CN115764542A - Dual-wavelength semiconductor laser and preparation method thereof - Google Patents

Dual-wavelength semiconductor laser and preparation method thereof Download PDF

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Publication number
CN115764542A
CN115764542A CN202111028108.8A CN202111028108A CN115764542A CN 115764542 A CN115764542 A CN 115764542A CN 202111028108 A CN202111028108 A CN 202111028108A CN 115764542 A CN115764542 A CN 115764542A
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grating
region
area
waveguide
layer
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邓秋芳
李玮淳
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Suzhou Luohe Leixin Optoelectronics Technology Co ltd
Zte Photonics Technology Co ltd
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Suzhou Luohe Leixin Optoelectronics Technology Co ltd
Zte Photonics Technology Co ltd
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Priority to CN202111028108.8A priority Critical patent/CN115764542A/en
Priority to PCT/CN2022/101229 priority patent/WO2023029691A1/en
Publication of CN115764542A publication Critical patent/CN115764542A/en
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • 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
    • H01S5/02—Structural details or components not essential to laser action
    • 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
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
    • 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
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
    • H01S5/125—Distributed Bragg reflector [DBR] lasers
    • 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
    • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30

Abstract

The invention provides a dual-wavelength semiconductor laser and a preparation method thereof, wherein the dual-wavelength semiconductor laser comprises: the first DBR laser area comprises a first grating area, and the first grating area is provided with a first bent waveguide; and the second DBR laser area comprises a second grating area, the first grating area is provided with a first curved waveguide, the second grating area is provided with a second curved waveguide, the first included angle and the second included angle are different, the gratings of the first grating area and the gratings of the second grating area have the same grating period, the first included angle is an included angle formed by the first curved waveguide and a grating direction perpendicular to the first grating area, and the second included angle is an included angle formed by the second curved waveguide and a grating direction perpendicular to the second grating area. According to the scheme provided by the embodiment of the invention, the equivalent chirped grating is realized by combining the grating with the curved waveguide, the reflection spectrum range of the DBR laser region is enlarged by utilizing different included angles between the curved waveguide and the grating, and the tuning range of the laser and the microwave tuning range realized by beat frequency are effectively improved.

Description

Dual-wavelength semiconductor laser and preparation method thereof
Technical Field
The invention relates to but is not limited to the field of photoelectron, in particular to a dual-wavelength semiconductor laser and a preparation method thereof.
Background
The dual-wavelength semiconductor laser has the characteristics of small volume, high power, stable output wavelength, easiness in preparation and the like, and is widely applied to the fields of wavelength division multiplexing, terahertz light sources, optical remote sensing, optical carrier microwaves and the like. The current dual-wavelength semiconductor laser is divided into a common-cavity type, a serial type and a parallel type, wherein the laser light of one of the optical cavities of the common-cavity dual-wavelength semiconductor laser and the serial dual-wavelength semiconductor laser can affect the other optical cavity, so that the dual-wavelength optical cavity is not uniform, and the device is unstable in working and other adverse effects. The parallel dual-wavelength semiconductor laser realizes dual-wavelength output by two single-mode lasers with different lasing wavelengths through a light-combined wave zone, can well avoid crosstalk between optical cavities of the two single-mode lasers, and realizes stable wavelength output.
For a common parallel dual-wavelength semiconductor laser, the parallel dual-wavelength semiconductor laser is mainly implemented by a Distributed Feedback (DFB) laser, but the DFB laser has high preparation difficulty and cost and a small range, so that the microwave tuning range of the final beat frequency implementation is small.
Disclosure of Invention
The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.
The embodiment of the invention provides a dual-wavelength semiconductor laser and a preparation method thereof, which can enlarge the tunable range of the dual-wavelength semiconductor laser.
In a first aspect, an embodiment of the present invention provides a dual-wavelength semiconductor laser, including:
a first Distributed Bragg Reflector (DBR) laser region, the first DBR laser region including a first grating region, the first grating region being provided with a first curved waveguide;
the laser device comprises a first DBR laser area, a second DBR laser area and a first grating area, wherein the first grating area is provided with a first curved waveguide, the second grating area is provided with a second curved waveguide, a first included angle of the first curved waveguide is different from a second included angle of the second curved waveguide, gratings of the first grating area and gratings of the second grating area have the same grating period, the first included angle is an included angle formed by the first curved waveguide and a grating direction perpendicular to the first grating area, and the second included angle is an included angle formed by the second curved waveguide and a grating direction perpendicular to the second grating area.
In a second aspect, an embodiment of the present invention further provides a method for manufacturing a dual-wavelength semiconductor laser, where the dual-wavelength semiconductor laser is sequentially divided into a tunable filter region, a grating region, a phase region, a gain region, a wavelength combining region, and an SOA region from a reflection end to an exit end, where the grating region includes a first grating region and a second grating region, and the method includes the following steps:
preparing a first selected area medium SAG mask strip pair and a second SAG mask strip pair on a substrate, wherein the position of the first SAG mask strip pair corresponds to the SOA area, and the position of the second SAG mask strip pair corresponds to the gain area;
sequentially growing a lower respective limiting layer, a waveguide layer and an upper respective limiting layer on the substrate through one-time epitaxy, wherein the waveguide layer comprises a first curved waveguide and a second curved waveguide, the first curved waveguide is located at a position corresponding to the first grating region, and the second curved waveguide is located at a position corresponding to the second grating region;
removing the first SAG mask strip pair and the second SAG mask strip pair, and preparing gratings at positions of the upper limiting layer corresponding to the first grating region and the second grating region respectively, wherein grating periods of the gratings of the first grating region and the gratings of the second grating region are the same, a first included angle of the first curved waveguide is different from a second included angle of the second curved waveguide, the first included angle is an included angle formed by the first curved waveguide and a grating direction perpendicular to the first grating region, and the second included angle is an included angle formed by the second curved waveguide and a grating direction perpendicular to the second grating region;
and growing a covering layer in a secondary epitaxial mode, wherein the covering layer is a P-type covering layer.
The embodiment of the invention comprises the following steps: a first DBR laser region including a first grating region provided with a first curved waveguide; the laser device comprises a first DBR laser area, a second DBR laser area and a first grating area, wherein the first grating area is provided with a first curved waveguide, the second grating area is provided with a second curved waveguide, a first included angle of the first curved waveguide is different from a second included angle of the second curved waveguide, gratings of the first grating area and gratings of the second grating area have the same grating period, the first included angle is an included angle formed by the first curved waveguide and a grating direction perpendicular to the first grating area, and the second included angle is an included angle formed by the second curved waveguide and a grating direction perpendicular to the second grating area. According to the scheme provided by the embodiment of the invention, equivalent chirped grating is realized by combining the grating with the curved waveguide, and the included angles between the first curved waveguide and the grating are different from those between the second curved waveguide and the grating, so that the reflection spectrum range of the DBR laser region can be effectively enlarged, and the tuning range of the laser and the microwave tuning range realized by beat frequency can be effectively enlarged.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the example serve to explain the principles of the invention and do not constitute a limitation thereof.
Fig. 1 is a top view of a dual wavelength semiconductor laser provided by the present invention;
fig. 2 is a longitudinal sectional view of a two-wavelength semiconductor laser provided by the present invention;
FIG. 3 is a schematic diagram of a grating and a curved waveguide in a dual wavelength semiconductor laser provided by the present invention;
fig. 4 is a reflection spectrum of a grating region of a dual wavelength semiconductor laser provided by the present invention;
fig. 5 is a transmission spectrum of two ring resonance regions of the tunable filter region of the two-wavelength semiconductor laser provided by the present invention;
fig. 6 is a combined transmission spectrum of two ring-shaped resonance regions of the tunable filter region of the two-wavelength semiconductor laser provided by the present invention;
FIG. 7 is a transmission spectrum of a tunable filter region of a dual wavelength semiconductor laser including a ring resonator region according to the present invention;
fig. 8 is a schematic diagram of the lasing principle of the tunable filter region of the dual-wavelength semiconductor laser provided by the present invention including two ring-shaped resonance regions;
fig. 9 is a schematic diagram of the lasing principle of the tunable filter region of the dual wavelength semiconductor laser provided by the present invention including a ring-shaped resonance region;
fig. 10 is a flow chart of a method of fabricating a dual wavelength semiconductor laser provided by the present invention;
FIG. 11 is a schematic diagram of a Selective Area medium (SAG) mask stripe provided by the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
It should be noted that although functional blocks are partitioned in a schematic diagram of an apparatus and a logical order is shown in a flowchart, in some cases, the steps shown or described may be performed in a different order than the partitioning of blocks in the apparatus or the order in the flowchart. The terms "first," "second," and the like in the description, in the claims, or in the drawings described above, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
The invention provides a dual-wavelength semiconductor laser and a preparation method thereof, wherein the dual-wavelength semiconductor laser comprises: a first DBR laser region including a first grating region provided with a first curved waveguide; the laser device comprises a first DBR laser area, a second DBR laser area and a first grating area, wherein the first grating area is provided with a first curved waveguide, the second grating area is provided with a second curved waveguide, a first included angle of the first curved waveguide is different from a second included angle of the second curved waveguide, gratings of the first grating area and gratings of the second grating area have the same grating period, the first included angle is an included angle formed by the first curved waveguide and a grating direction perpendicular to the first grating area, and the second included angle is an included angle formed by the second curved waveguide and a grating direction perpendicular to the second grating area. According to the scheme provided by the embodiment of the invention, equivalent chirped grating is realized by combining the grating with the curved waveguide, and the included angles between the first curved waveguide and the grating are different from those between the second curved waveguide and the grating, so that the reflection spectrum range of a DBR laser region can be effectively enlarged, and the tuning range of a laser and the microwave tuning range realized by beat frequency can be effectively enlarged.
The embodiments of the present invention will be further explained with reference to the drawings.
As shown in fig. 1, fig. 1 is a dual-wavelength semiconductor laser according to an embodiment of the present invention, including:
the first DBR laser area comprises a first grating area 5a, and the first grating area 5a is provided with a first curved waveguide;
the second DBR laser area comprises a second grating area 5b, the first grating area 5a is provided with a first curved waveguide, the second grating area 5b is provided with a second curved waveguide, a first included angle of the first curved waveguide is different from a second included angle of the second curved waveguide, gratings of the first grating area 5a and gratings of the second grating area 5b have the same grating period, the first included angle is an included angle formed by the first curved waveguide and a grating direction perpendicular to the first grating area 5a, and the second included angle is an included angle formed by the second curved waveguide and a grating direction perpendicular to the second grating area 5 b.
It should be noted that when the grating period of the grating is Λ 0 And is provided with a curved waveguide for equalizing the grating along the waveguide directionPeriod Λ 1 ＝Λ 0 The angle between the vertical grating direction and the curved waveguide is theta, and the equivalent period lambda is gradually increased along the direction of the curved waveguide along with the increase of theta 1 Gradually increasing to obtain equivalent grating period with gradually changing period, and when the bending radii of the bending waveguides of the grating regions 5 of the two DBR laser regions are the same, the maximum equivalent grating periods of the grating regions 5 of the two DBR lasers are respectively lambda max ＝Λ 0 The tuning range of the microwave obtained by the beat frequency of the dual-wavelength laser is 0 to Lambda 0 The lasing wavelength corresponding to/cos θ. As shown in FIG. 3, when the maximum angle between the first curved waveguide and the vertical grating direction is α, the maximum angle between the second curved waveguide and the vertical grating direction is β, where α is>Beta, then the maximum equivalent grating period of the grating region 5 of the two DBR laser regions is Lambda respectively 1max ＝Λ 0 α and Λ,/cos 2max ＝Λ 0 Per cos beta. The wavelength ranges output by the two tunable lasers are respectively Lambda 0 Corresponding lasing wavelength to Λ 0 A lasing wavelength corresponding to/cos α, and Λ 0 Corresponding lasing wavelength to Λ 0 The laser wavelength corresponding to/cos beta, and the tuning range of the microwave obtained by the beat frequency of the dual-wavelength laser is 0 to Lambda 0 The first bending waveguide and the second bending waveguide form different included angles with the grating, so that the tuning range of the dual-wavelength laser can be effectively enlarged.
In addition, referring to fig. 1, in an embodiment, the first DBR laser section includes a first gain section 3a and a first phase section 4a, the first phase section 4a is located at the light-emitting side of the first grating section 5a, and the first gain section 3a is located at the light-emitting side of the first phase section 4 a; the second DBR laser section includes a second gain section 3b and a second phase section 4b, the second phase section 4b is located on the light exit side of the second grating section 5b, and the second gain section 3b is located on the light exit side of the second phase section 4 b.
It should be noted that the light-emitting side is a side from which the laser is emitted, for example, the first phase region 4a is located on the light-emitting side of the first grating region 5a, and then the laser enters the first phase region 4a after being emitted from the first grating region 5a, and the description of other parts is the same, and will not be repeated later.
It should be noted that, according to the direction from the reflection end to the emission end, the DBR laser section sequentially includes a grating section 5, a phase section 4 and a gain section 3, the refractive index of the optical waveguide layer of the phase section 4 of the DBR laser changes with the change of the injection current, and by changing the refractive index of the phase section 4, the optical path of the phase section 4 can be changed, so that the resonator length of the whole optical waveguide in the dual-wavelength semiconductor laser changes. Therefore, by adjusting the amount of current injected into the optical waveguide layer in the phase region 4, the emission wavelength of the semiconductor laser can be adjusted.
In addition, referring to fig. 1, in an embodiment, the method further includes:
the first tunable filter area 6a, the first grating area 5a is located at the light-emitting side of the first tunable filter area 6 a;
and the second tunable filter area 6b, and the second grating area 5b are located at the light-emitting side of the second tunable filter area 6 b.
It should be noted that, by arranging the tunable filter region on the reflection side of the DBR laser region, a semiconductor single-mode laser with a wide tunable range can be formed by the tunable filter region and the DBR laser region, thereby achieving the tunable wavelength range.
Additionally, in an embodiment, the first tunable filter section 6a and the second tunable filter section 6b each comprise at least two ring resonance regions.
It should be noted that, when the tunable filter region 6 is composed of only one ring-shaped resonance region, its transmission spectrum is shown in fig. 7, where R2 is the DBR reflection spectrum without current, and P1 is the emission peak waveform of the first ring-shaped resonance region, as shown in fig. 9, when the peak wavelength in the transmission spectrum of the ring-shaped resonance region coincides with the reflection peak wavelength of the DBR, that is, it is necessary that P4 coincides with the peak wavelength of R2, which will be excited in the laser cavity, where P4 is the transmission peak waveform of the first ring-shaped resonance region.
It should be noted that, when the tunable filter region 6 is composed of a plurality of ring-shaped resonance regions, the wavelength is excited in the laser cavity when the peak wavelength of the combined transmission spectrum of the plurality of ring-shaped resonance regions coincides with the peak wavelength of the reflection peak of the DBR. For example, the tunable filter section 6 is composed of two ring resonators, transmission spectra of the two ring resonators are shown in fig. 5, where P1 is an emission peak waveform of the first ring resonator, P2 is an emission peak waveform of the second ring resonator, R3 is a transmission spectrum of the first ring resonator, and R4 is a transmission spectrum of the second ring resonator, and a combined transmission spectrum obtained by the two is shown in fig. 6, where P3 is a transmission peak waveform of the combined transmission spectrum, the transmission peak waveform P3 has the same Free Spectral Range (FSR) as the emission peak waveform P1 of the first ring resonator region, and the transmission peak waveform R3 has substantially the same Full Width At Half maximum (FWHM) as the reflection spectrum R1 of the DBR laser region. As shown in fig. 8, only if the peak wavelength P3 in the combined transmission spectrum coincides with the wavelength of the reflection peak R2 of the DBR, the wavelength will be excited in the laser cavity, so that the line width of the laser region of the DBR is narrow by using at least two ring-shaped resonance regions, and it is ensured that the microwave finally output at the beat frequency has good line width characteristics.
In addition, referring to fig. 1, in an embodiment, the dual wavelength semiconductor laser further includes:
the wave combining area 2 is positioned on the light emitting sides of the first gain area 3a and the second gain area 3 b;
a Semiconductor Optical Amplifier (SOA) region, and the SOA region 1 is located on the light-emitting side of the wavelength combining region 2.
It should be noted that the wave combining region 2 can combine the two lasers with different wavelengths output by the two DBR laser regions, and input the two lasers into the SOA region 1, and amplify the output light through the SOA region 1, so as to realize the output light of the dual-wavelength semiconductor laser.
In addition, referring to fig. 2, in an embodiment, the first DBR laser section, the second DBR laser section, the first tunable filter section 6a, the second tunable filter section 6b, the wavelength combining section 2, and the SOA section 1 sequentially include, from bottom to top: the optical waveguide comprises a substrate, a buffer layer, a lower respective limiting layer, a waveguide layer, an upper respective limiting layer and a P-type cover layer.
It should be noted that, the substrate, the buffer layer, the lower respective confinement layer, the waveguide layer, and the upper respective confinement layer corresponding to the first DBR laser region, the second DBR laser region, the first tunable filter region 6a, the second tunable filter region 6b, the wave combining region 2, and the SOA region 1 can realize the band gap wavelength deviation between the active layer of the gain region 3 and the waveguide layers of other regions by only one epitaxial growth, thereby realizing the integration of different band gap materials.
In addition, referring to fig. 2, in an embodiment, the upper side of the P-type cover layer corresponding to the SOA region 1, the first DBR laser region, the second DBR laser region, the first tunable filter region 6a, and the second tunable filter region 6b further includes a P-type electrode layer.
Note that the P-type electrode layers of the first and second grating regions 5a and 5b may be provided with a plurality of electrodes, and when a current is injected from one of the electrodes, the reflectance spectrum of the DBR laser region is as shown by R1 in fig. 4, where R2 is the DBR reflectance spectrum when no current is applied. When a current is injected into one of the electrodes of the grating region 5, the refractive indices of the waveguide layer and the diffraction grating layer below the electrode decrease, the reflection peak wavelength of the diffraction grating changes to the short wavelength side, and the reflection peak wavelengths of the other portions of the diffraction grating where no current is injected do not change, so that the reflectance of the wavelength region (region a in the drawing) corresponding to the grating period below the current injection electrode in the reflection spectrum of the DBR region increases. The current can be applied to the electrode of the grating region 5 alone, and the reflectivity of the wavelength region corresponding to the diffraction grating section below the electrode can be increased, so that the lasing wavelength of the laser can be adjusted in the wavelength region with increased reflectivity. The current may be provided to two or more node electrodes of the grating region 5, and of course, the current may also be injected to a plurality of electrodes simultaneously according to the requirement of reflectivity, which is not described herein.
It should be noted that the emission peak wavelength of the ring resonance region in the tunable filter region 6 may vary with the injection current, and only if the peak wavelength in the transmission spectrum of the ring resonance region coincides with the reflection peak wavelength of the DBR, the wavelength will be excited in the laser cavity, so that the wavelength can be tunable by changing the injection current.
Since the SOA region 1 is used to amplify an optical signal to be output from the wavelength combining region 2, the total output power of the two-wavelength semiconductor laser can be adjusted by injecting a current into the SOA region 1.
In addition, referring to fig. 2, in an embodiment, a diffraction grating layer is further included between the P-type cap layer and the upper limit layer corresponding to the first grating region 5a and the second grating region 5 b.
It should be noted that the diffraction grating layers of the first grating region 5a and the second grating region 5b can realize the change of the refractive index under the action of the current, so as to realize the tunable wavelength, when the injection current is passed through one of the electrodes, the refractive indexes of the waveguide layer and the diffraction grating layer below the electrode are reduced, the reflection peak wavelength of the diffraction grating is changed to the short wavelength side, and the reflection peak wavelengths of the other diffraction gratings without the injection current are not changed, so in the reflection spectrum of the DBR laser region, the reflectivity of the wavelength region corresponding to the grating period below the current injection electrode is increased.
In addition, in an embodiment, the waveguide layers include a first waveguide layer and a second waveguide layer, and the first waveguide layer and the second waveguide layer are made of different materials, where the first waveguide layer is a waveguide layer corresponding to the SOA region 1, the first gain region 3a, and the second gain region 3b, and the second waveguide layer is a waveguide layer corresponding to the first phase region 4a, the second phase region 4b, the first grating region 5a, the second grating region 5b, the first tunable filter region 6a, the second tunable filter region 6b, and the multiplexing region 2.
It should be noted that the active layer materials of the SOA region 1, the first gain region 3a and the second gain region 3b may be the same, and the waveguide layer materials of other regions are the same, and the multiple quantum well materials of these two different band gap waveguides may be obtained by SAG growth technology under the condition of one-time epitaxial growth.
It is to be noted that, due to the difference of the materials, the spontaneous emission wavelength of the SOA region 1, the first gain region 3a and the second gain region 3b is longer than the wavelength of other regions, that is, the Photoluminescence (PL) peak wavelength of the multiple quantum well material of the SOA region 1, the first gain region 3a and the second gain region 3b is longer than the wavelength of other regions, thereby ensuring that the absorption loss of other waveguide regions is low.
In addition, referring to fig. 1, fig. 2, and fig. 10, an embodiment of the present invention further provides a method for manufacturing a dual-wavelength semiconductor laser, where the dual-wavelength semiconductor laser is sequentially divided from a reflection end to an exit end into a tunable filter region 6, a grating region 5, a phase region 4, a gain region 3, a wavelength combining region 2, and an SOA region 1, where the grating region 5 includes a first grating region 5a and a second grating region 5b, and the method includes the following steps:
step S1010, preparing a first SAG mask strip pair and a second SAG mask strip pair on a substrate, wherein the position of the first SAG mask strip pair corresponds to an SOA region, and the position of the second SAG mask strip pair corresponds to a gain region;
step S1020, sequentially growing a lower difference limiting layer, a waveguide layer, and an upper difference limiting layer on a substrate by one-time epitaxy, wherein the waveguide layer includes a first curved waveguide and a second curved waveguide, the first curved waveguide is located at a position corresponding to the first grating region, and the second curved waveguide is located at a position corresponding to the second grating region;
step S1030, removing the first SAG mask strip pair and the second SAG mask strip pair, and preparing gratings at positions corresponding to the first grating region and the second grating region on the upper limiting layer respectively, wherein grating periods of the gratings of the first grating region and the gratings of the second grating region are the same, a first included angle of the first curved waveguide and a second included angle of the second curved waveguide are different from each other, the first included angle is an included angle formed by the first curved waveguide and a grating direction vertical to the first grating region, and the second included angle is an included angle formed by the second curved waveguide and a grating direction vertical to the second grating region;
and step S1040, secondary epitaxial growth of a cover layer, wherein the cover layer is a P-type cover layer.
It should be noted that the first SAG mask stripe pair and the second SAG mask stripe pair may be arranged in the substrate 101 as shown in fig. 11, and after completing the preparation of the SAG mask stripe pairs, the epitaxial wafer is cleaned and subjected to a first epitaxial growth in Metal-organic Chemical Vapor Deposition (MOCVD), and the structure of the first epitaxial growth is as follows: on a substrate 101 on which a first SAG mask strip pair and a second SAG mask strip pair are grown, a buffer layer 101-1, a lower respective confinement layer 102, a waveguide layer 103 and an upper respective confinement layer 104 are epitaxially grown in sequence, wherein the waveguide layer 103 is a multiple quantum well layer, and the number, thickness and composition parameters of wells of the multiple quantum well layer are grown according to the requirements of material structures in an SOA region 1 and a gain region 3.
It should be noted that the wavelength of the spontaneous emission of the SOA region 1 and the gain region 3 is longer than the wavelength of other regions, that is, the peak wavelength of the PL of the multiple quantum well material of the SOA region 1 and the gain region 3 is longer than the wavelength of other regions, thereby ensuring that the absorption loss of other waveguide regions is low.
The diffraction grating layer 104-2 of the grating region 5 of the DBR laser region may be formed on the upper confinement layer 104, or may be formed separately for the formation of a diffraction grating. When the grating layer is prepared independently for preparing the grating, and when a part of the grating is prepared by the method of holographic exposure and selective area photoetching, except that the grating area of the DBR laser is prepared into the grating, the material of the layer in other areas is etched.
After the completion of the fabrication of the diffraction grating layer 104-2, a P-type cap layer 105 is grown by second epitaxy, as shown in fig. 2. The subsequent manufacturing process may be completed by preparing the waveguide structure according to the process of a general laser, and growing the insulating medium layer, which is not described herein.
It should be noted that, in order to implement the injection current, a P-plane metal may be prepared after windowing, for example, taking a DBR laser as an example, as shown in fig. 2, the electrode 106 includes a first electrode 106a of the SOA region 1, a second electrode 106c of the gain region 3 of the DBR laser region, a third electrode 106d of the phase region 4, and a fifth electrode 106f of the tunable filter region 6, the grating region 5 of the DBR laser region has a plurality of fourth electrodes 106e, and the heavily doped contact layers between the regions are etched away to implement electrical isolation from each other, when the dual-wavelength semiconductor laser operates, the electrodes of the regions are respectively loaded with bias current, and the N-plane electrode 107 is prepared after the chip is thinned, thereby completing the preparation of the whole laser. It should be noted that, the description of the above region takes one DBR laser region as an example, and since the dual-wavelength semiconductor laser has a structure of two DBR laser regions, the above structure may be symmetrically arranged, and details are not described herein.
It should be noted that, in order to implement different optical paths, the first tunable filter region 6a and the second tunable filter region 6b may be respectively provided with two annular resonance regions, and the radii of the two annular resonance regions are different, and those skilled in the art have an incentive to adjust a specific radius value according to actual needs, which is not described herein.
Additionally, referring to fig. 11, in an embodiment, the first pair of SAG mask stripes and the second pair of SAG mask stripes are graded-shaped pairs of mask stripes.
It should be noted that, when the SOA region 1 and the gain region 3 are epitaxially grown, the intermediate region exhibits a red shift of wavelength due to the combined action of the thickness enhancement and the indium-rich, that is, the wavelength of the spontaneous emission of the material in the growth region of the selection region is longer than that of the large-area region. Therefore, the growth of the two band gap wavelength materials can be realized in the process of one-time epitaxial growth, and complex integration technologies such as butt-joint growth and the like are not needed. The SAG mask strip pair can be arranged in a gradual shape from the side of the emergent end to the side of the reflecting end, and the width of the SAG mask strip is gradually changed from wide to narrow, so that the materials of the transition region are smoothly transited.
It should be noted that, due to the arrangement of the SAG mask stripe pairs, the obtained waveguide layer 103 has different materials in each region, and the waveguide layer includes a first waveguide layer and a second waveguide layer, where the first waveguide layer includes a first waveguide 103a corresponding to the SOA region and a third waveguide 103c corresponding to the gain region 3; the second waveguide layer comprises a second waveguide 103b corresponding to the wave-combining region, a fourth waveguide 103d corresponding to the phase region 4, a fifth waveguide 103e corresponding to the grating region 5, and a sixth waveguide 103f corresponding to the tunable filter region 6.
In addition, in an embodiment, the substrate 101 is made of InP, and the upper confinement layer 104, the lower confinement layer 102, and the waveguide layer 103 are made of InGaAsP quaternary materials.
It should be noted that, the substrate 101 is an InP substrate 101, and the upper confinement layer 104 and the multiple quantum well are InGaAsP quaternary materials, and in the SAG growth technology, the InGaAsP quaternary material in the selective growth window has a red shift of wavelength due to the combined action of thickness enhancement and indium enrichment, that is, the wavelength of spontaneous emission of the material in the selective growth region is longer than that in a large area.
Additionally, in one embodiment, the grating is fabricated by holographic exposure and selective area lithography.
It should be noted that, after one-time epitaxial growth, the diffraction grating layer 104-2 may be prepared on the respective limiting layer 104 on the grating region 5 by using a holographic exposure and selective lithography method, so that the manufacturing process can be effectively simplified, and the specific grating period may be adjusted according to actual requirements, so as to ensure that the grating periods of the first grating region and the second grating region are the same.
In addition, in one embodiment, the band gap wavelength offset of the selective growth region corresponding to the first SAG mask strip pair and the second SAG mask strip pair and the large-area region is in a range of 50 to 100 nanometers.
It should be noted that the shift of the band gap wavelength between the waveguide layer 103 in the SOA region 1 and the gain region 3 and the waveguide layer 103 in other regions is determined by the size of the mask pattern, such as the mask stripe spacing and the mask stripe width, and the size of the mask stripe pair can control the shift of the band gap wavelength between the selective growth region and the large-area region to be between 50 nm and 100 nm. The offset is too large, the growth quality of the material is influenced, and the transition interface is not smooth enough, so that the reliability of the device is influenced; and the offset is too small, the offset of the final laser lasing wavelength and the peak wavelength of the PL of the passive waveguide region is too small, the absorption loss of the waveguide region to light is too large, and the final output power of the device is small.
While the preferred embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that the foregoing and various other changes, omissions and deviations in the form and detail thereof may be made without departing from the scope of this invention.

Claims (14)

1. A dual wavelength semiconductor laser comprising:
the distributed Bragg reflector DBR laser area comprises a first DBR laser area, wherein the first DBR laser area comprises a first grating area, and the first grating area is provided with a first curved waveguide;
the laser device comprises a first DBR laser area, a second DBR laser area and a first grating area, wherein the first grating area is provided with a first bent waveguide, the second grating area is provided with a second bent waveguide, a first included angle of the first bent waveguide is different from a second included angle of the second bent waveguide, gratings of the first grating area and gratings of the second grating area have the same grating period, the first included angle is an included angle formed by the first bent waveguide and a grating direction perpendicular to the first grating area, and the second included angle is an included angle formed by the second bent waveguide and a grating direction perpendicular to the second grating area.
2. The dual wavelength semiconductor laser of claim 1, wherein: the first DBR laser region comprises a first gain region and a first phase region, the first phase region is located on the light-emitting side of the first grating region, and the first gain region is located on the light-emitting side of the first phase region; the second DBR laser section includes a second gain section and a second phase section, the second phase section is located on the light exit side of the second grating section, and the second gain section is located on the light exit side of the second phase section.
3. The dual wavelength semiconductor laser of claim 2, further comprising:
the first tunable filter area is positioned on the light emitting side of the first tunable filter area;
and the second grating area is positioned at the light-emitting side of the second tunable filter area.
4. The dual wavelength semiconductor laser of claim 3, wherein: the first tunable filter region and the second tunable filter region each include at least two ring resonator regions.
5. The dual wavelength semiconductor laser of claim 4, further comprising:
the wave combining area is positioned on the light emitting sides of the first gain area and the second gain area;
and the SOA region of the semiconductor optical amplifier is positioned on the light emitting side of the combined wave region.
6. The dual wavelength semiconductor laser of claim 5, wherein: the first DBR laser area, the second DBR laser area, the first tunable filter area, the second tunable filter area, the wave combining area and the SOA area sequentially include from bottom to top: the optical waveguide device comprises a substrate, a buffer layer, a lower respective limiting layer, a waveguide layer, an upper respective limiting layer and a P-type cover layer.
7. The dual wavelength semiconductor laser of claim 6, wherein: the upper sides of the P-type cover layers corresponding to the SOA region, the first DBR laser region, the second DBR laser region, the first tunable filter region and the second tunable filter region further comprise P-type electrode layers.
8. The dual wavelength semiconductor laser of claim 6, wherein: and a diffraction grating layer is also arranged between the P-type cover layer and the upper limit layer corresponding to the first grating area and the second grating area.
9. The dual wavelength semiconductor laser of claim 6, wherein: the waveguide layers include a first waveguide layer and a second waveguide layer, and the first waveguide layer and the second waveguide layer are made of different materials, where the first waveguide layer is a waveguide layer corresponding to the SOA region, the first gain region, and the second waveguide layer is a waveguide layer corresponding to the first phase region, the second phase region, the first grating region, the second grating region, the first tunable filter region, the second tunable filter region, and the combining region.
10. A method for preparing a dual-wavelength semiconductor laser is characterized in that the dual-wavelength semiconductor laser is sequentially divided into a tunable filter area, a grating area, a phase area, a gain area, a wave combination area and an SOA area from a reflection end to an emergent end, wherein the grating area comprises a first grating area and a second grating area, and the method comprises the following steps:
preparing a first selected area medium SAG mask strip pair and a second selected area medium SAG mask strip pair on a substrate, wherein the position of the first SAG mask strip pair corresponds to the SOA area, and the position of the second SAG mask strip pair corresponds to the gain area;
sequentially growing a lower respective limiting layer, a waveguide layer and an upper respective limiting layer on the substrate through one-time epitaxy, wherein the waveguide layer comprises a first curved waveguide and a second curved waveguide, the first curved waveguide is located at a position corresponding to the first grating region, and the second curved waveguide is located at a position corresponding to the second grating region;
removing the first SAG mask strip pair and the second SAG mask strip pair, and preparing gratings at positions of the upper limiting layer corresponding to the first grating region and the second grating region respectively, wherein grating periods of the gratings of the first grating region and the gratings of the second grating region are the same, a first included angle of the first curved waveguide is different from a second included angle of the second curved waveguide, the first included angle is an included angle formed by the first curved waveguide and a grating direction perpendicular to the first grating region, and the second included angle is an included angle formed by the second curved waveguide and a grating direction perpendicular to the second grating region;
and growing a covering layer in a secondary epitaxial mode, wherein the covering layer is a P-type covering layer.
11. The method of claim 10, wherein the first and second pairs of SAG mask stripes are progressively shaped pairs of mask stripes.
12. The method of claim 10, wherein the substrate is InP and the upper confinement layer, the lower confinement layer, and the waveguide layer are InGaAsP quaternary materials.
13. The method of claim 10, wherein the grating is prepared by holographic exposure and selective area lithography.
14. The method of claim 10, wherein the band gap wavelength offset of the selective growth region corresponding to the first and second pairs of SAG mask stripes from the large area region is in a range of 50 to 100 nanometers.
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