A side-coupled beam-converting ridge waveguide distributed feedback semiconductor laser

Abstract

The embodiments of the present application relate to the field of semiconductor laser technology, and more particularly to a side-coupled, bunched ridge waveguide distributed feedback semiconductor laser, comprising: a bunched ridge waveguide region and a side-coupled grating region; the side-coupled grating region comprising two sets of side-coupled gratings and ridge waveguides with the same period and duty cycle, the two sets of side-coupled gratings being disposed on either side of the ridge waveguide. The side-coupled, bunched ridge waveguide distributed feedback semiconductor laser provided in the present application can maintain good longitudinal mode characteristics in a wider ridge waveguide, facilitating an increase in the output power of the side-coupled distributed feedback semiconductor laser. This solves the problem of traditional side-coupled distributed feedback semiconductor lasers, which are limited in output power due to the narrow ridge waveguide width, while also reducing the difficulty of the laser device manufacturing process.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of semiconductor laser technology, and in particular to a side-coupled beam-converting ridge waveguide distributed feedback semiconductor laser. Background Art

[0002] Laterally coupled distributed feedback semiconductor lasers (DFLSs) are key devices for achieving narrow-linewidth, single-longitudinal-mode laser output and are widely used in fields such as optical fiber communications and space communications. With the development of industries such as long-distance optical fiber communications and ground-to-space communications, there is a growing demand for DFLSs to achieve higher power while maintaining their original longitudinal-mode characteristics.

[0003] However, to ensure sufficient coupling capability of the side-coupled distributed feedback semiconductor lasers, current side-coupled distributed feedback semiconductor lasers typically employ narrow ridge waveguides (approximately 2μm to 5μm). This narrower ridge waveguide allows for smaller current injection, resulting in a smaller active area and difficulty generating high-power laser output. Consequently, output power is severely constrained by the ridge waveguide width. Increasing the ridge waveguide width expands the current injection area, allowing for a larger active area and thus increasing output power. This approach is both more convenient and simpler, but suffers from the following drawbacks: A wider ridge waveguide not only reduces the coupling capability of the side-coupled grating but also generates higher-order side modes, both of which degrade the longitudinal mode characteristics. Summary of the Invention

[0004] The embodiments of the present application provide a side-coupled bunched ridge waveguide distributed feedback semiconductor laser, which can maintain good longitudinal mode characteristics under a wider ridge waveguide, which is conducive to improving the output power of the side-coupled distributed feedback semiconductor laser, solving the problem of traditional side-coupled distributed feedback semiconductor lasers being limited in output power improvement due to the narrow ridge waveguide width, while reducing the process difficulty.

[0005] In order to solve the above technical problems, an embodiment of the present application provides a side-coupled bunched ridge waveguide distributed feedback semiconductor laser, including a bunched ridge waveguide region and a side-coupled grating region; a wide ridge waveguide and a transition waveguide are provided in the bunched ridge waveguide region; the wide ridge waveguide is connected to the side-coupled grating region via a transition waveguide with a gradually changing width; the side-coupled grating region includes two groups of side-coupled gratings and ridge waveguides with the same period and duty cycle, and the two groups of side-coupled gratings are respectively arranged on both sides of the ridge waveguide.

[0006] In some exemplary embodiments, a wide ridge waveguide is used to expand the light field distribution to increase the light field confinement factor of the side-coupling grating region; the width of the wide ridge waveguide in the converging ridge waveguide region is greater than the ridge width of the ridge waveguide in the side-coupling grating region, and the side-coupling grating region is used for longitudinal mode selection.

[0007] In some exemplary embodiments, the wide ridge waveguide is connected to the side-coupling grating region through a transition waveguide and loses high-order modes; the ridge width of the transition waveguide gradually decreases along the direction from the wide ridge waveguide to the side-coupling grating region until it is equal to the ridge width of the ridge waveguide of the side-coupling grating region.

[0008] In some exemplary embodiments, the ridge width of the ridge waveguide in the side-coupling grating region is 5 μm to 60 μm.

[0009] In some exemplary embodiments, the ridge width of the wide-ridge waveguide is 5 μm to 120 μm.

[0010] In some exemplary embodiments, along the cavity length direction, the length of the ridge waveguide in the side-coupling grating coupling region is 500 μm to 1500 μm; the cavity length direction is the direction of laser resonance in the cavity.

[0011] In some exemplary embodiments, the length of the transition waveguide is 50 μm to 200 μm.

[0012] In some exemplary embodiments, the wide ridge waveguide has a length of 50 μm to 500 μm.

[0013] In some exemplary embodiments, the etching depth of the wide ridge waveguide and the transition waveguide in the convergent ridge waveguide region is adjusted according to different epitaxial structures; the etching depth of the wide ridge waveguide and the transition waveguide in the convergent ridge waveguide region is 0.6 μm to 2 μm.

[0014] In some exemplary embodiments, the semiconductor laser further includes a stacked structure; the stacked structure includes, from bottom to top, an N-side electrode, a substrate, an N-type confinement layer, an N-type waveguide layer, an active gain layer, a P-type waveguide layer, a P-type confinement layer, and a P-type cap layer; the wide ridge waveguide and the transition waveguide together constitute a converged ridge waveguide; the converged ridge waveguide is formed by etching the stacked structure from top to bottom.

[0015] The technical solution provided by the embodiments of the present application has at least the following advantages:

[0016] An embodiment of the present application provides a side-coupled bunching ridge waveguide distributed feedback semiconductor laser, which includes a bunching ridge waveguide region and a side-coupling grating region; the bunching ridge waveguide includes a wide ridge waveguide and a transition waveguide; in the length direction of the bunching ridge waveguide, the ridge width of the transition waveguide gradually decreases along the direction from the wide ridge waveguide to the side-coupling grating region until it is equal to the ridge waveguide width of the side-coupling grating region; the side-coupling grating region includes two groups of side-coupling gratings and ridge waveguides with the same period and duty cycle, and the two groups of side-coupling gratings are respectively arranged on both sides of the ridge waveguide.

[0017] The embodiment of the present application provides a side-coupled convergent ridge waveguide distributed feedback semiconductor laser, which can maintain good longitudinal mode characteristics under a wider ridge waveguide, which is beneficial to the improvement of the output power of the side-coupled distributed feedback semiconductor laser, solves the problem that the narrow ridge waveguide width of the traditional side-coupled distributed feedback semiconductor laser limits the output power improvement, and reduces the process difficulty. The present application adopts a convergent ridge waveguide, which is different from the straight ridge waveguide used in the previous side-coupled distributed feedback semiconductor laser. Secondly, the wide ridge waveguide in the convergent ridge waveguide region of the present application plays a role in expanding the light field, thereby achieving the purpose of enhancing the coupling ability of the side-coupled grating. In addition, the side-coupled convergent ridge waveguide distributed feedback semiconductor laser of the present application can generate additional losses for the high-order side modes in the resonant cavity, has good mode discrimination ability, and maintains the advantage of the fundamental mode in mode competition. The side-coupled convergent ridge waveguide distributed feedback semiconductor laser designed in the present application has low manufacturing difficulty, simple structure, does not require the use of a narrow ridge waveguide, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] One or more embodiments are exemplarily described by the pictures in the corresponding drawings. These exemplifications do not constitute limitations on the embodiments. Unless otherwise stated, the pictures in the drawings do not constitute proportional limitations.

[0019] Figure 1A A top view of a side-coupled beam-converting ridge waveguide distributed feedback semiconductor laser provided in an embodiment of the present application;

[0020] Figure 1B A three-dimensional structural diagram of a side-coupled beam-converting ridge waveguide distributed feedback semiconductor laser provided in an embodiment of the present application;

[0021] Figure 2 The fundamental transverse mode light field distribution in the ridge waveguide region of the side-coupled distributed feedback semiconductor laser with ridge waveguide widths of 30 μm, 40 μm, and 60 μm, respectively, provided in the embodiments of the present application;

[0022] Figure 3 The fundamental transverse mode light field distribution in the ridge waveguide region of the side-coupled distributed feedback semiconductor laser provided in the embodiment of the present application is 30 μm in the ridge waveguide width of the side-coupled grating region, and the wide ridge waveguide widths are 30 μm, 40 μm, and 60 μm respectively;

[0023] Figure 4 Output spectra of the side-coupled distributed feedback semiconductor laser at room temperature provided in an embodiment of the present application at different currents measured by a high-precision spectrometer;

[0024] Figure 5Output spectra of a side-coupled, convergent ridge waveguide distributed feedback semiconductor laser with a 60 μm wide ridge waveguide at room temperature provided by an embodiment of the present application at different currents measured by a high-precision spectrometer;

[0025] Figure 6 The output spectrum of the side-coupled distributed feedback semiconductor laser provided in the embodiment of the present application changes with temperature;

[0026] Figure 7 The wide ridge waveguide provided in the embodiment of the present application is a 60 μm side-coupled beam-contracted ridge waveguide distributed feedback semiconductor laser output spectrum change with temperature;

[0027] Figure 8 Far-field distribution test diagram of a side-coupled distributed feedback semiconductor laser under high current provided by an embodiment of the present application;

[0028] Figure 9 Far-field distribution test diagram of a side-coupled, bunched ridge waveguide distributed feedback semiconductor laser with a wide ridge waveguide width of 60 μm under high current provided by an embodiment of the present application;

[0029] Figure 10 The power-current test diagram of a side-coupled bunched ridge waveguide distributed feedback semiconductor laser with a wide ridge waveguide width of 60 μm and a side-coupled distributed feedback semiconductor laser at room temperature provided in the embodiments of the present application. DETAILED DESCRIPTION

[0030] As can be seen from the background technology, existing side-coupled distributed feedback semiconductor lasers have technical problems such as difficulty in manufacturing narrow ridge waveguides, low yield, high requirements for manufacturing equipment, and low output power.

[0031] Current side-coupled distributed feedback semiconductor lasers usually adopt a narrow ridge waveguide design to ensure that the side-coupled grating has sufficient coupling capability. The output power and longitudinal mode characteristics are seriously affected by the width of the ridge waveguide, which brings the following problems: (1) The narrow ridge waveguide is difficult to manufacture, with low yield and high cost, and has high requirements for manufacturing equipment; (2) The ridge waveguide is very narrow, resulting in a very small current injection area and a small active area, which seriously limits the power increase.

[0032] To address the aforementioned technical issues, embodiments of the present application provide a side-coupled, bunched ridge waveguide distributed feedback semiconductor laser. The semiconductor laser comprises a bunched ridge waveguide region and a side-coupled grating region. The bunched ridge waveguide comprises a wide ridge waveguide and a transition waveguide. The side-coupled grating region comprises two sets of side-coupled gratings and ridge waveguides with the same period and duty cycle, and the two sets of side-coupled gratings are disposed on either side of the ridge waveguide. By providing a side-coupled, bunched ridge waveguide distributed feedback semiconductor laser, the present application can maintain good longitudinal mode characteristics in a wider ridge waveguide, thereby facilitating an increase in the output power of the side-coupled distributed feedback semiconductor laser. This addresses the problem of traditional side-coupled distributed feedback semiconductor lasers, where the narrow ridge waveguide width limits output power increases, while also reducing process difficulty.

[0033] The following detailed description of the various embodiments of the present application is provided in conjunction with the accompanying drawings. However, those skilled in the art will appreciate that many technical details are provided in the various embodiments of the present application to facilitate a better understanding of the present application. However, even without these technical details and the various variations and modifications based on the following embodiments, the technical solutions claimed in the present application can still be implemented.

[0034] See Figure 1A and Figure 1B An embodiment of the present application provides a side-coupled bunched ridge waveguide distributed feedback semiconductor laser, which includes a bunched ridge waveguide region 1 and a side-coupled grating region 2; a wide ridge waveguide 11 and a transition waveguide 12 are provided in the bunched ridge waveguide region 1; the side-coupled grating region 2 includes two groups of side-coupled gratings 21 and a ridge waveguide 22 with the same period and duty cycle, and the two groups of side-coupled gratings 21 are respectively arranged on both sides of the ridge waveguide 22.

[0035] In some embodiments, the wide ridge waveguide 11 is used to expand the light field distribution and increase the light field confinement factor of the laterally coupled grating region 2; the width of the wide ridge waveguide in the converging ridge waveguide region 1 is greater than the ridge width of the ridge waveguide in the laterally coupled grating region 2, and the laterally coupled grating region is used for longitudinal mode selection.

[0036] In some embodiments, the wide ridge waveguide 11 is connected to the side-coupling grating region 2 via the transition waveguide 12, and loses the high-order modes; the ridge width of the transition waveguide 12 gradually decreases along the direction of the wide ridge waveguide 11 pointing to the side-coupling grating region 2 until it is equal to the ridge waveguide width of the side-coupling grating region 2.

[0037] In some embodiments, the ridge width of the ridge waveguide 22 of the side-coupling grating region 2 is 5 μm to 60 μm. For example, the ridge width of the ridge waveguide 22 of the side-coupling grating region 2 can be 5 μm, 10 μm, 20 μm, 30 μm, 50 μm, or 60 μm. Preferably, the ridge width of the ridge waveguide 22 of the side-coupling grating region 2 is 30 μm.

[0038] In some embodiments, the ridge width of the wide ridge waveguide 11 is 5 μm to 120 μm. For example, the ridge width of the wide ridge waveguide 11 can be 5 μm, 10 μm, 20 μm, 40 μm, 60 μm, 80 μm, 100 μm or 120 μm. Preferably, the ridge width of the wide ridge waveguide 11 is 60 μm.

[0039] In some embodiments, the length of the ridge waveguide 22 of the lateral coupling grating region 2 along the cavity length direction is 500 μm to 1500 μm, where the cavity length direction is the direction of laser resonance. For example, the length of the ridge waveguide 22 of the lateral coupling grating region 2 can be 500 μm, 800 μm, 1000 μm, 1200 μm, 1400 μm, or 1500 μm. Preferably, the length of the ridge waveguide 22 of the lateral coupling grating region 2 is 800 μm.

[0040] In some embodiments, the length of the transition waveguide 12 is 50 μm to 200 μm. For example, the length of the transition waveguide 12 can be 50 μm, 60 μm, 80 μm, 100 μm, 150 μm or 200 μm. Preferably, the length of the transition waveguide 12 is 100 μm.

[0041] In some embodiments, the length of the wide ridge waveguide 11 is 50 μm to 500 μm. For example, the length of the wide ridge waveguide 11 can be 50 μm, 60 μm, 80 μm, 100 μm, 150 μm, 200 μm, 300 μm, 400 μm or 500 μm. Preferably, the length of the wide ridge waveguide 11 is 200 μm.

[0042] In some embodiments, the etching depth of the ridge waveguide in the convergent ridge waveguide region 1 is adjusted according to the different epitaxial structures; the etching depth of the ridge waveguide in the convergent ridge waveguide region 1 is 0.6 μm to 2 μm. For example, the etching depth of the ridge waveguide in the convergent ridge waveguide region 1 may be 0.6 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.5 μm or 2 μm. Preferably, the etching depth of the ridge waveguide in the convergent ridge waveguide region 1 is 1 μm. It should be noted that the ridge waveguide in the convergent ridge waveguide region 1 is a wide ridge waveguide 11 and a transition waveguide 12, and the etching depths of the wide ridge waveguide 11 and the transition waveguide 12 are 1 μm. The wide ridge waveguide 11 and the transition waveguide 12 together constitute the convergent ridge waveguide.

[0043] In some embodiments, see Figure 1B The semiconductor laser also includes a stacked structure; the stacked structure includes, from bottom to top, an N-side electrode 101, a substrate 102, an N-type confinement layer 103, an N-type waveguide layer 104, an active gain layer 105, a P-type waveguide layer 106, a P-type confinement layer 107 and a P-type cap layer 108; the wide ridge waveguide 11 and the transition waveguide 12 together constitute a convergent ridge waveguide; the convergent ridge waveguide is formed by etching the stacked structure from top to bottom.

[0044] The side-coupled beam-converting ridge waveguide distributed feedback semiconductor laser provided by the present application is described in detail below through specific embodiments.

[0045] The three-dimensional structure of the side-coupled beam-converting ridge waveguide distributed feedback semiconductor laser is shown in Figure 2. Figure 1B As shown, the yellow area is the P-side current injection area.

[0046] The coupling coefficient κ of the side-coupled grating can be expressed as Equation (1), where k0 refers to the vacuum wave vector, n eff refers to the effective refractive index, γ refers to the grating duty cycle, m refers to the grating order, n2 and n1 represent the high and low refractive index of the material constituting the grating, respectively, and Γ g is the light field confinement factor of the grating. From formula (1), we can see that increasing the light field confinement factor of the grating can effectively improve the coupling ability of the grating.

[0047]

[0048] For side-coupled distributed feedback semiconductor lasers, although simply increasing the ridge waveguide width can effectively increase the output power, it will cause the longitudinal mode characteristics to deteriorate. There are two specific reasons for this deterioration in longitudinal mode characteristics. The first is that the wide ridge waveguide reduces the grating coupling ability. The second is that the wide ridge waveguide generates high-order side modes, which affect the longitudinal mode characteristics.

[0049] The widening of the ridge waveguide of the side-coupled distributed feedback semiconductor laser will confine the light field more to the ridge waveguide area, making the light field distribution in the grating area less, resulting in a decrease in the grating coupling ability, such as Figure 2 As shown. The side-coupled bunched ridge waveguide distributed feedback semiconductor laser improves the light field distribution in the wide ridge waveguide side-coupled grating area by diffusing more light fields into the grating area, as shown Figure 3 As shown in Figure 2, the side-coupled convergent ridge waveguide distributed feedback semiconductor laser can achieve an increase in the light field confinement factor in the grating region because the wide-ridge waveguide structure is introduced into the convergent ridge waveguide region, increasing the current injection area and thus generating a larger fundamental-side mode light field distribution. When the light field generated by the wide-ridge waveguide is coupled into the ridge waveguide in the side-coupled grating region, more light field leaks into the side-coupled grating region, ultimately enhancing the grating's coupling capability due to the increase in the light field confinement factor.

[0050] In addition, a wider ridge waveguide not only reduces the coupling ability of the grating, but also often supports multiple transverse modes under high drive current, which also affects the longitudinal mode characteristics of the output laser. Laterally coupled convergent ridge waveguide distributed feedback semiconductor lasers have a certain inhibitory effect on high-order side modes under high current. This is because when two waveguides of different widths are coupled, the energy spatial distribution of side modes of different orders in the resonant cavity is different, resulting in different degrees of loss during the coupling process, which makes the resonant cavity have good side mode discrimination ability.

[0051] The above analysis proves that the side-coupled bunching ridge waveguide distributed feedback semiconductor laser provided in this application can enhance the coupling ability of the wide ridge waveguide side-coupled grating and suppress high-order side modes. Therefore, it can maintain good longitudinal mode characteristics under a wider ridge waveguide, and at the same time is conducive to the improvement of the output power of the side-coupled distributed feedback semiconductor laser, solving the problem that the traditional side-coupled distributed feedback semiconductor laser is limited in output power improvement due to the narrow ridge waveguide width.

[0052] In order to verify the effectiveness of the side-coupled bunching ridge waveguide distributed feedback semiconductor laser provided by this application, this application experimentally produced a side-coupled bunching ridge waveguide distributed feedback semiconductor laser with a ridge waveguide width of 30 μm in the side-coupling grating area and a wide ridge waveguide width of 60 μm in the bunching ridge waveguide area, and produced a side-coupled distributed feedback semiconductor laser with the same ridge waveguide width in the side-coupling grating area as a control. Figure 4 The output spectrum of a side-coupled distributed feedback semiconductor laser varies with current. Figure 5 The output spectrum of a side-coupled converged ridge waveguide distributed feedback semiconductor laser with a wide ridge waveguide width of 60μm is shown as a function of current. It can be seen that its output spectrum has a narrower linewidth and a higher side mode suppression ratio. Since the ridge waveguide width of the side-coupled distributed feedback semiconductor laser reaches 30μm, the ridge waveguide is relatively wide. Although the output power will be greatly improved compared to the side-coupled distributed feedback semiconductor laser with a narrow ridge waveguide, it will lead to insufficient coupling ability. Figure 4 From the illustration, we can see that there are still obvious side modes, and the 3dB linewidth reaches 0.97nm. Figure 5The illustration shows the output spectrum of the side-coupled beam-ridge waveguide distributed feedback semiconductor laser at 0.4A. It can be seen that the output spectrum has been significantly improved. This is because the wide ridge waveguide in the side-coupled beam-ridge waveguide distributed feedback semiconductor laser can distribute more light fields to the side-coupled grating area, the coupling ability of the side-coupled grating is enhanced, the optical feedback effect of the grating in the resonant cavity is enhanced, the longitudinal mode selection characteristics of the grating are fully reflected, the 3dB linewidth of the output spectrum is narrowed to 0.07nm, and the side mode suppression ratio is increased to 23.2dB. The improvement of the longitudinal mode characteristics of the side-coupled beam-ridge waveguide distributed feedback semiconductor laser has been experimentally verified. Figure 6 、 Figure 7 The temperature drift test diagrams of the two devices at 0.4A are shown respectively. It can be seen that the temperature drift coefficient of the side-coupled beam-ridge waveguide distributed feedback semiconductor laser is significantly lower than that of the side-coupled distributed feedback semiconductor laser, which also proves that the coupling degree between the optical mode in the resonant cavity and the grating is enhanced.

[0053] Figure 8 、 Figure 9 The far-field spot distributions of the side-coupled distributed feedback semiconductor laser and the side-coupled bunched ridge waveguide distributed feedback semiconductor laser at 1A, 1.1A, and 1.2A are shown respectively. The inset shows the horizontal far-field angle distribution at 1.1A. It can be seen that the side-coupled distributed feedback semiconductor laser has a wider ridge waveguide width of 30μm, and although the output power is higher than that of the side-coupled distributed feedback semiconductor laser with a narrow ridge waveguide, obvious high-order side modes appear at a current of 1A. However, the side-coupled bunched ridge waveguide distributed feedback semiconductor laser still maintains fundamental side mode output until multi-side mode lasing occurs at 1.2A, verifying that the side-coupled bunched ridge waveguide distributed feedback semiconductor laser has a stronger suppression effect on the high-order side modes in the wider ridge waveguide. Figure 10 The power-current curve test diagrams of the side-coupled distributed feedback semiconductor laser and the side-coupled beam-ridge waveguide distributed feedback semiconductor laser at room temperature are respectively shown. It can be seen that the output power of the side-coupled beam-ridge waveguide distributed feedback semiconductor laser is greater than that of the side-coupled distributed feedback semiconductor laser at all currents. When the injection current is 0.4A, the output power of the side-coupled beam-ridge waveguide distributed feedback semiconductor laser is increased by 32%.

[0054] Based on the above technical solution, an embodiment of the present application provides a side-coupled bunched ridge waveguide distributed feedback semiconductor laser, which includes a bunched ridge waveguide region 1 and a side-coupled grating region 2; a wide ridge waveguide 11 and a transition waveguide 12 are provided in the bunched ridge waveguide region 1; the side-coupled grating region 2 includes two groups of side-coupled gratings 21 and a ridge waveguide 22 with the same period and duty cycle, and the two groups of side-coupled gratings 21 are respectively arranged on both sides of the ridge waveguide 22.

[0055] The embodiment of the present application provides a side-coupled convergent ridge waveguide distributed feedback semiconductor laser, which can maintain good longitudinal mode characteristics under a wider ridge waveguide, which is beneficial to the improvement of the output power of the side-coupled distributed feedback semiconductor laser, solves the problem that the narrow ridge waveguide width of the traditional side-coupled distributed feedback semiconductor laser limits the output power improvement, and also reduces the process difficulty. First, the present application adopts a convergent ridge waveguide, which is different from the straight ridge waveguide used in the previous side-coupled distributed feedback semiconductor laser. Secondly, the wide ridge waveguide in the convergent ridge waveguide region of the present application plays a role in expanding the light field, thereby achieving the purpose of enhancing the coupling ability of the side-coupled grating. In addition, the side-coupled convergent ridge waveguide distributed feedback semiconductor laser provided by the present application can generate additional losses for the high-order side modes in the resonant cavity, has good mode discrimination ability, and maintains the advantage of the fundamental mode in mode competition. The side-coupled convergent ridge waveguide distributed feedback semiconductor laser designed in the present application has a low structural difficulty in manufacturing, a simple structure, and does not require the use of a narrow ridge waveguide, and has good application prospects.

[0056] Those skilled in the art will appreciate that the above-described embodiments are specific examples for implementing the present application, and that in actual applications, various changes in form and detail may be made thereto without departing from the spirit and scope of the present application. Any person skilled in the art may make changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be subject to the scope defined in the claims.

Claims

1. A side-coupled beam-guided distributed feedback semiconductor laser, characterized in that: include: The semiconductor laser comprises a beam-converging ridge waveguide region and a side-coupling grating region; A wide ridge waveguide and a transition waveguide with a gradually changing width are provided in the convergent ridge waveguide region; The side-coupling grating region includes two groups of side-coupling gratings and ridge waveguides with the same period and duty cycle, and the two groups of side-coupling gratings are respectively arranged on both sides of the ridge waveguide in the side-coupling grating region; The wide ridge waveguide is used to expand the light field distribution to increase the light field confinement factor of the side-coupling grating region; the width of the wide ridge waveguide in the bunching ridge waveguide region is greater than the ridge width of the ridge waveguide in the side-coupling grating region, and the side-coupling grating region is used for longitudinal mode selection; The wide ridge waveguide is connected to the side-coupling grating region through the transition waveguide and loses high-order modes; the ridge width of the transition waveguide gradually decreases along the direction of the wide ridge waveguide pointing to the side-coupling grating region until it is equal to the ridge width of the ridge waveguide of the side-coupling grating region.

2. The side-coupled beam-guided distributed feedback semiconductor laser according to claim 1, characterized in that: The ridge width of the ridge waveguide in the side-coupling grating region is 5 μm to 60 μm.

3. The side-coupled beam-guided distributed feedback semiconductor laser according to claim 1, characterized in that: The ridge width of the wide ridge waveguide is 5 μm to 120 μm.

4. The side-coupled beam-converting ridge waveguide distributed feedback semiconductor laser according to claim 1, characterized in that: Along the cavity length direction, the length of the ridge waveguide in the coupling region of the side-coupling grating is 500 μm to 1500 μm; the cavity length direction is the direction of laser resonance in the cavity.

5. The side-coupled beam-guided distributed feedback semiconductor laser according to claim 1, characterized in that: The length of the transition waveguide is 50 μm to 200 μm.

6. The side-coupled beam-guided distributed feedback semiconductor laser according to claim 1, characterized in that: The length of the wide ridge waveguide is 50 μm to 500 μm.

7. The side-coupled beam-guided distributed feedback semiconductor laser according to claim 1, characterized in that: The etching depth of the wide ridge waveguide and the transition waveguide in the convergent ridge waveguide region is adjusted according to the different epitaxial structures; the etching depth of the wide ridge waveguide and the transition waveguide in the convergent ridge waveguide region is 0.6 μm to 2 μm.

8. The side-coupled beam-converting ridge waveguide distributed feedback semiconductor laser according to claim 1, characterized in that: The semiconductor laser further includes a stacked structure; The stacked structure includes, from bottom to top, an N-side electrode, a substrate, an N-type confinement layer, an N-type waveguide layer, an active gain layer, a P-type waveguide layer, a P-type confinement layer, and a P-type cap layer; The wide ridge waveguide and the transition waveguide together constitute a convergent ridge waveguide; the convergent ridge waveguide is formed by etching the stacked structure from top to bottom.

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