CN111262130A - Laser structure and preparation method and application thereof - Google Patents

Abstract

The present invention provides a laser structure, a preparation method and application thereof. The laser structure includes: a substrate; an epitaxial layer, which is arranged on the substrate, and the epitaxial layer includes a stacked lower cladding layer, an active layer, an upper a cladding layer and an ohmic contact layer; a ridge waveguide formed on the upper cladding layer; a plurality of periodic modulation gratings formed on the upper cladding layer and located on both sides of the ridge waveguide; wherein the There is a preset distance between the plurality of periodic modulation gratings and the active layer, and the preset distance is 50-200 nm. The laser proposed by the invention has the advantages of simple manufacturing process, high side-mode suppression ratio, fast modulation speed and excellent dynamic single-mode characteristics.

Description

A kind of laser structure and its preparation method and application

technical field

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

Background technique

In the technical field of semiconductor lasers, distributed feedback (DFB) semiconductor lasers have excellent differential gain, dynamic single-mode characteristics and large modulation bandwidth, and are widely used in near-infrared optical communication, 3D biometrics and other fields.

At present, the grating structure included in the laser structure is a phase-shift grating, which is prone to occur due to the spatial hole burning effect, which limits the modulation speed of the optical communication laser, that is, as the current increases, the threshold gain difference decreases, and the main mode and the first The gain difference of the side modes becomes smaller, and mode competition or even mode hopping fails to realize dynamic single mode, so that it is difficult to ensure that the laser has stable dynamic single mode characteristics, thereby affecting the application range of the laser.

In addition, at present, DFB lasers are mainly fabricated by grating buried structure and grating deep etching structure. For the grating buried structure, a two-step epitaxy process is required during manufacture. When the epitaxy grows to the vicinity of the active region, it needs to be stopped, then the grating is etched, and then the secondary epitaxy is performed. The preparation process is complicated and tedious, and not only requires strict cleaning process, And it is troublesome to the high-efficiency production of the laser. At present, the preparation of the deep grating etching structure is extremely difficult, the quality of the mask is high, and the stability and consistency of the performance are difficult to guarantee.

SUMMARY OF THE INVENTION

In view of the above-mentioned defects of the prior art, one of the objects of the present invention is to provide a laser structure with stable structure, low optical loss, high power, ideal side-mode suppression ratio and modulation speed, and excellent dynamic single-mode characteristics .

Another object of the present invention is to provide a preparation method of the above-mentioned laser structure.

Another object of the present invention is to provide an application of the above-mentioned laser structure.

In order to achieve the above object and other objects, a first aspect of the present invention proposes a laser structure, the laser structure includes: a substrate; an epitaxial layer disposed on the substrate, and the epitaxial layer includes a stacked lower cladding layer , an active layer, an upper cladding layer and an ohmic contact layer; a ridge waveguide formed on the upper cladding layer; a plurality of periodic modulation gratings formed on the upper cladding layer and located on two sides of the ridge waveguide side; wherein, there is a preset distance between the plurality of periodic modulation gratings and the active layer, and the preset distance is 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 period modulated grating is 0.1-0.9.

Optionally, the period modulated grating includes a plurality of grating regions, and the 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.

Another aspect of the present invention also provides a method for preparing a laser structure, the method comprising the steps of: providing a substrate; forming an epitaxial layer on the semiconductor substrate, the epitaxial layer comprising a stacked lower cladding layer, an active layer, an upper cladding layer and an ohmic contact layer; etching the upper cladding layer and the ohmic contact layer to form a ridge waveguide; forming a plurality of periodic modulation gratings on the upper cladding layer and located on the upper cladding layer On both sides of the ridge waveguide, there is a preset distance between the plurality of periodic modulation gratings and the active layer, and the preset distance is 50-200 nm.

Another aspect of the present invention provides a laser module, the laser module includes: a circuit board; a laser structure is disposed on the circuit board; wherein, the laser structure includes a substrate; an epitaxial layer is disposed on the circuit board. On the substrate, the epitaxial layer includes a stacked lower cladding layer, an active layer, an upper cladding layer and an ohmic contact layer; a ridge waveguide is formed on the upper cladding layer; a plurality of periodic modulation gratings are formed on the upper cladding layer. on the upper cladding layer and located on both sides of the ridge waveguide; a preset distance between the plurality of periodic modulation gratings and the active layer, and the preset distance is 50-200 nm.

To sum up, the present invention proposes a laser structure, a preparation method and application thereof. The laser structure is epitaxially grown and a plurality of periodic modulation gratings are shallowly etched on both sides of a ridge waveguide. There is a preset distance of 50-200 nm between the modulation grating and the active layer. According to the principle of evanescent field coupling, the optimal coupling between the optical field and the grating is realized, which not only improves the quality of the grating, but also solves the spatial hole burning caused by the previous phase-shift grating, realizes the dynamic single-mode of the laser, and enables optical communication. The modulation speed and output power of the laser are within the ideal range. Moreover, the invention reduces the etching aspect ratio of the grating, greatly simplifies the process, reduces the manufacturing cost, and reduces the defects and losses of the epitaxial wafer, thereby laying a foundation for the industrialization of the laser. For other features, advantages and benefits, reference is made to the contents of the claims and description of the present disclosure.

Description of drawings

FIG. 1 shows an overall block diagram of the optical transmitter proposed in this embodiment.

FIG. 2 shows a flow chart of the fabrication method of the laser structure proposed in this embodiment.

FIG. 3 shows a schematic diagram of the substrate of the laser structure in this embodiment.

FIG. 4 shows a schematic diagram of forming an epitaxial layer.

FIG. 5 shows a schematic diagram of forming a mask layer and a photoresist layer.

FIG. 6 shows a schematic diagram of etching the photoresist layer and the mask layer.

FIG. 7 shows a schematic diagram of forming a ridge waveguide.

FIG. 8 is a schematic diagram showing the formation of an electron beam micelle layer.

FIG. 9 shows a side view of FIG. 8 .

Figure 10 shows a schematic diagram for preparing a grating pattern.

FIG. 11 shows a schematic diagram of etching the upper cladding layer.

Figure 12 shows a schematic diagram of forming a grating.

FIG. 13 shows a schematic diagram after removing the mask layer.

FIG. 14 shows the top view of FIG. 13 .

FIG. 15 shows a schematic structural diagram of the periodically modulated 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 shows the top view of FIG. 17 .

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

FIG. 20 is shown as the top view of FIG. 19 .

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

FIG. 22 shows the top view of FIG. 21 .

FIG. 23 is a schematic diagram showing the formation of filling layers and insulating layers.

FIG. 24 is a front view of FIG. 23 .

FIG. 25 is a schematic diagram showing the formation of the upper electrode region.

FIG. 26 is a top view of FIG. 25 .

FIG. 27 is a schematic diagram showing the formation of upper and lower electrodes.

FIG. 28 shows the side view of FIG. 27 .

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

It should be noted that the drawings provided in this embodiment are only to illustrate the basic concept of the present invention in a schematic way, so the drawings only show the components related to the present invention rather than the number, shape and the number of components in actual implementation. For dimension drawing, the type, quantity and proportion of each component can be changed at will in actual implementation, and the component layout may also be more complicated.

Optical fiber communication system is the physical basis of information transmission, which includes data source, optical transmitter, optical channel and optical receiver, etc. It is based on converting the information transmitted by the sender into an electrical signal, and then modulates it into an optical transmitter for transmission. On the light source, the intensity of the light changes with the frequency of the electrical signal, and is sent out through the optical fiber, and then the receiving end receives the optical signal and converts it into an electrical signal, which is restored to form the original information after demodulation. The components used as light sources, such as laser modules including lasers, use the received electrical signals to emit laser signals, with small size, low energy consumption, high luminous efficiency, and good reliability, and are widely used in optical fiber communication systems.

As shown in FIG. 1 , the present invention provides a block diagram of an exemplary laser module 100 , which acts as a light emitting component and emits a laser signal using a received electrical signal. The laser module 100 includes, for example, a circuit board, such as an input circuit 200 , a driving circuit 300 , and a laser structure 400 disposed on the circuit board. It should be understood that the laser module 100 is for illustration purposes only and the present invention is not limited to a specific 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, as well as the interface, all of which may vary based on specific requirements and intended use.

As shown in FIG. 1 , in the laser module 100 , the input circuit 200 performs scrambling and encoding operations on the input electrical signal. The driving circuit 300 is electrically connected to the input circuit 200 for modulating the scrambled and encoded electrical signals to form a modulated signal. The laser structure 400 is electrically connected to the driving circuit 300 for driving the laser structure 400 according to a modulation signal and generating an optical signal. The laser light emitted by the laser structure 400 is modulated by the driving circuit 300 to emit laser light.

As shown in FIG. 1 , in the laser module 100 , the laser structure 400 is used for emitting laser light, for example, emitting light from the side. In some embodiments of the present invention, the output wavelength range of the laser structure 400 is 850-1600 nm, such as 1550 nm, 1310 nm, and 850 nm. Further, the output wavelength of the laser structure 400 is 1310 nm. As near-infrared light, it is widely used in Sensing systems for mobile devices, optical communication light sources, lidars, AR/VR, and security monitoring.

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

As shown in FIG. 2 and FIG. 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 III-V compound types or alloys thereof, which may be a suitably doped substrate, such as silicon (Si) doped gallium arsenide (GaAs) ), sapphire substrate, silicon, silicon carbide, aluminum nitride, gallium nitride, on which the epitaxial layer 420 is formed. The thickness of the substrate 410 is, for example, 10-200 μm, such as 100 μm and 70 μm, which is the thickness of the substrate after thinning.

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

In some embodiments, the lower cladding layer 421 includes an N-type semiconductor layer, and specifically the material may include an aluminum-containing material, for example, n-Al _0.3 Ga _0.7 As, n-Al _0.25 Ga _0.75 As, etc. The thickness of the cladding layer 421 is, for example, 1000-5000 nm, such as 2800 nm, 3000 nm.

In some embodiments, the active layer 422 includes a stacked quantum dot composite structure. Specifically, an indium arsenide/indium gallium arsenide/gallium arsenide (InAs/InGaAs/GaAs) quantum dot laser structure can be cited. The quantum dot laser structure includes, for example, 8 layers of quantum dots, and each layer of quantum dots can be, for example, 33nm GaAs. The spacer layers are separated, and each layer of quantum dots contains 2.7ML (mono layer) InAs, and the InAs is covered with a 6nm InGaAs stress release layer. Further, the active layer 422 can also be doped with p-type modulation, for example, beryllium (Be), carbon (C), zinc (Zn), silicon (Si) and other elements to improve mode gain and optical stability Specifically, for example, the doping concentration is 3×10 ¹⁷ cm ⁻³ , the doping region is in the GaAs layer 17 nm above the InAs/InGaAs quantum dot layer, and the width of the doping 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 efficiency, thereby improving the performance of the laser structure 400 . Of course, it is not limited to this, and in some embodiments of the present invention, the active layer 422 may also adopt a composite structure of 5-12 layers of quantum dots. The active layer 422 emits light by transitioning between energy bands through the semiconductor substance of the quantum dot composite structure (that is, using electrons), and using the cleavage surface or cavity surface coating of the semiconductor crystal to form two parallel mirror surfaces 4221 and 4222 as mirrors A resonant cavity is formed (Fig. 9), so that the light is oscillated and fed back, and the radiation of the light is amplified, and the laser light 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 1260-1600 nm, for example, 1310 nm.

In some embodiments, the upper cladding layer 423 includes a P-type semiconductor layer, and specifically, the material may include an aluminum-containing material, for example, p-Al _0.3 Ga _0.7 As, p-Al _0.25 Ga _0.75 As, etc. The thickness of the cladding layer 404 is 1000-3000 nm, eg, 1800 nm, 2100 nm.

In some embodiments, the ohmic contact layer 424 is located on the upper cladding layer 423, and further, on the ridge waveguide 430 as described above in detail below, for connecting electrodes formed subsequently. In some embodiments of the present invention, the ohmic contact layer 424 can be, for example, heavily doped p-type GaAs, and the thickness of the ohmic contact layer 424 is, for example, 100 μm-500 μm, such as 200 μm, 230 μm, 250 μm, 300 μm, and There is no particular limitation.

Further, in some embodiments of the present invention, the epitaxial layer 420 may further include a barrier layer (not shown in the figure), and the barrier layer is located on the upper cladding layer 423, so that the etching can be performed as above When the ridge waveguide 430 described below is described in detail, to ensure the depth of etching, the thickness of the barrier layer is 30-150 nm, for example, 50 nm, 85 nm, and 120 nm.

In some embodiments, the epitaxial layer 420 is formed by sequentially growing on the substrate 410 using a molecular beam epitaxy (MBE) process. Of course, the epitaxial layer 420 is not limited thereto. Epitaxial deposition of organic chemical vapor deposition (MOCVD) is formed on the substrate 410 .

As shown in FIG. 2 and FIGS. 5 to 7 , the step S3 is performed, the ohmic contact layer 424 and the upper cladding layer 423 are etched to form a ridge waveguide 430 and a part of the upper cladding layer 423 is exposed. The shaped waveguide 430 can confine the current and shape the spot.

As shown in FIGS. 5-7 , the ridge waveguide 430 is located on the upper cladding layer 423, and the distance between the bottoms of the trenches on both sides of the ridge waveguide 430 and the active layer 422 is 230-400 nm. Further, for example, 230 to 300 nm, further for example, 270 to 295 nm, such as 295 nm, 290 nm, 280 nm, and 275 nm, when the distance is within the above range, the grooves on both sides of the ridge waveguide 430 A plurality of periodic modulation gratings with the following structures are formed at the bottom, for example, the first periodic modulation grating 440a and the second periodic modulation grating 440b as shown in FIG. The connection is tight and not 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, 440b can form an ideal coupling effect, thereby completing the screening of light modes . The ridge width of the ridge waveguide 430 is, for example, 2-5 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 preparing the ridge waveguide 430 and the plurality of first periodic modulation gratings 440a. The material of the mask layer 450 can be, for example, silicon dioxide (SiO ₂ ) or silicon nitride (SiN). The thickness of the mask layer 450 is, for example, 50 nm-100 nm, such as 50 nm, 60 nm, 70 nm, and 80 nm. The thickness of the mask layer 450 within the above range can sufficiently protect the ridge waveguide 430 as described above in detail below. It avoids being damaged in the process of preparing the periodic modulation gratings 440a and 440b, and further, avoids the problems of increased surface roughness of the current injection window and poor electrode adhesion when the laser structure 400 is growing electrodes.

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 present invention, a photoresist 460 is coated on the mask layer 450, and the photoresist 460 is patterned to develop the etching window of the ridge waveguide 430, A part of the mask layer 450 is first etched by dry etching, such as reactive ion etching (Reactive Ion Etching, RIE) process.

As shown in FIG. 6, in some embodiments of the present invention, dry etching, such as a combination of an inductively coupled plasma (ICP) etching process and a wet etching process, is used to The contact layer 424 and the upper cladding layer 423 are etched down 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 FIGS. 8 to 14 , the step S4 is performed to form a plurality of periodically modulated gratings, such as Bragg gratings, on the upper cladding layer 423 and are located on both sides of the ridge waveguide 430 , wherein, There is a preset distance H between the plurality of periodic modulation gratings and the active layer 422 , and the preset distance H is 50˜200 nm. The invention adopts the periodic modulation grating to expand the phase shift from a point to an area distributed along the resonant cavity, so that the light field distribution is more flat and uniform, and the problem of space hole burning caused by the phase shift grating in the past is avoided. Therefore, as the current increases, the threshold gain difference remains relatively stable, maintaining the dynamic single-mode characteristic. By changing the structure and position of the periodic modulation grating, the coupling effect on light is adjusted, so that the laser structure 400 can stably output light, and achieve single longitudinal mode continuous output and an ideal side mode suppression ratio.

As shown in FIGS. 8 to 22 , the periodic modulation grating, for example, includes a first periodic modulation grating 440 a and a second periodic modulation grating 440 b , formed on the upper cladding layer 423 and arranged on the ridge waveguide 430 respectively. The two sides of the laser beam form a laterally coupled grating, and 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, for example, have the same structure, and of course, may have different structures.

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

As shown in FIG. 15 , the first periodic modulation grating 440a has multiple grating regions, and the lengths and periods of the multiple grating regions are different. For example, in some embodiments of the present invention, the multiple grating regions For example, it includes 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 length S of the resonant cavity of the laser structure 400 is 0.3-3 mm, such as 1 mm, and the distance S1 between the midpoint of the first grating region 441 and the left cavity surface is 80-200 μm, such as 120 μm, 130 μm , 135 μm, the period λ1 of the first grating region 441 is 150˜500 nm, such as 190 nm, 196 nm, 197 nm, 198 nm, and the length Δ1 of the _first grating area 441 is 200˜280 μm, such as 260 μm, 280 μm. The distance S2 between the midpoint 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 ₂ of the second grating region 442 is 150-500 nm, such as 190 nm, 196 nm, 197 nm, 198 nm, the length Λ ₂ of the second grating region 442 is 200-250 μm, for example, 230 μm and 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 λ3 of the _third grating region 443 is 150-500 nm, such as 190 nm, 196 nm, 197 nm, 198 nm, The length Λ ₃ of the third grating region 443 is 250-350 μm, for example, 290 μm and 300 μm. The period λ ₀ of the fourth grating region 444 is 150-500 nm, further, for example, 150-200 nm, such as 190 nm, 196 nm, 197 nm, 198 nm.

As shown in FIGS. 16-23 , the second periodically modulated grating 440b and the first periodically modulated grating 440a have the same structure, for example, and of course may have different structures. For example, the period, grating shape, and grating height of the first periodic modulation grating 440a are different from those of the second periodic modulation grating 440b, and the exit angle of light can be further modulated by the difference in the etching shapes.

As shown in FIG. 16 , specifically, in some embodiments, for example, the period of the second periodic modulation grating 440b is different from the period of the first periodic modulation grating 440a, and the difference referred to here is the main body of the grating Part of the period difference, the period difference is, for example, 0.1 to 75 nm, such as 1 nm, 2 nm, 10 nm, 50 nm, 75 nm, specifically, the period λ ₁ of the first period modulation grating 440 can be listed as 196 nm, 200 nm , the period λ ₂ of the second periodic modulation grating 440b is 197 nm and 196 nm. When the period of the second periodic modulation grating 440b is different from the period of the first periodic modulation grating 440a, the two periods are different, the The laser 400 can further provide dual single-mode lasers, such as a light source in the wavelength range of 1260-1600 nm, so as to obtain THz waves, such as THz waves of 0.03 mm-3 mm, by using the difference frequency technology, which is of course not limited to this.

As shown in FIGS. 17-18 , specifically, in some embodiments, the second periodic modulation grating 440b may have, for example, a prismatic shape, which is different from the strip shape of the first periodic modulation grating 440a, and is respectively They are evenly arranged on both sides of the ridge waveguide 430 .

As shown in FIGS. 21 to 22 , specifically, in some embodiments, the second periodic modulation grating 440b may be, for example, formed in a strip shape with a certain inclination angle, which is the same as the length of the first periodic modulation grating 440a. The bar shapes are arranged differently.

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, 140 nm, The height of the second periodic modulation grating 440b is, for example, 150 nm. Further, for example, it may further include that the grating duty cycle of the second periodic modulation grating 440b is different from the grating duty cycle of the first periodic modulation grating 440a, specifically, the duty cycle of the first periodic modulation grating 440a The duty ratio is, for example, 0.5, and the duty ratio of the second periodic modulation grating 440b is, for example, 0.3. It should be understood that any grating structure of the first periodically modulated grating 440a that is different from that of the second periodically modulated grating 440b should be included within the scope of protection of the present invention, and is not limited thereto.

As shown in FIG. 13 , in some embodiments, the value of the preset distance H between the bottoms of the periodic modulation gratings 440a and 440b and the active layer 422 is further, for example, 100˜200 nm, and further For example, 100 to 145 nm, such as 120 nm, 135 nm, 140 nm, and 145 nm, when the preset distance H is within the above range, the periodic modulation gratings 440a and 440b are etched on the upper cladding layer 423, that is, built into all the near the active region. And further, the reduction of the aspect ratio of grating etching within the above range makes it possible to use a first-order grating for this shallow etching structure, thereby greatly improving the coupling effect of the laser structure 400, that is, the grating can form a With better coupling, single longitudinal mode continuous output and ideal side-mode suppression ratio are achieved, and the modulation speed and output power of the laser structure 400 are improved.

As shown in FIGS. 8-10 , in some embodiments, the mask pattern, that is, the grating pattern, is prepared by, for example, 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 electron beam glue layer 470 of the EBL is, for example, 50nm-100nm, such as 50nm, 60nm, 70nm, 75nm, and when the thickness is less than 50nm, the The electron beam glue layer 470 is too thin, which is easily damaged during the process of etching to form the periodic modulation gratings 440a and 440b, so that the gratings cannot be formed. When the thickness is higher than the 100 nm, the electron beam glue layer 470 is too thick, and the sidewall glue buildup is likely to occur at the ridge waveguide 430, and it is easy to form the periodic modulation gratings 440a and 440b during the etching process. As a result, the connection with the ridge waveguide 430 is not tight, and the coupling ability of the periodic modulation gratings 440a and 440b is reduced. The materials of the electron beam glue layer 470 of the EBL can be, for example, polymethyl methacrylate (PMMA), hydrogen silsesquioxane (HSQ), and ZEP materials, such as PMMA. It should be noted that, for example, atomic force microscopy (AFM) can be employed to detect the mask pattern. The EBL process provided by the invention is simple and easy to operate, the mask pattern can be prepared according to the required shape of the grating, and the fidelity of the grating can be effectively improved, so that it is not easily deformed during the etching process. In addition, the present invention adopts extremely thin electron beam glue, which can greatly reduce the EBL time and save the process cost.

As shown in FIGS. 11-12 , in some embodiments, dry etching, such as ICP etching, is used to etch down the upper cladding layer 423 on both sides of the ridge waveguide 430 and stop at the on the upper cladding layer 423, and remove the electron beam glue layer 470. That is, periodic modulation gratings 440 a and 440 b are formed on the upper cladding layer 423 . It should be noted that the grating quality was determined using a step meter and AFM.

As shown in FIGS. 13-22 , in some embodiments of the present invention, after the periodic modulation gratings 440 a and 440 b are fabricated, the remaining part of the mask layer 450 is removed, for example, using a buffered oxide etchant (Buffered Oxide Etch , BOE) etching the mask layer 450 to expose the ridge of the ridge waveguide 430 , the ridge waveguide 430 is located on the upper cladding layer 423 .

As shown in FIGS. 13-22 , in some embodiments of the present invention, the filling layer 480 and the insulating layer 490 are prepared on the periodically modulated gratings 440 a and 440 b and the ohmic contact layer 424 by using a PECVD process.

As shown in FIGS. 23-24, the filling layer 480 is filled in the periodic modulation gratings 440a and 440b, so as to make a difference between the effective refractive index of the grating region and the refractive index of the active region. The coupling effect of the evanescent field and the Bragg grating completes the screening of the light mode. Based on the viewpoint of achieving an ideal coupling effect, the filling layer 480 is made of a medium material with a small refractive index such as a silicon-based compound or a medium such as a high-molecular polymer. Examples include SiO ₂ , SiN, benzocyclobutene (BCB), polyimide. The thickness is 200 to 600 nm, for example, 400 nm, of course, not limited to this. 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 FIGS. 23-24 , the insulating layer 490 is located 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 integrally formed by the PECVD or other processes. The insulating layer 490 is located on the ridge waveguide 430 for forming a current Inject the window.

As shown in FIGS. 25-28 , in some embodiments, electrodes can be grown on the surface of the laser structure 400 provided by the present invention, and the laser emission operation can be performed after being powered on. 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 FIGS. 25-28 , in some embodiments, dry etching, such as reactive ion etching (Reactive Ion Etching, RIE) process, is used to etch the part of the insulating layer 490 on the ridge waveguide 430 , to expose the ohmic contact layer 424 , and form an upper electrode 510 on the ohmic contact layer 424 .

As shown in FIGS. 27-28 , in some embodiments of the present invention, the backside of the substrate 410 is thinned and polished first, and then the lower electrode 520 is formed on the backside of the substrate 410 and annealed.

As shown in FIGS. 27-28 , when the laser structure 400 is in operation, the current is injected from the upper electrode 510 after being energized, passes through the upper cladding layer 423 , and enters the active layer 422 . The semiconductor substances in the active layer 422 are Inter-band transitions emit light, form laser oscillation in the resonant cavity composed of the reflective surfaces 4221, 4222, feedback, generate radiation amplification of light, and utilize the coupling effect of the evanescent field outside the active layer and the periodic modulation grating The screening of the light mode is completed, and finally the laser is output laterally. In the present invention, the grating structure is prepared by one-time epitaxy method, the epitaxial quality is improved, and the grating shallow etching is used to reduce the manufacturing cost. At the same time, periodic modulation gratings 440a and 440b are designed and fabricated on both sides of the ridge waveguide by the lateral coupling shallow etching method, which can realize the dynamic single mode of the laser structure and improve its modulation speed and light output power.

It should be noted that the laser structure 400 provided by the present invention can include a variety of packaging methods in order to achieve an ideal output laser, and an existing structure can be appropriately added to meet the requirements of various fields such as the sensing system (Sensing) of mobile devices. , optical communication light source, lidar, AR/VR, and actual needs in the field of security monitoring, it should be understood that these should be covered within the scope of protection required by the present invention.

As mentioned above, according to the preparation method of the laser structure 400 provided by the present invention, the epitaxial structure and the shallow etching of a plurality of periodic modulation gratings on both sides of the ridge waveguide 430 not only improves the quality of the gratings, but also solves the problem of the previous phase. The spatial hole burning brought about by shifting the grating realizes the dynamic single-mode of the laser, which makes the modulation speed and output power of the optical communication laser within the ideal range, and greatly simplifies the epitaxy and manufacturing process, and reduces the manufacturing cost.

The above description is only a preferred embodiment of the application and an illustration of the applied technical principle. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solution formed by the specific combination of the above technical features , and shall also cover 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 above features are similar to those disclosed in this application (but not limited to) A technical solution formed by replacing the technical features of the functions with each other.

Except for the technical features described in the specification, the other technical features are known technologies by those skilled in the art, and in order to highlight the innovative features of the present invention, the remaining technical features are not repeated here.

Claims (10)

1. 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.

2. The laser structure of claim 1, wherein the laser structure has an output wavelength of 1260 nm to 1600 nm.

3. The laser structure of 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 period of the periodic modulation grating is 150-250 nm.

5. The laser structure of claim 1, wherein the height of the periodic modulation grating is 30-350 nm.

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

7. The laser structure of claim 1, wherein the periodic modulation grating comprises a plurality of grating regions, the length and period being different between the grating regions.

8. The laser structure of claim 1, wherein the filling medium of the periodic modulation grating is a silicon-based compound or a high molecular polymer.

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

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.

10. 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;

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.

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