CN107069417A - A plasmonic random laser array device based on two-dimensional materials - Google Patents

Abstract

The invention discloses a plasmonic random laser array device based on two-dimensional materials, which is composed of arrayed laser chamber units, and the overall structural positional relationship of the random laser array device is pumping light source in sequence from bottom to top (1), substrate (2), bottom electrode (31), dielectric layer (4), laser chamber unit (6), top electrode (32) surrounded by spacer layer (5); peripheral drive circuit (7 ) are respectively connected to the bottom electrode (31) and the top electrode (32), and the bottom electrode (31), the dielectric layer (4), the laser chamber unit (6), and the top electrode (32) form a closed loop. The random laser array of the present invention uses two-dimensional material nanosheets with high photoluminescence efficiency as a random gain medium, and effectively enhances light scattering through the localized surface plasmon effect (LSPR) of metal nanoparticles, reducing the threshold of the laser . By changing the operating voltage of the laser chamber, the dynamic adjustment of the radiation spectrum and directivity can be realized.

Description

A plasmonic random laser array device based on two-dimensional materials

technical field

The invention belongs to the fields of laser technology, two-dimensional materials, metal nanomaterials and micro-opto-electromechanical technology, and in particular relates to a plasmon random laser array device based on two-dimensional materials.

Background technique

Random laser is a new type of laser that does not require a resonant cavity. Compared with traditional lasers, it does not require a resonant cavity. The laser is formed by the multiple scattering effect in the random gain medium contained in it. The random gain medium can absorb light Achieve effective scattering and amplification. For random lasers, it is usually necessary to introduce a new nano-light source technology, using various nanostructures to enhance the interaction between light and matter. The scattering characteristics of the random gain medium are further enhanced, thereby reducing the threshold of the random laser and improving the energy consumption of the random laser and other aspects of performance. The future development trend of random lasers is arraying, fast tunable and dynamic laser wavelength and radiation direction. However, the current existing technologies are far from meeting the above requirements. For example, random lasers of TiO ₂ thin films, ZnO thin films, and random lasers doped with dye particles in colloidal solutions cannot be dynamically tunable, which will greatly Limit the application of random lasers in a series of aspects such as optoelectronic integration and photon integration. In order to fully expand the application of random lasers, some new technologies need to be introduced to meet the above application requirements.

Two-dimensional materials, they have strong planar chemical bonds, but the coupling between layers is weak, so the layered bulk materials can be separated into independent atomic layers. Materials of the van der Waals family are the most common 2D materials. It includes graphene, hexagonal boron nitride h-BN, molybdenum disulfide (MoS2) and other transition metal sulfides. For molybdenum disulfide, the layers are coupled by van der Waals force, and the upper and lower layers of each layer are hexagonal planes composed of sulfur atoms, which are separated by the middle metal molybdenum atom layer, thus forming a "sandwich". Two-dimensional materials such as molybdenum disulfide have many excellent optical properties, such as: the band gap is related to the number of layers of the material; under the irradiation of an external light source, bound excitons will be formed between the layers to produce a strong photoluminescence effect. Localized Surface Plasmon Resonance (LSPR) is a resonance enhancement effect caused by the strong interaction between metal nanostructures and light in the sub-wavelength range, forming a strong optical field on the surface of metal nanostructures. In addition, for the composite structure of two-dimensional materials such as molybdenum disulfide and metal nanoparticles, the hot electron-hole pairs generated by the LSPR effect of metal nanoparticles can realize the doping of two-dimensional materials and adjust the band gap of two-dimensional materials.

Electrowetting (Electrowetting, EW) refers to the phenomenon of changing the wettability of the droplet on the substrate by changing the voltage between the droplet and the insulating substrate, that is, changing the contact angle, so that the droplet is deformed and displaced. Electrowetting technology is a dynamic tuning of droplets at the micron scale by using the oil-water two-phase interface effect. This technology has the advantages of fast response speed, large adjustable range, adjustable area and radian, and low cost. It is a new type of dynamic tunable technology, and has been widely used in microlens, electrowetting display and microfluidic laboratory. The present invention proposes to combine this technology with the LSPR effect of plasmonic nanoparticles to develop a random laser with a new concept, which will have the characteristics of low laser threshold, directivity, and dynamic tunable laser spectrum.

The present invention aims at bottleneck problems such as high threshold value of existing random lasers and untunable laser wavelength and radiation direction, and combines the above-mentioned new principles, new technologies and new materials to propose a spectrum-tunable random laser array in the visible light to near-infrared band, And it has the advantages of low threshold value and simple process. It is of great significance for the application of random lasers in photonic and optoelectronic devices.

Contents of the invention

Technical problem: The purpose of this invention is to solve the bottleneck problems of existing random lasers such as high laser threshold, radiation spectrum, and non-tunable directivity. A plasmonic random laser array device based on two-dimensional materials is proposed. By using a two-dimensional material with high photoluminescence effect as a random gain medium, it can effectively reduce the laser threshold and dynamically tune the laser wavelength and laser direction. properties, the preparation process is simple, and can be prepared into an array of random lasers.

Technical solution: The positional relationship of the overall structure of a tunable random laser array device based on two-dimensional materials of the present invention is pumping light source, substrate, bottom electrode, dielectric layer, and laser cavity surrounded by spacer layers from bottom to top. The chamber unit and the top electrode; the two ends of the peripheral drive circuit are respectively connected to the bottom electrode and the top electrode, and the bottom electrode, the dielectric layer, the laser chamber unit and the top electrode form a closed loop.

The substrate is a flexible substrate formed of silicon wafer, sapphire, mica substrate or polymer material.

The bottom electrode and the top electrode are transparent conductive film electrodes, and the optional materials are indium tin oxide ITO, aluminum-doped zinc oxide AZO or graphene; the optional materials for the spacer layer are polyethylene glycol, polyacrylamide, polyamide, etc. Hydrophilic polymer material.

The dielectric layer is composed of two dielectric layers, the lower layer is an inorganic insulating dielectric layer, the optional material is SiN, Al ₂ O ₃ or Si, the upper layer is a polymer dielectric layer with low surface stress, and the optional material is a fluoropolymer Cytop or Teflon; the upper dielectric layer is spin-coated directly on the lower dielectric layer in a thickness range of 0.7 microns to 0.9 microns.

The laser chamber unit includes a first solvent, a second solvent, a metal nanoparticle film self-assembled by metal nanoparticles at the interface of the first solvent and the second solvent, and a two-dimensional material assembled on the surface of the metal nanoparticle film The metal nanoparticles will form Schottky contacts with the two-dimensional material nanosheets. The hot electron-hole pairs generated by the local surface plasmon resonance effect of metal nanoparticles will be doped into the two-dimensional material nanosheets and regulate the energy band of the two-dimensional material nanosheets; metal nanoparticles need to undergo surface coordination. The body is modified, and the two-dimensional material nanosheet needs to be modified by the surface ligand. The optional materials include tetrabutylammonium bromide, hexadecyltrimethylammonium bromide, polyvinylpyrrolidone or carboxymethyl fiber sodium.

The optional material for the first solvent is polar liquid of water or brine, and the surface stress range is 50-90 dynes/cm; the optional material for the second solvent is alkanes, hydrocarbons or alcohols, and the surface stress range is 20-40 dynes/cm cm, the second solvent is insoluble or slightly soluble in the first solvent.

The optional materials of the metal nanoparticles are gold, silver, copper or composite materials of the metals, the morphology is nanorod, nanosphere, nanocone or nanocore-shell structure, and the size ranges from tens of nanometers to hundreds of nanometers. Nano.

The metal nanoparticle film is self-assembled at the interface between the first solvent and the second solvent, and the local surface plasmon resonance peak of the metal nanoparticle film is in the visible light to near-infrared band; before self-assembly, the metal nanoparticle needs to pass through Specific surface ligands are surface modified.

The two-dimensional material nanosheet is self-assembled at the interface between the first solvent and the second solvent after surface ligand treatment; the optional materials for the two-dimensional material nanosheet are graphene, hexagonal boron nitride h-BN, Molybdenum disulfide, tungsten disulfide, hafnium disulfide or hafnium diselenide; the size ranges from tens of nanometers to tens of microns, the thickness is one layer to tens of layers, and the band gap is in the visible to near-infrared band.

The peripheral drive circuit is used to control the operating voltage of the laser chamber unit, and then control the hydrophobic angle of the droplet formed by the second solvent.

Beneficial effect: compared with the prior art, the present invention has the following advantages:

1. The present invention proposes a tunable random laser array device based on two-dimensional materials. For the first time, the relationship between the LSPR resonance peak of metal nanoparticles and its spacing, and the thermal electron-hole pairs generated by the LSPR of metal nanoparticles are used for the two-dimensional material nanometer. The doping effect of sheets, the Schottky contact structure formed by metal nanoparticles and two-dimensional material nanosheets, the dynamic tuning of liquid droplets by electrowetting, and the two-phase interface self-assembly of metal nanomaterials and two-dimensional material nanosheets Effect and other physical mechanisms and mechanisms to prepare dynamically tunable random laser array devices. It can well solve the shortcomings of existing random lasers such as ZnO thin film random lasers and random lasers doped with dye particles in colloidal solutions, such as high threshold, narrow radiation spectrum, and untunable spectral directionality. Moreover, a programmable laser array can be realized through a peripheral driving circuit, and the directivity of different laser units can be controlled separately to realize laser synthesis, and a random laser with high power and high beam quality can be obtained. It is of great significance for the integrated application of random lasers.

2. The present invention proposes a tunable random laser array device based on plasmonic nanostructures, which has the advantages of wide-spectrum tuning. A two-dimensional material with high photoluminescence efficiency is selected as the random gain medium, and its band gap is mostly located at 1.0 ~2.0ev or so, the LSPR peak value of the metal nanoparticles can be adjusted by the two parameters of the intensity of the pump light source and the working voltage of the laser chamber during specific work, thereby tuning the doping effect of the hot electrons generated by the metal nanoparticles on the two-dimensional material, increasing the The spectral range of the random laser radiated by the Institute, the wavelength range of the radiated random laser is from visible light to near-infrared band.

3. The present invention proposes a tunable random laser array device based on plasmonic nanostructures, which has the advantages of low power consumption and low threshold. The field can effectively enhance the light absorption and scattering efficiency of two-dimensional material nanosheets, which enables random lasers to be excited when the intensity of the external pump light source is low. It is a low-power, low-threshold random laser array device.

Description of drawings

Figure 1 is a cross-sectional view of the entire random laser array,

Figure 2 is a top view of the entire laser array.

Figure 3 is a cross-sectional view of the laser chamber unit when the voltage is off or the voltage is low,

Fig. 4 is a top view of the laser chamber unit at high voltage.

In the figure, there are: pump light source 1, substrate 2, bottom electrode 31, top electrode 32, dielectric layer 4, spacer layer 5, laser chamber unit 6, and peripheral drive circuit 7, first solvent 61, second solvent 62, Metal nanoparticles 63 and two-dimensional material nanosheets 65 .

detailed description

The present invention proposes a plasmonic random laser array device based on two-dimensional materials. The overall structure of the random laser array device consists of a substrate, a bottom electrode, a top electrode, a dielectric layer, a spacer layer, a laser chamber unit, a pump Pu light source and peripheral drive circuit. Its positional relationship consists of substrate, bottom electrode, dielectric layer, laser chamber unit surrounded by spacer layers, top electrode, pump light source, and peripheral drive circuit from bottom to top. The peripheral driving circuit forms a closed loop by connecting the bottom electrode and the top electrode.

The laser chamber unit has a first solvent, a second solvent, a metal nanoparticle film self-assembled by metal nanoparticles at the interface of the first solvent and the second solvent, and a two-dimensional material assembled on the surface of the metal nanoparticle film composed of nanosheets. Metal nanoparticles need to be modified by surface ligands. The surface ligands can effectively reduce the surface activation energy of the metal nanoparticles, reduce the repulsion between the metal nanoparticles, and thus can efficiently self-assemble into a thin film at the interface between the first solvent and the second solvent. Two-dimensional material nanosheets also need to be modified by surface ligands to self-assemble on the surface of the first solvent and the second solvent as effectively as metal nanoparticles.

The driving method of the laser chamber unit is as follows: when the pump light source is used to excite the photoluminescence of the two-dimensional material nanosheets in the laser chamber and the localized surface plasmon resonance of the metal nanoparticles from the bottom of the laser chamber, the laser The side of the chamber unit can emit low-threshold random laser light. For the overall directivity of the laser array, the digital programming of the driving signal and the control of the addressing circuit can be realized through the peripheral driving circuit. Achieving Directional Dynamically Tunable Random Lasers.

In the present invention, the random laser array structure and preparation process are as follows: first, on the Si sheet (or sapphire, mica sheet, etc.), an ITO electrode is prepared by photolithography, etching, etc., and then a dielectric layer is prepared on the top, an inorganic insulating dielectric layer It is prepared by PECVD and ALD, and the low surface stress polymer dielectric layer is prepared by spin coating. Then, a hydrophilic laser cavity wall grid layer is prepared by nanoimprinting technology to form an array cavity structure. The hydrophilic material is generally a hydrophilic polymer material such as polyethylene glycol or polyacrylamide. The metal nanoparticles and the two-dimensional material nanosheets modified by the surface ligands are added into the first solvent and the second solvent, and then respectively filled into the laser chamber unit and sealed. The surface ligands can effectively ensure the self-assembly of metal nanoparticles and two-dimensional material nanosheets into thin films at the interface between the first solvent and the second solvent.

In the present invention, a two-dimensional material such as molybdenum disulfide is used as a random gain medium. The structure of the two-dimensional material such as molybdenum disulfide is similar to that of graphene, which is an interlayer structure, and the layers are coupled by weak van der Waals force. Compared with other photoluminescent random gain media, multilayer molybdenum disulfide will form strong bound excitons between layers after absorbing photons, and the existence of these bound excitons makes molybdenum disulfide have a stronger photoluminescence effect , so random lasers made of two-dimensional materials such as molybdenum disulfide have a lower lasing threshold.

In the present invention, the metal nanoparticle film assembled at the interface of two immiscible solvents can further reduce the threshold value of the random laser, and can effectively tune the wavelength of the radiated laser. First of all, metal nanoparticles will produce localized surface plasmon effect (Localized Surface Plasmon Resonance, LSPR) under the irradiation of pump light source, which can localize the light in the deep sub-wavelength range and form a strong resonance near the resonance peak. Local light field, this local light field can more effectively enhance the photoluminescence efficiency of two-dimensional material nanosheets, thereby further reducing the laser threshold. In the present invention, the metal nanoparticles and the two-dimensional material nanosheets are self-assembled at the two-phase interface, so the distance between the metal nanoparticles and the two-dimensional material nanosheets is very small, and when the metal nanoparticles are illuminated to produce the LSPR effect, it will be greatly enhanced. For light absorption, hot electron-hole pairs are generated after absorbing enough photon energy. The generated thermal electrons can play a role in doping the two-dimensional material nanosheets to realize the regulation of the light absorption and photoluminescence spectrum of the two-dimensional material. When the laser array of the present invention is working, by changing the working voltage of the laser chamber, the electrowetting effect can realize the contraction and relaxation of the droplet formed by the second solvent, and then change the particle distance of the metal nanoparticle film. The change of particle spacing will change the LSPR peak of the metal nanoparticle film, thereby regulating the doping of the thermal electrons generated by the metal nanoparticles to the two-dimensional nanomaterial, and realizing the change of the photoluminescence spectrum, that is, realizing the improvement of the random laser radiation spectrum of the present invention. adjust.

Example:

1. Prepare an M×N laser array structure as shown in Figure 1, prepare transparent electrodes on the substrate by photolithography, etching and other processes, and then prepare a dielectric layer and a low surface stress polymer dielectric layer by ALD on the top Prepared by spin-coating process. Then, an M×N grid layer is prepared by nanoimprinting technology to form an array chamber structure, and the hydrophilic material is generally a hydrophilic polymer material such as polyethylene glycol or polyacrylamide. After the overall structure of the device is prepared, metal nanoparticles and two-dimensional material nanosheets are added to the first solvent or the second solvent, and then the first solvent and the second solvent are filled into the laser chamber and passed through the photoresist. seal.

2. Connect the prepared random laser array to the peripheral drive circuit through the bottom electrode and the top electrode, and control the laser chamber unit through the digital signal of the drive circuit.

3. Turn on the pump light source to irradiate the laser chamber from the bottom to emit laser light. The radiation spectrum and directionality of the entire laser array can be controlled by the digital signal of the peripheral circuit. The digital signal is used to control the unit working voltage of the laser chamber. When the operating voltage is changed from low voltage to high voltage, the radiation spectrum will be red-shifted.

Claims (10)

1. A tunable random laser array device based on two-dimensional materials, characterized in that: the overall structural positional relationship of the random laser array device is sequentially pumping light source (1), substrate (2), and bottom electrode from bottom to top (31), dielectric layer (4), laser chamber unit (6) surrounded by spacer layer (5), top electrode (32); the two ends of peripheral driving circuit (7) are respectively connected to bottom electrode (31) It forms a closed loop with the top electrode (32), the bottom electrode (31), the dielectric layer (4), the laser chamber unit (6) and the top electrode (32). 2. A kind of tunable random laser array device based on two-dimensional material as claimed in claim 1, characterized in that: said substrate (2) is formed by silicon wafer, sapphire, mica substrate or polymer material flexible base. 3. a kind of tunable random laser array device based on two-dimensional material as claimed in claim 1, is characterized in that: described bottom electrode (31) and top electrode (32) are transparent conductive film electrodes, optional The material is indium tin oxide ITO, aluminum-doped zinc oxide AZO or graphene; the optional material for the spacer layer (5) is polyethylene glycol, polyacrylamide, polyamide and other hydrophilic polymer materials. 4. A kind of tunable random laser array device based on two-dimensional material as claimed in claim 1, it is characterized in that: described dielectric layer (4) is made up of two layers of dielectric materials, and the lower layer is an inorganic insulating dielectric layer, for The selected material is SiN, Al ₂ O ₃ or Si, the upper layer is a polymer dielectric layer with low surface stress, and the optional material is fluoropolymer Cytop or Teflon; the upper dielectric layer is directly spin-coated on the lower dielectric layer, and the thickness range is 0.7 microns to 0.9 microns. 5. a kind of tunable random laser array device based on two-dimensional material as claimed in claim 1, is characterized in that: described laser chamber unit (6) comprises the first solvent (61), the second solvent ( 62), the metal nanoparticle film (64) self-assembled by the metal nanoparticle (63) at the interface of the first solvent (61) and the second solvent (62), and the two-dimensional material nanoparticle assembled on the surface of the metal nanoparticle film sheet (65), the metal nanoparticle (63) will form a Schottky contact with the two-dimensional material nanosheet (65). The hot electron-hole pairs generated by the localized surface plasmon resonance effect of metal nanoparticles (63) will be doped into two-dimensional material nanosheets (65) and regulate the energy band of two-dimensional material material nanosheets; metal Nanoparticles (63) need to be modified by surface ligands (8), and two-dimensional material nanosheets (65) need to be modified by surface ligands (9). Optional materials include tetrabutylammonium bromide, hexadecyltrimethyl ammonium bromide, polyvinylpyrrolidone, or sodium carboxymethylcellulose. 6. A kind of tunable random laser array device based on two-dimensional material as claimed in claim 5, characterized in that: said first solvent (61) can be selected from the polarity of water or saline liquid, the surface stress range is 50-90 dynes/cm; the second solvent (62) can be selected from alkanes, hydrocarbons or alcohols, and the surface stress range is 20-40 dynes/cm, and the second solvent (62) is insoluble or slightly soluble in the first solvent (61). 7. A kind of tunable random laser array device based on two-dimensional materials as claimed in claim 5, characterized in that: the metal nanoparticle (63) optional material is gold, silver, copper or the The metal composite material has the shape of nanorod, nanosphere, nanocone or nanocore-shell structure, and the size ranges from tens of nanometers to hundreds of nanometers. 8. A kind of tunable random laser array device based on two-dimensional materials as claimed in claim 5, characterized in that: the metal nanoparticle film (64) self-assembles in the first solvent (61) and the second At the interface of the solvent (62), the localized surface plasmon resonance peak of the metal nanoparticle film (64) is in the visible to near-infrared band; before self-assembly, the metal nanoparticle (63) needs to pass through a specific surface ligand (8 ) for surface modification. 9. A kind of tunable random laser array device based on two-dimensional material as claimed in claim 5, characterized in that: said two-dimensional material nanosheet (65) is modified by surface ligands (9) to automatically Assembled at the interface of the first solvent (61) and the second solvent (62); the optional material of the two-dimensional material nanosheet (65) is graphene, hexagonal boron nitride h-BN, molybdenum disulfide, disulfide Tungsten, hafnium disulfide or hafnium diselenide; the size ranges from tens of nanometers to tens of microns, the thickness is from one layer to dozens of layers, and the band gap is in the visible to near-infrared band. 10. A kind of tunable random laser array device based on two-dimensional materials as claimed in claim 1, characterized in that: the peripheral drive circuit (7) is used to control the operating voltage of the laser chamber unit, and then control The hydrophobic angle of the droplet formed by the second solvent (62).