CN114300923A - Semiconductor saturable absorption mirror and preparation method thereof - Google Patents
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Abstract
The invention provides a semiconductor saturable absorption mirror and a preparation method thereof, wherein the semiconductor saturable absorption mirror comprises the following steps: the substrate is sequentially stacked on a buffer layer, a distributed Bragg reflector layer, a lower isolation layer, a strain compensation multi-quantum well layer, an upper isolation layer, a lower dielectric film layer and an upper dielectric film layer. The strain compensation multi-quantum well layer is formed by alternately overlapping a tensile strain quantum barrier layer and a compressive strain quantum well layer, and the tensile strain quantum barrier layer is uniformly arranged on the outer surface of the strain compensation multi-quantum well layer. The total optical thickness of the lower isolation layer, the strain compensation multi-quantum well layer and the upper isolation layer is one of lambda, 1.5 lambda and 2 lambda, wherein lambda is the lasing wavelength of the Yb-doped ultrafast fiber laser. The semiconductor saturable absorber mirror has higher modulation depth, can realize automatic mode locking when being applied to an Yb-doped fiber ultrafast laser, and has stable repetition period.
Description
Technical Field
The invention belongs to the technical field of ultrafast lasers, and particularly relates to a semiconductor saturable absorber mirror and a preparation method thereof.
Background
The ultrafast laser is widely applied to the fields of material fine processing, biological medical treatment, scientific research, military, national defense and the like by virtue of the advantages of high peak power, narrow pulse width and the like. The semiconductor saturable absorption mirror is used as a mode locking device, and has the advantages of self-starting, easy integration, wide coverage wave band range, compact structure, flexible design and the like, so that the semiconductor saturable absorption mirror is widely applied to various types of ultrafast lasers such as solid, optical fibers, semiconductors and the like. Currently, picosecond-level solid-state and optical fiber lasers in the industrial market are passive mode-locked lasers based on semiconductor saturable absorber mirror (SESAM), and with the wide application of the Yb-doped optical fiber ultrafast laser, the SESAM meeting the requirements becomes the focus of attention of the ultrafast laser industry.
The requirements of the fiber laser on the characteristic parameters of the SESAM are different from those of the solid laser, the solid laser generally requires the modulation depth of the SESAM to be 0.5-3%, and the fiber laser requires the modulation depth of the SESAM to be as high as 10-30%, namely the SESAM is required to have a thicker absorption layer. The absorption layer of the SESAM applied to the Yb-doped fiber ultrafast laser is generally made of InGaAs material, wherein the In component range is 25% -32%, so that the InGaAs material and the GaAs substrate have large mismatch, the critical thickness of the InGaAs is only about 10nm, and the absorption layer of the SESAM with high modulation depth is hundreds of nanometers. The quality of the epitaxial material of the absorption layer is very easy to deteriorate due to larger lattice mismatch, so that the problems of low damage threshold and short service life of the SESAM required by the Yb-doped fiber ultrafast laser are generally caused.
At present, the domestic SESAM applied to the Yb-doped fiber laser mainly depends on import, however, the imported commodity also has the problems of low damage threshold value and short service life, and partial domestic ultrafast laser manufacturers prolong the service life of the SESAM and simplify the maintenance work by adding a point changing device. These measures only increase the number of times of using the same SESAM, but do not fundamentally solve the problems of low damage threshold and short service life.
Disclosure of Invention
Technical problem to be solved
Aiming at the technical problem, the invention provides a semiconductor saturable absorption mirror and a preparation method thereof; starting from the SESAM itself, optimizing its epitaxial structure and improving the material quality is used to at least partially solve one of the above-mentioned technical problems.
(II) technical scheme
One aspect of the present invention provides a semiconductor saturable absorber mirror, comprising: the substrate comprises a buffer layer, a distributed Bragg reflector layer, a lower isolation layer, a strain compensation multi-quantum well layer and an upper isolation layer which are sequentially stacked on the substrate; the strain compensation multi-quantum well layer is formed by alternately overlapping a tensile strain quantum barrier layer and a compressive strain quantum well layer, and the tensile strain quantum barrier layer is uniformly arranged on the outer surface of the strain compensation multi-quantum well layer.
Optionally, the substrate material comprises a GaAs material.
Optionally, the physical thickness of the upper isolation layer and the lower isolation layer is 4-10 nm.
Optionally, the total optical thickness of the lower isolation layer, the strain compensation multiple quantum well layer and the upper isolation layer is one of λ, 1.5 λ and 2 λ, where λ is the lasing wavelength of the Yb-doped ultrafast fiber laser.
Optionally, the number of cycles of the strain compensation multiple quantum well layer is 10-45.
Optionally, the tensile strain quantum barrier layer material includes GaAsP material, and the compressive strain quantum well layer material includes InGaAs material.
Optionally, the physical thicknesses of the tensile strain quantum barrier layer and the compressive strain quantum well layer are 6-15 nm.
Optionally, the photoluminescence spectrum of the tensile strain quantum well layer is λ - λ +20nm, where λ is the lasing wavelength of the Yb-doped ultrafast fiber laser.
Optionally, the semiconductor saturable absorber mirror further includes a lower dielectric film layer and an upper dielectric film layer sequentially stacked on the surface of the upper isolation layer 160, the optical thicknesses of the lower dielectric film layer and the upper dielectric film layer are both λ/4, and λ is a lasing wavelength of the Yb-doped ultrafast fiber laser.
The invention also provides a preparation method of the semiconductor saturable absorption mirror, which comprises the following steps: sequentially stacking a buffer layer, a distributed Bragg reflector layer, a lower isolation layer, a strain compensation multi-quantum well layer, an upper isolation layer, a lower dielectric film layer and an upper dielectric film layer on the surface of a substrate; the strain compensation multi-quantum well layer is formed by alternately overlapping a tensile strain quantum barrier layer and a compressive strain quantum well layer, and the tensile strain quantum barrier layer is uniformly arranged on the outer surface of the strain compensation multi-quantum well layer.
(III) advantageous effects
(1) By adopting the strain compensation multi-quantum well layer in the structure, the material quality deterioration caused by the mismatching of the heterogeneous crystal lattices can be effectively relieved, the damage threshold value is effectively improved, and the service life is effectively prolonged.
(2) The total optical thickness of the lower isolation layer, the upper isolation layer and the strain compensation multi-quantum well layer is one of lambda, 1.5 lambda and 2 lambda; the absorption of other materials to incident light is reduced, the unsaturated loss is effectively reduced, the mode locking is easy to realize, and the heat effect of the SESAM is reduced, so that the service life is longer.
(3) And a lower medium film layer and an upper medium film layer are sequentially prepared on the surface of the upper isolation layer, so that the SESAM wafer is protected, and the damage threshold of the SESAM is improved.
Drawings
FIG. 1 is a schematic diagram of the structure of an SESAM in an embodiment of the present invention;
FIG. 2 is a photoluminescence spectrum test chart of a SESAM epitaxial wafer in an embodiment of the invention;
FIG. 3 is a flow chart of a method for fabricating a semiconductor saturable absorber mirror according to an embodiment of the present invention;
FIG. 4 is a graph showing a rocking curve test of a high resolution X-ray double-crystal diffraction of a SESAM epitaxial wafer according to an embodiment of the present invention;
FIG. 5 is a graph of reflectivity measurements of a SESAM in an embodiment of the present invention;
FIG. 6 is a graph of the output spectrum of an SESAM mode-locked Yb-doped fiber laser in an embodiment of the present invention;
FIG. 7 is a mode-locked pulse sequence output by an SESAM mode-locked Yb-doped fiber laser on an oscilloscope in an embodiment of the present invention;
fig. 8 is a test chart of an autocorrelator for outputting pulses of the SESAM mode-locked Yb-doped fiber laser in the embodiment of the present invention.
110-substrate, 120-buffer layer, 130-distributed Bragg reflector layer, 140-lower isolation layer, 150-strain compensation multi-quantum well layer, 160-upper isolation layer, 170-lower dielectric film layer, 180-upper dielectric film layer, 131-GaAs layer in distributed Bragg reflector layer structure, 132-AlGaAs layer in distributed Bragg reflector layer structure, 151-tensile strain quantum barrier layer and compressive strain quantum well layer-152.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present disclosure will be described in further detail below with reference to specific embodiments and the accompanying drawings. It is to be understood that the described embodiments are only a few embodiments of the present disclosure, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the disclosure without making creative efforts, shall fall within the protection scope of the disclosure.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure; the terms "upper", "lower", "front", "rear", "left", "right", and the like, which indicate the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship that the claimed product is conventionally placed in use, and are used for convenience in describing and simplifying the description, but do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and should not be construed as limiting the present application; the terms "comprises," "comprising," and the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.
In order to overcome the defects of the prior art, the semiconductor saturable absorption mirror and the preparation method thereof are provided by the disclosure, and the problems of low damage threshold and short service life of the SESAM are solved fundamentally by optimizing the epitaxial structure and improving the material quality of the SESAM.
Fig. 1 schematically illustrates a semiconductor saturable absorption mirror provided by an embodiment of the present disclosure, and it should be noted that fig. 1 is only an example to which the embodiment of the present disclosure may be applied to help those skilled in the art understand the technical content of the present disclosure, and does not mean that the embodiment of the present disclosure may not be used in other situations.
As shown in fig. 1, the semiconductor saturable absorber mirror of the present invention comprises: the strained-layer structure includes a substrate 110, a buffer layer 120, a Distributed Bragg Reflector (DBR) layer 130, a lower isolation (space) layer 140, a strain-compensating multiple quantum well layer 150, an upper isolation (space) layer 160, a lower dielectric film layer 170, and an upper dielectric film layer 180.
In the embodiment of the present invention, the substrate 110 material includes a GaAs material, and further may include an N-type Si doped GaAs material, the physical thickness may be 450 μm, for example, and the epitaxial growth surface is a (100) surface inclined by 2 ° toward the (110) direction. The buffer layer 120 is disposed on the surface of the substrate 110, and the material includes GaAs material, and the physical thickness may be 0.5-2 μm. The DBR layer 130 is disposed on the surface of the buffer layer 120, and includes a GaAs layer 131 and an AlGaAs layer 132 sequentially stacked on the buffer layer 120, the material of the GaAs layer 131 may include a GaAs material, the material of the AlGaAs layer 132 may include an AlGaAs material, the period for forming the DBR layer may be 30, for example, the composition of the AlGaAs layer 132 may be 0.9 for the Al composition, 0.1 for the Ga composition, 1 for the As composition, and λ/4 for the optical thicknesses of the AlGaAs layer 132 and the GaAs layer 131, where λ is the lasing wavelength of the Yb-doped ultrafast fiber laser, and λ may be 1064nm, for example.
For the AlGaAs material with high Al component, the physical thickness of the buffer layer is very critical for improving the quality of the AlGaAs material, when the physical thickness of the buffer layer is more than or equal to 0.5 mu m, the high-quality AlGaAs material can be obtained, and the physical thickness of the buffer layer is required to be thicker along with the increase of the Al component value; the AlGaAs layer 132 may have a composition of, for example, 0.9 for Al, 0.1 for Ga, and 1 for As, and may effectively reduce the incorporation of "oxygen", thereby improving the material quality of the DBR130 and reducing the unsaturated absorption loss of the SESAM.
In the embodiment of the present invention, the lower space layer 140, the strain compensating multiple quantum well layer 150, and the upper space layer 160 are sequentially stacked on the surface of the AlGaAs layer 132, and the strain compensating multiple quantum well layer 150 includes the tensile strain quantum barrier layer 151 and the compressive strain quantum well layer 152 sequentially stacked on the surface of the lower space 140. The order of the strain-compensating multiple quantum well layer 150 stacked on the surface of the lower space layer 140 is the quantum barrier layer 151, the quantum well layer 152, the quantum barrier layer 151 … …, the quantum well layer 152, and the quantum barrier layer 151, and the cycle number may be, for example, 10 to 45. In the process of stacking the strain compensation multiple quantum well layer 150, the quantum barrier layer 151 is stacked on the surface of the lower space layer 140 first, and the quantum barrier layer 151 is stacked last at the end, so that the stacking period of the quantum barrier layer 151 is more than 1 than the stacking period of the quantum well layer 152. The quantum barrier layer 151 material comprises GaAsP material, wherein the As component is 0.7-0.95, the P component is 0.05-0.3, the quantum well layer 152 material comprises InGaAs material, the In component is 0.25-0.32, and the Ga component is 0.68-0.75. The lower space layer 140 and the upper space layer 160 comprise GaAs materials; the physical thicknesses of the quantum barrier layer 151 and the quantum well layer 152 are 6-15nm, and the physical thicknesses of the lower space layer 140 and the upper space layer 160 are 4-10 nm.
In the strained layer, since each monolayer has strain energy, each monolayer has a critical thickness, and when the thickness of the strained layer exceeds the critical thickness, the strained layer will undergo a relaxation phenomenon, which may deteriorate the material quality of the strained layer, thereby affecting the performance of the device. Based on the theory of a strain compensation structure, the strain compensation multi-quantum well layer 150 is arranged in a shape that a tensile strain quantum barrier layer 151 and a compressive strain quantum well layer 152 are overlapped in a crossed mode, the tensile strain quantum barrier layer 151 comprises a GaAsP material, the compressive strain quantum well layer 152 comprises an InGaAs material, strain of the GaAsP material in the tensile strain quantum barrier layer 151 relative to a GaAs substrate and strain of the InGaAs material in the compressive strain quantum well layer 152 relative to the GaAs substrate are two opposite types of strain, and a net strain value of the whole structure can be offset. Therefore, the net strain of the multiple quantum well layer 150 in each period is small, the stability of the whole strain quantum well structure is kept, and the strain relaxation phenomenon does not occur, so that the material quality is ensured.
For convenience of description, the physical thicknesses of the lower space layer 140, the quantum barrier layer 151, the quantum well layer 152, and the upper space layer 160 are respectively denoted as h1、h2、h3、h4The optical thicknesses of the lower space layer 140, the quantum barrier layer 151, the quantum well layer 152, and the upper space layer 160 are represented as h1’、h2’、h3’、h4' the refractive indices of the materials of the lower space layer 140, the quantum barrier layer 151, the quantum well layer 152, and the upper space layer 160 are represented by n1、n2、n3、n4The number of stacking periods of the strain-compensated mqw layer 150 is represented as n. h is1、h2、h3、h4And n must be selected to satisfy h1’、(n+1)h2’、nh3’、h4The total optical thickness of the sum is one of lambda, 1.5 lambda and 2 lambda, and the total optical thickness is one of lambda, 1.5 lambda and 2 lambda, so that the SESAM is a resonance type, the resonance type SESAM can obtain larger modulation depth through a multi-quantum well structure with less period, has higher saturation flux, meets the requirement of a Yb-doped fiber laser on a mode locking device, and can obtain larger modulation depth through the multi-quantum well structure with less period. The specific choice of the total optical thickness depends on the modulation depth requirement, wherein the conversion formula of the optical thickness and the physical thickness is as follows: h isi’＝hi*ni。
Fig. 2 is a photoluminescence spectrum test chart of the SESAM epitaxial wafer in the embodiment of the present invention, a photoluminescence spectrum (PL) of the compressively strained quantum well layer 152 in the strain compensation multiple quantum well layer 150 is λ - λ +20nm, and the photoluminescence spectrum of the compressively strained quantum well layer 152 is slightly longer than a lasing wavelength of the fiber laser, which is beneficial to saturation absorption of the SESAM.
In the embodiment of the invention, the lower dielectric film layer 170 and the upper dielectric film layer 180 are sequentially stacked on the surface of the upper space layer 160, and the material of the lower dielectric film layer 170 comprises Si3N4The material of the upper dielectric film layer 180 comprises SiO2The optical thicknesses of the lower medium film layer 170 and the upper medium film layer 180 can be lambda/4, the physical thicknesses can be 132.3nm and 180.9nm respectively, the medium films can play a good role in protecting the SESAM wafer, and meanwhile, the damage threshold of the SESAM can be improved.
Based on the semiconductor saturable absorber mirror, the embodiment of the invention also provides a preparation method of the semiconductor saturable absorber mirror.
Fig. 3 schematically shows a flowchart of a method for manufacturing a semiconductor saturable absorber mirror provided by an embodiment of the present invention.
As shown in fig. 3, the method may for example comprise steps S201-S207.
S201, depositing and preparing a buffer layer 120 on the surface of the substrate 110.
Specifically, the substrate 110 material includes an N-type GaAs material, and before the buffer layer 120 is prepared, the substrate 110 needs to be subjected to a deoxidation process, which may include, for example: placing the substrate 110 in a reaction chamber of Metal Organic Chemical Vapor Deposition (MOCVD), changing nitrogen gas introduced into the MOCVD reaction chamber into hydrogen gas under computer automated program control, reducing the pressure in the reaction chamber to, for example, 50mbar, then raising the temperature, and opening the AsH when the temperature in the reaction chamber rises to, for example, 350 deg.C3Valve and introducing it into the reaction chamber at AsH3Raising the temperature of the reaction chamber to, for example, 750 ℃ under the protection of an atmosphere, and stabilizing for 10 minutes; the high temperature deoxidation of the substrate 110 prior to material deposition is necessary because by the high temperature heat treatment the oxide layer on the surface of the substrate 110 is removed and the quality of the material deposited thereon is significantly improved. Meanwhile, since the substrate 110 is decomposed at a high temperature, AsH needs to be introduced3And (5) protecting.
After the substrate 110 is deoxidized, AsH is introduced3The chamber temperature is lowered to, for example, 690 c with protection, and after it has stabilized, the TMGa source is turned on for buffer layer 120 deposition, the buffer layer material comprising a GaAs material.
S202, depositing and preparing a Distributed Bragg Reflector (DBR) layer on the surface of the buffer layer 120.
Specifically, after the buffer layer 120 is deposited, the TMGa source is turned off and the chamber temperature is maintained at 690 ℃ for 30 cycles of DBR layer 130 deposition, wherein the DBR layer material comprises AlGaAs/GaAs material.
And S203, depositing a lower isolation (space) layer 140 on the surface of the DBR layer 130.
Specifically, after the deposition of the DBR layer 130 is completed, the chamber temperature is maintained at 690 ℃ to perform the deposition of the lower space layer, and the material of the lower space layer 140 includes GaAs material.
And S204, depositing and preparing the strain compensation multi-quantum well layer 150 on the surface of the lower space layer 140.
Specifically, after the deposition of the lower space layer 140 is completed, the temperature of the reaction chamber is reduced to, for example, 580 ℃, and after the temperature is stabilized, the periodic strain compensation multiple quantum well layer 150 is deposited, the strain compensation multiple quantum well layer 150 is formed by alternately stacking the tensile strain quantum barrier layer 151 and the compressive strain quantum well layer 152, and the tensile strain quantum barrier layer 151 is uniformly arranged on the outer surface of the strain compensation multiple quantum well layer 150. 151 material comprises GaAsP material and the compressively strained quantum well layer 152 material comprises InGaAs material. The temperature of the reaction chamber is lowered to, for example, 580 c In order to obtain a high-quality strained quantum well material, and the InGaAs/GaAsP multiple quantum well growth mode is suppressed from being converted from two-dimensional (2D) to three-dimensional (3D), mainly because the lattice mismatch between the InGaAs epitaxial layer having a high In composition and the GaAs substrate is large, and the induced stress causes lattice relaxation. In the process of rapid migration of III and V group atoms, In atoms easily reach the growth surface defects to form certain nucleation positions with lower energy, so that In-rich islands are formed, and the epitaxial layer is converted from 2D growth to 3D growth, thereby forming a large number of defects to influence the quality of the material.
And S205, overlaying a deposition preparation upper isolation (space) layer 160 on the surface of the strain compensation multi-quantum well layer 150.
Specifically, after the strain compensation multiple quantum well layer 150 is deposited, the temperature of the reaction chamber is kept at 580 ℃, the deposition of the upper space layer 160 is carried out, the material of the upper space layer 160 comprises a GaAs material, and after the deposition of the upper space layer 160 in an overlapping mode is finished, the total optical thickness of the lower space140, the strain compensation multiple quantum well layer 150 and the upper space layer 160 is one of lambda, 1.5 lambda and 2 lambda.
S206, depositing a lower dielectric film layer 170 on the surface of the upper space layer 160.
After the deposition of the upper space layer 160 is completed, the temperature of the reaction chamber is reduced to 500 ℃, for example, after the temperature is stabilized, the hydrogen introduced into the reaction chamber is switched to nitrogen, and annealing is performed for 10 minutes in a nitrogen environment, so that a wafer 1 is obtained; the wafer after deposition and annealing is placed in a reaction chamber of a Plasma Enhanced Chemical Vapor Deposition (PECVD) device for preparing the lower dielectric film layer 170. The lower dielectric film layer 170 may be, for example, Si3N4The preparation conditions of the dielectric film layer can be, for example: when the temperature of the reaction chamber is raised to, for example, 280 deg.C, SiH is added4And NH3Introducing into a reaction chamber, and adjusting SiH4And NH3Flow rate of gas such that Si3N4The growth rate of the dielectric film is 1.0 nm/s.
S207, depositing the upper dielectric film layer 180 on the surface of the lower dielectric film layer 170.
Specifically, after the preparation of the lower dielectric film 170 is completed, the preparation of the upper dielectric film 180 is continued in the reaction chamber of the PECVD apparatus. The upper dielectric film layer 180 can be, for example, SiO2The preparation conditions of the dielectric film layer can be, for example: keeping the temperature of the reaction chamber at 280 ℃ and adding SiH4And N2Introducing O into the reaction chamber, and regulating SiH4And N2Flow of O gas such that SiO2The growth rate of the dielectric film is 1.0 nm/s.
The characteristic parameters of the epitaxial wafer are correspondingly tested by relevant testing methods before the preparation of the lower dielectric film layer 170 and the upper dielectric film layer 180, and the consistency with the design structure is ensured.
It should be noted that: in order to meet the requirement that the modulation depth of the SESAM reaches 10-30% of the requirement of the optical fiber laser, the technical scheme provided by the application can meet the requirement by setting the total optical thickness of the lower space layer 140, the multiple quantum well layer 150 and the upper space layer 160 to be one of lambda, 1.5 lambda and 2 lambda, so that the total optical thickness of the lower space layer 140, the multiple quantum well layer 150 and the upper space layer 160 is set to be one of lambda, 1.5 lambda and 2 lambda, and the physical thicknesses of the lower space layer 140, the multiple quantum well layer 150 and the upper space layer 160 and the periodicity of the multiple quantum well layer 150 can be freely selected in respective parameter ranges without specifically specifying the physical thicknesses of the lower space layer 140, the multiple quantum well layer 150 and the upper space layer 160 and the periodicity of the multiple quantum well layer 150.
In order to more clearly illustrate the technical solution of the present application, the following description is given by way of illustrative specific embodiments.
Example 1; the substrate 110 is made of an N-type Si-doped GaAs material, the physical thickness of the substrate is 450 mu m, and the epitaxial growth surface is a (100) surface with a deflection angle of 2 degrees towards the (110) direction; the buffer layer is arranged on the surface of the substrate 110, and is made of GaAs material with the physical thickness of 1 μm; the Distributed Bragg Reflector (DBR) layer 130 is disposed on the surface of the buffer layer 120, and includes a plurality of layers sequentially stacked on the buffer layer 1The period of forming the DBR layer is 30 for the GaAs layer 131 and the AlGaAs layer 132 on the substrate 20, the composition of the AlGaAs layer 132 is that Al component is 0.9, Ga component is 0.1, As component is 1, the optical thicknesses of the AlGaAs layer 132 and the GaAs layer 131 are both lambda/4, lambda is the lasing wavelength of the Yb-doped ultrafast fiber laser and is 1064nm, and the surface of the AlGaAs layer 132 is sequentially provided with a lower space layer 140, a strain compensation multi-quantum well layer 150, an upper space layer 160, a lower dielectric film layer 170 and an upper dielectric film layer 180 in a stacking mode. The lower space layer 140 and the upper space layer 160 are made of GaAs, the physical thicknesses of the lower space layer and the upper space layer are both 4nm, and the refractive index of the GaAs is 3.454; the strain compensation multi-quantum well layer 150 has the cycle number of 30 and comprises a quantum barrier layer 151 and a quantum well layer 152 which are sequentially stacked on the surface of the lower space 140; wherein the quantum barrier layer 151 is made of GaAsP material, has a refractive index of 3.521, a physical thickness of 9.7nm, a periodicity of 31, the quantum well layer 152 is made of InGaAs material, has a refractive index of 3.472, a thickness of 10nm, a periodicity of 30, and the lower dielectric film layer 170 is made of Si3N4The material of the upper dielectric film layer 180 is SiO2A material; the physical thicknesses of the lower dielectric film layer 170 and the upper dielectric film layer 180 are 132.3nm and 180.9nm respectively. The optical thickness of the lower space140 is: 4 × 3.454 ═ 13.816nm, the total optical thickness of the quantum barrier layer 151 is: 31 × 9.7 × 3.521 ═ 1058.7647nm, the total optical thickness of the quantum well layers 152 was: 30 × 10 × 3.472 ═ 1041.6nm, the optical thickness of the upper space layer 160 is: 4 × 3.454 ═ 13.816 nm; the total optical thickness of the lower space140, the strain-compensating multiple quantum well layer 150 and the upper space160 is as follows: 13.816+1058.7647+1041.6+13.816 ≈ 2127.9967nm ≈ 2 λ 2128 nm; the total optical thickness of the lower space140, the strain compensation multi-quantum well layer 150 and the upper space160 is 2 lambda, and the requirements of the optical fiber laser on the SESAM modulation depth are met.
Example 2, example 2 differs from example 1 in that: the number of cycles of the strain compensation multiple quantum well layer 150 is 45, the physical thickness of the quantum barrier layer 151 is 7.18nm, the number of cycles is 46, the physical thickness of the quantum well layer 152 is 6nm, the number of cycles is 45, and the total optical thickness of the quantum barrier layer 151 is as follows: 46 × 7.18 × 3.521 ═ 1162.9159nm, the total optical thickness of the quantum well layers 152 was: 45 × 6 × 3.472 ═ 937.44nm, and the other parameters were the same as in example 1. The total optical thickness of the lower space140, the strain-compensating multiple quantum well layer 150 and the upper space160 is as follows: 13.816+1162.9159+937.44+13.816 is 2127.9879nm and 2 lambda is 2128nm, the total optical thickness of the lower space140, the strain compensation multiple quantum well layer 150 and the upper space160 is 2 lambda, and the requirements of the optical fiber laser on the SESAM modulation depth are met.
Other implementation details are similar to those of embodiment 1 and are not described herein again.
Example 3, example 3 differs from example 1 in that: the number of cycles of the strain compensation multiple quantum well layer 150 is 20, the physical thickness of the quantum barrier layer 151 is 8.381nm, the number of cycles is 21, the physical thickness of the quantum well layer 152 is 6nm, the number of cycles is 20, and the total optical thickness of the quantum barrier layer 151 is as follows: 21 × 8.381 × 3.521 ═ 619.7nm, the total optical thickness of the quantum well layers 152 was: 20 × 6 × 3.472 ═ 416.64nm, and the other parameters were the same as in example 1. The total optical thickness of the lower space140, the strain-compensating multiple quantum well layer 150 and the upper space160 is as follows: 13.816+619.7+416.64+13.816 is 1063.972nm and lambda is 1064nm, the total optical thickness of the lower space140, the strain compensation multiple quantum well layer 150 and the upper space160 is lambda, and the requirements of the fiber laser on the SESAM modulation depth are met.
Other implementation details are similar to those of embodiment 1 and are not described herein again.
Example 4, example 4 differs from example 1 in that: the number of cycles of the strain compensation multiple quantum well layer 150 is 30, the physical thickness of the quantum barrier layer 151 is 6.735nm, the number of cycles is 31, the physical thickness of the quantum well layer 152 is 6nm, the number of cycles is 30, and the total optical thickness of the quantum barrier layer 151 is as follows: 31 × 6.735 × 3.521 ═ 735.132nm, the total optical thickness of the quantum well layers 152 was: 30 × 8 × 3.472 ═ 833.28nm, and the other parameters were the same as in example 1. The total optical thickness of the lower space140, the strain-compensating multiple quantum well layer 150 and the upper space160 is as follows: 13.816+735.132+833.28+13.816 is 1596.044nm which is approximately equal to 1.5 lambda is 1596nm, the total optical thickness of the lower space140, the strain compensation multi-quantum well layer 150 and the upper space160 is 1.5 lambda, and the requirements of the optical fiber laser on the SESAM modulation depth are met.
Other implementation details are similar to those of embodiment 1 and are not described herein again.
Fig. 4 is a high resolution X-ray twin diffraction rocking curve of the SESAM epitaxial wafer according to the embodiment of the present invention, and since the AlGaAs/GaAs DBR and the strain-compensated InGaAs/GaAsP multi-quantum well are both multi-period structures, as shown in fig. 4, the rocking curve will have periodic diffraction peaks, and the periodic thickness of the epitaxial material can be calculated by the distance between adjacent diffraction peaks.
Fig. 5 is a reflectivity test chart of the SESAM according to the embodiment of the present invention, where the reflectivity is a comprehensive characterization of the AlGaAs/GaAs DBR and the InGaAs/GaAsP multiple quantum well, and the epitaxial growth parameters of the AlGaAs/GaAs DBR and the InGaAs/GaAsP can be adjusted accordingly according to the reflectivity to obtain the epitaxial material meeting the requirement.
Fig. 6 is an output spectrum of an SESAM applied to a Yb-doped fiber ultrafast laser in a linear cavity according to an embodiment of the present invention, wherein the center wavelength of an output pulse is 1064.5 nm.
Fig. 7 is a mode-locked pulse sequence of the SESAM applied to the output of the Yb-doped fiber ultrafast laser of the wire cavity in the embodiment of the present invention on an oscilloscope.
Fig. 8 shows the result of an autocorrelation apparatus test in which an SESAM according to an embodiment of the present invention is applied to an output pulse of a Yb-doped fiber ultrafast laser in a linear cavity, where the pulse width of the output pulse is 9.6 ps.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A semiconductor saturable absorber mirror, comprising:
a substrate (110);
the substrate comprises a buffer layer (120), a distributed Bragg reflector layer (130), a lower isolation layer (140), a strain compensation multi-quantum well layer (150) and an upper isolation layer (160) which are sequentially stacked on the substrate (110);
the strain compensation multi-quantum well layer (150) is formed by alternately overlapping a tensile strain quantum barrier layer (151) and a compressive strain quantum well layer (152), and the tensile strain quantum barrier layer (151) is uniformly arranged on the outer surface of the strain compensation multi-quantum well layer (150).
2. A semiconductor saturable absorber mirror as claimed in claim 1, wherein the substrate (110) material comprises GaAs material.
3. The semiconductor saturable absorber mirror of claim 1, wherein the physical thickness of the lower isolation layer (140), the upper isolation layer (160) is 4-10 nm.
4. The semiconductor saturable absorber mirror of claim 1, wherein the lower isolation layer (140), the strain compensating multiple quantum well layer (150), and the upper isolation layer (160) have a total optical thickness of one of λ, 1.5 λ, and 2 λ, where λ is a lasing wavelength of the Yb-doped ultrafast fiber laser.
5. The semiconductor saturable absorber mirror of claim 1, wherein the strain compensating multiple quantum well layer (150) has a cycle number of 10-45.
6. The semiconductor saturable absorber mirror of claim 1, wherein the tensile strained quantum barrier layer (151) material comprises GaAsP material, and the compressively strained quantum well layer (152) material comprises InGaAs material.
7. The semiconductor saturable absorber mirror of claim 1, wherein the tensile strained quantum barrier layer (151), the compressively strained quantum well layer (152) have a physical thickness of 6-15 nm.
8. The semiconductor saturable absorber mirror of claim 1, wherein the compressively strained quantum well layer (152) has a photoluminescence spectrum of λ - λ +20nm, where λ is a lasing wavelength of a Yb-doped ultrafast fiber laser.
9. The semiconductor saturable absorber mirror of claim 1, further comprising: the lower dielectric film layer (170) and the upper dielectric film layer (180) are sequentially stacked on the surface of the upper isolation layer (160), the optical thicknesses of the lower dielectric film layer (170) and the upper dielectric film layer (180) are lambda/4, and lambda is the lasing wavelength of the Yb-doped ultrafast fiber laser.
10. A method for preparing a semiconductor saturable absorber mirror applied to any one of claims 1 to 9, comprising: the method comprises the steps that a buffer layer (120), a distributed Bragg reflector layer (130), a lower isolation layer (140), a strain compensation multi-quantum well layer (150), an upper isolation layer (160), a lower dielectric film layer (170) and an upper dielectric film layer (180) are sequentially stacked on the surface of a substrate (110), wherein the strain compensation multi-quantum well layer (150) is formed by alternately stacking a tensile strain quantum barrier layer (151) and a compressive strain quantum well layer (152), and the tensile strain quantum barrier layer (151) is uniformly distributed on the outer surface of the strain compensation multi-quantum well layer (150).
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| CN116316032A (en) * | 2023-05-23 | 2023-06-23 | 青岛翼晨镭硕科技有限公司 | Doped semiconductor saturable absorber mirror, preparation method thereof and laser |
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