An electrically injected hybrid cavity DFB laser and a manufacturing method thereof

Abstract

The application discloses an electric injection mixed cavity DFB laser and a manufacturing method thereof. The epitaxial structure of the laser includes a phase shift region and an active region along the laser cavity length direction, and one end of the cavity length direction is a reflection end face, wherein the phase shift region is close to the reflection end face; the epitaxial structure of the active region includes an active layer and a grating; the epitaxial structure of the phase shift region does not include the active layer and the grating, and includes a passive waveguide layer, the passive waveguide layer is connected with the active layer; a positive electrode metal for injecting current into the active layer is arranged on the active region, and an electric injection electrode metal for injecting current into the passive waveguide layer to modulate the refractive index of the phase shift region is arranged on the phase shift region. The active region and the passive phase shift region are butted to form a mixed cavity laser, the passive waveguide is electrically injected to cause the change of the carrier concentration, the phase change and the wavelength tuning of the laser are realized, the tuning rate and efficiency are good, the laser is beneficial to realizing the separate linear and high-speed frequency modulation application, and the influence on the threshold and the slope efficiency is small.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lasers, and particularly relates to an electrically injected mixed cavity DFB laser and a manufacturing method thereof. BACKGROUND

[0002] The laser radar adopting the frequency-modulated continuous wave (FMCW) technology has the advantages of simultaneously measuring distance and speed and strong anti-environmental light interference capability, and is an important development direction of the laser radar. The FMCW radar needs a laser with a narrow linewidth (about 100 kHz), fast and wide tuning range (about 20 GHz), and the narrow linewidth semiconductor laser has a small volume and high efficiency, and has an ideal application prospect in the field of FMCW radar light sources.

[0003] The conventional narrow linewidth semiconductor lasers mainly include a distributed feedback laser (DFB), a distributed Bragg reflection laser (DBR) and an external cavity semiconductor laser (ECL). The narrow linewidth DFB has the advantages of large-scale production and low cost due to its simple and mature epitaxy and production process, but the tuning range is generally small. When the DFB laser works above the threshold, the carrier concentration in the laser cavity is clamped at the threshold Nth level after reaching the steady state, and the carrier concentration almost remains unchanged with the increase of the current. Therefore, when the modulation current is added to the laser above the threshold, the carrier concentration in the cavity only changes slightly near the threshold Nth. Therefore, the tuning range of the laser through the positive current of the DFB laser is relatively small, and the laser power is also modulated, which increases the intensity noise. Due to the above limitations, the electrically injected fast jump-free mode tuning range is generally several GHz, which is difficult to meet the demand of the FMCW tuning range of about 20 GHz. SUMMARY

[0004] The application provides an electrically injected mixed cavity DFB laser and a manufacturing method thereof to solve the problems in the prior art.

[0005] To achieve the above object, the technical scheme of the application is as follows.

[0006] An electrically injected mixed cavity DFB laser, the epitaxial structure of which includes a phase shift region and an active region along the cavity length direction of the laser, and one end of the cavity length direction is a reflection end face, wherein the phase shift region is close to the reflection end face; the epitaxial structure of the active region includes an active layer and a grating; the epitaxial structure of the phase shift region does not include the active layer and the grating, and includes a passive waveguide layer, the passive waveguide layer being connected with the active layer; the active region is provided with an anode metal for injecting current into the active layer, and the phase shift region is provided with an electrically injected electrode metal for injecting current into the passive waveguide layer to modulate the refractive index of the phase shift region.

[0007] Optionally, the phase shift region accounts for 2% to 20% of the cavity length of the laser.

[0008] Optionally, the material band gap of the passive waveguide layer is greater than the material band gap of the active region, and the photoluminescence wavelength is less than the laser operating wavelength.

[0009] Optionally, the epitaxial structure is provided with a ridge waveguide penetrating through the phase shift region and the active region, and the anode metal and the electrical injection electrode metal are both arranged on the ridge waveguide.

[0010] Optionally, the epitaxial structure is formed with two grooves on the surface, the ridge waveguide is formed between the two grooves, and the electrical injection electrode metal covers the surfaces of the two grooves and the ridge waveguide.

[0011] Optionally, the epitaxial structure is a buried heterostructure, the active layer and the passive waveguide layer are surrounded by clamping layers on the left and right sides in the cavity length direction, the anode metal is arranged above the active layer, and the electrical injection electrode metal is arranged above the passive waveguide layer.

[0012] Optionally, the epitaxial structure of the active region includes a substrate, a lower cladding layer, an active layer, and an upper cladding layer, and the grating is arranged in the upper cladding layer or the lower cladding layer; the epitaxial structure of the phase shift region includes, from bottom to top, a substrate, a lower cladding layer, a passive waveguide layer, and an upper cladding layer, and the upper cladding layer and the lower cladding layer have opposite doping types.

[0013] Optionally, the lower cladding layer, the passive waveguide layer, and the upper cladding layer form a PN junction.

[0014] Optionally, the material band gap of the passive waveguide layer is less than the material band gap of the lower cladding layer and the upper cladding layer, and the material band gap of the active layer is less than the material band gap of the lower cladding layer and the upper cladding layer.

[0015] Optionally, a passivation layer is further arranged on the epitaxial structure, the passivation layer is provided with openings for the anode metal and the electrical injection metal to contact the epitaxial structure, respectively, and the epitaxial structure further includes a top contact layer arranged at least corresponding to the openings.

[0016] Optionally, the passivation layer can be selected from a silicon dioxide film or a silicon nitride film.

[0017] Optionally, the electrical injection electrode metal and the anode metal are arranged in a spaced manner, and the electrical injection electrode metal is closer to the side of the reflection end face for better effect.

[0018] Optionally, the lengths of the electrical injection electrode metal and the anode metal account for more than 70% of the lengths of the phase shift region and the active region, respectively, and an electrical isolation region is arranged between the electrical injection electrode metal and the anode metal, and the length of the electrical isolation region in the cavity length direction is not less than 3 microns.

[0019] Optionally, the electrical injection electrode metal and the anode metal can be selected from the same metal material or metal layer structure, and specifically can be a metal with good electrical conductivity.

[0020] A method for manufacturing the above-mentioned electrically injected hybrid cavity DFB laser, comprising the steps of:

[0021] 1) growing a first epitaxial layer of the DFB laser on a substrate, including an active layer and a grating forming layer, defining a phase shift region and an active region, and making a grating pattern by electron beam exposure or full system exposure, and forming a grating in the grating forming layer by etching;

[0022] 2) etching away the grating forming layer and the active layer of the phase shift region, and performing a second epitaxial butt joint growth of a passive waveguide layer;

[0023] 3) performing a third epitaxial growth and manufacturing a waveguide structure;

[0024] 4) depositing gold in the active region to manufacture a positive electrode metal, and synchronously depositing gold in the phase shift region to manufacture an electrically injected electrode metal;

[0025] 5) thinning the back of the substrate, and then depositing a negative electrode metal.

[0026] Optionally, between step 3) and step 4), the following step is further included:

[0027] defining an electrical isolation region by photolithography, etching away part of the epitaxial layer below the defined electrical isolation region to form the electrical isolation region, then depositing a passivation layer on the front surface, and setting an opening in the passivation layer above the waveguide structure by photolithography for the epitaxial layer to contact the positive electrode metal and the electrically injected electrode metal.

[0028] Optionally, in step 3), a third epitaxial growth of an upper cladding layer and a contact layer is performed, and then a ridge waveguide is manufactured by etching groove process.

[0029] Optionally, in step 3), a laser waveguide mesa etching is performed, then a third epitaxial growth of a restriction layer on both sides of the laser waveguide is performed, and then a fourth epitaxial growth of an upper cladding layer and a contact layer is performed.

[0030] The beneficial effects of the present application are:

[0031] 1) The active region and the passive phase shift region are butt jointed to form a hybrid cavity laser, the DFB active region provides optical gain and grating basic mode selection function, the phase shift region provides fine jump-free frequency tuning function, the resonant frequency of the laser is mainly determined by the period of the DFB grating and the cavity length of the hybrid cavity, realizing fast and wide range laser tuning controlled by current, realizing fine jump-free frequency tuning function, improving the tuning range and tuning rate of the DFB laser, so as to meet the FMCW radar application;

[0032] 2) Electrical injection into the passive waveguide causes a change in carrier concentration, thereby achieving phase change and wavelength tuning of the laser. The tuning rate and efficiency are good, which is beneficial for the laser to achieve standalone linear, high-speed frequency modulation applications, while maintaining minimal impact on threshold and skew efficiency. Attached Figure Description

[0033] Figure 1 This is a top view of the electrically injected hybrid cavity DFB laser of Example 1;

[0034] Figure 2 for Figure 1 Cross-sectional view along the a-a' direction;

[0035] Figure 3 for Figure 1 Cross-sectional view along the b-b' direction;

[0036] Figure 4 This is a cross-sectional schematic diagram of the electrically injected hybrid cavity DFB laser of Example 2 (corresponding to...). Figure 1 (in the c-c' direction);

[0037] Figure 5 This is a cross-sectional schematic diagram of the electrically injected hybrid cavity DFB laser of Example 2 (corresponding to...). Figure 1 (in the b-b' direction). Detailed Implementation

[0038] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. The accompanying drawings are merely illustrative to facilitate understanding of the invention, and their specific proportions can be adjusted according to design requirements. The vertical relationships of relative elements and the definitions of front / back in the graphics described herein should be understood by those skilled in the art to refer to the relative positions of the components; therefore, they can all be flipped to present the same component, and all of this should fall within the scope disclosed in this specification.

[0039] Example 1

[0040] refer to Figures 1 to 3The electrically injected hybrid cavity DFB laser 100 of Example 1 comprises an epitaxial structure 110, a passivation layer 120, a positive electrode metal 130, an electrically injected electrode metal 140 and a negative electrode metal 150. The epitaxial structure 110 comprises a phase-shift region A and an active region B along the cavity length direction (indicated as the x direction in the figure). One end of the DFB laser along the cavity length direction is a reflective end face, the end face is coated with a high-reflection film HR, and the other end is a transmissive end face, the end face is coated with an anti-reflection film AR, and the phase-shift region A is close to the reflective end face HR. The active region B comprises, from bottom to top, a substrate 111, a lower cladding layer 112, an active layer 113, an upper cladding layer 114 and a contact layer 115, and the upper cladding layer 114 is provided with a grating 116; the phase-shift region A comprises, from bottom to top, a substrate 111, a lower cladding layer 112, a passive waveguide layer 117, an upper cladding layer 114 and a contact layer 115, the passive waveguide layer 117 is in contact with the active layer 113, and no grating is provided in the epitaxial structure of the phase-shift region A. The front surface of the epitaxial structure 110 is provided with a ridge waveguide 118 along the cavity length direction (indicated as the transverse direction in the figure). The passivation layer 120 covers the surface of the epitaxial structure 110, and the passivation layer 120 is provided with openings on the ridge waveguides of the active region and the phase-shift region; the positive electrode metal 130 is provided on the ridge waveguide of the active region and is in contact with the contact layer 115 through the corresponding opening; and the electrically injected electrode metal 140 is provided on the ridge waveguide of the phase-shift region and is in contact with the contact layer 115 through the corresponding opening. The negative electrode metal 150 is located on the back surface of the substrate 111.

[0041] The positive electrode metal 130 is used to inject current into the active layer 113, and the electrically injected electrode metal 140 is used to inject current into the passive waveguide layer to modulate the refractive index of the phase-shift region. Thus, the active region B provides optical gain and grating basic mode selection functions, and the phase-shift region A provides the function of fine jumpless mode frequency tuning.

[0042] When the DFB active layer is not modulated, the period and the equivalent refractive index of the DFB grating remain stable, and the resonant frequency is mainly affected by the cavity length, which is specifically represented as: υ*(<n a >*La+<n p >*Lp)=m*c / 2. Wherein, υ is the resonant frequency, <na> 、 <np>respectively, La and Lp are the length of DFB active region and phase shift region respectively, c is the speed of light in vacuum, and m represents the longitudinal mode number. When the temperature and current of the DFB active region are kept constant, <n a The mode m remains unchanged when the material refractive index of the phase shift region is slightly changed, and the resonant frequency is mode-hop-free tuned.

[0043] The refractive index of the phase shift region is affected by the carrier concentration, which can be controlled by electrical injection, thereby achieving laser tuning. The refractive index of the phase shift region changes with the injected current density. When the injected current density of the phase shift region increases, the frequency of the laser decreases. The frequency change has a good linear relationship with the injected current density, which is beneficial to meet the demand of FMCW laser radar for linear frequency modulation. Since the phase shift region is a passive structure without gain effect, the gain of the entire cavity is small during phase shift tuning, which is beneficial to maintain the stability of the output power during tuning.

[0044] The length of the phase shift region A accounts for 2% to 20% of the length of the cavity, for example, 10% can achieve better tuning effect. The electrical injection electrode metal 140 covers more than 70% of the length of the ridge waveguide of the phase shift region A and extends to the passivation layer 120 on one side of the ridge waveguide to form a circular electrode, for example. The electrical injection electrode 140 is in contact with the ridge waveguide of the phase shift region A, and the upper cladding layer, passive waveguide layer and lower cladding layer form a PN junction. The injected carriers are limited near the passive waveguide layer under the action of the PN junction, thereby causing the carrier concentration of the passive waveguide layer of the phase shift region to change, thereby changing its refractive index and forming laser tuning. The anode metal 130 covers more than 70% of the length of the ridge waveguide of the active region B and extends to the passivation layer on one side of the ridge waveguide (corresponding to the wire bonding area). The anode metal 130 and the electrical injection electrode metal 140 can be made of the same metal in the same process, for example, using Ti / Pt / Au as the metal material with a thickness of 520 nm. To ensure electrical isolation between the two, an electrical isolation region 121 is provided between them. The length of the electrical isolation region 121 is not less than 3um. The passivation layer electrical isolation region 121 can be formed by etching, forming a groove by removing the contact layer and part of the upper cladding layer, and covering the surface with a passivation layer 120. The passivation layer 120 is a silicon dioxide or silicon nitride film with a thickness of 100nm-1000nm.

[0045] The conventional DFB laser ridge waveguide epitaxial structure can be applied to the active region B of the embodiment, and the grating 116 can be arranged above or below the active layer 113. The grating types include uniform grating, 1 / 4 phase shift grating, multiple phase shift grating, and periodic modulation grating, etc. The period of the grating is determined according to the emission wavelength of the laser. For example, the upper cladding layer 114 of the active region B includes a grating forming layer, an upper waveguide layer, etc. The grating is made by etching the grating forming layer. The carriers injected by the positive electrode metal 130 are applied to the active layer 113 to provide gain for the laser.

[0046] The material of the passive waveguide layer 117 is selected according to the laser operating wavelength, the material of the active layer of the active region, the refractive index, etc. However, the lattice constant of the passive waveguide layer needs to be the same as that of the substrate material, and the optical radiation wavelength (PL) of the passive waveguide layer material needs to be less than the laser operating wavelength. The passive waveguide layer material can be bulk semiconductor material InGaAsP or InGaAlAs, AlGaAs, InGaAs. For example, the 1550 nm band laser can select InGaAsP or InGaAlAs material, or keep the same as the material of the active layer 113, just change the composition so that the PL wavelength is less than the laser operating wavelength, and the band gap is greater than that of the active layer 113. The material band gap of the passive waveguide layer is less than that of the lower cladding layer and the upper cladding layer, and the material band gap of the active layer is less than that of the lower cladding layer and the upper cladding layer; the active layer 113 and the passive waveguide layer 117 constitute the core layer of the laser waveguide, and the refractive index is greater than that of the lower cladding layer 212 and the upper cladding layer 214, so as to realize light confinement and transmission.

[0047] The conventional DFB laser ridge waveguide structure can be applied to the embodiment. For example, two grooves 119 are etched on the front surface of the epitaxial structure 110, and the bottoms of the two grooves 119 are formed at any position of the upper cladding layer 114. The stable etching stop can be achieved by setting a stop etching layer, and the ridge waveguide 118 is formed between the two grooves 119. The width of the ridge waveguide 118 is about 2-3 um, and the width of the groove 119 is about 15 um. The electrode metal 140 extends along the cavity length direction, and covers the surfaces of the two grooves 119 and the surface of the ridge waveguide 118.

[0048] The method for manufacturing the above-mentioned electrically injected hybrid cavity DFB laser includes the following steps:

[0049] 1) growing a first epitaxial layer of the DFB laser on a substrate, including an active layer and a grating forming layer, defining a phase shift region and an active region, making a grating pattern by electron beam exposure or full system exposure, and forming a grating by etching the grating forming layer;

[0050] 2) etching away the grating forming layer and the active layer of the phase shift region, and growing a passive waveguide layer by secondary epitaxial butt joint;

[0051] 3) three epitaxial layers are formed to form the upper waveguide layer and the contact layer;

[0052] 4) a ridge waveguide is made by etching groove process;

[0053] 5) an electrically isolated region is made on the ridge waveguide by photolithography and etching process;

[0054] 6) a passivation layer is deposited, and the passivation layer on the active region and the phase shift region of the ridge waveguide is respectively opened to expose the contact layer;

[0055] 7) gold is synchronously deposited on the ridge waveguide of the active region and the corresponding metal wire region to form the positive electrode metal, and the ridge waveguide of the phase shift region and the corresponding metal wire region to form the electric injection electrode metal;

[0056] 8) the back of the substrate is thinned and the negative electrode metal is deposited.

[0057] Example 2

[0058] Reference Figures 4 to 5 , the electric injection hybrid cavity DFB laser 200 of Example 2, the difference between the epitaxial structure and Example 1 is that it adopts a buried heterojunction structure. Referring to Figure 1 , which also includes a phase shift region A and an active region B along the cavity length direction; the active region B includes a substrate 211, a lower cladding layer 212, an active layer 213, an upper cladding layer 214 and a contact layer 215 from bottom to top, and a grating 216 is arranged in the upper cladding layer 214; the phase shift region A includes a substrate 211, a lower cladding layer 212, a passive waveguide layer 217, an upper cladding layer 214 and a contact layer 215 from bottom to top, the passive waveguide layer 217 is connected with the active layer 213, and no grating is arranged in the epitaxial structure of the phase shift region A, the upper cladding layer 212 is P-type doped, the lower cladding layer 214 is N-type doped, and the contact layer 215 is P-type heavily doped. The active layer 213 and the passive waveguide layer 217 are surrounded by a confinement layer 218 on both sides in the cavity length direction, thereby forming a strip structure buried in the confinement layer 218. A passivation layer 220 is also arranged on the epitaxial structure, and the passivation layer 220 also has openings for the positive electrode metal 230 and the electric injection electrode metal 240 to contact the contact layer 215, the positive electrode metal 230 corresponds to being located above the active layer 213 and contacting the contact layer 215, and the electric injection electrode metal 240 corresponds to being located above the passive waveguide layer 217 and contacting the contact layer 215. The confinement layer 218 is a material with a higher band gap, which can realize current limitation and light limitation. The passive waveguide layer 217 and the active layer 213 constitute the core layer of the laser waveguide, and the refractive index is greater than that of the lower cladding layer 212 and the upper cladding layer 214, thereby realizing light limitation and conduction. The active layer 213 can be a multi-quantum well structure, and the material energy level band gap is smaller than that of the passive waveguide layer 217, the lower cladding layer 212 and the upper cladding layer 214. The passive waveguide layer 217 can be a bulk material structure, and the material band gap is greater than that of the active layer 213, which is transparent to the working wavelength of the laser.

[0059] Conventional buried heterostructure DFB lasers can be applied to the present application. The material of the confinement layer 218 is, for example, InP or GaAs, and the confinement layer 218 can be non-doped or grown as a reverse-biased PN junction, so that current can only flow from the active layer 213 and the passive waveguide layer 217.

[0060] The method for manufacturing the above-mentioned electrically-injected hybrid-cavity DFB laser includes, for example, the following steps:

[0061] 1) growing a first epitaxial layer of the DFB laser on an n-type doped substrate, including an active layer and a grating-forming layer, defining a phase-shift region and an active region, and fabricating a grating pattern by electron beam exposure or full-system exposure, and etching the grating-forming layer and the active layer in the phase-shift region to form a grating;

[0062] 2) etching away the grating-forming layer and the active layer in the phase-shift region, and performing a second epitaxial growth to grow a passive waveguide layer by butt joint;

[0063] 3) etching the active layer and part of the substrate near the transverse waveguide to form a mesa structure for the laser waveguide;

[0064] 4) performing a third epitaxial growth to grow a confinement layer on both sides of the laser waveguide;

[0065] 5) performing a fourth epitaxial growth to grow an upper cladding layer and a contact layer;

[0066] 6) depositing a passivation layer, and respectively opening the passivation layer on the active region and the phase-shift region to expose the contact layer;

[0067] 7) synchronously depositing gold on the laser waveguide in the active region to form a positive electrode, and depositing an electrically-injected electrode metal on the laser waveguide in the phase-shift region;

[0068] 8) thinning the substrate on the back side and depositing a negative electrode.

[0069] The above-mentioned embodiment is only used to further illustrate an electrically-injected hybrid-cavity DFB laser and a method for manufacturing the same according to the present application, but the present application is not limited to the embodiment. Any simple modification, equivalent change and modification made according to the technical essence of the present application to the above-mentioned embodiment all fall within the protection scope of the technical solution of the present application.< / np> < / na>

Claims

1. An electrically injected hybrid cavity DFB laser, characterized in that: The epitaxial structure of the DFB laser includes a phase-shifting region and an active region along the cavity length direction, with one end of the cavity length direction serving as a reflecting end face, wherein the phase-shifting region is close to the reflecting end face; the epitaxial structure of the active region includes an active layer and a grating; the epitaxial structure of the phase-shifting region does not include an active layer and a grating, but includes a passive waveguide layer, which is connected to the active layer; the material bandgap of the passive waveguide layer is larger than that of the active layer; the active region is provided with a positive electrode metal for injecting current into the active layer, and the phase-shifting region is provided with an electrically injected electrode metal for injecting current into the passive waveguide layer to modulate the refractive index of the phase-shifting region.

2. The electrically injected hybrid cavity DFB laser according to claim 1, characterized in that: The phase-shifting region occupies 2% to 20% of the cavity length of the laser.

3. The electrically injected hybrid cavity DFB laser according to claim 1, characterized in that: The photoluminescence wavelength of the passive waveguide layer material is shorter than the operating wavelength of the laser.

4. The electrically injected hybrid cavity DFB laser according to claim 1, characterized in that: The epitaxial structure is provided with a ridge waveguide that runs through the phase shift region and the active region, and the positive electrode metal and the electrically injected electrode metal are both disposed on the ridge waveguide.

5. The electrically injected hybrid cavity DFB laser according to claim 4, characterized in that: The surface of the epitaxial structure has two grooves, and the ridge waveguide is formed between the two grooves. The electrically injected electrode metal covers the surfaces of the two grooves and the ridge waveguide.

6. The electrically injected hybrid cavity DFB laser according to claim 1, characterized in that: The epitaxial structure is a buried heterojunction structure. The active layer and the passive waveguide layer are surrounded by confinement layers on the left and right sides of the cavity length direction. The positive electrode metal is located above the active layer, and the electrically injected electrode metal is located above the passive waveguide layer.

7. The electrically injected hybrid cavity DFB laser according to claim 1, characterized in that: The epitaxial structure of the active region includes a substrate, a lower cladding layer, an active layer, and an upper cladding layer, and the grating is disposed in the upper cladding layer or the lower cladding layer; the epitaxial structure of the phase-shifting region includes a substrate, a lower cladding layer, a passive waveguide layer, and an upper cladding layer from bottom to top, and the upper cladding layer and the lower cladding layer have opposite doping types.

8. The electrically injected hybrid cavity DFB laser according to claim 7, characterized in that: The lower cladding, passive waveguide layer, and upper cladding form a PN junction.

9. The electrically injected hybrid cavity DFB laser according to claim 7, characterized in that: The material bandgap of the passive waveguide layer is smaller than that of the lower cladding and the upper cladding, and the material bandgap of the active layer is smaller than that of the lower cladding and the upper cladding.

10. The electrically injected hybrid cavity DFB laser according to claim 1, characterized in that: The epitaxial structure is further covered with a passivation layer, which has openings that allow the positive electrode metal and the electrically injected metal to contact the epitaxial structure respectively. The epitaxial structure also includes at least a top contact layer corresponding to the openings.

11. The electrically injected hybrid cavity DFB laser according to claim 1, characterized in that: The lengths of the electrically injected electrode metal and the positive electrode metal account for more than 70% of the lengths of the phase shift region and the active region, respectively, and an electrically isolated region is provided between the electrically injected electrode metal and the positive electrode metal, wherein the length of the electrically isolated region along the cavity length direction is not less than 3 micrometers.

12. A method for fabricating an electrically injected hybrid cavity DFB laser according to any one of claims 1 to 11, characterized in that, Including the following steps: 1) Grow a primary epitaxial layer of a DFB laser on a substrate, including an active layer and a grating forming layer, define the phase shift region and the active region, fabricate the grating pattern by electron beam exposure or full-system exposure, and form the grating by etching the grating forming layer. 2) Etch away the grating forming layer and active layer in the phase-shifted region, and perform secondary epitaxial docking to grow a passive waveguide layer; 3) Perform further epitaxial growth and fabricate the waveguide structure; 4) Deposit metal in the active region to fabricate positive electrode metal, and simultaneously deposit metal in the phase-shift region to fabricate electro-injection electrode metal; 5) Thin the back side of the substrate and then deposit the negative electrode metal.

13. The method for fabricating an electrically injected hybrid cavity DFB laser according to claim 12, characterized in that, Between step 3) and step 4), the following steps are also included: An electrically isolated region is defined by photolithography, and part of the epitaxial layer below the defined electrically isolated region is etched away to form an electrically isolated region; then a passivation layer is deposited on the front side, and an opening for contact between the epitaxial layer and the positive electrode metal and the electrically injected electrode metal is formed on the passivation layer above the waveguide structure by photolithography.

14. The method for fabricating an electrically injected hybrid cavity DFB laser according to claim 12, characterized in that: In step 3), the cladding and contact layers are grown three times via epitaxial growth, and then the ridge waveguide is fabricated by etching trenches.

15. The method for fabricating an electrically injected hybrid cavity DFB laser according to claim 12, characterized in that: In step 3), the laser waveguide mesa is etched, then the confinement layer is grown three times on both sides of the laser waveguide, and then the cladding and contact layer are grown four times.

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