Near-infrared laser based on silver selenide nanocrystals and its preparation method

Abstract

The present invention provides a near-infrared laser based on silver selenide nanocrystals and a preparation method thereof. The near-infrared laser based on silver selenide nanocrystals sequentially includes: a substrate, a distributed feedback grating layer, and a silver selenide nanocrystal layer; the silver selenide nanocrystal layer is composed of silver selenide nanocrystals, and the silver selenide nanocrystals are in a tetragonal crystal phase with a diameter range of 6 nm to 10 nm. The present invention uses silver selenide nanocrystals as the optical gain medium of the laser to achieve zero-threshold band-edge state optical gain; by using the quantum confinement effect, the relative position of the bottom of the conduction band of the silver selenide nanocrystals and the environmental Fermi level is adjusted by adjusting the size of the silver selenide nanocrystals, so as to obtain the band-edge electron state 1S e Silver selenide nanocrystals occupied by electrons, with an adjustable near-infrared emission wavelength, without the need to add a hole trapping agent that is easily oxidized. The silver selenide nanocrystals are stable in the atmospheric environment, and the crystal structure and surface state will not be damaged; the silver selenide material of the present invention is a low-toxic and environmentally friendly material, which is friendly to the environment.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor optoelectronic devices, and particularly to a near-infrared laser based on silver selenide nanocrystals and a preparation method thereof. Background Art

[0002] Laser technology has been widely used in the fields of communication, medical treatment, scientific research, etc., and has a great market demand. The laser threshold is one of the core issues in the research of the laser field. How to reduce the laser threshold and find new materials with low thresholds is a key topic in laser technology.

[0003] In recent years, semiconductor nanocrystals have become a research hotspot of optical gain materials due to their excellent luminescent properties such as continuously tunable wavelength, narrowband emission, and high photoluminescence quantum yield. Benefiting from the quantum confinement effect, semiconductor nanocrystals as optical gain materials exhibit various superior properties, such as emission wavelength tunable with the size of semiconductor nanocrystals and optical gain threshold insensitive to temperature. However, due to the multiple degeneracy of the band-edge states, to achieve optical gain of the band-edge states, the number of excitons contained in the semiconductor nanocrystals must be greater than half of the band-edge state degeneracy, that is, half of the number of electrons that can be accommodated. For example, for PbSe nanocrystals with 8-fold degenerate band-edge states to achieve optical gain, the excitons in the semiconductor nanocrystals must be greater than 4. This severely limits the optical gain threshold of semiconductor nanocrystals, making it difficult to achieve continuous optical pumping or electrical pumping excitation emission, and only pulsed laser pumping can be used.

[0004] In view of the above, it is necessary to provide a near-infrared laser based on silver selenide nanocrystals and a preparation method thereof to obtain a laser with zero threshold, high stability, adjustable emission wavelength in the near-infrared range, and environmental protection. Summary of the Invention

[0005] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a near-infrared laser based on silver selenide nanocrystals and a preparation method thereof to obtain a laser with zero threshold, high stability, adjustable emission wavelength in the near-infrared range, and environmental protection.

[0006] To achieve the above object and other related objects, the present invention provides a near-infrared laser based on silver selenide nanocrystals, and the near-infrared laser based on silver selenide nanocrystals successively includes:

[0007] A substrate, a distributed feedback grating layer, and a silver selenide nanocrystal layer;

[0008] The silver selenide nanocrystal layer is composed of silver selenide nanocrystals, and the silver selenide nanocrystals are in a tetragonal crystal phase with a diameter range of 6 nm to 10 nm.

[0009] Optionally, the silver selenide nanocrystal layer is composed of closely packed silver selenide nanocrystals.

[0010] Optionally, the product of the grating period and the effective refractive index of the distributed feedback grating is equal to the wavelength of the edge emission peak of the silver selenide nanocrystals.

[0011] Optionally, the near-infrared laser based on silver selenide nanocrystals further includes a packaging layer located above the silver selenide nanocrystal layer.

[0012] Optionally, the material of the substrate is one of silicon, mica, aluminum oxide, and silicon dioxide; the material of the distributed feedback grating layer is one of silicon dioxide, aluminum oxide, magnesium difluoride, and lithium fluoride; the material of the packaging layer is one of silicon dioxide, aluminum oxide, magnesium difluoride, and lithium fluoride.

[0013] The present invention also provides a method for preparing a near-infrared laser based on silver selenide nanocrystals for preparing the above-mentioned near-infrared laser based on silver selenide nanocrystals, and the preparation method includes:

[0014] S1: Provide a substrate, prepare silver selenide nanocrystals with a diameter range of 6 nm to 10 nm and a cubic crystal phase, and then disperse the silver selenide nanocrystals in a toluene solution to obtain a silver selenide nanocrystal toluene dispersion.

[0015] S2: Form a distributed feedback grating layer on the substrate.

[0016] S3: Spin-coat the silver selenide nanocrystal toluene dispersion obtained in step S1 on the distributed feedback grating layer to obtain a silver selenide nanocrystal layer.

[0017] Optionally, in step S3, after spin-coating the silver selenide nanocrystal toluene dispersion on the distributed feedback grating layer, it further includes a step of annealing under the protection of an inert gas.

[0018] Optionally, in step S3, after obtaining the silver selenide nanocrystal layer, it further includes a step of forming a packaging layer on the silver selenide nanocrystal layer.

[0019] As described above, the near-infrared laser based on silver selenide nanocrystals and the preparation method thereof of the present invention have the following beneficial effects:

[0020] The present invention uses cubic crystal phase silver selenide nanocrystals with a diameter of 6 nm to 10 nm as the optical gain medium. When the band gap of the cubic crystal phase bulk material silver selenide nanocrystals 11 is only 0.07 eV, the environmental Fermi level 60 is higher than the bottom of the conduction band (such as Figure 3 (a) and Figure 3(as shown in (b)), the bottom of the conduction band is occupied by electrons. Due to the quantum confinement effect, silver selenide nanocrystals exhibit discrete energy levels similar to atoms, and the bandgap increases with the decrease in the size of silver selenide nanocrystals. When the diameter of the cubic-phase silver selenide nanocrystals decreases to 6 nm (as shown in Figure 4 (a) and Figure 4 (b)), the ambient Fermi level 60 of the silver selenide nanocrystals 12 with a diameter of 6 nm is still higher than the band-edge electron state 1S e , and the band-edge electron state 1S e is occupied by electrons in the unexcited state (as shown in Figure 6 (a)). At this time, the band-edge absorption is bleached, that is, the transition of excitons from the 1S h state to the 1S e state is prohibited. At the same time, the band-edge emission is also prohibited. That is to say, in the unexcited state, the silver selenide nanocrystal population is transparent to photons with the same energy as the bandgap, neither absorbing nor generating gain. As long as one silver selenide nanocrystal in the silver selenide nanocrystal layer 40 is excited by a photon with an energy greater than or equal to the energy gap between the 1S h state and the 1P e state (as shown in Figure 6 (b)), the electrons in the band-edge hole state 1S h are excited to the 1P e state or excited to higher energy levels and then relax to the 1P e state, leaving a hole in the 1S h state. This silver selenide nanocrystal realizes population inversion of the band-edge state, and the entire silver selenide nanocrystal layer 40 forms optical gain at the band-edge emission wavelength. Therefore, zero-threshold band-edge state optical gain can be achieved using cubic-phase silver selenide nanocrystals with a diameter greater than 6 nm. When the diameter of the silver selenide nanocrystals is less than 6 nm, for example, the ambient Fermi level 60 of the silver selenide nanocrystals 13 with a diameter of 3 nm is lower than the band-edge electron state 1S e , and the band-edge electron state 1S e is not occupied by electrons (as shown in Figure 5 (a) and Figure 5 (b)). At this time, the band-edge absorption is not bleached, that is, the transition of electrons from 1S h to 1S e is not prohibited. That is to say, in the unexcited state, the silver selenide nanocrystal population absorbs photons with the same energy as the bandgap. Because the silver selenide band-edge state is two-fold degenerate, population inversion can only be obtained when the number of excitons in each silver selenide nanocrystal in the silver selenide nanocrystal population, that is, the number of absorbed photons, is greater than 1. Restricting the diameter of the silver selenide nanocrystals to be greater than 10 nm is to enhance the quantum confinement effect and obtain the general advantages of nanocrystals as optical gain materials, namely the near-infrared emission wavelength tunable with the size of silver selenide nanocrystals and the temperature-insensitive optical gain threshold.

[0021] The present invention uses silver selenide nanocrystals with a cubic crystal phase and a diameter of 6 nm to 10 nm as the optical gain medium of a laser, achieving zero-threshold band-edge optical gain; the present invention utilizes the quantum confinement effect to adjust the relative position of the bottom of the conduction band of the cubic silver selenide nanocrystals and the environmental Fermi level by adjusting the size of the silver selenide nanocrystals, thereby obtaining band-edge electron state 1S e The silver selenide nanocrystals occupied by electrons have an adjustable emission wavelength within the near-infrared band, without the need to add easily oxidized hole-trapping agents, and the band-edge electron state 1S e The silver selenide nanocrystals occupied by electrons are stable in an atmospheric environment, and their crystal structure and surface state will not be damaged; the silver selenide material of the present invention is a low-toxic environmental protection material, which is friendly to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It shows a schematic structural diagram of the silver selenide nanocrystals of the present invention.

[0023] Figure 2 It shows a schematic structural diagram of a near-infrared laser based on silver selenide nanocrystals of the present invention.

[0024] Figure 3 (a) It shows a schematic structural diagram of the bulk silver selenide nanocrystals of the present invention, Figure 3 (b) It shows a schematic energy level structure diagram of the bulk silver selenide nanocrystals of the present invention.

[0025] Figure 4 (a) It shows a schematic structural diagram of the silver selenide nanocrystals with a diameter of 6 nm of the present invention, Figure 4 (b) It shows a schematic energy level structure diagram of the silver selenide nanocrystals with a diameter of 6 nm of the present invention.

[0026] Figure 5 (a) It shows a schematic structural diagram of the silver selenide nanocrystals with a diameter of 3 nm of the present invention, Figure 5 (b) It shows a schematic energy level structure diagram of the silver selenide nanocrystals with a diameter of 3 nm of the present invention.

[0027] Figure 6 (a) It shows a schematic diagram of the exciton state and energy level structure of the silver selenide nanocrystals with a diameter of 6 nm of the present invention in the unexcited state, Figure 6 (b) It shows a schematic diagram of the exciton state and energy level structure of the silver selenide nanocrystals with a diameter of 6 nm of the present invention after excitation.

[0028] Figure 7 It shows a schematic flow chart of the preparation method of a near-infrared laser based on silver selenide nanocrystals of the present invention.

[0029] Figures 8 to 11A schematic structural diagram showing the steps of the method for preparing a near-infrared laser based on silver selenide nanocrystals according to the present invention is presented.

[0030] Description of component labels

[0031] 10, silver selenide nanocrystals; 11, bulk silver selenide nanocrystals; 12, silver selenide nanocrystals with a diameter of 6 nm; 13, silver selenide nanocrystals with a diameter of 3 nm; 20, substrate; 30, distributed feedback grating; 40, silver selenide nanocrystal layer; 50, encapsulation layer; 60, environmental Fermi level. Specific embodiments

[0032] The following illustrates the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0033] Please refer to Figures 1 to 11 . It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The types, quantities, and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0034] Example 1

[0035] As Figures 1 to 2 shown, the present invention provides a near-infrared laser based on silver selenide nanocrystals, and the near-infrared laser based on silver selenide nanocrystals sequentially includes:

[0036] A substrate 20, a distributed feedback grating layer 30, and a silver selenide nanocrystal layer 40 (as Figure 2 shown);

[0037] The silver selenide nanocrystal layer 40 is composed of silver selenide nanocrystals 10, and the silver selenide nanocrystals 10 are in a tetragonal crystal phase with a diameter range of 6 nm to 10 nm (as Figure 1 shown).

[0038] The working principle of this embodiment is: The excitation photon energy received by the near-infrared laser based on silver selenide nanocrystals is greater than or equal to the energy gap between the 1S h state and the 1P e state of the silver selenide nanocrystals. The edge electron state 1S eWhen occupied by electrons in the unexcited state, the laser emission of the silver selenide nanocrystal-based near-infrared laser can be output from the upper surface of the silver selenide nanocrystal layer 40 or the lower surface of the substrate 20.

[0039] In this embodiment, silver selenide nanocrystals with a cubic crystal phase and a diameter of 6 nm to 10 nm are used as the optical gain medium. When the bandgap of the bulk silver selenide nanocrystals 11 with a cubic crystal phase is only 0.07 eV, the ambient Fermi level 60 is higher than the bottom of the conduction band (as shown in Figure 3 (a) and Figure 3 (b)), and the bottom of the conduction band is occupied by electrons. Due to the quantum confinement effect, the silver selenide nanocrystals exhibit discrete energy levels similar to atoms, and the bandgap increases with the decrease in the size of the silver selenide nanocrystals. When the diameter of the cubic silver selenide nanocrystals decreases to 6 nm (as shown in Figure 4 (a) and Figure 4 (b)), the ambient Fermi level 60 of the silver selenide nanocrystals 12 with a diameter of 6 nm is still higher than the band-edge electron state 1S e , and the band-edge electron state 1S e is occupied by electrons in the unexcited state (as shown in Figure 6 (a)). At this time, the band-edge absorption is bleached, that is, the transition of excitons from the 1S h state to the 1S e state is prohibited. At the same time, the band-edge emission is also prohibited. That is to say, in the unexcited state, the silver selenide nanocrystal population is transparent to photons with an energy equal to the bandgap, neither absorbing nor generating gain. As long as one silver selenide nanocrystal in the silver selenide nanocrystal layer is excited by a photon with an energy greater than or equal to the energy gap between the 1S h state and the 1P e state (as shown in Figure 6 (b)), the electrons in the band-edge hole state 1S h are excited to the 1P e state or excited to higher energy levels and then relax to the 1P e state, leaving a hole in the 1S h state. This silver selenide nanocrystal then realizes population inversion of the band-edge state, and the entire silver selenide nanocrystal layer forms optical gain at the band-edge emission wavelength. Therefore, zero-threshold band-edge state optical gain can be achieved using cubic silver selenide nanocrystals with a diameter greater than 6 nm. When the diameter of the silver selenide nanocrystals is less than 6 nm, for example, the ambient Fermi level 60 of the silver selenide nanocrystals 13 with a diameter of 3 nm is lower than the band-edge electron state 1S e , and the band-edge electron state 1S e is not occupied by electrons (as shown in Figure 5 (a) and Figure 5 (b)). At this time, the band-edge absorption is not bleached, that is, the electrons from 1S h to 1Se The transition is not forbidden, that is, in the unexcited state, the silver selenide nanocrystal population absorbs photons with the same energy as the bandgap width. Since the band-edge states of silver selenide are two-fold degenerate, population inversion can only be achieved when the number of excitons in each silver selenide nanocrystal on average in the silver selenide nanocrystal population, that is, the number of absorbed photons, is greater than 1. Restricting the diameter of silver selenide nanocrystals to be greater than 10 nm is to enhance the quantum confinement effect and obtain the general advantages of nanocrystals as optical gain materials, namely, the near-infrared emission wavelength tunable with the size of silver selenide nanocrystals and the optical gain threshold insensitive to temperature.

[0040] In this embodiment, silver selenide nanocrystals with a cubic crystal phase and a diameter of 6 nm to 10 nm are used as the optical gain medium of the laser, and zero-threshold band-edge state optical gain is achieved; in this embodiment, the quantum confinement effect is utilized to adjust the relative position of the bottom of the conduction band of cubic-phase silver selenide nanocrystals and the environmental Fermi level 60 by adjusting the size of silver selenide nanocrystals, so as to obtain the band-edge electron state 1S e Silver selenide nanocrystals occupied by electrons have an adjustable emission wavelength in the near-infrared band, without the need to add an easily oxidized hole trapping agent, and the band-edge electron state 1S e Silver selenide nanocrystals occupied by electrons are stable in the atmospheric environment, and the crystal structure and surface state will not be damaged; the silver selenide material in this embodiment is a low-toxic environmental-friendly material and is friendly to the environment.

[0041] As an example, the silver selenide nanocrystal layer 40 is composed of densely packed silver selenide nanocrystals 10.

[0042] Densely packing the silver selenide nanocrystals 10 can increase the net modal gain of the silver selenide nanocrystal layer 40, which is beneficial to increasing the laser emission intensity.

[0043] As an example, the product of the grating period and the effective refractive index of the distributed feedback grating 30 is equal to the band-edge emission peak wavelength of the silver selenide nanocrystals 10.

[0044] Such a setting can provide optical feedback for the gain medium of the laser, that is, the silver selenide nanocrystal layer 40, so as to obtain laser emission.

[0045] As an example, the near-infrared laser based on silver selenide nanocrystals further includes a packaging layer 50, and the packaging layer 50 is located above the silver selenide nanocrystal layer 40.

[0046] Forming the packaging layer 50 on the silver selenide nanocrystal layer 40 can further improve the stability of the near-infrared laser based on silver selenide nanocrystals and extend its lifespan.

[0047] As an example, the gratings of the distributed feedback grating 30 are arranged periodically, and the shape can be set according to the actual situation and is not limited herein. For example, they can be rectangular bodies, cylinders or polygonal columns with regular periodic protrusions.

[0048] As an example, the material of the substrate 20 is one of silicon, mica, aluminum oxide and silicon dioxide; the material of the distributed feedback grating layer 30 is one of silicon dioxide, aluminum oxide, magnesium difluoride and lithium fluoride; the material of the encapsulation layer 50 is one of silicon dioxide, aluminum oxide, magnesium difluoride and lithium fluoride.

[0049] The materials used in the device structure of the near-infrared laser based on silver selenide nanocrystals can be the same or different, as long as the device has good heat dissipation and stable performance, which is not limited herein and can be set according to actual needs.

[0050] In this embodiment, the material of the substrate 20 is preferably aluminum oxide, the material of the distributed feedback grating layer 30 is preferably aluminum oxide, and the material of the encapsulation layer 50 is preferably aluminum oxide.

[0051] Aluminum oxide material is preferably used as the material of the device structure of the near-infrared laser based on silver selenide nanocrystals because of its low cost, good heat dissipation and good stability.

[0052] As an example, the near-infrared laser based on silver selenide nanocrystals further includes a pump source for exciting the silver selenide nanocrystal layer 40.

[0053] The emitted photon energy of the pump source is greater than or equal to the energy gap between the 1S h state and the 1P e state of the silver selenide nanocrystals. The pump photons are injected from the upper surface of the encapsulation layer 50 or the lower surface of the substrate 20 to excite the near-infrared laser based on silver selenide nanocrystals, so that the laser emission of the laser is output from the upper surface of the encapsulation layer 50 or the lower surface of the substrate 20.

[0054] It should be noted here that since the laser emission is output in the vertical direction of the device from the upper surface of the encapsulation layer 50 or the lower surface of the substrate 20, the pump photons need to be injected obliquely from the upper surface of the encapsulation layer 50 or the lower surface of the substrate 20 to avoid overlapping with the laser emission. The oblique injection angle of the pump photons can be set according to the actual situation and is not limited herein.

[0055] Embodiment 2

[0056] This embodiment provides a method for preparing a near-infrared laser based on silver selenide nanocrystals, which is used to prepare the near-infrared laser based on silver selenide nanocrystals in the first embodiment above. The preparation method includes:

[0057] S1: Provide a substrate, prepare silver selenide nanocrystals 10 with a diameter range of 6 nm to 10 nm and a cubic crystal phase, and then disperse the silver selenide nanocrystals 10 in a toluene solution to obtain a silver selenide nanocrystal toluene dispersion;

[0058] S2: Form a distributed feedback grating layer 30 on the substrate 20;

[0059] S3: Spin-coat the silver selenide nanocrystal toluene dispersion obtained in step S1 on the distributed feedback grating layer 30 to obtain a silver selenide nanocrystal layer 40.

[0060] As Figures 7 to 11 shown, the following further introduces this embodiment in conjunction with the accompanying drawings.

[0061] As Figure 7 and Figure 8 shown, as an example, first perform step S1, provide a substrate 20, prepare silver selenide nanocrystals 10 with a diameter range of 6 nm to 10 nm and a cubic crystal phase, and then disperse the silver selenide nanocrystals 10 in a toluene solution to obtain a silver selenide nanocrystal toluene dispersion.

[0062] Using the metal-organic method, and by controlling the reaction time, prepare the cubic crystal phase silver selenide nanocrystals 10 with a diameter of 6 nm to 10 nm, and disperse the silver selenide nanocrystals 10 in a toluene solution, where the concentration of the toluene solution needs to be adjusted to 20 mg / ml. The material of the substrate 20 is one of silicon, mica, aluminum oxide, and silicon dioxide. In this embodiment, the aluminum oxide material is preferably used because of its low cost, good heat dissipation, and good stability.

[0063] As Figure 7 and Figure 9 shown, as an example, then perform step S2 to form a distributed feedback grating layer 30 on the substrate 20.

[0064] The material of the distributed feedback grating 30 in this embodiment is one of silicon dioxide, aluminum oxide, magnesium difluoride, and lithium fluoride. In this embodiment, aluminum oxide material is preferably used because of its low cost, good heat dissipation, and good stability. The distributed feedback grating 30 is arranged periodically, and its shape can be set according to actual conditions, which is not limited here. For example, it can be a regularly periodic raised rectangular body, cylinder, or polygonal column. Due to the simplicity of the process, a regularly periodic raised rectangular body is preferably used. It should be noted here that the product of the grating period and the effective refractive index of the distributed feedback grating 30 is equal to the band-edge emission peak wavelength of the silver selenide nanocrystal 10, providing optical feedback for the silver selenide nanocrystal layer 40, thereby obtaining laser emission. In this embodiment, a layer of aluminum oxide is first formed on the substrate 20, and then a distributed feedback grating of aluminum oxide is etched on the surface of the aluminum oxide by reactive ion etching.

[0065] In another preferred embodiment, the substrate 20 and the distributed feedback grating layer 30 are both made of aluminum oxide material and can be integrally provided. A thick aluminum oxide substrate can be directly provided, and a distributed feedback grating of aluminum oxide is etched on the surface of the aluminum oxide substrate by reactive ion etching.

[0066] Such as Figure 7 and Figure 10 As shown, as an example, then step S3 is carried out. The silver selenide nanocrystal toluene dispersion obtained in step S1 is spin-coated on the distributed feedback grating layer 30 to obtain the silver selenide nanocrystal layer 40.

[0067] The silver selenide nanocrystal toluene dispersion obtained in step S1 is spin-coated on the distributed feedback grating 30 at a rotation speed of 2500 revolutions per minute. In this embodiment, the silver selenide nanocrystal toluene dispersion is spin-coated on the aluminum oxide distributed feedback grating at a rotation speed of 2500 revolutions per minute.

[0068] As a preferred example, in step S3, after the silver selenide nanocrystal toluene dispersion is spin-coated on the distributed feedback grating layer 40, it further includes a step of annealing under inert gas protection.

[0069] The distributed feedback grating layer 30 spin-coated with the silver selenide nanocrystal toluene dispersion is annealed at 60 °C for half an hour under inert gas protection to increase the density of the stacked silver selenide nanocrystals to obtain the silver selenide nanocrystal layer 40. The annealed silver selenide nanocrystals 10 can increase the net mode gain of the silver selenide nanocrystal layer 40, which is beneficial to increasing the laser emission intensity.

[0070] Such as Figure 11 As shown, as a preferred example, after obtaining the silver selenide nanocrystal layer 40 in step S3, it further includes a step of forming a packaging layer 50 on the silver selenide nanocrystal layer 40.

[0071] The encapsulation layer 50 is deposited on the silver selenide nanocrystal layer 40 by atomic layer deposition. In this embodiment, the material of the encapsulation layer 50 is aluminum oxide, that is, a layer of aluminum oxide is deposited on the silver selenide nanocrystal layer 40 by atomic layer deposition to form the encapsulation layer 50.

[0072] Depositing the encapsulation layer 50 on the silver selenide nanocrystal layer 40 can further improve the stability of the laser device and extend the life of the laser.

[0073] In summary, the present invention provides a near-infrared laser based on silver selenide nanocrystals and a preparation method thereof. The near-infrared laser based on silver selenide nanocrystals sequentially includes: a substrate, a distributed feedback grating layer, and a silver selenide nanocrystal layer; the silver selenide nanocrystal layer is composed of silver selenide nanocrystals, and the silver selenide nanocrystals are in a tetragonal crystal phase with a diameter range of 6 nm to 10 nm. The present invention uses silver selenide nanocrystals in a tetragonal crystal phase with a diameter of 6 nm to 10 nm as the optical gain medium of the laser, realizing zero-threshold band-edge state optical gain; the present invention utilizes the quantum confinement effect to adjust the relative position of the conduction band bottom of the tetragonal crystal phase silver selenide nanocrystals and the environmental Fermi level by adjusting the size of the silver selenide nanocrystals, thereby obtaining band-edge electron state 1S e Silver selenide nanocrystals occupied by electrons have an adjustable emission wavelength, do not require the addition of easily oxidized hole-trapping agents, and the band-edge electron state 1S e Silver selenide nanocrystals occupied by electrons are stable in an atmospheric environment, and their crystal structure and surface state will not be damaged; the silver selenide material of the present invention is a low-toxic environmental protection material and is friendly to the environment. Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0074] The above embodiments are only illustrative of the principles and effects of the present invention and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A near-infrared laser based on silver selenide nanocrystals, characterized in that, the near-infrared laser based on silver selenide nanocrystals sequentially includes: a substrate, a distributed feedback grating layer, and a silver selenide nanocrystal layer; the silver selenide nanocrystal layer is composed of silver selenide nanocrystals, the silver selenide nanocrystals are in a tetragonal crystal phase, the diameter range is 6 nm to 10 nm, and the product of the grating period of the distributed feedback grating and the effective refractive index is equal to the band-edge emission peak wavelength of the silver selenide nanocrystals.

2. The near-infrared laser based on silver selenide nanocrystals according to claim 1, characterized in that: the silver selenide nanocrystal layer is composed of closely packed silver selenide nanocrystals.

3. The near-infrared laser based on silver selenide nanocrystals according to claim 1, characterized in that: the near-infrared laser based on silver selenide nanocrystals further includes a packaging layer, and the packaging layer is located above the silver selenide nanocrystal layer.

4. The near-infrared laser based on silver selenide nanocrystals according to claim 3, characterized in that: the material of the substrate is one of silicon, mica, aluminum oxide, and silicon dioxide; the material of the distributed feedback grating layer is one of silicon dioxide, aluminum oxide, magnesium fluoride, and lithium fluoride; the material of the packaging layer is one of silicon dioxide, aluminum oxide, magnesium fluoride, and lithium fluoride.

5. The near-infrared laser based on silver selenide nanocrystals according to claim 1, characterized in that: the near-infrared laser based on silver selenide nanocrystals further includes a pump source for exciting the silver selenide nanocrystal layer.

6. A preparation method of a near-infrared laser based on silver selenide nanocrystals for preparing the near-infrared laser based on silver selenide nanocrystals according to any one of claims 1 to 5, characterized in that, the preparation method includes: S1: Provide a substrate, prepare silver selenide nanocrystals with a diameter range of 6 nm to 10 nm and in a tetragonal crystal phase, and then disperse the silver selenide nanocrystals in a toluene solution to obtain a silver selenide nanocrystal toluene dispersion; S2: Form a distributed feedback grating layer on the substrate; S3: Spin-coat the silver selenide nanocrystal toluene dispersion obtained in step S1 on the distributed feedback grating layer to obtain a silver selenide nanocrystal layer.

7. The preparation method of the near-infrared laser based on silver selenide nanocrystals according to claim 6, characterized in that: in step S3, after spin-coating the silver selenide nanocrystal toluene dispersion on the distributed feedback grating layer, it further includes a step of annealing under the protection of an inert gas.

8. The preparation method of the near-infrared laser based on silver selenide nanocrystals according to claim 6, characterized in that: in step S3, after obtaining the silver selenide nanocrystal layer, it further includes a step of forming a packaging layer on the silver selenide nanocrystal layer.

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