CN115864134B - Multi-bend waveguide DFB laser chip - Google Patents
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Abstract
The invention discloses a multi-bend waveguide DFB laser chip, which relates to the technical field of DFB laser chips and comprises a first laser cavity and a second laser cavity which are arranged on a substrate at intervals; the first ridge stripe and the second ridge stripe are etched in the y direction respectively, and the first ridge stripe and the second ridge stripe are provided with a first bending section and a second bending section which are bent in the x direction respectively, so that the straight waveguides of the first laser cavity and the second laser cavity are changed into bent waveguides, and compared with a traditional DFB laser chip with multiple laser cavities and straight ridge waveguides, the single-mode test cost is lower. According to the invention, the third bending section is arranged on the first ridge, so that the grating of the first laser cavity extends from the cleavage surface of the first AR coating to the front of the third bending section, and the total grating length of the second laser cavity is equal to that of the first laser cavity, thereby enabling the DFB laser chip to have higher SMSR and Shan Moliang rate to reach 100%.
Description
Technical Field
The invention relates to the technical field of DFB laser chips, in particular to a multi-bend waveguide DFB laser chip.
Background
With the rapid development of optical communication technology, the demand for semiconductor lasers is increasing. A Distributed Feedback (DFB) laser chip is a core device for high-speed optical communication, and the laser mainly relies on bragg gratings in a structure to provide feedback in a laser cavity, unlike a reflecting mirror surface of an FP cavity. Gratings in DFB lasers are classified into gain-type coupled gratings and refractive index-type coupled gratings.
Whether to operate in a single longitudinal mode and whether to have a high Side Mode Suppression Ratio (SMSR) is a key performance feature of DFB lasers. The related data show that after a DFB laser with a uniform index grating is coated with an anti-reflection (AR) film on both sides of the end facet, there are two degenerate longitudinal modes that have the same minimum gain. Degeneracy is eliminated when the two ends of the laser are asymmetrically coated (i.e., one end is coated with an AR film and the other end is coated with a High Reflection (HR) film). However, the wavelength at which the DFB laser is ultimately lasing depends on the end-face reflectivity and phase (i.e., the position of the HR coating cleavage plane at the grating), the randomness of the end-face phase results in a low single-mode yield for a uniform grating DFB laser.
The DFB laser chip is fabricated by cleaving the wafer into chips of a certain cavity length using cleaving techniques. The maximum difference between the cleavage end face and the ideal position can reach +/-5 mu m due to the process error, which causes randomness of the phase between the end face and the grating. DFB lasers may also employ photolithographic techniques to define etched facets, but the alignment accuracy of the photolithographic system and the angular deviation between the grating and etched facets are insufficient to determine the phase between the end facet of the entire wafer and the grating.
The uniform grating DFB semiconductor laser produced in industry is coated with AR film on one end surface and HR film on the other end surface, and the single-mode yield is about 66%. The introduction of lambda/4 phase shift in the center of the grating is another effective way to realize single-mode lasing, and the single-mode yield theory can reach 100%. However, λ/4 phase shift uniform grating DFB semiconductor lasers suffer from spatial hole burning effects and optical power waste. Research shows that the single-mode yield can reach about 80% when one end surface of the lambda/4 phase shift uniform grating DFB semiconductor laser is coated with an AR film and the other end surface is coated with an HR film.
In conclusion, the reflection end face forms an FP cavity effect and the uncertainty of the phase of the reflection end face caused by the cleavage process makes the lasing mode and the SMSR of the produced chip difficult to predict, thereby greatly reducing the single-mode yield of the DFB chip. After the DFB semiconductor laser is subjected to lengthy epitaxial, grating manufacturing, secondary epitaxial, front/back, cleavage and AR/HR coating processes, the value of a unit chip is highest, and the Shan Moliang rate loss can be avoided, so that the production efficiency of the DFB chip can be greatly improved, and the production cost can be reduced.
Disclosure of Invention
The invention provides a multi-bend waveguide DFB laser chip, which mainly aims to solve the problems existing in the prior art.
The invention adopts the following technical scheme:
a multi-bend waveguide DFB laser chip, comprising a substrate;
forming at least two laser cavities which are arranged at intervals above the substrate, wherein each laser cavity is internally provided with a grating layer;
the two end surfaces of each laser cavity along the y direction are respectively an HR coating cleavage surface and an AR coating cleavage surface;
etching a first ridge and a second ridge along the y direction of the first laser cavity and the second laser cavity respectively; the first ridge is provided with a first bending section and a third bending section which are bent along the x direction at a position close to the cleavage surface of the first HR coating; the second ridge strip is provided with a second bending section which is bent along the x direction at a corresponding position of the first bending section;
the first laser cavity and the second laser cavity are internally provided with grating layers, and the grating of the first laser cavity extends from the cleavage surface of the first AR coating to the front of the third bending section; the total grating length of the second laser cavity is equal to the total grating length of the first laser cavity.
As an embodiment: the first bending section, the second bending section and the third bending section are straight sections which are bent along the positive direction or the reverse direction of x.
As another embodiment: the first bending section, the second bending section and the third bending section are arc-shaped sections which are bent along the positive direction or the reverse direction of x, and tangents at the head end and the tail end of the first bending section, the second bending section and the third bending section are parallel to the y direction.
Further, the calculation formula of the design parameters of the first bending section and the second bending section is as follows:
wherein:
representing the period length of the grating; />
Representing the effective length of the first bending section or the second bending section along the y direction; />
Indicating the relative bending angle of the first bending section or the second bending section along the x direction.
Further, the relative bending angles of the first bending section and the second bending section along the x direction
The range of the values is as follows: 5 DEG </i>
＜30°。
Further, the vertical distance between the center point of the first bending section and the cleavage surface of the first HR coating, and the vertical distance between the center point of the second bending section and the cleavage surface of the second HR coating are both H, and the range of values is:
wherein L represents the length of the first ridge or the second ridge in the y-direction.
Further, the calculation formula of the design parameter of the third bending section is as follows:
wherein:
representing the effective length of the third bending section along the y direction; />
The relative bending angle of the third bending section along the x direction is shown.
Further, the third bending section has a relative bending angle along the x direction
The range of the values is as follows: 5 DEG </i>
＜30°。
Further, the distance between the first laser cavity and the second laser cavity is S, and the range of values is: s is more than or equal to 5 mu m and less than or equal to L W μm, where L W Representing the length of the DFB laser chip in the x-direction.
Further, the epitaxial structure of each laser cavity is a ridge waveguide structure or a buried heterojunction structure.
Further, the grating layer is fabricated using holographic exposure lithography.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention respectively configures the first bending section and the second bending section to change the straight waveguides of the first laser cavity and the second laser cavity into bent waveguides, wherein the end surface reflectivity of the bent waveguides at the HR coating cleavage surface is relative to the end surface reflectivity of the straight waveguides at the HR coating cleavage surface
The laser Shan Moliang rate of a single curved waveguide is higher, so that compared with the traditional DFB laser chip with double straight ridge waveguides, the invention has lower test cost and higher economic benefit.
2. The invention sets the third bending section between the first bending section of the first ridge and the cleavage surface of the first HR coating, and enables the first laser cavityThe grating extends from the cleavage surface of the first AR coating to the front of the third bending section, and the total grating length of the second laser cavity is equal to that of the first laser cavity, so that the end surface reflectivity of the first ridge at the cleavage surface of the first HR coating is compared with that of the second ridge at the cleavage surface of the second HR coating
When any one of the two ridge stripes works in a dual-mode state, the other ridge stripe can be separated from a phase region of dual-mode operation and is necessarily in single-longitudinal mode operation, so that the DFB laser chip has higher SMSR and the Shan Moliang rate can reach 100%.
3. Compared with a mode of adopting a refractive index coupling type phase shift grating to solve dual-mode operation, the method does not need to manufacture a complex phase shift grating; compared with a mode of adopting gain or loss coupling type gratings to solve dual-mode operation, the method does not need to manufacture gain or loss coupling type gratings with lower performance reliability and complex process steps; compared with a mode of adopting a passive Bragg grating to solve dual-mode operation, the invention does not relate to a monolithic integration process of active and passive waveguides. Compared with the prior art, the invention has the advantages of high device reliability, simple production process, low manufacturing cost and the like.
4. In the aspect of grating manufacture, the invention adopts holographic exposure lithography to manufacture the grating, and compared with electron beam lithography, the holographic exposure lithography has the advantages of short manufacturing period, easy manufacture of large area, low cost and the like.
Drawings
Fig. 1 is a top view of a multi-bend waveguide DFB laser chip according to a first embodiment of the invention.
Fig. 2 is a left side view of an epitaxial structure of a multi-bend waveguide DFB laser chip according to a first embodiment of the invention.
Fig. 3 is a front view of an epitaxial structure of a multi-bend waveguide DFB laser chip according to a first embodiment of the invention.
Fig. 4 is a schematic diagram of a positional relationship between each laser cavity and a grating in accordance with a first embodiment of the present invention.
Fig. 5 is a front view of an epitaxial structure of a multi-bend waveguide DFB laser chip according to a second embodiment of the invention.
Fig. 6 is a top view of a multi-bend waveguide DFB laser chip according to a third embodiment of the invention.
Fig. 7 is a schematic diagram of relative bending angles in a third embodiment of the present invention.
In the figure: 1. a DFB laser chip; 10. a first laser cavity; 11. a second laser cavity; 12. a first ridge; 120. a first bending section; 121. a third bending section; 13. a second ridge; 130. a second bending section; 14. a first contact electrode; 15. a second contact electrode; 16. a first HR coating cleavage plane; 17. a first AR coating cleavage face; 18. a second HR coating cleavage plane; 19. a second AR coating cleavage face; 21. an n-InP substrate; 22. an n-InP buffer layer; 23. a lower confinement layer; 24. a quantum well layer; 25. An upper confinement layer; 26. a grating layer; 27. a contact layer; 28. a P-InP layer; 29. a semi-insulating InP layer; 210. n-InP layer.
Detailed Description
Specific embodiments of the present invention will be described below with reference to the accompanying drawings. Numerous details are set forth in the following description in order to provide a thorough understanding of the present invention, but it will be apparent to one skilled in the art that the present invention may be practiced without these details.
Embodiment one:
as shown in fig. 1, the present embodiment provides a DFB laser chip 1 of a multi-bend waveguide, including an n-InP substrate 21 and two first and second laser cavities 10 and 11 formed above the n-InP substrate 21 and disposed at a distance from each other. The two end surfaces of the first laser cavity 10 along the y direction are respectively a first HR coating cleavage surface 16 and a first AR coating cleavage surface 17; the second laser cavity 11 has two end surfaces in the y direction, which are a second HR coating cleavage surface 18 and a second AR coating cleavage surface 19, respectively. The first laser cavity 10 is etched with a first ridge 12 in the y-direction and the second laser cavity 11 is etched with a second ridge 13 in the y-direction.
As shown in fig. 1 and 4, the main innovation of the present invention is: the first ridge stripe 12 is provided with a first bending section 120 and a third bending section 121 which are bent along the x direction near the first HR coating cleavage surface 16, and the second ridge stripe 13 is provided with a second bending section 130 which is bent along the x direction at the corresponding position of the first bending section 120; the first laser cavity 10 and the second laser cavity 11 are provided with a grating layer 26, and the grating of the first laser cavity 10 extends from the first AR coating cleavage surface 17 to the front of the third bending section 121; the total grating length of the second laser cavity 11 is equal to the total grating length of the first laser cavity 10.
As shown in fig. 1 and 4, based on the above innovation points, the relevant design parameters of the present embodiment are:
1. size of DFB laser chip (L W ×L H ) The lengths L of the first ridge stripe 12 and the second ridge stripe 13 (i.e., the lengths of the first laser cavity 10 and the second laser cavity 11 in the y direction) which are configured to be 250 μm×250 μm are both 250 μm; the width W of the first ridge stripe 12 and the second ridge stripe 13 in the x direction is 1.6 μm; the distance S between the first laser cavity 10 and the second laser cavity 11 is 20 μm.
2. The first inventive concept of the present invention is that by configuring the first bending section 120 and the second bending section 130, the straight waveguides of the first laser cavity 10 and the second laser cavity 11 become curved waveguides, and the end surface reflectivity of the curved waveguides at the HR coating cleavage plane exists relative to the end surface reflectivity of the straight waveguides at the HR coating cleavage plane
Phase shift, thereby enabling each laser cavity of the DFB laser chip to have a higher SMSR and Shan Moliang ratio. This is because, in the single mode yield test, assuming that the Shan Moliang rate of the single curved waveguide provided by the present embodiment is 80% and the Shan Moliang rate of the DFB laser chip of the single conventional straight-bar ridge waveguide is 60%, when the single mode yield test is performed on the first laser cavities of all the chips, the Shan Moliang rate of the first laser cavities of the present embodiment is 80% and the Shan Moliang rate of the first laser cavities of the DFB laser chip of the conventional dual straight-bar ridge waveguide is 60%; when Shan Moliang rate test of the second laser cavity is performed on the chips with the first laser cavity failing to be excited in a single mode, the number of the sample to be sampled of the second laser cavity in this embodiment is 20% of the total number of chips, and the number of the sample to be sampled of the DFB laser chips of the conventional dual-straight ridge waveguide is 40% of the total number of chips. It can be seen that the present embodiment is in a single modeThe yield test aspect has lower test cost and higher economic benefit.
In order to improve the production efficiency and save the design cost, the present embodiment sets the effective lengths of the first bending section 120 and the second bending section 130 along the y-direction
The same, the relative bending angles of the first bending section 120 and the second bending section 130 along the x-direction
The same applies. Thus, the effective length of the first bending section 120 and the second bending section 130 in the y-direction +.>
The following conditions should be satisfied at the time of design:
wherein:
representing the period length of the grating +.>
， />
Indicating the emission wavelength of the device, +.>
Representing the effective index of the grating; />
Indicating the effective grating period length corresponding to the bending section.
The simplification of equation (1) can be obtained:
further, the deviceThe light emitted by the piece is at a relative bending angle
When propagating in the bending section, the calculation formula of the effective grating period length is as follows: />
The simultaneous formulas (2) and (3) can be obtained:
therefore, when designing the first bending section 120 and the second bending section 130, the optimal effective length can be obtained by performing the simulation test according to the formula (4)
And relative bending angle->
。
In order to ensure that the structural designs of the first ridge stripe 12 and the second ridge stripe 13 are reasonable and reliable, after repeated experiments, the following rules can be obtained: relative bending angle of the first bending section 120 and the second bending section 130 along the x direction
The range of the values is as follows: 5 DEG <
Less than 30 deg.. It should be noted that the relative bending angle +.>
The angle of the acute angle between the bending section and the y axis is the absolute value of the included angle regardless of whether the bending section bends along the positive direction or the negative direction of x.
In the present embodiment
1.31 μm,/d>
About 3.2, the period length of the corresponding grating +.>
204.7nm, the effective lengths of the first and second bending sections 120 and 130 in the y direction are obtained by performing the simulation test based on the formula (4)
The relative bending angle of the first bending section 120 and the second bending section 130 along the x-direction is 6.86 μm +.>
Is 10 deg.. It is verified that the relative bending angle of this embodiment +.>
The value of the number is within the set value range, and meets the design requirement.
In addition, in the present embodiment, the positions of the first bending section 120 and the second bending section 130 are simulated, and according to the test result, when the vertical distance between the center point of the first bending section 120 and the first HR coating cleavage surface 16 and the vertical distance between the center point of the second bending section 130 and the second HR coating cleavage surface 18 are both H, the range of values is
The best effect can be obtained. Therefore, the value of H in this example is preferably 60. Mu.m.
3. The second inventive concept of the present invention is to provide a third bending section 121 between the first bending section 120 of the first ridge stripe 12 and the first HR coating cleavage face 16, and to make the grating of the first laser cavity 10 extend from the first AR coating cleavage face 17 to the front of the third bending section 121, and the total grating length of the second laser cavity 11 is equal to the total grating length of the first laser cavity 10, thereby realizing that the two laser cavities have a relative position difference, so that the end surface reflectivity of the first ridge stripe 12 at the first HR coating cleavage face 16 is compared with that of the second laser cavityThe ridge 13 has an end surface reflectivity at the second HR coating cleavage plane 18
When any one of the two ridge stripes works in a dual-mode state, the other ridge stripe can be separated from a phase region of dual-mode operation and is necessarily in single-longitudinal mode operation, so that the DFB laser chip has higher SMSR and the Shan Moliang rate can reach 100%.
Based on the above inventive concept, the calculation formula of the design parameter of the third bending section is:
wherein:
representing the effective length of the third bending section along the y direction; />
The relative bending angle of the third bending section along the x direction is shown.
Likewise, in order to ensure that the structural design of the first ridge 12 is reasonably reliable, after trial and error, the following rules can be derived: relative bending angle of the third bending section 121 along the x direction
The range of the values is as follows: 5 DEG </i>
Less than 30 deg.. It should be noted that the relative bending angle +.>
Refer to the acute angle between the bending section and the y-axis, and the absolute value of the included angle is taken regardless of whether the third bending section 121 is bent in the positive direction or the negative direction of x. />
In the present embodiment
1.31μm, the effective length of the third bending section 121 is obtained after the simulation test based on the formula (5)>
The relative bending angle of the second bending section 121 in the x direction is 5.1 μm +.>
20 deg.. It is verified that the relative bending angle of the third bending section 121 in this embodiment ∈>
The value of the number is within the set value range, and meets the design requirement.
Because different end face phases can cause obvious difference of SMSR and other performances of the laser cavities, the SMSR and other performances of one laser cavity can meet the index requirement, so that a DFB laser with better performance can be selected for packaging during packaging, and the single-mode yield of the DFB laser chip is further improved.
As shown in fig. 1 and 4, as a preferable scheme: in this embodiment, the first bending section 120 and the second bending section 130 are both straight sections bending along the opposite direction of x, and the third bending section 121 is a straight section bending along the positive direction of x. In practice, the first ridge 12 forms a five-section bent waveguide structure of straight waveguide, bent straight waveguide, bent straight waveguide and straight waveguide, and the second ridge 13 forms a three-section bent waveguide structure of straight waveguide, bent straight waveguide and straight waveguide, and the two structures cooperate with each other to form a double-bent waveguide structure with novel structure.
As shown in fig. 1 to 3, as a preferable scheme: the epitaxial structure of each laser cavity is a ridge waveguide structure, which comprises an n-InP buffer layer 22, a lower confinement layer 23, a quantum well layer 24, an upper confinement layer 25, a grating layer 26 and a contact layer 27 in order from bottom to top. The first ridge stripe 12 and the second ridge stripe 13 are etched to the upper limiting layer 25 by the contact layer 27, and the surface of the first ridge stripe 12 is provided with a first contact electrode 14, and the surface of the second ridge stripe 13 is provided with a second contact electrode 15. The material design of each layer in this embodiment is as follows:
the n-InP substrate 21 has a thickness of 350 mum, the doping atom is Si and the doping concentration is 3e 18 cm -3 ；
The n-InP buffer layer 22 has a thickness of 400nm, a doping atom of Si and a doping concentration of 1e 18 cm -3 ；
The lower confinement 23 is from bottom to top for undoped InGaAsP having a bandgap wavelength of 1050nm, undoped InGaAsP having a bandgap wavelength of 1100nm, undoped InGaAsP having a bandgap wavelength of 1150nm, and undoped InGaAsP having a bandgap wavelength of 1200nm, each layer having a thickness of 50nm;
the quantum well layer 24 is an InGaAsP quantum well with 6 pairs of well layers of 1% compressive strain and 2% tensile strain, and the lasing wavelength is 1310nm;
the upper confinement layer 25 is from bottom to top InGaAsP with undoped bandgap wavelength of 1200nm, inGaAsP with undoped bandgap wavelength of 1150nm, inGaAsP with undoped bandgap wavelength of 1100nm and InGaAsP with undoped bandgap wavelength of 1050nm, each layer having thickness of 37nm;
grating layer 26 is an InP buried undoped InGaAsP grating layer with a 1200nm band gap wavelength, the grating layer 26 being of period length
A uniform grating of 204.7nm, the grating layer 26 can select the longitudinal mode of the laser to realize single longitudinal mode output of the laser; in actual production, holographic exposure lithography, nanoimprint lithography, electron beam lithography or the like can be adopted to manufacture uniform gratings, and the embodiment is preferably a holographic exposure lithography technology, and compared with electron beam lithography, the holographic exposure lithography has the advantages of short manufacturing period, easiness in manufacturing large area, low cost and the like;
the contact layer 27 is InGaAs, the contact layer 27 is directly connected to an electrode layer, and the material of the electrode layer may be conductive metal.
As shown in fig. 1 and 2, the operation of the DFB laser chip provided by the present invention is described as follows: current is first injected from the first contact electrode 14 and the second contact electrode 15, respectively, and then the spectra output by the first laser cavity 10 and the second laser cavity 11 at the first AR coating cleavage face 17 and the second AR coating cleavage face 19 are detected, respectively. When one of the laser cavities is operated in dual mode, the other laser cavity must be operated in single longitudinal mode. Then, the electrode on the laser cavity capable of generating the single longitudinal mode operation is determined as the final operation electrode, and the current injection to the laser chip in the actual operation is completed.
The practice shows that the DFB laser chip produced by adopting the inventive concept of the embodiment can ensure that one of the two laser cavities realizes single longitudinal mode operation, thereby improving the Shan Moliang rate of the chip, achieving the purpose of improving the single longitudinal mode yield in the process of manufacturing the batched tube cores, effectively avoiding the loss of the single mode yield after the processes of epitaxy, grating manufacture, secondary epitaxy, front/back, cleavage and AR/HR coating, greatly improving the production efficiency of the DFB chip and reducing the production cost.
Embodiment two:
referring to fig. 5, unlike the first embodiment, the epitaxial structures of the first laser cavity 10 and the second laser cavity 11 in the present embodiment are buried heterojunction structures comprising, in order from bottom to top, an n-InP buffer layer 22, a lower confinement layer 23, a quantum well layer 24, an upper confinement layer 25, a grating layer 26, and a P-InP layer 28; the first ridge stripe 12 and the second ridge stripe 13 are each etched to the n-InP buffer layer 22 by the P-InP layer 28, and the first ridge stripe and the second ridge stripe are filled with the semi-insulating InP layer 29 and the n-InP layer 210, and the contact layer 27 is covered over the first ridge stripe 12 and the second ridge stripe 13.
It should be noted that the epitaxial structures provided in the first embodiment and the second embodiment are not limited by the only structure, and may be reasonably designed according to practical requirements during application, for example, the substrate may be GaAs, gaN, inP or GaSb material; the active region gain structure can be a single quantum well, a multiple quantum well, a tunnel junction cascade quantum well, a quantum cascade or a quantum dot; grating layer 26 may be a striped grating of equal doping levels or a graded index grating of different doping levels, and may be a buried, semiconductor buried or metal buried structure.
Embodiment III:
referring to fig. 6, unlike the first and second embodiments, the first, second and third bending sections 120, 130 and 121 in the present embodiment are arc-shaped sections bent in the positive or negative direction of x, and the tangents of the front and rear ends of the first, second and third bending sections 120, 130 and 121 are parallel to the y direction. Specifically, the first bending section 120 and the second bending section 130 are arc-shaped sections that are bent along the positive direction of x, and the third bending section 121 is an arc-shaped section that is bent along the negative direction of x. The loss of a single arcuate segment waveguide is much less than the loss of a single straight segment waveguide, thus providing better performance and substantially reducing the overall loss of a multi-segment curved waveguide structure.
Since the first bending section 120, the second bending section 130 and the third bending section 121 are smooth arc sections in the embodiment, the relative bending angles
And relative bending angle->
Is different from the first and second embodiments. Referring to fig. 7, assuming that the horizontal distances between the head and tail ends of the first bending section 120 and the second bending section 130 are a and the horizontal distance between the head and tail ends of the third bending section 121 is B, in this embodiment, the relative bending angle ∈>
Is defined as
Relative bending angle->
Is defined as +.>
But->
And->
Still ranging from 5 deg. -30 deg.. In designing the first bending section 120 and the second bending section 130, according to the aboveThe formula (4) is subjected to a simulation test to obtain the optimal effective length +.>
And relative bending angle->
. When the third bending section 121 is designed, the optimal effective length can be obtained by performing the simulation test according to the above formula (5)>
And relative bending angle->
。
The foregoing is merely a specific embodiment of the present invention, but the design concept of the present invention is not limited thereto. The design concept of the invention is utilized to make insubstantial changes on the invention, which belongs to the behavior of infringement of the protection scope of the invention.
Claims (10)
1. A multi-bend waveguide DFB laser chip, characterized by:
comprises a substrate;
a first laser cavity and a second laser cavity which are arranged at intervals are formed above the substrate, and two end surfaces of the first laser cavity along the y direction are a first HR coating cleavage surface and a first AR coating cleavage surface respectively; two end surfaces of the second laser cavity along the y direction are a second HR coating cleavage surface and a second AR coating cleavage surface respectively;
etching a first ridge and a second ridge along the y direction of the first laser cavity and the second laser cavity respectively; the first ridge is provided with a first bending section and a third bending section which are bent along the x direction at a position close to the cleavage surface of the first HR coating; the second ridge strip is provided with a second bending section which is bent along the x direction at a corresponding position of the first bending section;
the first laser cavity and the second laser cavity are internally provided with grating layers, and the grating of the first laser cavity extends from the cleavage surface of the first AR coating to the front of the third bending section; the total grating length of the second laser cavity is equal to the total grating length of the first laser cavity.
2. A multi-bend waveguide DFB laser chip according to claim 1, wherein: the first bending section, the second bending section and the third bending section are straight sections which are bent along the positive direction or the reverse direction of x.
3. A multi-bend waveguide DFB laser chip according to claim 1, wherein: the first bending section, the second bending section and the third bending section are arc-shaped sections which are bent along the positive direction or the reverse direction of x, and tangents at the head end and the tail end of the first bending section, the second bending section and the third bending section are parallel to the y direction.
4. A multi-bend waveguide DFB laser chip according to any of claims 1-3, wherein: the calculation formula of the design parameters of the first bending section and the second bending section is as follows:
5. A multi-bend waveguide DFB laser chip as recited in claim 4, wherein: the relative bending angles of the first bending section and the second bending section along the x direction
The range of the values is as follows: 5 DEG </i>
＜30°。
6. A multi-bend waveguide DFB laser chip according to claim 1, wherein: the vertical distance between the central point of the first bending section and the cleavage surface of the first HR coating and the vertical distance between the central point of the second bending section and the cleavage surface of the second HR coating are H, and the range of values is as follows:
wherein L represents the length of the first ridge or the second ridge in the y-direction.
7. A multi-bend waveguide DFB laser chip according to claim 1, wherein: the calculation formula of the design parameters of the third bending section is as follows:
wherein:
representing the effective length of the third bending section along the y direction; />
The relative bending angle of the third bending section along the x direction is shown.
8. A multi-bend waveguide DFB laser chip as recited in claim 7, wherein: the relative bending angle of the third bending section along the x direction
The range of the values is as follows: 5 DEG </i>
＜30°。
9. A multi-bend waveguide DFB laser chip according to claim 1, wherein: the distance between the first laser cavity and the second laser cavity is S, and the range of the distance is as follows: s is more than or equal to 5 mu m and less than or equal to L W μm, where L W Representing the length of the DFB laser chip in the x-direction.
10. A multi-bend waveguide DFB laser chip according to claim 1, wherein: and manufacturing the grating layer by adopting a holographic exposure lithography technology.
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