CN116646820A - Ridge waveguide structure for improving beam quality - Google Patents
Ridge waveguide structure for improving beam quality Download PDFInfo
- Publication number
- CN116646820A CN116646820A CN202310720777.4A CN202310720777A CN116646820A CN 116646820 A CN116646820 A CN 116646820A CN 202310720777 A CN202310720777 A CN 202310720777A CN 116646820 A CN116646820 A CN 116646820A
- Authority
- CN
- China
- Prior art keywords
- waveguide
- quality
- refractive index
- epitaxial structure
- semiconductor substrate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 239000000463 material Substances 0.000 claims abstract description 40
- 239000004065 semiconductor Substances 0.000 claims abstract description 22
- 239000000758 substrate Substances 0.000 claims abstract description 18
- 229910003460 diamond Inorganic materials 0.000 claims description 7
- 239000010432 diamond Substances 0.000 claims description 7
- 239000000945 filler Substances 0.000 claims description 6
- 238000005516 engineering process Methods 0.000 claims description 3
- 238000000407 epitaxy Methods 0.000 claims description 3
- 238000002488 metal-organic chemical vapour deposition Methods 0.000 claims description 3
- 230000000694 effects Effects 0.000 abstract description 16
- 238000010586 diagram Methods 0.000 description 15
- 238000000034 method Methods 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- 238000005530 etching Methods 0.000 description 2
- 230000001151 other effect Effects 0.000 description 2
- 239000002210 silicon-based material Substances 0.000 description 2
- 238000013459 approach Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
- H01S5/227—Buried mesa structure ; Striped active layer
- H01S5/2275—Buried mesa structure ; Striped active layer mesa created by etching
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Landscapes
- Physics & Mathematics (AREA)
- Geometry (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Optics & Photonics (AREA)
- Semiconductor Lasers (AREA)
Abstract
The ridge waveguide structure for improving the quality of light beams comprises a semiconductor substrate, wherein an epitaxial structure grows on the semiconductor substrate, a groove is etched on the epitaxial structure, and a material is filled in the groove; the trenches are filled with material, and the number of modes that can be supported by the epitaxial structure is reduced, resulting in an improvement in beam quality. The refractive index of the filling material is large enough to form an anti-waveguide effect, and the propagation of light in the epitaxial structure depends on a gain waveguide mechanism, so that the quality of the light beam is also improved sufficiently. After the groove is filled with the material, the transverse heat conduction energy of the epitaxial structure is improved, so that the gradient distribution of the temperature between the waveguide and the groove areas on two adjacent sides of the waveguide is reduced, the effect of a thermal lens is reduced, and the quality of the light beam is improved.
Description
Technical Field
The invention belongs to the technical field of semiconductor lasers, and particularly relates to a ridge waveguide structure for improving the quality of a light beam.
Background
In many applications of semiconductor lasers it is desirable to obtain as high a beam quality as possible, whereas in practice the beam quality of single-mode and multimode lasers is far from such ideal. In practical semiconductor laser fabrication, the fast axis direction (material growth direction) can be designed for single mode operation in general, while the number of modes supported by the waveguide in the slow axis direction (horizontal direction perpendicular to the material growth direction) depends on the design parameters of the lateral waveguide including the waveguide width and the etching depth of the waveguide. For single transverse mode designs, single mode operation can be ensured when the operating current is low, however when the operating current is high, kinks (Kink) occur in the photo-current characteristics of the epitaxial structure due to thermal effects of the epitaxial structure and other effects such as carrier effects, and the optical field quality is deteriorated due to the occurrence of multimode (see fig. 1). For a broad-stripe high-power laser, the near-field/far-field quality in the slow-axis direction is highly undesirable as the waveguide supports many waveguide modes, the result of which is a superposition of these waveguide modes (see fig. 2).
Disclosure of Invention
It is an object of the present invention to provide a ridge waveguide structure that improves the quality of a light beam by increasing the effective refractive index of the light by filling the trench with a material, and by reducing the effect of a thermal lens.
The technical scheme adopted by the invention is that the ridge waveguide structure for improving the quality of light beams comprises a semiconductor substrate, an epitaxial structure grows on the semiconductor substrate, a groove is etched on the epitaxial structure, and a material is filled in the groove.
The invention is also characterized in that:
the epitaxial structure growing process on the semiconductor substrate comprises the following steps: and (3) epitaxy of a 900-1000nm wavelength laser epitaxial structure on the semiconductor substrate by MOCVD technology.
The refractive index of the high refractive material is 2.5-3.8, and the heat conductivity coefficient is 34W/(m.k) -24W (cm.k).
The refractive index of the semiconductor substrate is in the range of 3.4-3.6.
The filler material is Si or diamond.
The beneficial effects of the invention are as follows:
1) In the invention, the material is filled in the groove, so that the number of modes supported by the epitaxial structure can be reduced, thereby improving the quality of the light beam. The refractive index of the filling material is large enough to form an anti-waveguide effect, and the propagation of light in the epitaxial structure depends on a gain waveguide mechanism, so that the quality of the light beam is also improved sufficiently.
2) After the groove is filled with the material, the transverse heat conduction energy of the epitaxial structure is improved, so that the gradient distribution of the temperature between the waveguide and the groove areas on two adjacent sides of the waveguide is reduced, the effect of a thermal lens is reduced, and the quality of the light beam is improved.
Drawings
FIG. 1 is a schematic diagram showing Kink (Kink) in a light-current curve under high current;
FIG. 2 is a schematic diagram of the result of a prior art near field (a)/far field (b) waveguide mode superposition;
FIG. 3 is a schematic diagram of a conventional ridge waveguide perspective structure;
FIG. 4 is a schematic diagram of the result of a typical waveguide structure;
FIG. 5 is a schematic diagram of a ridge waveguide perspective structure for improving beam quality in accordance with the present invention;
FIG. 6 is a schematic view of the horizontal zonal view of the waveguide structure of the present invention;
FIG. 7 (a) is a graph showing the refractive index vs. light ray position after filling with a silicon material;
FIG. 7 (b) is a schematic diagram showing the refractive index vs. light ray position after filling with diamond material;
FIG. 8 is a schematic diagram showing the temperature distribution as a function of position without filling silicon material and diamond material in the trench;
FIG. 9 is a schematic diagram of near-field spot distribution in a single waveguide mode according to an embodiment of the present invention;
FIG. 10 is a schematic diagram of near field spot distribution during dual waveguide mode in an embodiment of the present invention;
FIG. 11 is a schematic diagram of near field spot distribution for three waveguide modes in an embodiment of the present invention;
FIG. 12 is a schematic diagram of near field spot distribution for four waveguide modes in an embodiment of the present invention;
FIG. 13 is a schematic diagram of near field spot distribution for five waveguide modes in an embodiment of the present invention;
FIG. 14 is a schematic diagram of near field spot distribution for six waveguide modes in an embodiment of the present invention;
FIG. 15 is a schematic diagram of near field spot distribution for nine waveguide modes in an embodiment of the present invention;
fig. 16 is a schematic diagram of near field spot distribution in ten waveguide modes in an embodiment of the present invention.
Detailed Description
The invention will be described in detail below with reference to the drawings and the detailed description.
For single transverse mode designs, single mode operation can be ensured when the operating current is low, however when the operating current is high, kinks (Kink) occur in the photo-current characteristics of the epitaxial structure due to thermal effects of the epitaxial structure and other effects such as carrier effects, and the optical field quality is deteriorated due to the occurrence of multimode (see fig. 1). For a broad-stripe high-power laser, the near-field/far-field quality in the slow-axis direction is highly undesirable as the waveguide supports many waveguide modes, the result of which is a superposition of these waveguide modes (see fig. 2). In order to achieve better beam quality, the invention provides a ridge waveguide structure for improving beam quality and a beam quality improving method.
The ridge waveguide structure for improving the quality of light beams comprises a semiconductor substrate, an epitaxial structure is grown on the semiconductor substrate, a groove is etched on the epitaxial structure, and a material is filled in the groove.
Conventional waveguides as shown in fig. 3, the spatial confinement of light in the lateral (horizontal) direction results from the effective refractive index difference of the optical waveguide modes. In the trench regions on both sides of the waveguide, the semiconductor material is etched away, and instead, air with a refractive index of 1 is used, so that a typical waveguide structure with a high effective refractive index in the waveguide region and a small effective refractive index in the trench region is formed, as shown in fig. 4. In order to solve the problem of divergence angles of a near field and a far field, the invention is filled with a material compatible with high heat conduction and high refractive index, and the material has great improvement effect on the thermal performance and the effective refractive index of the device. The shadow filling is shown in fig. 5.
The essence of the invention is that on the basis of the traditional groove semiconductor laser epitaxial structure, the grooves on the two sides of the waveguide are filled with materials with high heat conductivity and high refractive index, so that the effect of improving the quality of the light beam can be achieved as shown in fig. 5.
The improvement of the beam quality is based on the following physical principles:
1) The waveguide structure can be seen as three different regions, seen in the horizontal direction, namely the left region of the waveguide, the waveguide region and the right region of the waveguide, as shown in fig. 6. After the high refractive index material is filled into the groove, the effective refractive indexes in the region 1 and the region 3 at the two sides of the waveguide are increased, wherein the increase is related to the refractive index of the filling material and the filling thickness, and the larger the refractive index of the filling material is, the more the effective refractive indexes in the region 1 and the region 3 are increased; the thicker the filler material, the more the effective refractive index increases in regions 1 and 3. The increase in effective refractive index in region 1 and region 3 further reduces the waveguide effect, since the spatial confinement capacity of the waveguide for light waves can be characterized by a so-called waveguide normalized thickness V parameter:
wherein lambda is 0 Is the wavelength of light in vacuum, W is the waveguide width, n 2 And n 11 The effective refractive indices of the waveguide region 2 and the trench region (region 1 and region 3), respectively. The larger the V parameter, the more modes the waveguide supports. It is apparent that the parameter V is positively correlated with the effective index difference of the waveguide region and the trench region.
When the trench structure is filled with material, the refractive index of the trench (region 1 and region 3) is reduced, and the number of modes that the waveguide can support is reduced, resulting in an improvement in beam quality. If the refractive index of the filler material is sufficiently large, then even the reverse waveguide effect can be formed, where light propagation in the epitaxial structure relies on a gain waveguide mechanism, and the beam quality is substantially improved. The refractive index changes after filling with materials having different refractive indexes as shown in fig. 7 (a) and 7 (b).
2) After filling the trenches with the material, the lateral heat transfer energy of the chip structure formed by the epitaxial structure and the substrate is improved, thereby reducing the temperature gradient distribution between the waveguide and the trench regions on both sides adjacent thereto, reducing the effect of the thermal lens, and resulting in an improvement of the beam quality (fig. 8).
The epitaxial structure growing process on the semiconductor substrate comprises the following steps: and (3) epitaxy of a 900-1000nm wavelength laser epitaxial structure on the semiconductor substrate by MOCVD technology.
The refractive index of the high refractive index material is 2.5-3.8, the number of modes supported by the epitaxial structure can be reduced, so that the quality of a light beam is improved, the thermal conductivity coefficient range is 34W/(m.k) -24W (cm.k), and the gradient distribution of the temperature between the waveguide and the groove areas on two adjacent sides of the waveguide can be reduced.
The refractive index of the semiconductor substrate is in the range of 3.4-3.6.
The filler material is Si or diamond.
The beam quality of the edge-emitting laser can be improved through the ridge waveguide structure for improving the beam quality, and the effective refractive index in the ridge waveguide groove is increased through the filling material; meanwhile, the transverse heat conduction capacity of the epitaxial structure is changed through filling materials in the grooves, so that the temperature gradient distribution between the epitaxial structure and the groove areas on two adjacent sides of the epitaxial structure is reduced, the effect of a thermal lens is reduced, and the quality of light beams is improved.
Examples
For a high power 976nm laser with a waveguide width of 95 μm, the relationship between the number of modes supported by the waveguide and the refractive index difference (the difference between the effective refractive index of the waveguide region and the effective refractive index of the trench region) was calculated, and the calculation results are shown in table 1.
TABLE 1
As can be seen from table 1, the larger the refractive index difference, the larger the number of supported waveguide modes.
For a given epitaxial material structure, the effective index difference between the waveguide and trench regions is shown in table 2 for an etch depth of 700nm, and the change in refractive index between the waveguide region and trench region after filling with Si (n=3.67) material is shown in table 3. After filling with diamond material (n= 2.3981) material, the refractive index of the waveguide region and the trench region changes.
TABLE 2
| Depth of etching (nm) | Refractive index difference between waveguide region and trench region |
| 0 | 0 |
| 700 | 2.47e-4 |
TABLE 3 Table 3
TABLE 4 Table 4
| Filling thickness (nm) | Refractive index difference between waveguide region and trench region |
| 0 (without filling) | 2.47e-4 |
| 350 | 2.31e-4 |
| 700 | 2.0e-4 |
From table 2, tables 3 and 4, it can be seen that the distribution is the refractive index change after filling the trench region with Si and diamond material. It is apparent that there is a certain decrease in the refractive index difference after the filler. For Si filled structures the refractive index difference may even become negative, i.e. a so-called reverse waveguide effect is formed, where the laser can only rely on a so-called gain waveguide for light propagation.
The near field spot distribution at different numbers of waveguide modes was simulated according to fig. 9-16. Obviously, when the mode number is 1, the near field distribution approaches an ideal gaussian beam. For a wide-stripe high-power laser, a single mode can obtain an ideal Gaussian beam, namely a high-quality light spot.
By the mode, the ridge waveguide structure filled with the high-refraction and high-heat-conductivity material can be used for lasers with different wavelengths, and the quality of light beams can be effectively improved.
Claims (5)
1. The ridge waveguide structure for improving the quality of light beams comprises a semiconductor substrate, wherein an epitaxial structure is grown on the semiconductor substrate, and a groove is etched on the epitaxial structure.
2. The ridge waveguide structure of claim 1, wherein the growing epitaxial structures on the semiconductor substrate comprises: and (3) epitaxy of a 900-1000nm wavelength laser epitaxial structure on the semiconductor substrate by MOCVD technology.
3. The ridge waveguide structure of claim 1, wherein the refractive index of the refractive material is 2.5-3.8 and the thermal conductivity is in the range of 34W/(m.k) -24W (cm.k).
4. The ridge waveguide structure of claim 1, wherein the refractive index of the semiconductor substrate is in the range of 3.4-3.6.
5. A ridge waveguide structure according to claim 3, wherein the filler material is Si or diamond.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310720777.4A CN116646820A (en) | 2023-06-16 | 2023-06-16 | Ridge waveguide structure for improving beam quality |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310720777.4A CN116646820A (en) | 2023-06-16 | 2023-06-16 | Ridge waveguide structure for improving beam quality |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116646820A true CN116646820A (en) | 2023-08-25 |
Family
ID=87639995
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310720777.4A Pending CN116646820A (en) | 2023-06-16 | 2023-06-16 | Ridge waveguide structure for improving beam quality |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116646820A (en) |
-
2023
- 2023-06-16 CN CN202310720777.4A patent/CN116646820A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US6411764B1 (en) | Double core spot size converter using selective area growth and fabricating method thereof | |
| CN109802296B (en) | Beam shaping structure of edge-emitting laser, laser chip and preparation method of laser chip | |
| CN1979982A (en) | Semiconductor laser device and method for manufacturing the same | |
| CN111711071B (en) | Tunable laser and manufacturing method thereof | |
| CN112868149A (en) | Optical amplifier | |
| CN111541149B (en) | 10G anti-reflection laser and preparation process thereof | |
| CN113991422A (en) | DFB laser manufacturing method based on deterministic grating coupling coefficient of medium side wall grating | |
| JP6722199B2 (en) | Wide-area laser with anti-guide region for high-order transverse mode suppression | |
| CN114421280B (en) | Semiconductor laser and method for manufacturing the same | |
| CN116646820A (en) | Ridge waveguide structure for improving beam quality | |
| US6552358B2 (en) | High power single mode laser and method of fabrication | |
| JP2960926B2 (en) | Manufacturing method of laser diode | |
| CN114006261B (en) | Vertical cavity surface emitting laser with circular light spot | |
| JP2010021430A (en) | Semiconductor photonic element | |
| JP5165002B2 (en) | Manufacturing method of semiconductor device | |
| LU502263B1 (en) | Tapered semiconductor laser modulated with a periodic layer structure | |
| CN117117630A (en) | Semiconductor laser with composite material thermo-optical effect compensation structure and preparation method thereof | |
| CN116960737A (en) | Semiconductor laser with cavity surface filtering structure and preparation method thereof | |
| KR101003970B1 (en) | Index guiding stripe type high power semiconductor laser diode and method for the fabricating the same | |
| CN117317808A (en) | Oval deep groove narrow ridge semiconductor laser | |
| CN116706669A (en) | Optical mode filtering semiconductor laser and preparation method thereof | |
| KR100269384B1 (en) | Laser diode and method for fabricating the same | |
| CN117895329A (en) | Method for improving output power and beam quality of wide-stripe high-power semiconductor laser | |
| JP2763781B2 (en) | Semiconductor laser device and method of manufacturing the same | |
| KR100226431B1 (en) | Structure for and method of high power semiconductor laser |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |