and a gain chip. The ring reflector and the adjustable ring mirror form a Fabry-Perot resonant cavity. The gain chip is used to provide laser gain.

4. The heterogeneous integrated tunable laser according to claim 3, characterized in that: include: The gain chip is a Group III-V gain chip, and the Group III-V gain chip is bonded to the silicon nitride waveguide layer of the silicon nitride photonic chip.

5. The heterogeneous integrated tunable laser according to claim 3, characterized in that: The gain unit includes two gain chips, which are designed to be connected in parallel. The same voltage is applied to the two gain chips at the same time to increase the laser gain.

6. The heterogeneous integrated tunable laser according to claim 5, characterized in that: A spot mode converter and a Y-shaped input waveguide are sequentially provided between the gain unit and the vernier microring filter. The spot mode converter is used to match the gain waveguide optical mode size in the gain unit with the waveguide spot size of the Y-shaped input waveguide.

7. The heterogeneous integrated tunable laser according to claim 1, characterized in that: The vernier microring filter includes three cascaded microrings with different circumferences, wherein the first microring and the second microring adjust the laser wavelength based on the vernier effect, and the third microring is used to narrow the line width and improve the side mode suppression ratio.

8. The heterogeneous integrated tunable laser according to claim 7, characterized in that: The third microring is an asymmetric AMZ.

9. The heterogeneous integrated tunable laser according to claim 7, characterized in that: The perimeters of the first microring and the second microring are both in the range of 600-800 microns, and the difference in perimeter between the first microring and the second microring is 5-15 microns.

10. The heterogeneous integrated tunable laser according to claim 1, characterized in that: By applying a square wave voltage to the first electrode of the vernier microring filter, wavelength switching of the output laser is achieved; by applying a triangle wave voltage to the second electrode of the phase modulator, linear frequency modulation of the output laser is achieved.

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