Composite semiconductor saturable absorption mirror, preparation method and application thereof

Abstract

The invention relates to a composite semiconductor saturable absorber mirror, a preparation method and application thereof. The composite semiconductor saturable absorption mirror comprises a substrate, a buffer layer, a Bragg reflection layer and a periodic grating layer which are sequentially arranged from bottom to top, the periodic grating layer comprises a plurality of first grating units, the plurality of first grating units are uniformly arranged on the Bragg reflection layer, and a second grating unit is arranged between every two adjacent first grating units; wherein the first grating unit comprises an absorption layer, a cover layer and a first dielectric film layer which are sequentially arranged from bottom to top, and the second grating unit comprises a second dielectric film layer. Based on the structure. By combining the saturable absorption mirror with the pulse width compression grating, the compression of the pulse width is realized, and the output power of the laser is effectively improved. In addition, the structural design also improves the integration level of the system, so that the whole laser system is more compact and efficient.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a composite semiconductor saturable absorber mirror, a preparation method and applications thereof. Background Art

[0002] Ultrashort pulse lasers are of great significance in scientific research and industrial applications, especially in the fields of time-resolved spectroscopy and precision machining, due to their narrow output pulse width, high peak power, and wide spectrum. The main means of achieving ultrashort pulses is mode-locking technology, in which the pulse width is limited by the gain linewidth of the gain medium. In order to obtain a narrower pulse width, a dispersion element is usually added to the mode-locking cavity.

[0003] At present, when using dispersive elements such as standards for pulse width broadening and compression, there are problems such as high processing accuracy requirements and large intra-cavity losses, which are not conducive to the stability of mode locking and system integration. Summary of the invention

[0004] The embodiments of the present application provide a composite semiconductor saturable absorber mirror, a preparation method and an application thereof, which at least solve the problems of poor locking stability and low system integration due to high processing precision requirements and large intra-cavity losses when using dispersion elements such as standard tools for pulse width broadening and compression in related technologies.

[0005] According to a first aspect of an embodiment of the present application, there is provided a composite semiconductor saturable absorber mirror, comprising: a substrate, a buffer layer, a Bragg reflection layer and a periodic grating layer arranged in sequence from bottom to top;

[0006] The periodic grating layer comprises a plurality of first grating units, wherein the plurality of first grating units are uniformly arranged on the Bragg reflection layer, and a second grating unit is arranged between two adjacent first grating units;

[0007] The first grating unit includes an absorption layer, a cover layer and a first dielectric film layer which are arranged in sequence from bottom to top, and the second grating unit includes a second dielectric film layer.

[0008] According to a second aspect of an embodiment of the present application, a method for preparing a composite semiconductor saturable absorber mirror is provided, comprising:

[0009] epitaxially growing a buffer layer, a Bragg reflection layer, an absorption layer and a cap layer on the substrate in sequence;

[0010] preparing a silicon dioxide mask layer on the cap layer by a plasma enhanced chemical vapor deposition method;

[0011] Spin coating an electron beam gel layer on the silicon dioxide mask layer, and generating a periodic one-dimensional grating pattern on the electron beam gel layer by electron beam exposure;

[0012] Performing a developing process on the periodic one-dimensional grating pattern by using a preset developing solution to remove the electron beam gel layer outside the periodic one-dimensional grating pattern area;

[0013] Generating a nanometer pattern structure corresponding to the periodic one-dimensional grating pattern on the silicon dioxide mask layer by a reactive ion etching method, and removing the electron beam gel layer on the silicon dioxide mask layer;

[0014] Using the nano-pattern structure as a mask, etching the cap layer and the absorption layer by inductively coupled plasma etching to remove the cap layer and the absorption layer corresponding to the nano-pattern structure on the Bragg reflection layer;

[0015] After removing the nano-pattern structure and cleaning the sample, a first dielectric film layer is deposited on the cover layer, and a second dielectric film layer is deposited on the Bragg reflection layer, so as to generate a first grating unit based on the absorption layer, the cover layer and the first dielectric film layer, and to generate a second grating unit based on the second dielectric film layer.

[0016] According to a third aspect of an embodiment of the present application, a saturable absorption device is provided, comprising: a compound semiconductor saturable absorption mirror, wherein the compound semiconductor saturable absorption mirror is the compound semiconductor saturable absorption mirror described in the first aspect, or is prepared based on the method described in the second aspect.

[0017] According to a fourth aspect of an embodiment of the present application, there is provided an application of the composite semiconductor saturable absorber mirror described in the first aspect in the field of semiconductor lasers.

[0018] A composite semiconductor saturable absorber mirror provided in an embodiment of the present application can improve the stability of mode locking and the integration of the system. Specifically, the composite semiconductor saturable absorber mirror includes a substrate, a buffer layer, a Bragg reflection layer and a periodic grating layer arranged in sequence from bottom to top. Further, the periodic grating layer includes a plurality of first grating units, the plurality of first grating units are evenly arranged on the Bragg reflection layer, and a second grating unit is arranged between two adjacent first grating units; wherein the first grating unit includes an absorption layer, a cover layer and a first dielectric film layer arranged in sequence from bottom to top, and the second grating unit includes a second dielectric film layer. The first grating unit and the second grating unit in the periodic grating layer are arranged alternately to form two groups of pulse width compression gratings. Based on the above structure, it is possible to achieve effective compression of the laser pulse width, thereby improving the pulse characteristics of the laser. At the same time, the resonant microcavity structure composed of the Bragg reflection layer and the first dielectric film layer can enhance the intensity of the light field within a specific wavelength range and significantly improve the output power of the laser. The resonant microcavity increases the standing wave field intensity of the photon in the cavity through multiple reflections and interference effects, thereby improving the output efficiency and stability of the laser. In summary, by combining the saturable absorber mirror with the pulse width compression grating, not only the pulse width is compressed, but also the output power of the laser is effectively improved. In addition, this structural design also improves the system integration, making the entire laser system more compact and efficient.

[0019] Details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can be obtained based on these drawings without creative work.

[0021] Figure 1 A schematic structural diagram of a composite semiconductor saturable absorber mirror provided in an embodiment of the present application.

[0022] Figure 2 A flow chart of a method for preparing a composite semiconductor saturable absorber mirror provided in an embodiment of the present application.

[0023] Figure 3 This is a reflection spectrum diagram of a composite semiconductor saturable absorber provided in an embodiment of the present application.

[0024] Figure 4A photoluminescence spectrum of a composite semiconductor saturable absorber provided in an embodiment of the present application.

[0025] Figure 5 This is a nonlinear test diagram of a composite semiconductor saturable absorber mirror provided in an embodiment of the present application.

[0026] In the figure, 1, substrate; 2, buffer layer; 3, Bragg reflection layer; 4, absorption layer; 5, cover layer; 6, first dielectric film layer; 7, second dielectric film layer. DETAILED DESCRIPTION

[0027] Embodiments of the present embodiment will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present embodiment are shown in the accompanying drawings, it should be understood that the present embodiment can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein, which are instead provided for a more thorough and complete understanding of the present embodiment. It should be understood that the drawings and embodiments of the present embodiment are only for exemplary purposes and are not intended to limit the scope of protection of the present embodiment.

[0028] Some embodiments of the present application are described in detail below in conjunction with the accompanying drawings. In the case where there is no conflict between the embodiments, the following embodiments and the features in the embodiments can be combined with each other. In addition, the step sequence in the following method embodiments is only an example and not a strict limitation.

[0029] In the field of modern optical communication and optoelectronics, mode-locked lasers are widely used in optical communication, precision measurement, and ultrafast spectroscopy because of their ability to produce ultrashort pulse widths and high peak powers. However, traditional mode-locked lasers still face many challenges in achieving high output power and stable mode locking. These challenges mainly lie in how to further compress pulse width and increase output power without increasing system complexity.

[0030] In order to solve the above problems, there are various improvement schemes, including the use of saturable absorber mirrors and Bragg reflectors. Saturable absorber mirrors can achieve passive mode locking through nonlinear absorption mechanism, thereby generating ultrashort pulses. However, conventional saturable absorber mirrors are prone to thermal effects under high power conditions, resulting in unstable mode locking. Bragg reflectors achieve high reflectivity through the interference effect of multilayer optical films, but their effect on pulse compression is limited.

[0031] To solve the above problems, the embodiments of the present application provide a composite semiconductor saturable absorber mirror and a method for preparing the same, so as to achieve the compression of laser pulse width and the improvement of output power by combining the saturable absorber mirror with a pulse width compression grating, while improving the stability of laser mode locking and the integration of the system.

[0032] Figure 1 This is a schematic diagram of the structure of a composite semiconductor saturable absorber provided in an embodiment of the present application. Figure 1 As shown, the composite semiconductor saturable absorber mirror comprises a substrate 1, a buffer layer 2, a Bragg reflection layer 3 and a periodic grating layer which are arranged in sequence from bottom to top.

[0033] Specifically, the periodic grating layer includes a plurality of first grating units, and the plurality of first grating units are uniformly arranged on the Bragg reflection layer 3, and a second grating unit is arranged between two adjacent first grating units. The first grating unit includes an absorption layer 4, a cover layer 5 and a first dielectric film layer 6 arranged in sequence from bottom to top, and the second grating unit includes a second dielectric film layer 7.

[0034] In this embodiment, the substrate 1 is located at the bottom layer, providing the base support of the entire structure; the buffer layer 2 is arranged on the substrate 1, and is used to alleviate the lattice mismatch between the substrate 1 and the upper layer material, thereby improving the quality of the overall structure; the Bragg reflection layer 3 is placed on the buffer layer 2, and is composed of multiple layers of materials, and forms a high reflectivity mirror by reflecting light of a specific wavelength; the periodic grating layer is located on the Bragg reflection layer 3, and includes a plurality of grating units. The periodic grating layer includes a plurality of first grating units uniformly distributed on the Bragg reflection layer 3, and a second grating unit is provided between every two adjacent first grating units. Through this structure, a periodic grating arrangement can be formed to improve the optical properties of the grating layer.

[0035] In this embodiment, the first grating unit includes an absorption layer 4, a cover layer 5 and a first dielectric film layer 6 which are arranged in sequence from bottom to top. The absorption layer 4 is located at the bottom layer and is used to absorb light of a specific wavelength; the cover layer 5 is arranged on the absorption layer 4 and is used to protect the absorption layer 4 and improve the optical properties; the first dielectric film layer 6 is located at the top layer and has an optical interference function.

[0036] The second grating unit includes a second dielectric film layer 7, which is alternately arranged with the first grating unit to form a periodic structure.

[0037] In an optional embodiment, the period of the first grating unit may be 300 nm to 1500 nm, and the width may be 100 nm to 800 nm.

[0038] Functionally, the Bragg reflection layer 3 in the composite semiconductor saturable absorber and the first grating unit and the second grating unit of the periodic structure respectively form two groups of pulse width compression gratings, which can effectively compress the pulse width. At the same time, the resonant microcavity formed by the Bragg reflection layer 3 and the first dielectric film layer 6 can significantly increase the output power of the laser.

[0039] By combining the saturable absorber mirror with a pulse width compression grating, and combining the pulse width compression grating with a resonant microcavity structure, the composite semiconductor saturable absorber mirror provided in the embodiment of the present application can not only effectively compress the pulse width, but also significantly increase the output power of the laser, thereby improving the stability of the mode locking and the integration of the system.

[0040] Furthermore, the composite semiconductor saturable absorber provided in the embodiment of the present application utilizes the ingenious structural combination of the Bragg reflection layer 3 and the periodic grating layer to achieve efficient compression of light pulses, and utilizes the resonant microcavity structure to improve the output power and performance stability of the system.

[0041] Through the above design, the present application can provide higher laser output power and stable mode-locking operation while achieving efficient optical pulse compression, and is suitable for laser system applications with high integration requirements.

[0042] In an optional embodiment, the absorption layer 4 includes a quantum dot layer or a quantum well layer. In this embodiment, the absorption layer 4 can be composed of a quantum dot layer or a quantum well layer. Quantum dots and quantum wells are both semiconductor nanostructures that can regulate the absorption and emission characteristics of light.

[0043] In this embodiment, the material of the quantum dot layer is a mixed material of indium arsenide (InAs) and gallium arsenide (GaAs), or a mixed material of indium arsenide (InAs) and indium phosphide (InP).

[0044] InAs / GaAs quantum dots: InAs has a narrow bandgap, suitable for operation in a shorter wavelength range, while GaAs provides good lattice matching and stability.

[0045] InAs / InP quantum dots: InP as substrate 1 material, combined with InAs, can work in different wavelength ranges, especially in the long wavelength range (such as infrared light).

[0046] Based on the above quantum dot layer, the wavelength of absorption and emission can be precisely adjusted by changing the size of the quantum dots. In addition, due to the quantum confinement effect, the quantum dots have higher absorption and emission efficiency.

[0047] In this embodiment, the material of the quantum well layer is a mixed material of InAs and GaAs, or a mixed material of InAs and InP.

[0048] InAs / GaAs quantum well: composed of InAs and GaAs. InAs provides high electron mobility, while GaAs as a cladding layer provides good lattice matching and stability.

[0049] InAs / InP quantum well: composed of InAs and InP, this combination performs well in different wavelength ranges, especially in the long-wavelength infrared range.

[0050] Based on the above quantum well layer, electrons and holes have high mobility, which helps to improve device performance. At the same time, the quantum well material has a narrow band gap, which helps to achieve efficient absorption and emission within a specific wavelength range. In addition, the thickness of the quantum well can be precisely controlled to adjust its electronic energy level and optical properties.

[0051] Both the quantum dot layer and the quantum well layer can achieve efficient light absorption and emission through the quantum confinement effect, enhancing the output performance and stability of the laser. The quantum dot layer achieves wavelength tunability by adjusting the size, while the quantum well layer achieves high mobility and narrow bandgap characteristics through thickness control and material selection.

[0052] In an optional embodiment, the thickness of the first dielectric film layer 6 and the second dielectric film layer 7 are both λ / 4n, where λ represents the designed operating wavelength and n is the refractive index of the dielectric film; the first dielectric film layer 6 and the second dielectric film layer 7 are silicon dioxide thin film layers.

[0053] In this embodiment, the thickness of the first dielectric film layer 6 and the second dielectric film layer 7 are both designed to be λ / 4n, where λ represents the designed working wavelength and n is the refractive index of the dielectric film. This thickness design is based on the principle of light interference. The dielectric film of this thickness can also be used as an anti-reflection film to achieve the best reflection and transmission effects and improve the overall optical performance. In addition, the silicon dioxide thin film layer can make the first dielectric film layer and the second dielectric film layer 7 have excellent transparency and durability.

[0054] Based on the above-mentioned composite semiconductor saturable absorber mirror, an embodiment of the present application further provides a method for preparing the composite semiconductor saturable absorber mirror.

[0055] Figure 2 This is a flow chart of a method for preparing a composite semiconductor saturable absorber mirror provided in an embodiment of the present application. Figure 2 As shown, the method comprises the following steps:

[0056] Step S201 , epitaxially growing a buffer layer, a Bragg reflection layer, an absorption layer and a cap layer in sequence on a substrate.

[0057] In this embodiment, appropriate substrate materials can be selected according to specific implementation needs, such as silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), etc., and the above substrate materials can provide good mechanical support and thermal conductivity. Optionally, after cleaning the substrate to remove surface contaminants and ensuring the surface is clean, a buffer layer, a Bragg reflection layer, an absorption layer and a cap layer can be epitaxially grown on the substrate in sequence.

[0058] In an optional embodiment, when cleaning the substrate, the cleaning solvent used may include acetone, isopropyl alcohol, etc., and deionized water may also be used for rinsing. After cleaning, the substrate is dried.

[0059] When epitaxially growing a buffer layer, a Bragg reflection layer, an absorption layer and a cap layer on a substrate in sequence, the operation can be performed by epitaxial growth technology. For example, each layer structure can be generated in sequence on the substrate by molecular beam epitaxy or metal organic chemical vapor deposition.

[0060] The buffer layer is used to reduce the lattice mismatch between the substrate and the upper material, and is usually made of a material that matches the substrate, such as aluminum gallium arsenide (AlGaAs), indium gallium phosphide (InGaP), etc.

[0061] In an optional embodiment, when preparing the buffer layer, the preparation temperature may be 500° C. to 700° C., and the growth rate may be 1 μm / h to 5 μm / h.

[0062] The Bragg reflector includes a multilayer structure of high-refractive index and low-refractive index materials, and achieves high reflectivity for light of a specific wavelength by controlling the thickness and order of each layer of material. Among them, the high-refractive index material may include gallium arsenide (GaAs), gallium nitride (GaN), etc., and the low-refractive index material may include silicon oxide (SiO2), silicon nitride (Si3N4), etc.

[0063] In an optional embodiment, the number of layers of the Bragg reflector may include 10 to 40 pairs of high refractive index and low refractive index materials; the thickness of each layer may be λ / 4n, wherein λ represents the designed operating wavelength and n is one quarter of the refractive index of the dielectric film. Optionally, the thickness of each layer may be 50nm to 100nm; the preparation temperature may be 500°C to 700°C.

[0064] An absorption layer is grown on the Bragg reflection layer, and the absorption layer is usually composed of a quantum dot or quantum well structure, and is specifically realized by using materials such as InAs and GaAs through epitaxial growth technology.

[0065] That is, the absorption layer includes a quantum dot layer or a quantum well layer, wherein the material of the quantum dot layer is a mixed material of InAs and GaAs, or a mixed material of InAs and InP; the material of the quantum well layer is a mixed material of InAs and GaAs, or a mixed material of InAs and InP.

[0066] In an optional embodiment, the thickness of the absorption layer of the quantum dot structure may be 2nm to 10nm, and the absorption layer of the quantum well structure may be 5nm to 20nm; the preparation temperature may be 450°C to 550°C.

[0067] A cap layer is grown on the absorption layer, which can be used to protect the absorption layer and provide additional optical functions. The material of the cap layer may include GaAs, etc., and can also be achieved by epitaxial growth technology.

[0068] In an optional embodiment, the thickness of the cap layer may be 50 nm to 200 nm, and the preparation temperature may be 500° C. to 700° C.

[0069] Step S202 , preparing a silicon dioxide mask layer on the cap layer by a plasma enhanced chemical vapor deposition method.

[0070] In this embodiment, when depositing the silicon dioxide mask layer, the thickness and uniformity of the silicon dioxide film layer can be ensured by controlling the flow rate of the reaction gas (such as silane and oxygen), the reaction temperature and the pressure.

[0071] In an optional embodiment, the thickness of the silicon dioxide mask layer may be 50 nm to 200 nm.

[0072] When a silicon dioxide mask layer is prepared on the cap layer by a plasma enhanced chemical vapor deposition method, the process parameters used include: a SiH4 flow rate of 10 sccm to 15 sccm; a N2O flow rate of 400 sccm to 600 sccm; a N2 flow rate of 200 sccm to 300 sccm; a pressure of 90 Pa; an RF power supply of 50 W; a temperature of 300° C. to 350° C.; and a deposition time of 10 s to 200 s.

[0073] Step S203, spin-coating an electron beam gel layer on the silicon dioxide mask layer, and generating a periodic one-dimensional grating pattern on the electron beam gel layer by an electron beam exposure method.

[0074] In this embodiment, electron beam glue (such as polymethyl methacrylate, etc.) is evenly spin-coated on the silicon dioxide mask layer to form a uniform electron beam glue layer.

[0075] In an optional embodiment, when spin coating the electron beam gel layer, the spin coating speed may be 1000 rpm to 5000 rpm; the spin coating thickness may be 100 nm to 500 nm; the baking temperature may be 80° C. to 200° C.; and the baking time may be 1 minute to 5 minutes.

[0076] Then, an electron beam exposure device can be used to generate the desired periodic one-dimensional grating pattern on the electron beam gel layer. Specifically, a precise grating pattern can be achieved by controlling the intensity of the electron beam, the exposure time and the pattern design. Optionally, the period of the periodic one-dimensional grating pattern can be 300nm to 1500nm, and the width can be 100nm to 800nm.

[0077] In an optional embodiment, when a periodic one-dimensional grating pattern is prepared by an electron beam exposure device, the electron beam energy may be 20 keV to 50 keV; the exposure dose may be 100 μC / cm 2 ~1000μC / cm 2 ; The exposure time can be set according to specific implementation needs.

[0078] Step S204 , developing the periodic one-dimensional grating pattern with a preset developer to remove the electron beam glue layer outside the periodic one-dimensional grating pattern area.

[0079] In this embodiment, the sample obtained in step S203 can be immersed in a preset developer, which selectively dissolves the unexposed electron beam glue. By controlling the development time and the developer concentration, it can be ensured that only the electron beam glue layer outside the periodic one-dimensional grating pattern area is removed.

[0080] The preset developer includes a mixed solution of methyl isobutyl ketone and isopropyl alcohol, wherein the ratio of methyl isobutyl ketone to isopropyl alcohol is 1:3.

[0081] In an optional embodiment, the developing time may be 30 seconds to 2 minutes. After the developing is completed, the developed sample may be cleaned with a cleaning solvent such as pure isopropanol for 30 seconds to 1 minute, and may be dried with nitrogen gas after cleaning.

[0082] Further optionally, after cleaning, the sample may be placed on a hot plate at 110° C. and baked for 1 min to further evaporate the water in the electron beam gel.

[0083] Step S205 , generating a nano pattern structure corresponding to the periodic one-dimensional grating pattern on the silicon dioxide mask layer by a reactive ion etching method, and removing the electron beam glue layer on the silicon dioxide mask layer.

[0084] In this embodiment, etching can be performed on the silicon dioxide mask layer by reactive ion etching technology to form a nano pattern structure corresponding to the grating pattern of the electron beam gel layer. Optionally, during the etching process, the etching gas, power and time can be controlled to ensure the etching depth and pattern accuracy. The etching gas can be CHF3, Ar, etc.

[0085] In an optional embodiment, a suitable solvent or plasma treatment is used to remove the residual electron beam glue layer on the silicon dioxide mask layer, leaving a clear nano pattern structure. The sample can be cleaned by acetone and isopropanol.

[0086] Step S206 , using the nano-pattern structure as a mask, etching the cap layer and the absorption layer by inductively coupled plasma etching to remove the cap layer and the absorption layer corresponding to the nano-pattern structure on the Bragg reflection layer.

[0087] In this embodiment, the cap layer and the absorption layer are etched based on the inductively coupled plasma etching technology and using the nano pattern structure as a mask. By controlling the etching gas, power and time, it is possible to ensure that the cap layer and the absorption layer corresponding to the Bragg reflection layer are accurately removed.

[0088] Step S207, after removing the nano-pattern structure and cleaning the sample, a first dielectric film layer is deposited on the cover layer, and a second dielectric film layer is deposited on the Bragg reflection layer, so as to generate a first grating unit based on the absorption layer, the cover layer and the first dielectric film layer, and generate a second grating unit based on the second dielectric film layer.

[0089] In this embodiment, chemical methods or plasma treatment can be used to remove residual materials in the nano-pattern structure. Specifically, the nano-pattern structure on the sample can be removed by a buffered oxide etchant. The sample is cleaned again with acetone and isopropanol to remove any residual etching byproducts and impurities to ensure a clean surface.

[0090] In this embodiment, the first dielectric film layer can be deposited on the cover layer by physical vapor deposition or chemical vapor deposition, and the deposition conditions can be controlled to ensure the thickness and uniformity of the first dielectric film layer; at the same time, based on the same method as the first dielectric film layer, the second dielectric film layer is deposited on the Bragg reflection layer.

[0091] In an optional embodiment, the thickness of the first dielectric film layer and the second dielectric film layer are both λ / 4n, wherein λ represents the designed operating wavelength and n is the refractive index of the dielectric film.

[0092] When preparing the first dielectric film layer and the second dielectric film layer, the process parameters used include: SiH4 flow rate is 10sccm~15sccm; N2O flow rate is 400sccm~600sccm; N2 flow rate is 200sccm~300sccm; pressure is 90Pa; RF power is 50W; temperature is 300℃~350℃; deposition time is 10s~200s.

[0093] Finally, the absorption layer, the cover layer and the first dielectric film layer constitute a first grating unit, and the second dielectric film layer constitutes a second grating unit.

[0094] Through the above detailed steps, the present application provides an efficient and stable method for preparing a composite semiconductor saturable absorber mirror, which can effectively improve the performance and stability of the laser.

[0095] The following is a detailed description of a method for preparing a composite semiconductor saturable absorber mirror provided in an embodiment of the present application in conjunction with a specific embodiment. The method specifically comprises the following steps:

[0096] Step 1: Using molecular beam epitaxy to sequentially grow a buffer layer, a Bragg reflection layer, an absorption layer and a cap layer on the surface of a substrate.

[0097] In this embodiment, the material of the substrate is GaAs, the material of the buffer layer is GaAs, the material of the Bragg reflection layer is GaAs / AlGaAs, the material of the absorption layer is InAs / GaAs quantum dots, and the material of the cap layer is GaAs.

[0098] Step 2: Deposit a silicon dioxide mask layer on the cap layer using a plasma enhanced chemical vapor deposition method.

[0099] In this embodiment, the thickness of the silicon dioxide mask layer is 117 nm.

[0100] The program parameters for depositing the silicon dioxide mask layer based on the ion enhanced chemical vapor deposition method are: SiH4 flow rate is 12 sccm; N2O flow rate is 480 sccm; N2 flow rate is 240 sccm; pressure is 90 Pa; RF power is 50 W; temperature is 350°C; deposition time is 11 s.

[0101] Step 3: Spin-coat an electron beam gel layer on the sample obtained in the above step.

[0102] In this embodiment, the rotation speed during spin coating of the electron beam gel layer is 3000 rad / min, the spin coating time is 40 s, and the layer is placed on a hot plate at 180° C. and baked for 1 min.

[0103] Step 4: Use an electron beam exposure machine to expose the spin-coated electron beam adhesive layer.

[0104] In this embodiment, the exposure pattern is a one-dimensional grating with a period of 900 nm and a line width of 315 nm.

[0105] Step 5: Develop the exposed sample.

[0106] In this embodiment, the sample can be developed in MIBK:IPA for 60 seconds, fixed in IPA for 30 seconds, and then the surface of the sample can be blown dry.

[0107] Step 6: Place the developed sample on a hot plate at 110° C. and bake for 1 min to further evaporate the water in the electron beam gel.

[0108] Step 7: Use a reactive ion etching device to etch the silicon dioxide mask layer to generate a nano pattern structure.

[0109] In this embodiment, CHF3 and Ar can be used as etching gases, and the depth of etching the silicon dioxide mask layer is 177nm. The process parameters for etching the silicon dioxide mask layer are: CHF3 is 35sccm, and the etching time is 3.5min; the flow rate of Ar is 15sccm, and the etching time is 3.5min; the pressure is 30torr, and the RF power is 500W.

[0110] Step 8: Use acetone and isopropanol to clean the sample in a 60°C water bath for 5 min each, for a total of two cleans.

[0111] Step 9: using an inductively coupled plasma etching device and the nano-pattern structure as a mask, etching the cap layer and the absorption layer to remove the cap layer and the absorption layer corresponding to the nano-pattern structure on the Bragg reflection layer.

[0112] In this embodiment, the etching depth is 560nm, until the Bragg reflection layer level. Etching process parameters: N2 flow rate is 4sccm, BCl3 flow rate is 8sccm, Cl2 flow rate is 10sccm, pressure is 10mtorr, inductively coupled plasma (ICP) RF power is 200W, bottom electrode RF power (TableRF) is 50W, and etching time is 72s.

[0113] Step 10: removing the nano-pattern structure on the sample by using a buffered oxide etching solution.

[0114] In this embodiment, the buffered oxide etching solution uses HF:H2O=1:1, and the etching time is 5 minutes.

[0115] Step 11: Clean the sample twice in a 60°C water bath using acetone and isopropanol for 5 min each.

[0116] Step 12: depositing a first dielectric film layer on the cap layer, and depositing a second dielectric film layer on the Bragg reflection layer.

[0117] In this embodiment, the thickness of the first dielectric film layer and the second dielectric film layer are both λ / 4n, and the process parameters include: the flow rate of SiH4 is 12sccm; the flow rate of N2O is 480sccm; the flow rate of N2 is 240sccm; the pressure is 90Pa; the RF power supply power is 50W; the temperature is 350℃; and the deposition time is 11s.

[0118] In this embodiment, the reflection spectrum of the composite semiconductor saturable absorber is as follows: Figure 3 shown.

[0119] like Figure 3The figure shows the variation of the reflectivity of the composite semiconductor saturable absorber mirror with wavelength. The horizontal axis is the wavelength in nanometers (nm), ranging from 950nm to 1250nm. The vertical axis is the reflectivity in percentage (%), ranging from 20% to 70%.

[0120] Curve characteristics: The curve in the reflection spectrum diagram shows the change in reflectivity of the compound semiconductor saturable absorber at different wavelengths. The curve has obvious peaks and valleys at multiple wavelengths, indicating that the reflectivity of the sample changes significantly at these specific wavelengths. These peaks and valleys correspond to the characteristic reflection of the Bragg reflection layer and the interference effect of the multilayer structure.

[0121] In this embodiment, the photoluminescence spectrum of the composite semiconductor saturable absorber is as follows: Figure 4 shown.

[0122] like Figure 4 The figure shows the variation of the photoluminescence intensity of the composite semiconductor saturable absorber mirror with wavelength. The horizontal axis is the wavelength in nanometers (nm) ranging from 950nm to 1250nm. The vertical axis is the photoluminescence intensity in arbitrary units (au) ranging from 0 to 14000.

[0123] Curve characteristics: The curves in the photoluminescence spectrum show the luminescence intensity of the composite semiconductor saturable absorber at different wavelengths. The curve reaches a maximum at about 1050nm, showing the strong photoluminescence characteristics of the sample at this wavelength. This intensity peak may be related to the quantum dots or quantum well structures in the sample, which have strong luminescence characteristics at this specific wavelength.

[0124] In this embodiment, the nonlinear test diagram of the composite semiconductor saturable absorber is as follows: Figure 5 shown.

[0125] like Figure 5 The figure shows the nonlinear test results of the compound semiconductor saturable absorber mirror. The vertical axis represents the power intensity in kilowatts per square centimeter (kW / cm 2 ), the horizontal axis represents reflectivity in percentage (%). The data points in the figure show the reflectivity tested at different power intensities, and the fitting curve depicts the trend of these data; it can be found that with the increase of power intensity, the reflectivity shows obvious nonlinear changes, indicating that the prepared composite semiconductor saturable absorber has strong nonlinear characteristics. This characteristic is crucial in mode-locking operation and pulse formation.

[0126] An embodiment of the present application further provides a saturable absorption device, comprising: a compound semiconductor saturable absorption mirror, wherein the compound semiconductor saturable absorption mirror is the compound semiconductor saturable absorption mirror in the above embodiment, or is prepared based on the preparation method provided in the above embodiment.

[0127] It should be noted that the term "including" and its variations used in the embodiments of the present application are open inclusions, that is, "including but not limited to". The term "based on" means "based at least in part on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments". The modifications of "one" and "multiple" mentioned in the embodiments of the present application are illustrative and not restrictive. Those skilled in the art should understand that unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0128] The user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in the embodiments of the present application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant laws, regulations and standards of relevant countries and regions, and provide corresponding operation entrances for users to choose to authorize or refuse.

[0129] The various steps described in the method implementation methods provided in the embodiments of the present application can be performed in different orders and / or in parallel. In addition, the method implementation methods may include additional steps and / or omit the steps shown. The scope of protection of the present application is not limited in this respect.

[0130] The term "embodiment" in this specification refers to specific features, structures or characteristics described in conjunction with the embodiment that can be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor does it mean that it is mutually exclusive with other embodiments and is independent or optional. The various embodiments in this specification are described in a related manner, and the same or similar parts between the various embodiments refer to each other. In particular, for the device, equipment, and system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts refer to the partial description of the method embodiment.

[0131] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of patent protection. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the scope of protection of the present application. Therefore, the scope of protection of the present application shall be subject to the attached claims.

Claims

1. A composite semiconductor saturable absorber mirror, characterized in that: include: A substrate, a buffer layer, a Bragg reflection layer and a periodic grating layer are sequentially arranged from bottom to top; The periodic grating layer comprises a plurality of first grating units, wherein the plurality of first grating units are uniformly arranged on the Bragg reflection layer, and a second grating unit is arranged between two adjacent first grating units; The first grating unit includes an absorption layer, a cover layer and a first dielectric film layer which are arranged in sequence from bottom to top, and the second grating unit includes a second dielectric film layer.

2. The composite semiconductor saturable absorber mirror according to claim 1, characterized in that: The absorption layer includes a quantum dot layer or a quantum well layer; The material of the quantum dot layer is a mixed material of indium arsenide and gallium arsenide, or a mixed material of indium arsenide and indium phosphide; the material of the quantum well layer is a mixed material of indium arsenide and gallium arsenide, or a mixed material of indium arsenide and indium phosphide.

3. The composite semiconductor saturable absorber mirror according to claim 1, characterized in that: The thickness of the first dielectric film layer and the second dielectric film layer are both λ / 4n, where λ represents the designed working wavelength and n is the refractive index of the dielectric film; The first dielectric film layer and the second dielectric film layer are silicon dioxide thin film layers.

4. A method for preparing a composite semiconductor saturable absorber mirror, characterized in that: include: epitaxially growing a buffer layer, a Bragg reflection layer, an absorption layer and a cap layer on the substrate in sequence; preparing a silicon dioxide mask layer on the cap layer by a plasma enhanced chemical vapor deposition method; Spin coating an electron beam gel layer on the silicon dioxide mask layer, and generating a periodic one-dimensional grating pattern on the electron beam gel layer by electron beam exposure; Performing a developing process on the periodic one-dimensional grating pattern by using a preset developing solution to remove the electron beam gel layer outside the periodic one-dimensional grating pattern area; Generating a nanometer pattern structure corresponding to the periodic one-dimensional grating pattern on the silicon dioxide mask layer by a reactive ion etching method, and removing the electron beam gel layer on the silicon dioxide mask layer; Using the nano-pattern structure as a mask, etching the cap layer and the absorption layer by inductively coupled plasma etching to remove the cap layer and the absorption layer corresponding to the nano-pattern structure on the Bragg reflection layer; After removing the nano-pattern structure and cleaning the sample, a first dielectric film layer is deposited on the cover layer, and a second dielectric film layer is deposited on the Bragg reflection layer, so as to generate a first grating unit based on the absorption layer, the cover layer and the first dielectric film layer, and to generate a second grating unit based on the second dielectric film layer.

5. The method according to claim 4, characterized in that The thickness of the silicon dioxide mask layer is 50nm to 200nm; When the silicon dioxide mask layer is prepared on the cap layer by the plasma enhanced chemical vapor deposition method, the process parameters used include: SiH4 flow rate is 10sccm~15sccm; N2O flow rate is 400sccm~600sccm; N2 flow rate is 200sccm~300sccm; pressure is 90Pa; RF power is 50W; temperature is 300℃~350℃; deposition time is 10s~200s.

6. The method according to claim 4, characterized in that The preset developer includes a mixed solution of methyl isobutyl ketone and isopropyl alcohol, wherein the ratio of the methyl isobutyl ketone to the isopropyl alcohol is 1:

3.

7. The method according to claim 4, characterized in that The thickness of the first dielectric film layer and the second dielectric film layer are both λ / 4n, where λ represents the designed working wavelength and n is the refractive index of the dielectric film; The first dielectric film layer and the second dielectric film layer are silicon dioxide thin film layers; When depositing the first dielectric film layer on the cover layer and the second dielectric film layer on the Bragg reflection layer, the process parameters used include: SiH4 flow rate is 10sccm~15sccm; N2O flow rate is 400sccm~600sccm; N2 flow rate is 200sccm~300sccm; pressure is 90Pa; RF power is 50W; temperature is 300℃~350℃; deposition time is 10s~200s.

8. The method according to claim 4, characterized in that The absorption layer includes a quantum dot layer or a quantum well layer; The material of the quantum dot layer is a mixed material of InAs and GaAs, or a mixed material of InAs and InP; the material of the quantum well layer is a mixed material of InAs and GaAs, or a mixed material of InAs and InP.

9. A saturable absorption device, comprising: A compound semiconductor saturable absorber mirror, wherein the compound semiconductor saturable absorber mirror is the compound semiconductor saturable absorber mirror according to any one of claims 1 to 3, or is prepared based on the method according to any one of claims 4 to 8.

10. Use of the composite semiconductor saturable absorber mirror according to any one of claims 1 to 3 in the field of semiconductor lasers.

Images