CN220138931U - Semiconductor laser and optical chip comprising same - Google Patents

Abstract

The embodiment of the application provides a semiconductor laser and an optical chip comprising the semiconductor laser, and belongs to the field of semiconductor lasers. The semiconductor laser provided by the embodiment of the application comprises a plurality of ridge waveguides, wherein each ridge waveguide comprises a ridge region and a flat plate region; the plurality of ridge waveguides include a first ridge waveguide, a second ridge waveguide, and a third ridge waveguide, and the first ridge waveguide is located between the second ridge waveguide and the third ridge waveguide. Because the heights of the ridge regions of the second ridge waveguide and the third ridge waveguide are not equal to the height of the ridge region of the first ridge waveguide, and the width of the ridge region of at least one of the plurality of ridge waveguides is smaller than or equal to the thickness of the slab region, the mode field distribution of the fundamental mode can be made to be significantly different from that of the high-order mode, while the loss of the high-order mode is significantly increased, but the loss of the fundamental mode is not significantly increased, so as to realize the fundamental mode lasing.

Description

Semiconductor laser and optical chip comprising same

Technical Field

The application belongs to the field of semiconductor lasers, and particularly relates to a semiconductor laser and an optical chip comprising the semiconductor laser.

Background

The large-mode-field high-power single-mode narrow-linewidth semiconductor laser has wider and wider application in the fields of pumping, optical communication, medical treatment and the like, thereby having larger application requirements.

When increasing the waveguide size to increase the fundamental mode field, one problem that is difficult to avoid is that the number of modes also becomes large. Although the mode losses of the higher order transverse modes (higher order modes for short) are slightly higher than those of the fundamental modes, they act more strongly with the grating and have a larger coupling coefficient, so that the power reflectivity may be higher than that of the fundamental mode when passing through a grating of a certain length, so that the laser may multimode lasing or lasing based on a certain higher order mode, and the lasing based on the fundamental mode, which is generally expected, cannot be achieved.

Disclosure of Invention

The utility model provides a semiconductor laser and an optical chip comprising the same, wherein the fundamental mode is preferentially excited to higher-order modes under the condition that the waveguide size is increased and the waveguide is a multimode waveguide.

The present utility model provides a semiconductor laser having such features that it includes:

a plurality of ridge waveguides including a ridge region and a slab region;

the plurality of ridge waveguides comprise a first ridge waveguide, a second ridge waveguide and a third ridge waveguide, and the first ridge waveguide is positioned between the second ridge waveguide and the third ridge waveguide;

the height of the ridge regions of the second ridge waveguide and the third ridge waveguide is not equal to that of the ridge region of the first ridge waveguide, and the width of the ridge region of at least one of the ridge waveguides is smaller than or equal to the thickness of the slab region.

The semiconductor laser described above has the following features:

the semiconductor laser is any one of a distributed feedback DFB laser, a distributed bragg reflector DBR laser, and an F-P cavity laser.

The semiconductor laser described above has the following features:

the light-emitting device further comprises a light-emitting unit and a lower cladding layer, the plurality of ridge waveguides are located on the lower cladding layer, and the light-emitting unit is located between the bottom of the ridge area of the ridge waveguides and the lower cladding layer.

The semiconductor laser described above has the following features:

the light emitting unit is any one of a pn junction, a single quantum well, a multiple quantum well, a quantum wire, and a quantum dot.

The semiconductor laser described above has the following features:

it also includes a grating for providing optical feedback.

The semiconductor laser described above has the following features:

the grating is disposed in at least one of both ends of the semiconductor laser.

The semiconductor laser described above has the following features:

the plurality of ridge waveguides are n-doped waveguides.

The semiconductor laser described above has the following features:

the plurality of ridge waveguides includes n-doped InGaAsP waveguides.

The semiconductor laser described above has the following features:

the lower cladding is an n-type doped InP cladding or a p-type doped InP cladding.

The application also provides an optical chip with the characteristics comprising the semiconductor laser.

The semiconductor laser provided by the embodiment of the application comprises a plurality of ridge waveguides, wherein each ridge waveguide comprises a ridge region and a flat plate region; the plurality of ridge waveguides include a first ridge waveguide, a second ridge waveguide, and a third ridge waveguide, and the first ridge waveguide is located between the second ridge waveguide and the third ridge waveguide. Because the heights of the ridge regions of the second ridge waveguide and the third ridge waveguide are not equal to the height of the ridge region of the first ridge waveguide, and the width of the ridge region of at least one of the plurality of ridge waveguides is smaller than or equal to the thickness of the slab region, the mode field distribution of the fundamental mode can be made to be significantly different from that of the high-order mode, while the loss of the high-order mode is significantly increased, but the loss of the fundamental mode is not significantly increased, so as to realize the fundamental mode lasing.

Drawings

Fig. 1 is a schematic view showing a partial perspective view of a semiconductor laser in embodiment 1 of the present application.

Fig. 2 is a schematic cross-sectional view of a semiconductor laser in embodiment 2 of the present application.

Fig. 3 is a schematic cross-sectional view of a semiconductor laser in embodiment 3 of the present application.

Fig. 4 is a schematic cross-sectional view and a cross-sectional view of a semiconductor laser in embodiment 4 of the present application.

Fig. 5 is a schematic cross-sectional view and a cross-sectional view of a semiconductor laser in embodiment 5 of the present application.

Fig. 6 is a schematic cross-sectional view and a cross-sectional view of a semiconductor laser in embodiment 6 of the present application.

Fig. 7 is a schematic cross-sectional view of a semiconductor laser in embodiment 7 of the present application.

Fig. 8 is a schematic view showing a partial perspective view of a semiconductor laser in embodiment 8 of the present application.

Fig. 9 is a schematic cross-sectional view of a semiconductor laser in embodiment 9 of the present application.

Fig. 10 is a schematic view showing a partial perspective view of a semiconductor laser in embodiment 10 of the present application.

Fig. 11 is a schematic cross-sectional view of a semiconductor laser in embodiment 11 of the present application.

Fig. 12 is a schematic cross-sectional view of a semiconductor laser in embodiment 12 of the present application.

Fig. 13 is a schematic cross-sectional view of a semiconductor laser in embodiment 13 of the present application.

Fig. 14 is a schematic view showing a partial perspective view of a semiconductor laser in embodiment 14 of the present application.

Fig. 15 is a schematic cross-sectional view of a semiconductor laser in embodiment 15 of the present application.

Fig. 16 is a schematic cross-sectional view of a semiconductor laser in embodiment 16 of the present application.

Fig. 17 is a schematic view showing a partial perspective view of a semiconductor laser in embodiment 17 of the present application.

Fig. 18 is a schematic cross-sectional view of a semiconductor laser in embodiment 18 of the present application.

Fig. 19 is a schematic cross-sectional view of a semiconductor laser in embodiment 19 of the present application.

Fig. 20 is a schematic view showing a partial perspective view of a semiconductor laser in embodiment 20 of the present application.

Figure number: semiconductor lasers 1 to 20, a lower cladding layer 30, a light emitting unit 40, a grating 50, a ridge waveguide 60, a ridge region 61, a slab region 62, a first ridge waveguide 63, a second ridge waveguide 64, a third ridge waveguide 65, an upper cladding layer 70, a metal electrode 80, and an electric isolation layer 90.

Detailed Description

In order to make the technical means, creation characteristics, achievement purposes and effects of the present application easy to understand, the semiconductor laser and the optical chip comprising the same provided by the present application are specifically described below with reference to the embodiments and the accompanying drawings.

Embodiments of the present application will be described in detail below. Throughout the present specification, the same or similar components and components having the same or similar functions are denoted by similar reference numerals. The embodiments described herein with respect to the drawings are of illustrative nature, of diagrammatic nature and are provided for the basic understanding of the present application. The embodiments of the present application should not be construed as limiting the application.

As used herein, unless specified or limited otherwise, relative terms such as: the terms "vertical," "side," "upper," "lower," and derivatives thereof (e.g., "upper surface" and the like) should be construed to refer to the orientation as described in the discussion or as illustrated in the drawing figures. These relative terms are for convenience of description only and do not require that the application be constructed or operated in a particular orientation.

Additionally, amounts, ratios, and other numerical values are sometimes presented herein in a range format. It is to be understood that such range format is used for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.

Moreover, for ease of description, "first," "second," and so forth may be used herein to distinguish one component or series of different operations of the component. "first," "second," and the like are not intended to describe corresponding components.

< example >

Fig. 1 is a schematic view showing a partial perspective view of a semiconductor laser in embodiment 1 of the present application.

Referring to fig. 1, the semiconductor laser 1 in fig. 1 includes a plurality of ridge waveguides 60 in a cavity axis direction of the semiconductor laser 1, the plurality of ridge waveguides 60 including a first ridge waveguide 63, a second ridge waveguide 64, and a third ridge waveguide 65, each ridge waveguide including a ridge region 61 and a slab region 62. The first ridge waveguide 63 is located between the second ridge waveguide 64 and the third ridge waveguide 65, the height of the ridge region 61 of the second ridge waveguide 64 and the third ridge waveguide 65 is not equal to the height of the ridge region 61 of the first ridge waveguide 63, and the width of the ridge region 61 of at least one of the plurality of ridge waveguides is smaller than or equal to the thickness of the slab region 62.

As shown in fig. 1, in the embodiment of the present application, each ridge waveguide includes a ridge region 61 and a slab region 62, and in fig. 1, the width of the ridge region 61 of the first ridge waveguide 63 is less than or equal to the thickness of the slab region 62 of the first ridge waveguide 63, so that most of the fundamental mode of laser light is confined in the slab region 62 of the ridge waveguide. And the first ridge waveguide 63, the second ridge waveguide 64 and the third ridge waveguide 65 have a height difference, so that the loss of the high-order mode at the height abrupt position of the ridge region 61 is obviously increased, and the fundamental mode has almost no loss, thereby realizing the single-mode lasing of the fundamental mode. The heights of the second ridge waveguide 64 and the third ridge waveguide 65 in the embodiment of the present application may be the same or slightly different from each other, as in the following embodiments.

Fig. 2 is a schematic cross-sectional view of a semiconductor laser in embodiment 2 of the present application.

Fig. 2 (a) is a schematic cross-sectional view taken along line a-a in fig. 1, fig. 2 (B) is a schematic cross-sectional view taken along line B-B in fig. 1, and fig. 2 (C) is a schematic cross-sectional view taken along line C-C in fig. 1 (the cavity axis direction of the semiconductor laser).

When the semiconductor laser shown in fig. 1 is a distributed bragg reflector DBR laser (hereinafter referred to as DBR laser), the semiconductor laser 2 shown in fig. 2 is a schematic cross-sectional view of the DBR laser.

As shown in fig. 2, the DBR laser shown in fig. 2 includes a lower cladding layer 30, a light emitting unit 40, a grating 50, a first ridge waveguide 63, a second ridge waveguide 64, a third ridge waveguide 65, and an upper cladding layer 70.

The lower cladding layer 30 in embodiment 2 of the present application may be a P-type doped low refractive index material, for example, an n-type doped InP (n-InP) material.

The light emitting unit 40 of the DBR laser of embodiment 2 of the present application is a gain medium for emitting light, and the light emitting unit 40 is disposed between the bottom of the ridge region 61 of the first ridge waveguide 63 and the upper surface of the lower cladding layer 30, that is, within the slab region 62 of the first ridge waveguide 63 but at the bottom of the ridge region 61 of the first ridge waveguide 63. Alternatively, the light emitting unit 40 may be disposed in the ridge region 61 of the first ridge waveguide 63 and disposed near the bottom of the ridge region 61 of the first ridge waveguide 63, that is, within the mode field distribution range of the fundamental mode, so as to avoid the gain of the fundamental mode from being too small or even not.

The ridge waveguide of the DBR laser of embodiment 2 of the present application is an n-type doped waveguide material, for example, the material of the ridge waveguide may be an n-type doped InGaAsP material for confining the light emitted from the light emitting unit 40 within the ridge waveguide. In other embodiments, the material of the ridge waveguide may also be other n-doped waveguide materials, such as InGaAs.

As shown in fig. 2 (a) and (c), the light emitting unit 40 of the DBR laser is located at the bottom of the slab region 62 of the first ridge waveguide 63, and the region corresponding to the first ridge waveguide 63 is the gain region. The grating 50 is located at the bottom of the second ridge waveguide 64, the third ridge waveguide 65, and the grating 50 is located in the feedback region for reflecting light to provide optical feedback. Grating 50 may be etched on the surface of lower cladding layer 30, i.e., grating 50 may be etched directly on lower cladding layer 30, or another film layer may be grown that is different from both the ridge waveguide material and the material of lower cladding layer 30 (and thus has a different refractive index), and grating 50 may be etched in this film.

The light emitting unit 40 of the DBR laser in embodiment 2 of the present application may be any one of a pn junction, a single quantum well, a multiple quantum well, a quantum wire, and a quantum dot.

The second ridge waveguide 64 and the third ridge waveguide 65 in the DBR laser correspond to two feedback regions, respectively, and a grating 50 for providing optical feedback is disposed in at least one of the two feedback regions. As shown in the schematic cross-section of fig. 2 (c), the grating 50 may be disposed in both feedback areas, and in other embodiments, the grating 50 may be disposed in only one of the feedback areas. In fig. 2 (c), the grating 50 and the light emitting unit 40 are located at the same level, and in other embodiments, the grating 50 may be etched on the upper surface of the lower cladding layer 30, or may be disposed in any area of the second ridge waveguide 64 and the third ridge waveguide 65, where the grating 50 is ensured to be in contact with the mode field of the fundamental mode, so as to provide optical feedback for the fundamental mode.

The upper surface of the ridge region 61 of the first ridge waveguide 63, the second ridge waveguide 64, and the third ridge waveguide 65 is provided with an upper cladding layer 70, and the upper cladding layer 70 may be an n-type doped cladding layer, for example, the material of the upper cladding layer 70 and the lower cladding layer 30 may be a material of different doping types having the same refractive index, that is, when the upper cladding layer 70 is an n-type doped material, the lower cladding layer 30 is a p-type doped material, and vice versa.

Fig. 2 (c) is a schematic cross-sectional view of the DBR laser along the cavity axis, i.e., the direction from left to right in the figure is the direction in which the laser oscillates back and forth in the cavity, and is a cross-sectional view at the center of each ridge waveguide in the width direction. A pumping current is injected into the upper surface of the upper cladding layer 70 of the DBR laser first ridge waveguide 63 to provide an energy input for laser lasing. The second ridge waveguide 64 and the third ridge waveguide 65 on both sides may not inject current. In other embodiments, the upper surfaces of the upper cladding layers 70 of the second and third ridge waveguides 64, 65 may also be injected with a current to make a Bragg wavelength change to achieve wavelength tuning of the laser.

Alternatively, a cleaved surface may be substituted in one of the feedback regions including grating 50, which cleaved surface may also be coated with a highly reflective film to enhance its reflectivity.

Compared with the existing DBR laser, in embodiment 2 of the present application, by increasing the size of the ridge region 61 of the ridge waveguide of the DBR laser, the first ridge waveguide 63, the second ridge waveguide 64, and the ridge region 61 of the third ridge waveguide 65 can have a significant height difference, so that the loss of the fundamental mode and the loss of the high-order mode of the laser can be significantly differentiated, i.e., the loss of the high-order mode is significantly increased, but the loss of the fundamental mode is not significantly increased, so that the fundamental mode preferentially emits the high-order mode, even when the waveguide size is large, and thus a single-mode DBR laser with a large mode field and high power can be prepared.

Fig. 3 is a schematic cross-sectional view of a semiconductor laser in embodiment 3 of the present application.

In fig. 3, (a), (b) and (c) are schematic cross-sectional views corresponding to the cross-sections in fig. 1, respectively, refer to fig. 2, and are not described herein again.

The semiconductor laser 3 shown in fig. 3 is a DBR laser including a lower cladding layer 30, a first ridge waveguide 63, a second ridge waveguide 64, a third ridge waveguide 65, a light emitting unit 40, a grating 50, and an upper cladding layer 70.

The DBR laser shown in fig. 3 produces ridge waveguides of varying heights by etching an inverted T-shaped groove in the lower cladding layer 30.

The material of the lower cladding layer 30 of the DBR laser of embodiment 3 of the present application may be an n-InP material doped with n-type, and the material of the ridge waveguide may be an InGaAsP material doped with n-type, as in embodiment 2.

Since the light emitting unit 40 needs to be disposed near the interface of the p-type region and the n-type region, the light emitting unit 40 of the DBR laser of embodiment 3 of the present application is located between the upper surface of the first ridge waveguide 63 and the lower surface of the upper cladding layer 70. Since the ridge waveguide is an n-doped waveguide material, the upper cladding layer 70 located in the ridge waveguide is a p-doped cladding material, e.g., the upper cladding layer 70 may be a p-doped n-InP material, and the lower cladding layer 30 is an n-doped cladding material.

The grating 50 of the DBR laser of embodiment 3 of the present application may be disposed horizontally at the junction between the lower surface of the upper cladding layer 70 and the upper surface of the ridge waveguide, as in the light emitting unit 40, and in other embodiments, the grating 50 may be disposed at any position in the second ridge waveguide 64 and the third ridge waveguide 65, but it is necessary to ensure that the grating 50 can be in contact with the mode field of the fundamental mode, so as to provide optical feedback for the fundamental mode.

The arrangement position of the DBR laser grating 50 in embodiment 3 of the present application is the same as that of the DBR laser in embodiment 2, and will not be described here again.

The height of the ridge region 61 of the first ridge waveguide 63 of the DBR laser shown in fig. 2 and 3 is greater than the height of the ridge region 61 of the second ridge waveguide 64 and the third ridge waveguide 65, and in other embodiments, the height of the ridge region 61 of the first ridge waveguide 63 may be smaller than the height of the ridge region 61 of the second ridge waveguide 64 and the third ridge waveguide 65.

In addition, the width of the ridge regions 61 of the second ridge waveguide 64 and the third ridge waveguide 65 may be slightly larger than the width of the ridge regions 61 of the first ridge waveguide 63.

Fig. 4 is a schematic cross-sectional view and a schematic cross-sectional view of a semiconductor laser according to embodiment 4 of the present application, wherein (a) and (b) in fig. 4 are schematic cross-sectional views of ridge regions of different heights along a ridge waveguide, respectively, and (c) in fig. 4 is a schematic cross-sectional view of a ridge waveguide at the center along the laser cavity axis direction.

The semiconductor laser 4 shown in fig. 4 is a distributed feedback DFB laser (hereinafter referred to as DFB laser) including a lower cladding layer 30, a first ridge waveguide 63, a second ridge waveguide 64, a third ridge waveguide 65, a light emitting unit 40, and a grating 50.

The difference from embodiment 2 is that the light emitting unit 40 and the grating 50 of the DFB laser in embodiment 4 of the present application are disposed in the entire DFB laser, and the light emitting unit 40 and the grating 50 include, but are not limited to, the positions shown in fig. 4, as in embodiment 2. The light emitting unit 40 and the grating 50 may be disposed at any position of the slab region 62.

The materials of the first ridge waveguide 63, the second ridge waveguide 64, and the third ridge waveguide 65 are the same as those of the ridge waveguide in embodiment 2, and may be n-type doped InGaAsP material, the material of the lower cladding layer 30 may be P-type doped InP (P-InP) material, and the material of the light emitting unit 40 is also the same as that of the light emitting unit 40 in embodiment 2, which is not described herein.

Fig. 5 is a schematic cross-sectional view and a cross-sectional view of the semiconductor laser of embodiment 5 of the present application, and the descriptions of (a), (b), and (c) in fig. 5 are the same as those of (a), (b), and (c) in fig. 4.

The semiconductor laser 5 shown in fig. 5 is different from the DFB laser of embodiment 4 only in that in the DFB laser shown in fig. 5, the height of the ridge region 61 of the first ridge waveguide 63 is lower than the heights of the ridge regions 61 of the second ridge waveguide 64 and the third ridge waveguide 65, and the other is the same as embodiment 4, and the details are not repeated here.

Fig. 6 is a schematic cross-sectional view and a cross-sectional view of the semiconductor laser in embodiment 6 of the present application, and the descriptions of (a), (b), and (c) in fig. 6 are the same as those of (a), (b), and (c) in fig. 4.

The semiconductor laser 6 shown in fig. 6 is an F-P cavity laser which differs from the DFB laser in embodiment 4 only in that the grating 50 is not provided in the F-P cavity laser.

Fig. 7 is a schematic cross-sectional view of a semiconductor laser in embodiment 7 of the present application.

The semiconductor laser 7 shown in fig. 7 is an F-P cavity laser, and the difference between the F-P cavity laser shown in fig. 6 and the F-P cavity laser is that the height of the ridge region 61 of the first ridge waveguide 63 of the F-P cavity laser shown in fig. 7 is lower than the heights of the ridge regions 61 of the second ridge waveguide 64 and the third ridge waveguide 65, and the other is the same as that of embodiment 6, and will not be described here.

Fig. 8 is a schematic view showing a partial perspective view of a semiconductor laser in embodiment 8 of the present application.

As shown in fig. 8, the width of the ridge region 61 of the ridge waveguide 60 in the semiconductor laser 8 shown in fig. 8 is smaller than or equal to the thickness of the slab region 62 to confine the fundamental mode of laser light within the n-doped slab region 62, thereby making the mode field distribution of the fundamental mode significantly distinguishable from that of the higher order modes. While ridge region 61 and slab region 62 are waveguides having the same refractive index, at least a portion of ridge region 61 is configured as a P-doped waveguide (i.e., a filled portion in the figure). The slab region 62 of the ridge waveguide 60 is provided as an n-type doped waveguide, and the ridge region 61 of the ridge waveguide 60 is provided as a p-type doped waveguide, so that a high-order mode can be lost in a p-type doped region where a high-order mode has a large number of mode field distributions and a fundamental mode has little mode field distribution, to increase a loss difference between the high-order mode and the fundamental mode, thereby achieving a single mode lasing based on the fundamental mode against a grating coupling coefficient where the high-order mode is larger than the fundamental mode.

Fig. 9 is a schematic cross-sectional view of a semiconductor laser in embodiment 9 of the present application.

Fig. 9 (a) is a schematic cross-sectional view taken along line D-D in fig. 8, and fig. 9 (b) is a schematic cross-sectional view taken along line C-C in fig. 8.

As shown in fig. 9, the semiconductor laser 9 in embodiment 9 of the present application is a DFB laser including, in order from bottom to top, a lower cladding layer 30, a ridge waveguide 60, a light emitting unit 40, a grating 50, and an upper cladding layer 70.

In embodiment 9 of the present application, the lower cladding layer 30 of the DFB laser is an n-type doped low refractive material, for example, the lower cladding layer 30 may be an n-type doped InP (n-InP) material. A ridge waveguide 60 is located above the lower cladding layer 30, the ridge waveguide 60 comprising a slab region 62 and a ridge region 61. The slab region 62 of the ridge waveguide 60 is of an n-doped low absorption material, for example the material of the slab region 62 of the ridge waveguide 60 may be an n-doped InGaAsP material. The light emitting unit 40 and the grating 50 are stacked in a region between the bottom of the ridge region 61 of the ridge waveguide 60 and the lower cladding layer 30. The light emitting unit 40 may be any one of a pn junction, a single quantum well, a Multiple Quantum Well (MQW), a quantum wire, and a quantum dot, as in the light emitting unit 40 in embodiment 2. The upper cladding layer 70 is located on the upper surface of the ridge region 61 of the ridge waveguide 60, and the upper cladding layer 70 may be a p-type doped low refractive material, for example, the material of the upper cladding layer 70 may be a p-type doped InP (p-InP) material.

As shown in fig. 9 (a), the width of the ridge region 61 of the ridge waveguide 60 is less than or equal to the thickness of the slab region 62, and the bottom of the ridge region 61 of the ridge waveguide 60 may be an n-doped InGaAsP material of the slab region 62, and the remainder of the ridge region 61 of the ridge waveguide 60 may be a p-doped waveguide material (upper portion of the grating 50 in the figure) of the same refractive index as the slab region 62, which may be InGaAsP or InGaAs.

As shown in fig. 9 (b), if a quarter-wavelength phase shift is provided near the center of the grating 50 to achieve single longitudinal mode operation, anti-reflection films (i.e., AR coating films) are typically coated at both ends of the DFB laser. To further increase the single-ended power output and increase the efficiency of the DFB laser, one end of the DFB laser is plated with a high-reflection coating (HR) and the other end is plated with an anti-reflection coating.

Fig. 9 (c) shows a mode field distribution diagram of the fundamental mode and the higher-order mode in the ridge waveguide 60.

In the figure, the P region corresponds to the ridge region 61 of the ridge waveguide 60, and the light emitting unit 40 is in the middle, for example, the light emitting unit 40 may be an MQW (multiple quantum well), and the n region corresponds to the slab region 62 of the ridge waveguide 60.

As shown in (f) of fig. 9 (c), the mode field of the fundamental mode is almost entirely distributed in the n region (n-type doped material) where the absorption loss is low. As shown in (h) of fig. 9 (c), a large portion of the mode field of the higher order modes is distributed in the high loss p-region (p-doped material) so that all higher order modes will experience greater loss than the fundamental mode. And as the thickness of the p-type doped material (e.g., p-InGaAsP) film layer of the ridge region 61 increases, the higher-order mode has a larger mode field proportion distributed in the p region, so that the loss of the higher-order mode is increased, and therefore, the possibility of single-mode lasing of the fundamental mode can be further ensured, so that the fundamental mode is prior to the high-order mode lasing.

In fig. 9 (a) and (b), the refractive index of the material of the grating 50 is larger than that of the ridge waveguide 60 (for example, the material of the ridge waveguide 60 is p-InGaAsP), so that the grating 50 and the light emitting unit 40 may be stacked. If the refractive index of the grating 50 is smaller than that of the ridge waveguide 60, for example, the material of the grating 50 is InP, so that a portion of the higher-order mode may be trapped between the grating 50 and the lower surface of the ridge waveguide 60 (for example, the interface between the slab region 62 and the lower cladding layer 30) due to the presence of the grating 50 (for example, an n-InGaAsP waveguide), so that the p-doped high-absorption material of the ridge region 61 of the ridge waveguide 60 cannot absorb the higher-order mode, and therefore, as shown in (d) of fig. 9, the grating 50 may be disposed on the upper surface of the lower cladding layer 30, thereby eliminating the possibility that the higher-order mode is trapped in the slab region 62 (n-doped region) due to the grating 50, so that the mode field of the higher-order mode is mostly distributed in the p-doped high-absorption material, and thus guaranteeing the possibility of fundamental mode lasing.

Specifically, grating 50 may be etched on the upper surface of lower cladding layer 30 and then deposited on each of the layers. Alternatively, grating 50 may be etched from another proportion of material (e.g., inGaAsP) having a composition between the cladding (e.g., inP) and the ridge waveguide 60 (e.g., inGaAsP), but lattice matched or nearly lattice matched to both, to facilitate post-holographic interference fabrication of a wide grating 50, and wet etching to obtain a width-defined grating 50, to maximize the loss of the high order modes in the p-doped superabsorbent material of the ridge region 61 of the ridge waveguide 60.

When a plurality of ridge waveguides are included in the semiconductor laser shown in fig. 8, a partial perspective view of the structure shown in fig. 10, i.e., the semiconductor laser in embodiment 10 of the present application, will be obtained.

As shown in fig. 10, the plurality of ridge waveguides 60 in the semiconductor laser 10 in the embodiment 10 of the present application includes a first ridge waveguide 63, a second ridge waveguide 64, and a third ridge waveguide 65, and the first ridge waveguide 63 is located between the second ridge waveguide 64 and the third ridge waveguide 65; the height of the ridge regions 61 of the second ridge waveguide 64, the third ridge waveguide 65 is not equal to the height of the ridge regions 61 of the first ridge waveguide 63, and at least one of the first ridge waveguide 63, the second ridge waveguide 64, and the third ridge waveguide 65 is the ridge waveguide in embodiment 8, that is, at least a part of at least one ridge waveguide ridge region 61 in fig. 10 is a P-type doped waveguide (color filled part in the figure).

Fig. 11 is a schematic cross-sectional view of a semiconductor laser in embodiment 11 of the present application.

Fig. 11 (a), (B), and (C) are schematic cross-sectional views along the line a-a, the line B-B, and the line C-C in fig. 10, respectively.

The semiconductor laser 11 shown in fig. 11 is a DFB laser including a first ridge waveguide 63, a second ridge waveguide 64, and a third ridge waveguide 65. The first ridge waveguide 63 is located between the second ridge waveguide 64 and the third ridge waveguide 65, and the height of the ridge region 61 of the first ridge waveguide 63 is greater than the height of the ridge regions 61 of the second ridge waveguide 64 and the third ridge waveguide 65 on both sides, so that the higher order modes are lost in the second ridge waveguide 64 and the third ridge waveguide 65 during transmission to the second ridge waveguide 64 and the third ridge waveguide 65 (particularly obvious loss points are near the junction of the first ridge waveguide 63 and the second ridge waveguide 64 or the third ridge waveguide 65). Because of the height difference, the high-order mode not only consumes in the first ridge waveguide 63 (the p-type doped high-absorption ridge region 61) but also in the second ridge waveguide 64 and the third ridge waveguide 65, so that the loss of the high-order mode is obviously larger than that of the fundamental mode, and the fundamental mode lasing is realized.

In addition, the p-doped superabsorbent material of the ridge regions 61 of the second and third ridge waveguides 64, 65 may remain partially or may be removed entirely (e.g. as shown in fig. 11), i.e. the material of the ridge regions 61 of the second and third ridge waveguides 64, 65 may comprise p-doped superabsorbent material.

Thus, when the height of the ridge region 61 of the first ridge waveguide 63 is greater than the height of the ridge regions 61 of the second and third ridge waveguides 64, 65, the ridge region 61 of the first ridge waveguide 63 may be a P-type doped waveguide, and the ridge regions 61 of the second and third ridge waveguides 64, 65 may be P-type doped waveguides and/or n-type doped waveguides; or the height of the ridge region 61 of the first ridge waveguide 63 is smaller than the height of the ridge region 61 of the second ridge waveguide 64, the third ridge waveguide 65, the ridge region 61 of the second ridge waveguide 64, the third ridge waveguide 65 is a P-type doped waveguide, the ridge region 61 of the first ridge waveguide 63 is a P-type doped waveguide and/or an n-type doped waveguide.

Fig. 12 is a schematic cross-sectional view of a semiconductor laser in embodiment 12 of the present application.

The semiconductor laser 12 shown in fig. 12 is a DBR laser, and differs from embodiment 11 only in that the grating 50 is located in the second ridge waveguide 64 and the third ridge waveguide 65, all of which are identical. And in embodiment 12, the height of the ridge region 61 of the first ridge waveguide 63 in the DBR laser is greater than the height of the ridge regions 61 of the second ridge waveguide 64 and the third ridge waveguide 65.

Fig. 13 is a schematic cross-sectional view of a semiconductor laser in embodiment 13 of the present application.

The semiconductor laser 13 shown in fig. 13 is a DFB laser, and compared with embodiment 11, the height of the ridge regions 61 of the first ridge waveguide 63 of the DFB laser in embodiment 13 is smaller than the heights of the ridge regions 61 of the second ridge waveguide 64 and the third ridge waveguide 65 on both sides, and the other is the same, and will not be described here again.

Fig. 14 is a schematic view showing a partial perspective view of a semiconductor laser in embodiment 14 of the present application.

The semiconductor laser provided by the embodiment of the application comprises one or more ridge waveguides 60, the ridge waveguides 60 comprise ridge regions 61 and flat regions 62, the width of the ridge regions 61 is smaller than or equal to the thickness of the flat regions 62, the ridge regions 61 comprise P-type doped waveguides (filled parts with different colors in the figure) with gradually increased refractive indexes along the direction from the upper surface of the flat regions 62 to the top of the ridge regions 61, and the flat regions 62 are n-type doped waveguides.

The semiconductor laser 14 shown in fig. 14 is a semiconductor laser including a ridge waveguide 60, where the ridge region 61 of the ridge waveguide 60 includes a P-type doped waveguide with increasing refractive index, such as a P-type doped InGaAsP material or InGaAs material, which is graded from the P-type doped InGaAsP material to a lattice-matched P-type doped InGaAs material along the upper surface of the slab region 62 toward the top of the ridge region 61 to strongly absorb the higher order modes for higher order mode loss. Slab region 62 of ridge waveguide 60 is an n-doped waveguide, such as an n-doped InGaAsP material or InGaAs material, and the refractive index of slab region 62 of ridge waveguide 60 is unchanged for confining the fundamental mode to slab region 62. The ridge region 61 of the ridge waveguide 60 is a P-type doped waveguide with an increasing refractive index, because as the doping concentration of the ridge region 61 of the ridge waveguide 60 increases, the P-type doped waveguide of the ridge region 61 has a higher and higher capability of absorbing higher-order modes along the upper surface of the slab region 62 to the top of the ridge region 61, so that higher-order mode loss can be in the ridge region 61 of the ridge waveguide 60, higher-order mode loss can be increased, and fundamental mode lasing can be realized. Meanwhile, because the top of the ridge region 61 of the ridge waveguide 60 has strong absorption and the fundamental mode does not need to be mode-bound at the top of the ridge region 61, the top of the ridge region 61 of the ridge waveguide 60 in embodiment 14 of the present application may not be provided with a cladding layer, so that the thickness of the highly-absorbing P-type doped waveguide at the top of the ridge region 61 may be appropriately increased, and the fundamental mode lasing is further ensured.

The bottom of ridge region 61 may be an n-doped waveguide material, such as an n-doped InGaAsP material or an InGaAs material.

Fig. 15 is a schematic cross-sectional view of a semiconductor laser in embodiment 15 of the present application.

The semiconductor laser 15 shown in fig. 15 is a DFB laser, and fig. 15 (a) is a schematic cross-sectional view along the height direction of the DFB laser ridge waveguide 60.

As shown in fig. 15 (a), in embodiment 15 of the present application, the height direction of the ridge waveguide 60, i.e., the direction from the upper surface of the slab region 62 of the ridge waveguide 60 to the top of the ridge region 61. The DFB laser includes a lower cladding layer 30, a ridge waveguide 60, a light emitting unit 40, and a grating 50. The lower cladding layer 30 in fig. 15 (a) may be an n-type doped InP cladding layer. Ridge waveguide 60 includes a ridge region 61 and a slab region 62, slab region 62 may be an n-doped InGaAsP waveguide, and the bottom of ridge waveguide 60 ridge region 61 may be an n-doped InGaAsP waveguide of equal refractive index to slab region 62. Ridge waveguide 60 ridge region 61 is a p-doped waveguide of increasing refractive index along the upper surface of slab region 62 to the top of ridge region 61. For example, the ridge region 61 may be graded from p-doped InGaAsP to p-doped InGaAs, so that as the forbidden band wavelength of the material becomes longer with increasing refractive index, the corresponding absorption capacity to the working wavelength of the laser becomes stronger, so that the higher-order mode with obvious mode field proportion distributed in the p-doped waveguide region is increased, and the loss difference between the higher-order mode and the fundamental mode is increased, thereby realizing the fundamental mode lasing.

Because the refractive index of the p-doped p-InGaAsP waveguide material of the ridge region 61 is equal to or slightly greater than the refractive index of the n-doped p-InGaAsP of the slab region 62, and there may be a graded (grading) of the doping concentration and composition (equivalent to the forbidden band wavelength under lattice matching constraints) in the ridge region 61 of the ridge waveguide 60 to reduce loss to the fundamental mode, i.e., the ridge region 61 (e.g., p-InGaAsP) near the light emitting cell 40 and the grating 50 is doped at a lower concentration and both the refractive index and the forbidden band wavelength are close to those of the n-InGaAsP waveguide material of the slab region 62. In addition, there may be a gradual change in doping concentration or composition between, for example, p-InGaAsP to p-InGaAs in the p-doped waveguide region of the ridge region 61 until heavily doped p-InGaAs is reached on top of the ridge region 61. The thickness of heavily doped p-InGaAs in embodiments of the present application includes, but is not limited to, 0.1 microns to 5 microns.

Fig. 15 (b) is a schematic cross-sectional view along the cavity axis of the DFB laser. In other embodiments, the end faces of the two ends of the DFB laser in fig. 15 may also be provided with a coating. For example, to provide a quarter-wavelength phase shift near the center of grating 50, the ends of the DFB laser may be coated, such as with an anti-reflection coating (AR coating), to achieve single longitudinal mode operation. Further, in order to increase the single-ended power output and the efficiency of the DFB laser, a high reflection film (HR) may be formed on one end of the DFB laser, and an anti-reflection film (AR film) may be formed on the other end of the DFB laser, in which case a quarter-wavelength phase shift is not typically provided.

Fig. 15 (c) is a schematic diagram showing the mode field distribution of the higher-order mode and the fundamental mode.

As shown in fig. 15 (c), the region where the dotted line is located in the drawing is the light emitting unit 40, and for example, the light emitting unit 40 may be MQW (multiple quantum well). The P-region refers to a P-doped waveguide with increasing refractive index of the ridge region 61 and the n-region is an n-doped waveguide of the slab region 62. The mode field distribution of the higher order mode and the fundamental mode shown in fig. 15 (c) is similar to that of fig. 9, except that the P-region in embodiment 15 refers to a P-doped waveguide with an increasing refractive index of the ridge region 61, and the P-region in fig. 9 in embodiment 9 refers to a P-doped waveguide with the same refractive index of the ridge region 61.

In addition, the p-doped waveguide region of the ridge region 61 of the ridge waveguide 60 of the present application may be entirely InGaAsP, because as the refractive index of the p-doped material in the ridge region 61 increases, the higher order modes may be entirely absorbed by the p-doped InGaAsP already when the doping concentration and composition do not reach p-InGaAs that of the detector material, because on top of the grating 50, if no cladding layer with a lower refractive index is provided on top of the ridge region 61 of the ridge waveguide 60, then no total reflection is formed between the slab region 62 of the ridge waveguide 60 and the ridge region 61, so that the higher order modes are not reflected to the slab region 62 of the ridge waveguide 60, and therefore the higher order modes in the slab region 62 of the ridge waveguide 60 are also substantially absent, thereby ensuring that the fundamental mode lases.

In addition, since the top of the ridge region 61 of the ridge waveguide 60 is a heavily doped high-absorption p-type doped waveguide, such as p-type doped InGaAs, the high-order mode can be almost entirely lost to the ridge region 61 of the ridge waveguide 60, so that the top of the ridge region 61 of the ridge waveguide 60 may not be provided with a cladding layer, and thus the thickness of the heavily doped high-absorption p-type doped waveguide can be appropriately increased, ensuring the possibility of fundamental mode lasing.

In some embodiments, if the refractive index of the grating 50 is smaller than the refractive index of the ridge waveguide 60 (e.g., inGaAsP), for example, the material of the grating 50 is InP, a portion of the higher order modes may be located between the grating 50 and the n-doped waveguide region at the bottom of the slab region 62, thereby causing the p-doped waveguide material of the ridge region 61 to fail to absorb the higher order modes and reducing the loss of the higher order modes. Thus, as shown in fig. 15 (d), where the refractive index of the grating 50 is less than the refractive index of the ridge waveguide 60 (e.g., inGaAsP), the grating 50 may be disposed at the bottom of the slab region 62 to reduce the coupling coefficient of the higher order modes to the grating 50, causing the higher order modes to be lost in the p-doped ridge region 61 of the ridge waveguide 60.

For example, grating 50 may be etched onto the upper surface of a cladding layer (e.g., inP) and then deposited thereon. Alternatively, grating 50 may be etched with another proportion of material (e.g., inGaAsP) having a composition between the cladding layer (e.g., inP) and the slab region 62 waveguide (e.g., n-InGaAsP), but lattice matched or nearly lattice matched to both, so that after holographic interferometry to produce a wide grating 50, a grating 50 of a particular width may be readily obtained by photolithography and wet etching, and the width of grating 50 may or may not be equal to the width of ridge region 61 of ridge waveguide 60.

Fig. 16 is a schematic cross-sectional view of a semiconductor laser in embodiment 16 of the present application.

The semiconductor laser 16 shown in fig. 16 is a DBR laser, and (a), (b), and (c) in fig. 16 are respectively a schematic cross-sectional view of the DBR laser at the light emitting unit 40, a schematic cross-sectional view of the ridge waveguide at the center along the laser cavity axis direction, and a schematic cross-sectional view of the DBR laser at the grating 50.

Embodiment 16 of the present application is the same as embodiment 15 of the present application, except that embodiment 16 is a DBR laser, and therefore the gratings 50 are located on both sides of the laser cavity (the cross section is shown in fig. 16 (c)), and the other embodiments are the same as embodiment 15, and will not be described again here.

Fig. 17 is a schematic cross-sectional view of a semiconductor laser in embodiment 17 of the present application.

The semiconductor laser 17 shown in fig. 17 is a DFB laser in which the ridge waveguide includes a first ridge waveguide 63, a second ridge waveguide 64, and a third ridge waveguide 65, the first ridge waveguide 63 is located between the second ridge waveguide 64 and the third ridge waveguide 65, and the ridge region 61 of the first ridge waveguide 63 and the ridge regions 61 of the second ridge waveguide 64, third ridge waveguide 65 have a height difference, that is, the height of the ridge region 61 of the first ridge waveguide 63 may be greater than or less than the height of the ridge regions 61 of the second ridge waveguide 64, third ridge waveguide 65, and at least one of the first ridge waveguide 63, the second ridge waveguide 64, and the third ridge waveguide 65 is the ridge waveguide in embodiment 14, that is, in the direction from the upper surface of the slab region 62 of the ridge waveguide to the top of the ridge region 61, the ridge region 61 includes P-type doped waveguides having an increasing refractive index, and the slab region 62 is n-type doped waveguide.

As shown in fig. 17, the height of the ridge region 61 of the first ridge waveguide 63 in the DFB laser is larger than the heights of the ridge regions 61 of the second and third ridge waveguides 64 and 65 on both sides. The schematic cross-sectional views of fig. 17 (a), (b), and (c) may be approximated to those of fig. 2 (a), (b), and (c), respectively, with the difference that the ridge waveguide ridge regions 61 of fig. 17 (a), (b), and (c) are p-doped waveguide materials (e.g., inGaAsP and/or InGaAs) with increasing refractive index (graded composition ratio under lattice matching, i.e., increasing forbidden band wavelength), so as to further increase the loss of the higher order modes.

Fig. 18 is a schematic cross-sectional view of a semiconductor laser in embodiment 18 of the present application.

The semiconductor laser 18 shown in fig. 18 is a DBR laser, and the DBR laser of this embodiment 18 is similar to the DFB laser of embodiment 17, except that the gratings 50 of embodiment 18 are located on both sides of the laser cavity, and are otherwise identical, and are not described in detail herein.

Fig. 19 is a schematic cross-sectional view of a semiconductor laser in embodiment 19 of the present application.

The semiconductor laser 19 shown in fig. 19 is a DFB laser, and the DFB laser in embodiment 19 is different from the DFB laser in embodiment 17 only in that the height of the ridge region 61 of the first ridge waveguide 63 is smaller than that of the second ridge waveguide 64 and the third ridge waveguide 65 on both sides, and the other is the same, and will not be described in detail here.

As shown in fig. 18 and 19, the p-type doped waveguide material (e.g., inGaAsP) of the ridge region 61 of the second ridge waveguide 64 and the third ridge waveguide 65 may be partially removed (as shown in fig. 18 and 19) or the p-type doped waveguide material (e.g., inGaAsP) may be completely removed, with the difference that the loss of the fundamental mode in the second ridge waveguide 64 and the third ridge waveguide 65 is slightly different.

In addition, as shown in fig. 19, when the height of the ridge region 61 of the first ridge waveguide 63 is lower than the heights of the ridge regions 61 of the second ridge waveguide 64 and the third ridge waveguide 65 on both sides, a part of the p-type doped waveguide material (for example, inGaAsP) of the ridge region 61 of the first ridge waveguide 63 may be removed, or the p-type doped waveguide material (for example, inGaAsP) of the ridge region 61 of the first ridge waveguide 63 may be completely removed, with the difference that the loss of the fundamental mode in the first ridge waveguide 63 is slightly different.

Fig. 20 is a schematic cross-sectional view of a semiconductor laser in embodiment 20 of the present application.

The semiconductor laser 20 shown in fig. 20 also shows an electrical isolation layer 90 (e.g., siO ₂ An electrical isolation layer), and a metal electrode 80 located above the electrical isolation layer 90 and on the lower surface of the lower cladding layer 30. It can also be seen from fig. 20 that the ridge region 61 is a P-doped waveguide with increasing refractive index along the upper surface of the slab region 62 of the ridge waveguide to the top of the ridge region 61. The top of the ridge region 61 of the ridge waveguide is not provided with an electrically isolating layer 90, since here it is necessary to allow a current to flow in for pumping. Since the top of the ridge region 61 is a heavily doped P-type waveguide material, such as P-type doped InGaAs, instead of InP, which is a low refractive index material at the top of the ridge waveguide in general, for all modes, not only is there No full emission mode confinement property, but a highly absorbing material will severely reduce the efficiency of reflection even due to the presence of some reflection at the interface (e.g., inGaAs contact interface with metal electrode 80), especially for the target mode of the laser (fundamental mode of the ridge waveguide), since its mode field is hardly in contact with the top of the ridge region 61 (ridge region 61 is high enough) and is not confined by reflection at any interface at the top of the ridge region 61 at all, such lasers are effectively free of the ridge region 61 top dielectric interface, and may be referred to as semiconductor lasers based on a top-free reflective surface ridge waveguide (e.g., no-Ceiling Ridge Laser, NCRL for short), corresponding NCR-DBR, NCR-DFB or NCR-FP. In all of the foregoing embodiments, the metal electrode 80, the electrical isolation layer 90 in embodiment 20 are also included.

The embodiment of the application also provides an optical chip, which comprises one or more semiconductor lasers in the embodiment.

Further, waveguide materials in embodiments of the present application include, but are not limited to, inGaAsP or InGaAs, and the lower cladding layer 30 may be InP, gaAs, silicon, glass, etc.

Further, the semiconductor laser in the embodiment of the application can avoid the high-order mode lasing commonly existing in the large-size waveguide due to the large waveguide size and low absorption loss, so that the high-power, large-mode-field single-mode narrow-linewidth laser based on the fundamental mode can be expected to be realized. In addition, because the mode field size is large and the divergence angle is small, the method is very favorable for coupling high-power laser into low-loss waveguide materials such as common single-mode fiber, lithium niobate, silicon nitride and the like, which are difficult to emit light, in an end face coupling scheme, reduces the complexity of an optical transmitter in optical communication (such as omitting the use of a lens), and simultaneously has a longer signal transmission distance due to the very high optical power, thereby having wide application prospects, such as a laser radar, an optical computing chip and an optical quantum computing chip.

In summary, the width of the ridge region 61 of the ridge waveguide is smaller than or equal to the thickness of the slab region 62, so that the mode field distribution of the fundamental mode is significantly different from that of the high-order mode, and the high-order mode loss is increased by combining the height difference of the ridge region 61, the p-type doped absorption material and the p-type heavily doped high-absorption material between the ridge waveguides on the basis of the structure. Whereas slab region 62 of the ridge waveguide is an n-doped low absorption material, so that the fundamental mode is bound in slab region 62, and finally, the high-order mode loss is increased, and the fundamental mode loss is reduced, thereby realizing the fundamental mode lasing. In addition, based on the same technical concept, the technical scheme obtained by combining or slightly adjusting the same size and unequal size of the embodiments by a person skilled in the art is also within the scope of the protection of the present application.

The foregoing description and drawings set forth exemplary embodiments of the specific structure of the embodiments, and the foregoing utility model provides presently preferred embodiments, without being limited to the precise arrangements and instrumentalities shown. Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above description. Therefore, the appended claims should be construed to cover all such variations and modifications as fall within the true spirit and scope of the utility model. Any and all equivalents and alternatives falling within the scope of the claims are intended to be embraced therein.

Claims (10)

1. A semiconductor laser, comprising:

a plurality of ridge waveguides including a ridge region and a slab region;

the plurality of ridge waveguides comprise a first ridge waveguide, a second ridge waveguide and a third ridge waveguide, and the first ridge waveguide is positioned between the second ridge waveguide and the third ridge waveguide;

the height of the ridge regions of the second ridge waveguide and the third ridge waveguide is not equal to the height of the ridge region of the first ridge waveguide, and the width of the ridge region of at least one of the plurality of ridge waveguides is smaller than or equal to the thickness of the slab region.

2. A semiconductor laser as claimed in claim 1, wherein:

the semiconductor laser is any one of a distributed feedback DFB laser, a distributed bragg reflector DBR laser, and an F-P cavity laser.

3. A semiconductor laser as claimed in claim 1, wherein:

the light emitting device further comprises a light emitting unit and a lower cladding layer, wherein the ridge waveguides are arranged on the lower cladding layer, and the light emitting unit is arranged between the bottom of the ridge waveguide ridge region and the lower cladding layer.

4. A semiconductor laser as claimed in claim 3, wherein:

the light emitting unit is any one of a pn junction, a single quantum well, a multiple quantum well, a quantum wire, and a quantum dot.

5. A semiconductor laser as claimed in claim 1, wherein:

it also includes a grating for providing optical feedback.

6. The semiconductor laser according to claim 5, wherein:

the grating is disposed in at least one of both ends of the semiconductor laser.

7. A semiconductor laser as claimed in claim 1, wherein:

the plurality of ridge waveguides are n-doped waveguides.

8. A semiconductor laser as claimed in claim 1, wherein:

The plurality of ridge waveguides includes n-doped InGaAsP waveguides.

9. A semiconductor laser as claimed in claim 3, wherein:

the lower cladding is an n-type doped InP cladding or a p-type doped InP cladding.

10. An optical chip comprising the semiconductor laser according to any one of claims 1 to 9.