CN114784616A - Conical semiconductor laser integrated with super lens - Google Patents
Conical semiconductor laser integrated with super lens Download PDFInfo
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- CN114784616A CN114784616A CN202210237548.2A CN202210237548A CN114784616A CN 114784616 A CN114784616 A CN 114784616A CN 202210237548 A CN202210237548 A CN 202210237548A CN 114784616 A CN114784616 A CN 114784616A
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- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/02—Structural details or components not essential to laser action
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- H01S5/0225—Out-coupling of light
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
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Abstract
The invention discloses a tapered semiconductor laser integrated with a superlens, belonging to the technical field of semiconductor lasers and comprising a tapered structure, wherein the tapered structure comprises a narrow ridge waveguide part and a tapered gain amplification part connected with the narrow ridge waveguide part; a superlens disposed at an end of the tapered gain amplifying section remote from the narrow ridge waveguide section; the super lens comprises a plurality of longitudinal low-refractive-index units and a plurality of remaining longitudinal waveguides, wherein the longitudinal low-refractive-index units and the remaining longitudinal waveguides are alternately arranged along the width direction of the tapered gain amplification part; the invention can greatly reduce the divergence angle in the horizontal direction, improve the beam quality of the semiconductor laser, improve the laser output power and realize stable lateral mode output.
Description
Technical Field
The invention relates to a tapered semiconductor laser integrated with a superlens, and belongs to the technical field of semiconductor lasers.
Background
The semiconductor laser has the advantages of light weight, small volume, low cost, convenient integration and the like, and is widely applied to various fields of material processing, communication, military, medical treatment and the like. However, in these applications, including as pump sources for solid state and fiber lasers, laser scalpels, laser weapons, metal cutting welds, laser displays, etc., there are high demands on the brightness of the lasers. The realization of high brightness requires both high output power and high beam quality. The traditional wide-contact semiconductor laser can obtain high single-tube output power and power conversion efficiency, but because the output aperture ratio is wide, lateral multi-mode is easily generated, and the quality of light beams is poor. Ridge waveguide lasers, on the other hand, are capable of achieving a lateral near diffraction-limited output, but are limited by a small output aperture and gain volume, and are relatively low power.
In some laser structure designs with both higher beam quality and high output power, the tapered laser has the advantages of simple structure and low process difficulty. Tapered lasers including a ridge waveguide section with fundamental mode selection and a tapered gain section for mode amplification have been reported for achieving high power and higher beam quality laser output at large taper angles of 4 to 6 degrees. However, the large gain cone angle on the one hand causes the light to become nearly freely propagating diverging in the tapered gain amplification section, greatly increasing the lateral far field divergence angle, 1/e2The full width of the laser is usually over 10 degrees under energy, and the laser can be applied only by combining complex beam shaping, so that the expansion of the application field of the laser is hindered, and on the other hand, the lateral aperture of the output end face is greatly widened, so that lateral multimode lasing is more easily caused, and the quality of a light beam is further reduced.
Therefore, there is a need for a tapered semiconductor laser integrated with a superlens, which has good overall performance: the laser can greatly reduce the divergence angle in the horizontal direction, improve the beam quality of the semiconductor laser, improve the laser output power and realize stable lateral mode output.
In view of the foregoing, it is apparent that the prior art has inconvenience and disadvantages in practical use, and thus, needs to be improved.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a tapered semiconductor laser integrated with a superlens, which can greatly reduce the divergence angle in the horizontal direction, improve the beam quality of the semiconductor laser, improve the laser output power and realize stable lateral mode output.
In order to solve the technical problems, the invention adopts the following technical scheme: a tapered semiconductor laser incorporating a superlens, comprising a tapered structure including a narrow ridge waveguide portion, a tapered gain amplification portion connected to the narrow ridge waveguide portion; the super lens is arranged at one end of the conical gain amplifying part far away from the narrow ridge waveguide part;
the super lens comprises a plurality of longitudinal low-refractive-index units and a plurality of residual longitudinal waveguides, wherein the longitudinal low-refractive-index units and the residual longitudinal waveguides are alternately arranged in the width direction of the tapered gain amplification part.
Further, all the longitudinal low-refractive-index units in the superlens have the same refractive index, and the refractive index difference between the longitudinal low-refractive-index units and the remaining longitudinal waveguides is larger than 0.5.
The epitaxial structure comprises an N-type substrate, an N-type limiting layer, an N-type waveguide layer, an active region, a P-type waveguide layer, a P-type limiting layer and a P-type contact layer which are sequentially arranged from bottom to top; the superlens spans the active region in an epitaxial direction.
Further, the longitudinal low refractive index unit is formed of one longitudinal refractive index partition;
or the longitudinal low-refractive-index unit consists of a plurality of longitudinal refractive-index partitions which are arranged in rows and at intervals; and the number of longitudinal refractive index partitions in the longitudinal low refractive index unit at different positions of the tapered gain amplifying section is the same or different.
Further, the quasi-period width of the superlens is in the sub-wavelength order.
Further, the longitudinal low-refractive-index unit includes a longitudinal low-refractive-index groove; the longitudinal low-refractive-index groove is formed by etching downwards along the upper surface of the conical gain amplifying part;
the longitudinal low-refractive-index groove independently forms a longitudinal low-refractive-index unit, or a material with a refractive index lower than that of the rest longitudinal waveguide is filled in the longitudinal low-refractive-index groove to form the longitudinal low-refractive-index unit.
Further, the depth of the longitudinal low-refractive-index groove exceeds the depth of the active region; the longitudinal low index grooves at different lateral positions of the tapered gain amplification section have different lengths and widths.
Furthermore, the conical structure is arranged on one surface of the epitaxial layer structure, which is provided with the P-type contact layer; the end surface of the tapered gain amplification part, which is far away from the narrow ridge waveguide part, is the front cavity surface of the laser; the end surface of the narrow ridge waveguide part, which is far away from the conical gain amplification part, is the back cavity surface of the conical semiconductor laser; the width of the conical gain amplification part is gradually increased along the light emitting direction.
Further, the width of the narrow ridge waveguide section is not greater than the cutoff width of the lateral high order mode generated at the abrupt transition of the tapered gain amplifying section;
the narrow ridge waveguide portion forms a refractive index guiding structure;
the contact layers on both sides of the tapered gain amplifying section are etched away to form a gain guide, or the tapered gain amplifying section is etched to the same depth as the narrow ridge waveguide section to form a refractive index guide structure.
Furthermore, an antireflection film is plated outside the front cavity, and the reflectivity is less than 1%;
and plating a high-reflectivity film outside the rear cavity surface, and etching the two sides of the narrow ridge waveguide part to destroy the groove, or etching the DBR grating in the rear cavity surface.
After the technical scheme is adopted, compared with the prior art, the invention has the following advantages:
(1) the super lens provided by the invention can be used for finely and locally adjusting the width and the length of the longitudinal low-refractive-index unit according to different lateral positions. The different length and width distributions enable the phase changed after the light is transmitted to be changed along with the change of the lateral position, so that the divergent light of the conical gain amplifying part is converted into parallel light or convergent light, and the lateral far-field divergent angle is greatly reduced. In the ideal case of fundamental-side mode lasing alone, a tapered waveguide of millimeter magnitude can theoretically achieve a horizontal divergence angle of less than 0.9 °, an order of magnitude lower than that of a conventional tapered laser.
(2) The different length and width distributions of the longitudinal low-refractive-index units enable the light reflectivity and the light loss to change along with the change of the lateral position, the main distribution position of the lateral fundamental mode light field has relatively high reflectivity and relatively low loss, and the main distribution position of the lateral high-order mode light field has relatively low reflectivity and relatively high loss, so that the high-order mode of the tapered cavity is inhibited, and the laser output with high beam quality is obtained.
(3) When light diffracts gain in the conical gain amplifying part, a high-order diffraction peak exists, the phase of the high-order diffraction peak is not continuous with that of a 0-order diffraction peak, abrupt change of the phase exists, the phenomenon of interference cancellation exists in a far field, and the optical power of the far field is reduced. In order to overcome the above problems, it is common to reduce the cone angle of the tapered gain amplification section to suppress the diffraction peak of the higher order, but this greatly reduces the gain area of the tapered gain amplification section, limiting the increase of the optical power. In the invention, the phase of the transmitted light of the super lens at the position of the diffraction peak of the high order is adjusted by designing the super lens, so that the destructive interference light can be converted into the constructive interference light, the device is allowed to have a larger cone angle and a larger gain area, and the output power of the device is greatly improved.
The present invention will be described in detail below with reference to the accompanying drawings and examples.
Drawings
FIG. 1 is a schematic diagram of an integrated superlens tapered semiconductor laser according to the present invention;
FIG. 2 is a schematic view of an enlarged configuration of the superlens of the present invention;
FIG. 3 is a schematic diagram of the electric field mode distribution of a simulation model of the tapered region of the tapered semiconductor laser of the integrated superlens of FIG. 1;
FIG. 4 is a schematic diagram of TE mode electric field distribution at a certain time of a simulation model of the area near the superlens shown in FIG. 2;
FIG. 5 is a graph that simulates the light transmission of the superlens of FIG. 2 as a function of longitudinal low index cell length and width;
FIG. 6 is a schematic diagram of a light reflectivity of the superlens of FIG. 2 simulated as a function of longitudinal low refractive index unit length and width;
FIG. 7 is a graph that models the optical loss of the superlens of FIG. 2 as a function of longitudinal low index element length and width;
FIG. 8 is a schematic diagram of the electric field mode distribution of another simulation model of the tapered region of the tapered semiconductor laser of the integrated superlens of FIG. 1;
FIG. 9 is a schematic diagram simulating the horizontal output far field of the tapered semiconductor laser of the integrated superlens of FIG. 8;
FIG. 10 is a schematic diagram of the propagation of an optical wave through a tapered gain amplification section;
FIG. 11 is a schematic top view of a tapered gain amplifying section of an integrated superlens;
FIG. 12 is a schematic diagram of phases modulated by a superlens with different lengths and widths of low refractive index units.
In the figure, the position of the first and second end faces,
11-rear cavity surface, 12-narrow ridge waveguide part, 13-tapered gain amplification part, 14-front cavity surface, 15-super lens, 16-longitudinal low refractive index groove and 17-residual longitudinal waveguide.
Detailed Description
In order to more clearly understand the technical features, objects, and effects of the present invention, embodiments of the present invention will now be described with reference to the accompanying drawings.
Example 1
As shown collectively in fig. 1 and 2, the present invention provides a superlens integrated tapered semiconductor laser comprising: the super-lens structure comprises an epitaxial layer structure, a conical structure and a super-lens 15, wherein the epitaxial layer structure comprises an N-type substrate, an N-type limiting layer, an N-type waveguide layer, an active region, a P-type waveguide layer, a P-type limiting layer and a P-type contact layer which are sequentially arranged from bottom to top.
The tapered structure is arranged on one surface of the epitaxial layer structure, which is provided with the P-type contact layer, the tapered structure comprises a narrow ridge waveguide part 12 and a tapered gain amplification part 13 connected with the narrow ridge waveguide part 12, the end surface of the narrow ridge waveguide part 12, which is far away from the tapered gain amplification part 13, is a rear cavity surface 11 of the tapered semiconductor laser, and the end surface of the tapered gain amplification part 13, which is far away from the narrow ridge waveguide part 12, is a front cavity surface 14 of the tapered semiconductor laser; the width of the tapered gain amplification section 13 gradually increases in the light exit direction.
The superlens 15 is disposed at an end of the tapered gain amplifying section 13 remote from the narrow ridge waveguide section 12; the superlens 15 spans the active region in the epitaxial direction. The superlens 15 comprises a plurality of longitudinal low refractive index units and a plurality of remaining longitudinal waveguides 17; the longitudinal low refractive index units and the remaining longitudinal waveguides 17 are alternately arranged in the width direction of the tapered gain amplification section 13.
All the longitudinal low-refractive-index units in the superlens 15 have the same refractive index, and the refractive index difference between the longitudinal low-refractive-index units and the remaining longitudinal waveguides 17 is greater than 0.5.
The longitudinal low-refractive-index unit is of a continuous structure, namely the longitudinal low-refractive-index unit is formed by a longitudinal refractive-index partition; or the longitudinal low-refractive-index unit is of a discontinuous structure, namely the longitudinal low-refractive-index unit is composed of a plurality of longitudinal refractive-index partitions which are arranged in rows and at intervals; and the number of longitudinal refractive index partitions in the longitudinal low refractive index unit at different positions of the tapered gain amplification section 13 is the same or different, the structure can reduce transmission loss and make mode selection.
Further, the longitudinal low refractive index unit includes longitudinal low refractive index grooves 16; the longitudinal low-refractive-index groove 16 is formed by etching down the upper surface of the tapered gain amplifying section 13; the longitudinal low-refractive-index groove 16 alone forms a longitudinal low-refractive-index unit, or a material having a lower refractive index than the remaining longitudinal waveguide 17 is filled in the longitudinal low-refractive-index groove 16 to form a longitudinal low-refractive-index unit.
It should be noted that, when the longitudinal low-refractive-index unit is composed of a plurality of longitudinal refractive-index partitions, a plurality of the longitudinal low-refractive-index grooves 16 are correspondingly disposed, and the plurality of the longitudinal low-refractive-index grooves 16 are disposed in rows and at intervals.
The quasi-period width of the superlens 15 is of sub-wavelength order, so that the formation of stray diffraction orders is avoided, and adverse effects such as virtual focal spots and halos caused by the formation of stray diffraction orders are avoided.
Wherein the depth of the longitudinal low-refractive-index grooves 16 exceeds the depth of the active region; the longitudinal low-index grooves 16 at different lateral positions of the tapered gain amplification section 13 differ in length and width.
It should be noted that: the position of the tapered gain amplification section 13 in the width direction is a lateral position in this application.
The width of the narrow ridge waveguide section 12 is no greater than the cut-off width of the lateral high order mode generated at the abrupt transition of the tapered gain amplification section 13.
Preferably, the narrow ridge waveguide portion 12 forms a refractive index guiding structure.
Preferably, the contact layers on both sides of the tapered gain amplification section 13 are etched away to form the gain guide, or the tapered gain amplification section 13 is etched to the same depth as the narrow ridge waveguide section 12 to form the refractive index guide structure.
The lengths of the tapered gain amplification section 13 and the ridge narrow ridge waveguide section 12 are selected according to device design requirements to ensure that sufficient lateral mode filtering characteristics and sufficient gain volume are achieved.
An antireflection film is plated outside the front cavity surface 14, and the reflectivity is less than 1%;
preferably, the back facet 11 is coated with a high reflectivity film and etched to destroy the grooves on both sides of the narrow ridge waveguide portion 12, or the DBR grating is etched in the back facet 11.
Specifically, the length and width of the longitudinal low refractive index groove 16 are adjusted as the lateral position of the tapered gain amplification section 13 is changed: the length and width distribution enables the phase distribution of emergent light to meet the convergence condition or the parallel emergent condition on one hand, and enables the main distribution positions of the lateral fundamental mode light field to have relatively high reflectivity and transmissivity on the other hand, and enables the main distribution positions of the lateral high-order mode light field to have relatively low reflectivity and relatively high loss.
Fig. 10 is a schematic diagram of propagation of a light wave after passing through the tapered gain amplification section, without considering the influence of temperature and carriers, where the refractive index of the tapered gain amplification section 13 is constant, and a phase difference caused by an optical path cannot be compensated, and if light emitted from the narrow ridge waveguide section is approximated to a point light source, a wavefront of the emitted wave is a divergent spherical wave, which obviously causes an increase in a far-field divergence angle.
In order to change the transmission phase of the electromagnetic wave, the superlens 15 is integrated in the area close to the exit end face, one or more longitudinal low refractive index units are placed at different lateral (y-direction, i.e. width direction of the tapered gain amplifying part), each small unit is equivalent to a resonant cavity, different transmission phases are realized by changing the size of the small unit, as shown in fig. 11, which is a top view of the tapered gain amplifying part of the integrated superlens, the left is a narrow ridge waveguide part, the middle is the tapered gain amplifying part and the superlens, the middle rectangle is the longitudinal low refractive index unit, and the coordinates of each small unit are respectively taken as y ridge waveguide part, the middle is the tapered gain amplifying part and the superlensiTaking the center of the inlet of the conical gain amplifying part as a phase zero point
Taking the y coordinate of the position as
The entrance of the conical gain amplifying section is at a distance L from the superlens.
The phase change of the light wave entering from the entrance of the tapered gain amplification part after passing through the super lens is composed of 2 parts, and the 1 st part is the phase change generated by the light transmitted from the entrance of the tapered gain amplification part to the super lens, and can be represented as follows:
In order to make the emergent light be convergent light or parallel light, the phase of the final emergent light meets the condition:
Then, the phase change of the 2 nd part can be calculated
I.e. the required phase change caused by the superlens is:
the phase change caused by the superlens at a certain position depends on the size of the low refractive index unit at the position, and as shown in fig. 12, the color shade reflects the phase change caused by the superlens when the low refractive index unit is at the corresponding length and width dimensions. Therefore, it is necessary to perform the operation sequentially at each
Next, the points with the phase variation equal to the calculated value of the above formula are found in fig. 12, and the horizontal and vertical coordinates corresponding to these points are the low refractive index unit size that can satisfy the phase modulation.
Further, the lateral fundamental mode optical field is mainly distributed at the lateral middle position of the conical amplification gain part, and the lateral high-order mode (taking the 1 st order mode as an example) is mainly distributed at two sides (near a quarter point), so that the superlens has relatively high reflectivity and transmissivity at the lateral middle position, and relatively low reflectivity and relatively large loss at the lateral two sides. Therefore, when designing the low refractive index unit size at the position where the lateral base film is mainly distributed, it is necessary to select a size in which the transmittance and reflectance are relatively high according to fig. 5 and 6 among different low refractive index unit sizes satisfying the phase modulation; when designing the low refractive index cell size at the position where the lateral high-order mode is mainly distributed, it is necessary to select a size having a relatively low reflectance and a relatively high loss according to fig. 6 and 7 among different low refractive index cell sizes satisfying the phase modulation.
It should be noted that: fig. 5 is a schematic diagram simulating the change of light transmittance of the superlens shown in fig. 2 along with the length and width of the longitudinal low-refractive-index groove, when the width of the low-refractive-index unit is smaller, the high-transmittance region and the low-transmittance region are alternately arranged approximately along the length increasing direction, and as the width of the low-refractive-index unit increases, the arrangement bends upward, and the transmittance of the low-transmittance region decreases significantly.
Fig. 6 is a schematic diagram simulating the relationship between the light reflectivity of the superlens shown in fig. 2 and the change of the length and the width of the longitudinal low-refractive-index groove, when the width of the low-refractive-index unit is smaller, the high-reflectivity region and the low-reflectivity region are alternately arranged approximately along the length increasing direction, the arrangement bends upwards along with the increase of the width of the low-refractive-index unit, the reflectivity of the high-reflectivity region is obviously increased, and the change is approximately opposite to the transmittance change as a whole.
Fig. 7 is a schematic diagram simulating the variation of the optical loss of the superlens shown in fig. 2 with the length and width of the longitudinal low-refractive-index groove, where the optical loss is smaller when the width and length of the low-refractive-index unit are smaller, and the high loss and the low loss are alternately arranged approximately along the direction perpendicular to the direction in which the length and the width of the low-refractive-index unit increase together with the increase of the length and the width of the low-refractive-index unit.
Fig. 3 is a schematic diagram of a simulation model of optical field distribution of a tapered gain amplification part of a 980 nm laser in this embodiment, where the tapered gain amplification part 13 of the simulation model adopts a gain guide structure, two side waveguides have loss, and the gain of a center waveguide is greater than the loss; the width of the narrow ridge waveguide part 12 on the left side is 1.5 mu m, so that the lateral high-order mode cutoff condition of the ridge waveguide is met, and almost only the base-side mode is ensured to be injected into the conical gain amplifying part 13; the total length of the tapered gain amplification section 13 is 50 μm, the full cone angle is 10 °, and a large cone angle provides a sufficiently large optical gain area; the total width of the right super-lens 15 is 22 microns, is larger than the width of an output aperture, the quasi-period width is 275nm, and the TE mode optical phases of the adjacent longitudinal low-refractive-index grooves 16 and the residual longitudinal waveguides 17 are ensured to be free of jitter; the longitudinal low-refractive-index groove 16 is formed by etching the surface inwards, the length of the groove is 0.5-2.7 microns, the width of the longitudinal low-refractive-index groove 16 is 66 nm, photons at different positions are controlled in a targeted mode, emergent light is converted into parallel light or convergent light from divergent light (see fig. 4), the far-field divergence angle is reduced, relatively high reflectivity and relatively low loss can be ensured at the main distribution position of a lateral fundamental mode light field, and relatively low reflectivity and relatively high loss are ensured at the main distribution position of a lateral high-order mode light field (see fig. 5, 6 and 7), so that the high-order mode of a conical cavity is restrained, the beam quality of the semiconductor laser is improved, the laser output power is improved, and stable lateral mode output is realized.
Fig. 8 shows another simulation model of optical field distribution in a tapered gain amplification section of a 980 nm wavelength laser according to this embodiment, in which the tapered gain amplification section of the simulation model adopts a gain guide structure, the width of a left narrow ridge waveguide is 4 μm, the length of the tapered gain amplification section 13 is 0.5 mm, and the total taper angle is 6 °; the total width of the right super-lens 15 is about 100 micrometers, the width of the right super-lens is larger than the width of an output aperture, the quasi-period width is 275nm, and the TE mode optical phases of the adjacent longitudinal low-refractive-index grooves 16 and the residual longitudinal waveguides 17 are ensured to be free of jitter; the longitudinal low-refractive-index grooves 16 are formed by surface inward etching, the length of the grooves is 0.1-1.535 micrometers, the width of the longitudinal low-refractive-index grooves 16 is 66 nm, the far-field divergence angle of the lateral fundamental mode obtained through simulation is smaller than 0.9 degrees (see fig. 9), the degree of divergence is reduced by one order of magnitude compared with that of a traditional device, and the divergence angle of a laser in the horizontal direction is reduced. And the main distribution position of the lateral fundamental mode light field can be ensured to have relatively high reflectivity and relatively low loss, and the main distribution position of the lateral high-order mode light field has relatively low reflectivity and relatively high loss (please refer to fig. 5, 6 and 7), so that the high-order mode of the conical cavity is inhibited, the beam quality of the semiconductor laser is improved, the laser output power is improved, and stable lateral mode output is realized.
It needs to be further explained that: since the lateral far-field divergence angle is approximately in inverse proportion to the light-emitting aperture, and the length of the tapered gain amplification part is one of the determining factors of the light-emitting aperture (i.e., the longer the tapered gain amplification part is, the larger the light-emitting aperture is, and the smaller the far-field divergence angle is), the length of the tapered gain amplification part in the simulation example is shorter, only 500um, and the lateral divergence angle has been reduced to 0.81 °, so that for a real device generally in the millimeter order, the lateral far-field divergence angle can be smaller than 0.5 °.
It should be noted that the far-field divergence angle in the above simulation model is obtained as follows: 1. after fourier transform is performed on the electric field distribution at the light-emitting end face (fig. 8 data at the light-emitting end face), the distribution of light normalized in the far field can be obtained (see fig. 9), and then the far field divergence angle (full width at half maximum, i.e., the abscissa interval between two points corresponding to the longitudinal axis y =0.5 in fig. 9) is obtained.
The foregoing is illustrative of the best mode contemplated for carrying out the present invention and the details not specifically mentioned are within the knowledge of one of ordinary skill in the art. The scope of the present invention is defined by the appended claims, and any equivalent modifications based on the technical teaching of the present invention are also within the scope of the present invention.
Claims (10)
1. A superlens integrated tapered semiconductor laser comprising a tapered structure including a narrow ridge waveguide portion (12), a tapered gain amplification portion (13) connected to the narrow ridge waveguide portion (12); the method is characterized in that: the super lens (15) is arranged at one end, far away from the narrow ridge waveguide part (12), of the conical gain amplification part (13);
the superlens (15) comprises a plurality of longitudinal low-refractive-index units and a plurality of remaining longitudinal waveguides (17), and the longitudinal low-refractive-index units and the remaining longitudinal waveguides (17) are alternately arranged in the width direction of the tapered gain amplification part (13).
2. A superlens integrated tapered semiconductor laser as claimed in claim 1 wherein: all the longitudinal low-refractive-index units in the superlens (15) have the same refractive index, and the refractive index difference between the longitudinal low-refractive-index units and the remaining longitudinal waveguides (17) is larger than 0.5.
3. A superlens integrated tapered semiconductor laser as claimed in claim 1 wherein: the epitaxial structure comprises an N-type substrate, an N-type limiting layer, an N-type waveguide layer, an active region, a P-type waveguide layer, a P-type limiting layer and a P-type contact layer which are sequentially arranged from bottom to top; the superlens (15) spans the active region in an epitaxial direction.
4. A superlens integrated tapered semiconductor laser as claimed in claim 1 wherein: the longitudinal low refractive index unit is formed by a longitudinal refractive index partition;
or the longitudinal low-refractive-index unit consists of a plurality of longitudinal refractive-index partitions which are arranged in rows and at intervals; and the number of longitudinal refractive index partitions in the longitudinal low refractive index unit at different positions of the tapered gain amplification section (13) is the same or different.
5. A superlens integrated tapered semiconductor laser as claimed in claim 1 wherein: the quasi-period width of the superlens (15) is in the order of sub-wavelength.
6. A superlens integrated tapered semiconductor laser as claimed in claim 3 wherein: the longitudinal low refractive index unit comprises a longitudinal low refractive index groove (16); the longitudinal low refractive index grooves (16) are formed by etching down along the upper surface of the tapered gain amplification section (13);
the longitudinal low-refractive-index groove (16) alone forms a longitudinal low-refractive-index unit, or a material with a lower refractive index than the remaining longitudinal waveguide (17) is filled in the longitudinal low-refractive-index groove (16) to form the longitudinal low-refractive-index unit.
7. A superlens integrated tapered semiconductor laser as claimed in claim 6 wherein: the depth of the longitudinal low-refractive-index groove (16) exceeds the depth of the active region; the longitudinal low-refractive-index grooves (16) at different lateral positions of the tapered gain amplification section (13) are different in length and width.
8. A superlens integrated tapered semiconductor laser as claimed in claim 3 wherein: the conical structure is arranged on one surface of the epitaxial layer structure, which is provided with the P-type contact layer; the end face, far away from the narrow ridge waveguide part (12), of the conical gain amplification part (13) is a front cavity face (14) of the laser; the end surface of the narrow ridge waveguide part (12) far away from the conical gain amplification part (13) is a rear cavity surface (11) of the conical semiconductor laser; the width of the conical gain amplification part (13) is gradually increased along the light emitting direction.
9. A superlens integrated tapered semiconductor laser as claimed in claim 1 wherein: the width of the narrow ridge waveguide part (12) is not more than the cut-off width of a lateral high-order mode generated at the abrupt change of the tapered gain amplification part (13);
the narrow ridge waveguide portion (12) forms a refractive index guiding structure;
the contact layers on both sides of the tapered gain amplifying part (13) are etched away to form a gain guide, or the tapered gain amplifying part (13) and the narrow ridge waveguide part (12) are etched to the same depth to form a refractive index guide structure.
10. An integrated superlens tapered semiconductor laser as claimed in claim 8 wherein: an anti-reflection film is plated outside the front cavity surface (14), and the reflectivity is less than 1%;
and a high-reflectivity film is plated outside the rear cavity surface (11), and grooves are etched and damaged on two sides of the narrow ridge waveguide part (12), or DBR gratings are etched in the rear cavity surface (11).
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115275785A (en) * | 2022-09-27 | 2022-11-01 | 潍坊先进光电芯片研究院 | Semiconductor laser array structure |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115275785A (en) * | 2022-09-27 | 2022-11-01 | 潍坊先进光电芯片研究院 | Semiconductor laser array structure |
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