CN111262130B

CN111262130B - Laser structure and preparation method and application thereof

Info

Publication number: CN111262130B
Application number: CN202010162903.5A
Authority: CN
Inventors: 李齐柱; 毛明明; 周特; 张鹏飞; 徐真真
Original assignee: Vertilite Co Ltd
Current assignee: Vertilite Co Ltd
Priority date: 2020-03-10
Filing date: 2020-03-10
Publication date: 2022-04-19
Anticipated expiration: 2040-03-10
Also published as: CN111262130A

Abstract

The invention provides a laser structure and a preparation method and application thereof, wherein the laser structure comprises the following components: a substrate; the epitaxial layer is arranged on the substrate and comprises a lower cladding layer, an active layer, an upper cladding layer and an ohmic contact layer which are laminated; a ridge waveguide formed on the upper cladding layer; a plurality of periodic modulation gratings formed on the upper cladding and located on both sides of the ridge waveguide; and preset distances are reserved between the plurality of periodic modulation gratings and the active layer, and the preset distances are 50-200 nm. The laser provided by the invention has the advantages of simple manufacturing process, high side mode rejection ratio, high modulation speed and excellent dynamic single-mode characteristic.

Description

Laser structure and preparation method and application thereof

Technical Field

The invention relates to the technical field of semiconductor lasers, in particular to a laser structure and a preparation method and application thereof.

Background

In the technical field of semiconductor lasers, Distributed Feedback (DFB) semiconductor lasers have excellent differential gain, dynamic single-mode characteristics and larger modulation bandwidth and are widely applied to the fields of near infrared light communication, 3D biological identification and the like

At present, a grating structure included in a laser structure is a phase-shift grating, which is prone to limit the modulation speed of an optical communication laser due to a spatial hole burning effect, that is, as a current increases, a threshold gain difference decreases, a gain difference between a main mode and a first side mode becomes smaller, mode competition starts to occur, and even a dynamic single mode cannot be realized due to mode hopping, so that it is difficult to ensure that the laser has a stable dynamic single mode characteristic, thereby affecting the use range of the laser.

In addition, DFB lasers are currently mainly fabricated by grating buried structures and grating deep etched structures. For the grating buried structure, a two-step epitaxial process is needed during manufacturing, the process is stopped when the grating buried structure grows to be close to an active region in an epitaxial mode, grating etching is carried out, secondary epitaxy is carried out, the preparation process is complex and tedious, a strict cleaning process is needed, and troubles are caused to high-efficiency production of a laser. The preparation difficulty of the existing grating deep etching structure is very high, the requirement on the mask quality is high, and the stability and consistency of the performance are difficult to guarantee.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a laser structure having a stable structure, a small optical loss, a large power, a desirable side mode suppression ratio and a desirable modulation speed, and an excellent dynamic single mode characteristic.

It is another object of the present invention to provide a method for fabricating a laser structure as described above.

It is a further object of the present invention to provide a use of a laser structure as described above.

To achieve the above and other objects, a first aspect of the present invention provides a laser structure comprising: a substrate; the epitaxial layer is arranged on the substrate and comprises a lower cladding layer, an active layer, an upper cladding layer and an ohmic contact layer which are laminated; a ridge waveguide formed on the upper cladding layer; a plurality of periodic modulation gratings formed on the upper cladding and located on both sides of the ridge waveguide; and preset distances are reserved between the plurality of periodic modulation gratings and the active layer, and the preset distances are 50-200 nm.

Optionally, the output wavelength of the laser structure is 1260-1600 nm.

Optionally, the length of the resonant cavity of the laser structure is 0.3-3 mm.

Optionally, the period of the periodic modulation grating is 150-250 nm.

Optionally, the height of the periodic modulation grating is 30-350 nm.

Optionally, the duty ratio of the periodic modulation grating is 0.1-0.9.

Optionally, the periodic modulation grating includes a plurality of grating regions, and lengths and periods of the plurality of grating regions are different.

Optionally, the filling medium of the periodic modulation grating is a silicon-based compound or a high molecular polymer.

The invention also provides a preparation method of the laser structure, which comprises the following steps: providing a substrate; forming an epitaxial layer on the semiconductor substrate, wherein the epitaxial layer comprises a lower cladding layer, an active layer, an upper cladding layer and an ohmic contact layer which are stacked; etching the upper cladding layer and the ohmic contact layer to form a ridge waveguide; and forming a plurality of periodic modulation gratings on the upper cladding layer and located on two sides of the ridge waveguide, wherein a preset distance is formed between the periodic modulation gratings and the active layer, and the preset distance is 50-200 nm.

In another aspect, the present invention provides a laser module, including: a circuit board; the laser structure is arranged on the circuit board; wherein the laser structure comprises, a substrate; the epitaxial layer is arranged on the substrate and comprises a lower cladding layer, an active layer, an upper cladding layer and an ohmic contact layer which are laminated; a ridge waveguide formed on the upper cladding layer; a plurality of periodic modulation gratings formed on the upper cladding and located on both sides of the ridge waveguide; and preset distances are reserved between the plurality of periodic modulation gratings and the active layer, and the preset distances are 50-200 nm.

In summary, the invention provides a laser structure, a manufacturing method thereof and an application thereof, the laser structure is formed by performing one-time epitaxial growth and shallow etching a plurality of periodic modulation gratings on two sides of a ridge waveguide, and a preset distance of 50-200 nm is formed between the plurality of periodic modulation gratings and the active layer. According to the evanescent field coupling principle, the optimal coupling between the optical field and the grating is realized, the quality of the grating is improved, the problem of space hole burning brought by the conventional phase-shift grating is solved, the dynamic single mode of the laser is realized, and the modulation speed and the light output power of the optical communication laser are in an ideal range. Moreover, the invention reduces the etching depth-to-width ratio of the grating, greatly simplifies the process, reduces the manufacturing cost, reduces the defects and the loss of the epitaxial wafer, and lays a foundation for the industrialization of the laser. Other features, advantages, and benefits may be apparent from consideration of the claims and description herein.

Drawings

Fig. 1 shows an overall block diagram of an optical transmitter proposed for the present implementation.

Fig. 2 shows a flow chart of a method for fabricating a laser structure according to the present embodiment.

Fig. 3 is a schematic diagram of a substrate of the laser structure in this embodiment.

Fig. 4 is a schematic diagram illustrating the formation of an epitaxial layer.

Fig. 5 is a schematic diagram illustrating the formation of a masking layer and a photoresist layer.

FIG. 6 is a schematic diagram illustrating the etching of the photoresist layer and the masking layer.

Fig. 7 is a schematic diagram illustrating the formation of a ridge waveguide.

Fig. 8 is a schematic diagram illustrating the formation of an e-beam glue layer.

Fig. 9 is shown as a side view in fig. 8.

Fig. 10 is a schematic view showing the preparation of the grating pattern.

FIG. 11 is a schematic illustration of etching the upper cladding layer.

Figure 12 shows a schematic view of forming a grating.

Fig. 13 is a schematic diagram showing the mask layer removed.

Fig. 14 is a top view of fig. 13.

Fig. 15 is a schematic diagram illustrating a structure of the periodic modulation grating provided in this embodiment.

Fig. 16 is a schematic structural diagram of a periodically modulated grating provided in another embodiment.

Fig. 17 is a schematic structural diagram of a periodically modulated grating provided in another embodiment.

Fig. 18 is a top view of fig. 17.

Fig. 19 is a schematic structural diagram of a periodically modulated grating provided in another embodiment.

Fig. 20 is a top view of fig. 19.

Fig. 21 is a schematic structural diagram of a periodically modulated grating provided in another embodiment.

Fig. 22 is shown as a top view in fig. 21.

Fig. 23 is a schematic view showing the formation of a filling layer and an insulating layer.

Fig. 24 is a front view of fig. 23.

Fig. 25 is a schematic view showing the formation of the upper electrode region.

Fig. 26 is a top view of fig. 25.

Fig. 27 is a schematic view showing the formation of upper and lower electrodes.

Fig. 28 is shown as a side view in fig. 27.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.

The optical fiber communication system is used as a physical basis for information transmission, and comprises a data source, an optical transmitter, an optical channel, an optical receiver and other parts, wherein the optical fiber communication system is based on the principle that information transmitted by a transmitting end is changed into an electric signal, then the electric signal is modulated onto a light source transmitted by the optical transmitter, the intensity of light is changed along with the frequency change of the electric signal, the electric signal is transmitted out through an optical fiber, then the optical signal is converted into the electric signal after being received by a receiving end, and the electric signal is demodulated and then recovered to form original information. The module used as the light source, such as a laser module comprising a laser, transmits a laser signal by using a received electric signal, has the advantages of small volume, low energy consumption, high luminous efficiency and good reliability, and is widely applicable to optical fiber communication systems.

As shown in fig. 1, the present invention provides a block diagram of an exemplary laser module 100, wherein the laser module 100 is used as a light emitting component, which emits a laser signal by using a received electrical signal. The laser module 100 includes, for example, a circuit board, for example, an input circuit 200, a driving circuit 300, and a laser structure 400 disposed on the circuit board. It should be understood that laser module 100 is for illustrative purposes only and that the present invention is not limited to a particular optical laser module 100. For example, the benefits and capabilities associated with the present invention may be realized regardless of the type and size of input circuit 200, driver circuit 300, and laser structure 400, and the interface, all of which may vary based on particular requirements and intended use.

As shown in fig. 1, in the laser module 100, an input circuit 200 performs scrambling and encoding operations on an input electrical signal. The driving circuit 300 is electrically connected to the input circuit 200, and is configured to modulate the electrical signal after scrambling and encoding to form a modulated signal. The laser structure 400 is electrically connected to the driving circuit 300, and is configured to drive the laser structure 400 according to a modulation signal and generate an optical signal, where laser emitted by the laser structure 400 is modulated by the driving circuit 300 to emit laser.

As shown in fig. 1, in the laser module 100, the laser structure 400 is used for emitting laser light, such as side light. In some embodiments of the invention, the output wavelength range of the laser structure 400 is 850-1600 nm, such as 1550nm, 1310nm, and 850nm, and further, the output wavelength of the laser structure 400 is 1310nm, which is widely used as near infrared light in Sensing systems (Sensing) of mobile devices, optical communication light sources, laser radars, AR/VR, and security monitoring fields.

As shown in fig. 2 to 21, the present invention provides a method for fabricating a laser structure 400, which includes, but is not limited to, the following steps S1 to S4.

As shown in fig. 2 and 3, the step S1 is performed to provide a substrate 410.

As shown in fig. 3, in step S1, the substrate 410 may be formed of a III-V compound type or an alloy thereof, which may be a suitably doped substrate, such as silicon (Si) -doped gallium arsenide (GaAs), a sapphire substrate, silicon carbide, aluminum nitride, gallium nitride, on which the epitaxial layer 420 is formed. The thickness of the substrate 410 is, for example, 10 to 200 μm, for example, 100 μm or 70 μm, which is the thickness of the substrate after thinning.

As shown in fig. 2 and 4, the step S2 is performed to form an epitaxial layer 420 on the substrate 410, where the epitaxial layer 420 includes a lower cladding layer 421, an active layer 422, an upper cladding layer 423, and an ohmic contact layer 424, which are stacked.

In some embodiments, the lower cladding layer 421 includes an N-type semiconductor layer, and the material may include an aluminum-containing material, such as N-Al_0.3Ga_0.7As、n-Al_0.25 Ga_0.75As, etc., the thickness of the lower cladding 421 is, for example, 1000-5000nm, such As 2800nm and 3000 nm.

In some embodiments, the active layer 422 includes a quantum dot composite structure disposed in a stack. Specifically, an indium arsenide/indium gallium arsenide/gallium arsenide (InAs/InGaAs/GaAs) quantum dot laser structure may be cited, which includes, for example, 8 layers of quantum dots, each layer of quantum dots may be separated by, for example, a 33nm GaAs spacer layer, each layer of quantum dots contains 2.7ml (mono layer) InAs, and the InAs is covered with a 6nm InGaAs stress relief layer. Further, the active layer 422 may also Be doped with p-type modulation, such as beryllium (Be), carbon (C), zinc (Zn), silicon (Si), etc., to improve mode gain and optical stability, specifically, for example, with a doping concentration of 3 × 10¹⁷cm^-3The doped region is arranged in the GaAs layer 17nm above the InAs/InGaAs quantum dot layer, and the width of the doped region is 6 nm. In the quantum dot laser structure within the above range, the number of carriers in the active layer 422 is ideal, and the laser structure 400 has good temperature stability and high external quantum efficiencyThe performance of the laser structure 400 is improved. Of course, the active layer 422 may also adopt a 5-12 quantum dot composite structure in some embodiments of the present invention. The active layer 422 transits between energy bands to emit light through the semiconductor substance (i.e., by using electrons) of the quantum dot composite structure, and forms two

parallel mirror surfaces

4221 and 4222 as mirrors by coating the cleavage surface or cavity surface of the semiconductor crystal to form a resonant cavity (fig. 9), so that light is oscillated and fed back to generate radiation amplification of the light, and laser is output from the side surfaces 4221 and/or 4222. In some embodiments, the material of the active layer 422 corresponds to an output wavelength of 1260 to 1600nm, such as 1310 nm.

In some embodiments, the upper cladding layer 423 includes a P-type semiconductor layer, and the material may include an aluminum-containing material, such as P-Al_0.3Ga_0.7As、p-Al_0.25 Ga_0.75As, etc., the thickness of the upper cladding layer 404 is 1000-3000nm, such As 1800nm, 2100 nm.

In some embodiments, the ohmic contact layer 424 is on the upper cladding layer 423, and further on the ridge waveguide 430 as described in detail below, for connection to subsequently formed electrodes. In some embodiments of the present invention, the ohmic contact layer 424 may be heavily doped p-type GaAs, for example, and the thickness of the ohmic contact layer 424 is, for example, 100 μm to 500 μm, such as 200 μm, 230 μm, 250 μm, 300 μm, but is not particularly limited.

Further, in some embodiments of the present invention, the epitaxial layer 420 may further include a barrier layer (not shown) on the upper cladding layer 423 to ensure a depth of etching when etching the ridge waveguide 430 as described in detail below, wherein the thickness of the barrier layer is 30-150 nm, such as 50nm, 85nm, or 120 nm.

In some embodiments, the epitaxial layer 420 is formed on the substrate 410 by sequential growth using a Molecular Beam Epitaxy (MBE) process, but is not limited thereto, and may also be formed on the substrate 410 by epitaxial deposition such as plasma enhanced chemical vapor deposition (PEVCD), Metal Organic Chemical Vapor Deposition (MOCVD), for example.

As shown in fig. 2 and fig. 5 to 7, the step S3 is performed to etch the ohmic contact layer 424 and the upper cladding layer 423 to form a ridge waveguide 430 and expose a portion of the upper cladding layer 423, where the ridge waveguide 430 can limit current and shape light spots.

As shown in fig. 5 to 7, the ridge waveguide 430 is located on the upper cladding layer 423, and a distance between the bottom of the grooves on both sides of the ridge waveguide 430 and the active layer 422 is 230 to 400nm, and further, for example, 230 to 300nm, further for example 270 to 295nm, for example 295nm, 290nm, 280nm and 275nm, and when the distance is within the above range, a plurality of periodic modulation gratings of the following structure are formed at the bottoms of the trenches at both sides of the ridge waveguide 430, such as the first periodic modulation grating 440a and the second periodic modulation grating 440b shown in figure 14, the

periodic modulation gratings

440a and 440b can be tightly coupled to the ridge waveguide 430 without being affected by the ridge height of the ridge waveguide 430, so that the evanescent field outside the active layer 422 and the

periodic modulation gratings

440a and 440b can form an ideal coupling effect, thereby completing the screening of the optical mode. The ridge width of the ridge waveguide 430 is, for example, 2 to 5 μm, such as 2 μm, 3 μm, and 3.5 μm.

As shown in fig. 5, in some embodiments of the present invention, the ridge waveguide 430 may be formed on the upper cladding layer 423 by, for example, a photolithography process, a dry etching process, and a wet etching process. In order to protect the ohmic contact layer, a mask layer 450 may be formed on the epitaxial layer 420 before the fabrication of the ridge waveguide 430 and the plurality of first periodic modulation gratings 440a is performed. The material of the mask layer 450 may be, for example, silicon dioxide (SiO)₂) Silicon nitride (SiN). The thickness of the mask layer 450 is, for example, 50nm to 100nm, such as 50nm, 60nm, 70nm, 80nm, and the thickness of the mask layer 450 in the above range may sufficiently protect the ridge waveguide 430 as described in detail below from being damaged during the process of manufacturing the

periodic modulation gratings

440a, 440b, and further, may avoid the problems of increased surface roughness of a current injection window and poor adhesion of an electrode when the laser structure 400 is used to grow an electrode.

As shown in fig. 5, in some embodiments of the present invention, the mask layer 450 may be prepared by a PECVD process.

As shown in fig. 5, in some embodiments of the invention, a photoresist 460 is coated on the mask layer 450, the photoresist 460 is patterned to develop an Etching window of the ridge waveguide 430, and a portion of the mask layer 450 is first etched using a dry Etching process, such as a Reactive Ion Etching (RIE) process.

As shown in fig. 6, in some embodiments of the present invention, a dry etching process, such as a combination of an Inductively Coupled Plasma (ICP) etching process and a wet etching process, is used to etch down the ohmic contact layer 424 and the upper cladding layer 423 and stop on the upper cladding layer 423, and the photoresist 460 is removed. That is, the ridge waveguide 430 is formed on the upper cladding layer 423.

As shown in fig. 2 and fig. 8 to 14, the step S4 is performed to form a plurality of periodic modulation gratings, such as bragg gratings, on the upper cladding 423 and located at two sides of the ridge waveguide 430, wherein a predetermined distance H is provided between the plurality of periodic modulation gratings and the active layer 422, and the predetermined distance H is 50 to 200 nm. The invention adopts the periodic modulation grating to expand the phase shift from a point to a region distributed along the resonant cavity, so that the optical field distribution is flatter and more uniform, and the problem of space hole burning caused by the conventional phase shift grating is avoided. Thus, as the current increases, the threshold gain difference remains relatively stable, maintaining dynamic single mode characteristics. The structure and position of the periodic modulation grating are changed to adjust the coupling effect on light, so that the laser structure 400 stably emits light, and single longitudinal mode continuous output and an ideal side mode suppression ratio are realized.

As shown in fig. 8 to 22, the periodic modulation grating, for example, includes a first periodic modulation grating 440a and a second periodic modulation grating 440b, which are formed on the upper cladding 423 and respectively disposed on two sides of the ridge waveguide 430 to form a lateral coupling grating, so that the obtained laser structure 400 is a laterally coupled distributed feedback (LC-DFB) laser. The first periodic modulation grating 440a and the second periodic modulation grating 440b have, for example, the same structure, but may have different structures.

As shown in FIGS. 12-22, in some embodiments, the height of the first periodic modulation grating 440a is 30-350 nm, such as 50-200 nm, such as 130nm, 140nm, 145nm, 150nm, and the duty cycle is 0.1-0.9, such as 0.5. The period lambda is 150 to 500nm, further, for example, 150 to 200nm, such as 190nm, 196nm, 197nm, and 198 nm.

As shown in fig. 15, the first periodic modulation grating 440a has a plurality of grating regions with different lengths and periods therebetween, such as, in some embodiments of the present invention, the plurality of grating regions including, for example, a first grating region 441, a second grating region 442, a third grating region 443, and a fourth grating region 444.

In some embodiments, the laser structure 400 has a resonant cavity with a length S of 0.3-3 mm, such as 1mm, a distance S1 between the center point of the first grating region 441 and the left cavity surface is 80-200 μm, such as 120 μm, 130 μm, 135 μm, a period λ 1 of the first grating region 441 is 150-500 nm, such as 190nm, 196nm, 197nm, 198nm, and a length Λ of the first grating region 441₁200 to 280 μm, such as 260 μm and 280 μm. The distance S2 between the center point of the second grating region 442 and the left cavity surface is 200-700 μm, such as 400 μm and 500 μm, and the period λ of the second grating region 442₂150-500 nm, such as 190nm, 196nm, 197nm, and 198nm, and the length Λ of the second grating region 442₂200 to 250 μm, for example 230 μm, 250 μm. The distance S3 between the midpoint of the third grating region 443 and the right cavity surface is 180-300 μm, such as 200 μm and 220 μm, and the period λ of the third grating region 443 is₃150-500 nm, such as 190nm, 196nm, 197nm and 198nm, and the length Λ of the third grating region 443₃Is 250 to 350 μm, such as 290 μm and 300 μm. The period λ of the fourth grating region 444₀Is 150 to 500nm, further, for example, 150 to 200nm, such as 190nm, 196nm, 197nm, 198 nm.

As shown in fig. 16 to 23, the second periodic modulation grating 440b and the first periodic modulation grating 440a have the same structure, but may have different structures. For example, the period, grating shape, grating height, etc. of the first periodic modulation grating 440a are different from those of the second periodic modulation grating 440b, and the exit angle of the light can be further modulated by the difference of the etching shapes of the two gratings.

Specifically, in some embodiments, for example, as shown in fig. 16, the period of the second periodic modulation grating 440b is different from the period of the first periodic modulation grating 440a, which is referred to herein as a difference in the period of the grating main body portion, and the difference in the periods is, for example, 0.1 to 75nm, such as 1nm, 2nm, 10nm, 50nm, 75nm, specifically, the period λ of the first periodic modulation grating 440 can be enumerated₁196nm, 200nm, the period λ of the second periodic modulation grating 440b₂The laser 400 may further provide a double single mode laser, for example, a light source with a wavelength range of 1260 to 1600nm, when the period of the second periodic modulation grating 440b is different from the period of the first periodic modulation grating 440a, so as to obtain a THz wave, for example, a THz wave of 0.03mm to 3mm, using a difference frequency technique, but is not limited thereto.

As shown in fig. 17 to 18, in some embodiments, it may be mentioned that the second periodic modulation grating 440b has, for example, a prism shape, which is different from the elongated shape of the first periodic modulation grating 440a, and is disposed on both sides of the ridge waveguide 430, respectively, in an even manner.

As shown in fig. 21 to 22, in some embodiments, for example, the second periodic modulation grating 440b is formed in a strip shape with a certain inclination angle, which is different from the arrangement of the strip shape of the first periodic modulation grating 440 a.

Specifically, in some embodiments, the grating height of the first periodic modulation grating 440a is different from the height of the second periodic modulation grating 440b, specifically, the height of the first periodic modulation grating 440a is, for example, 140nm, and the height of the second periodic modulation grating 440b is, for example, 150 nm. Further, for example, the duty cycle of the second periodic modulation grating 440b may be different from the duty cycle of the first periodic modulation grating 440a, specifically, the duty cycle of the first periodic modulation grating 440a is, for example, 0.5, and the duty cycle of the second periodic modulation grating 440b is, for example, 0.3. It should be understood that any grating structure of the first periodic modulation grating 440a different from the grating structure of the second periodic modulation grating 440b should be covered by the claimed invention, and is not limited thereto.

As shown in fig. 13, in some embodiments, the predetermined distance H between the bottom of the

periodic modulation gratings

440a, 440b and the active layer 422 is further, for example, 100 to 200nm, further, for example, 100 to 145nm, such as 120nm, 135nm, 140nm, 145nm, for example, and when the predetermined distance H is within the above range, the

periodic modulation gratings

440a, 440b are etched on the upper cladding layer 423, that is, embedded near the active region. And further, the grating etching depth-to-width ratio in the above range is reduced, so that the shallow etching structure can adopt a first-order grating, thereby greatly improving the coupling effect of the laser structure 400, that is, the grating can form better coupling to light, further realizing single longitudinal mode continuous output and ideal side mode suppression ratio, and improving the modulation speed and the light output power of the laser structure 400.

As shown in FIGS. 8-10, in some embodiments, the mask pattern, i.e., the grating pattern, is prepared, for example, using an Electron Beam Lithography (EBL) process. From the viewpoint of ensuring the quality of the grating and improving the coupling effect, the thickness of the e-beam glue layer 470 of the EBL is, for example, 50nm to 100nm, such as 50nm, 60nm, 70nm, and 75nm, and when the thickness is less than 50nm, the e-beam glue layer 470 is too thin, and is easily damaged during the etching process to form the

periodic modulation gratings

440a and 440b, so that the gratings cannot be formed. When the thickness is greater than 100nm, the electron beam glue layer 470 is too thick, so that glue accumulation on the side wall is likely to occur at the ridge waveguide 430, and the connection with the ridge waveguide 430 is not tight in the process of etching the

periodic modulation gratings

440a and 440b, so that the coupling capacity of the

periodic modulation gratings

440a and 440b is reduced. The material of the e-beam glue layer 470 of the EBL may be, for example, polymethyl methacrylate (PMMA), Hydrogen Silsesquioxane (HSQ), and ZEP material such as PMMA. It is noted that an Atomic Force Microscope (AFM), for example, may be employed to inspect the mask pattern. The EBL process provided by the invention is simple and easy to operate, can be used for preparing the mask pattern according to the shape of the required grating, and can effectively improve the fidelity of the grating so that the grating is not easy to deform in the etching process. In addition, the invention adopts extremely thin electron beam glue, thereby greatly shortening the EBL time and saving the process cost.

As shown in fig. 11-12, in some embodiments, a dry etching process, such as an ICP etching process, is used to etch down the upper cladding 423 on both sides of the ridge waveguide 430 and stop on the upper cladding 423, and the e-beam glue layer 470 is removed. That is, the

periodic modulation gratings

440a and 440b are formed on the upper cladding 423. It should be noted that the grating quality was determined using a step profiler and an AFM.

As shown in fig. 13 to 22, in some embodiments of the present invention, after the

periodic modulation gratings

440a and 440b are manufactured, the remaining portion of the mask layer 450 is removed, for example, the mask layer 450 is etched by using Buffered Oxide etching solution (BOE), so as to expose the ridge of the ridge waveguide 430, where the ridge waveguide 430 is located on the upper cladding 423.

13-22, in some embodiments of the present invention, the filling layer 480 and the insulating layer 490 are fabricated on the

periodic modulation gratings

440a, 440b and the ohmic contact layer 424 using a PECVD process.

As shown in fig. 23 to 24, the filling layer 480 is filled in the

periodic modulation gratings

440a and 440b, so as to generate a difference between an effective refractive index of the grating region and a refractive index of the active region, and the optical mode is screened by using a coupling effect of an evanescent field outside the active region and the bragg grating, and based on a viewpoint of realizing an ideal coupling effect, the filling layer 480 is made of a dielectric material with a small refractive index, such as a silicon-based compound or a high molecular polymer, and specific examples thereof include SiO₂SiN, benzocyclobutene (BCB), polyimide. The thickness is 200 to 600nm, for example, 400nm is not limited thereto. Further, the filling materials of the first periodic modulation grating 440a and the second periodic grating 440b may be the same or different, and are not particularly limited.

As shown in fig. 23 to 24, the insulating layer 490 is disposed on the filling layer 480 and covers the entire ridge waveguide 430. In some implementations, the insulating layer 490 is made of the same material as the filling layer 480 and is formed integrally by the PECVD or other processes, and the insulating layer 490 is located on the ridge waveguide 430 to form a current injection window.

As shown in fig. 25-28, in some embodiments, electrodes may be grown on the surface of the laser structure 400 provided by the present invention, and the electrodes may be powered on for performing laser emission operation, wherein the electrodes include an upper electrode 510 and a lower electrode 520.

In some embodiments, the material of the upper electrode 510 and the lower electrode 520 may include one or a combination of Au metal, Ag metal, Pt metal, Ge metal, Ti metal, and Ni metal.

As shown in fig. 25-28, in some embodiments, the insulating layer 490 is etched on the ridge waveguide 430 by a dry Etching process, such as a Reactive Ion Etching (RIE) process, to expose the ohmic contact layer 424, and an upper electrode 510 is formed on the ohmic contact layer 424.

In some embodiments of the present invention, as shown in fig. 27-28, the lower electrode 520 is formed on the back surface of the substrate 410 after the back surface of the substrate 410 is thinned and polished, and then annealed.

As shown in fig. 27 to 28, when the laser structure 400 operates, after power is turned on, current is injected from the upper electrode 510, passes through the upper cladding 423, enters the active layer 422, semiconductor material in the active layer 422 emits light in a transition between energy bands, laser oscillation is formed in the resonant cavity formed by the reflecting

surfaces

4221 and 4222, feedback is performed, radiation amplification of light is generated, screening of an optical mode is completed by using a coupling effect of an evanescent field outside the active layer and the periodic modulation grating, and finally laser is output laterally. The grating structure is prepared by a one-time epitaxy method, the epitaxy quality is improved, and the manufacturing cost is reduced by adopting shallow grating etching. Meanwhile, the

periodic modulation gratings

440a and 440b are designed and prepared on two sides of the ridge waveguide by adopting a lateral coupling shallow etching method, so that a dynamic single mode of a laser structure can be realized, and the modulation speed and the light output power of the laser structure are improved.

It should be noted that the laser structure 400 provided by the present invention may include various packaging methods for realizing ideal outgoing laser light, and may add the existing structure appropriately to meet the actual needs in various fields, such as Sensing system (Sensing) of mobile devices, optical communication light source, lidar, AR/VR, and security monitoring, which should be understood to be covered by the protection scope claimed by the present invention.

As described above, according to the method for manufacturing the laser structure 400 provided by the present invention, the grating quality is improved, the problem of spatial hole burning caused by the conventional phase shift grating is solved, the dynamic single mode of the laser is realized, the modulation speed and the light output power of the optical communication laser are in an ideal range, the epitaxy and the manufacturing process are greatly simplified, and the manufacturing cost is reduced by performing the once epitaxy structure and performing the shallow etching on the two sides of the ridge waveguide 430.

The above description is only a preferred embodiment of the present application and a description of the applied technical principle, and it should be understood by those skilled in the art that the scope of the present invention related to the present application is not limited to the technical solution of the specific combination of the above technical features, and also covers other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept, for example, the technical solutions formed by mutually replacing the above features with (but not limited to) technical features having similar functions disclosed in the present application.

Other technical features than those described in the specification are known to those skilled in the art, and are not described herein in detail in order to highlight the innovative features of the present invention.

Claims

1. A laser structure, comprising:

a substrate;

the epitaxial layer is arranged on the substrate and comprises a lower cladding layer, an active layer, a barrier layer, an upper cladding layer and an ohmic contact layer which are laminated, the barrier layer is positioned in the upper cladding layer, and the thickness of the barrier layer is 30-150 nm;

a ridge waveguide formed on the upper cladding layer, the ridge width of the ridge waveguide being 2-5 μm;

a plurality of periodic modulation gratings formed on the upper cladding and located on both sides of the ridge waveguide;

the filling layer is filled in the plurality of periodic modulation gratings;

the insulating layer is positioned on the filling layer and covers the ridge waveguide, and the material of the insulating layer is the same as that of the filling layer and is formed in an integrated forming mode;

the active layer comprises a plurality of layers of quantum dot composite structures, the quantum dot composite structures are arranged in a stacked mode and have 5-12 layers, a stress release layer is arranged in each quantum dot composite structure, and a spacing layer is arranged between every two adjacent quantum dot composite structures;

the plurality of periodic modulation gratings and the active layer are arranged at preset distances, and the preset distances are 50-200 nm;

the distance between the bottom of the groove on the two sides of the ridge waveguide and the active layer is 230-400 nm;

the period of the periodic modulation grating is 150-250 nm, and the height of the periodic modulation grating is 30-350 nm;

the periodic modulation grating comprises a plurality of grating areas, and the lengths and the periods of the grating areas are different; the periodic modulation grating comprises a first periodic modulation grating and a second periodic modulation grating, is formed on the upper cladding and is respectively arranged on two sides of the ridge waveguide to form a lateral coupling grating.

2. A laser structure according to claim 1, wherein the output wavelength of the laser structure is 1260-1600 nm.

3. A laser structure according to claim 1, wherein the length of the resonant cavity of the laser structure is 0.3-3 mm.

4. The laser structure of claim 1, wherein the periodic modulation grating has a duty cycle of 0.1 to 0.9.

5. A laser structure according to claim 1, characterized in that the filling medium of the periodic modulation grating is a silicon-based compound or a high molecular polymer.

6. A method of fabricating a laser structure, the method comprising the steps of:

providing a substrate;

forming an epitaxial layer on the substrate, wherein the epitaxial layer comprises a lower cladding layer, an active layer, a barrier layer, an upper cladding layer and an ohmic contact layer which are stacked, the barrier layer is located in the upper cladding layer, and the thickness of the barrier layer is 30-150 nm;

etching the upper cladding layer and the ohmic contact layer to form a ridge waveguide, wherein the ridge width of the ridge waveguide is 2-5 microns;

forming a plurality of periodic modulation gratings on the upper cladding layer, wherein the periodic modulation gratings are positioned on two sides of the ridge waveguide, filling layers are filled on the periodic modulation gratings, each periodic modulation grating comprises a plurality of grating regions, and the lengths and the periods of the grating regions are different;

forming an insulating layer on the filling layer and the ridge waveguide, wherein the material of the insulating layer is the same as that of the filling layer and is formed in an integrated forming mode;

the distance between the bottom of the groove on the two sides of the ridge waveguide and the active layer is 230-400 nm; the period of the periodic modulation grating is 150-250 nm, and the height of the periodic modulation grating is 30-350 nm;

the periodic modulation grating comprises a first periodic modulation grating and a second periodic modulation grating, is formed on the upper cladding, and is respectively arranged on two sides of the ridge waveguide to form a lateral coupling grating.

7. The utility model provides a laser module, its characterized in that, laser module includes:

a circuit board;

the laser structure is arranged on the circuit board; wherein the laser structure comprises a plurality of laser structures,

a substrate;

a plurality of periodic modulation gratings formed on the upper cladding and located on both sides of the ridge waveguide; the filling layer is filled in the plurality of periodic modulation gratings, each periodic modulation grating comprises a plurality of grating areas, and the lengths and the periods of the grating areas are different;

a preset distance is reserved between the plurality of periodic modulation gratings and the active layer, and the preset distance is 50-200 nm;