Nanometer laser with low threshold value and tunable wavelength at room temperature and research device

Abstract

The invention provides a scheme and a research device of a nano laser with a low threshold and a tunable wavelength at room temperature. The nano laser comprises a pump light source, a surface plasmon array providing a nano optical cavity, and a gain medium (working substance). The specially-made coaxial variable-angle research device is not only used for collecting nanometer laser signals, but also used for controlling continuous tuning of nanometer laser wavelengths. Different from an ultra-low temperature working environment or ultra-high energy pulse laser as a pumping source in the prior art, the ultra-low threshold nano laser at the room temperature is realized by adopting a method for optimizing the quality factor and the mode volume of the plasmon nano optical resonant cavity. Compared with the prior art, the invention provides a brand-new method for obtaining the low-threshold nano laser at room temperature, and provides an experimental device for developing the nano laser with a simple structure, and the experimental device has important significance for deep research and wide application of the nano laser in the future.

Description

A low-threshold, wavelength-tunable nanolaser at room temperature and its research device Technical Field

[0001] This invention relates to the fields of nanolaser technology and micro-nano optics, and in particular to a low-threshold, wavelength-tunable nanolaser and research device at room temperature. Background Technology

[0002] Combining the advantages of excellent directionality, high brightness, and high energy density, lasers (Light Amplification by Stimulated Emission of Radiation) are hailed as "the brightest light," "the most accurate ruler," and "the fastest knife," playing a vital role in all aspects of human production and life. Since Maiman invented the world's first ruby ​​laser in 1960, laser research has gradually embarked on a miniaturization process, with the core science and technology being the acquisition of micro- and nano-optical resonators. In the 20th century, with the development of micro- and nano-manufacturing and advanced processing technologies, various miniaturized micron-sized lasers were created, such as whispering gallery mode lasers, vertical-cavity surface-emitting lasers (VCSELs), and photonic crystal lasers. The size of lasers has also increased dramatically from the initial tensile strength of 10^12 microns to over 10^12 microns. 1 Reduce to 10 -6 However, the optical diffraction limit restricts laser cavity length to >λ / 2, thus limiting further miniaturization. Until 2003, DJ Bergman and MI Stockman proposed a nanolaser based on stimulated emission amplified surface plasmon resonance (SPR). By using SPR to amplify surface plasmons instead of photons, the optical diffraction limit could be overcome, and the laser size could be reduced to around 10 nm. SPR-based nanolasers are one of the important methods for obtaining coherent light sources at the nanoscale.

[0003] Surface plasmon resonance (SPR) is a collective oscillation between incident light and electrons on a metal surface. When SPR occurs, it can generate an electromagnetic field enhancement of nearly a million times on the metal surface and achieve localized effects on the incident light at the nanoscale. SPR-based nanolasers mainly fall into four types: metal-insulator-semiconductor (MIS), metal-insulator-semiconductor-insulator-metal (MISIM), core-shell type, and periodic arrays. However, regardless of the type, SPR nanolasers exhibit a high threshold, requiring ultra-high-energy pulsed lasers as pump sources or ultra-low temperature operating environments. These stringent operating conditions limit further research and application of nanolasers. Therefore, reducing the threshold of nanolasers and developing room-temperature operating nanolasers are of significant research and application value. Summary of the Invention

[0004] In view of the shortcomings mentioned in the background art, the purpose of the present invention is to provide a low threshold and wavelength-tunable nanolaser and research device at room temperature, which has the advantages of (1) operating at room temperature, (2) ultra-low threshold and (3) wide wavelength tuning range.

[0005] This invention provides a low-threshold, wavelength-tunable nanolaser at room temperature and a research device, comprising:

[0006] (1) An optical detection system consisting of a pump light source, a filter, a focusing lens, a self-made coaxial variable angle optical detection device, a long-pass filter, a linear polarizer, an optical fiber coupling lens, an optical fiber, and a compact small CCD spectrometer;

[0007] (2) Surface plasmon nanoarrays supporting nano-optical resonant cavities;

[0008] (3) Laser gain medium (working material) coated on the surface of the plasmonic array;

[0009] (4) The resonant wavelength of the plasmonic array and the emission wavelength of the laser gain medium have spectral overlap, and the two form a nanolaser system.

[0010] (5) The nanolaser system is placed in the above-mentioned optical detection system to conduct related studies on laser intensity, wavelength tuning, polarization characteristics, etc.

[0011] In this invention, the pump source provides optical excitation and can be a pulsed laser, a continuous laser, or an LED. The emission wavelength of the pump source should match the maximum absorption band of the gain medium, and the intensity is adjustable; this invention does not impose strict limitations on this.

[0012] In this invention, the coaxial variable-angle optical detection device consists of a support base, a perforated rotary stage, a lens cantilever, a rotary stage, a support, a support rod, and a rotating sample holder from bottom to top. The lens cantilever is connected to the perforated rotary stage, allowing control of its rotation within the xoy plane. The rotary stage controls the rotation of the sample stage within the xoy plane, and the rotating sample holder controls the rotation of the nanolaser system within the xoz plane.

[0013] In this invention, the preparation method of the surface plasmon nanoarray is not strictly limited, including but not limited to chemical self-assembly, direct-write lithography, nanoimprint lithography, ultraviolet holographic lithography, or nanosphere lithography, etc. The period of the surface plasmon nanoarray can range from 100 nm to 2000 nm; the arrangement of nanoparticles in the surface plasmon nanoarray can be orthogonal, hexagonal, or other arrangements; the shape of nanoparticles in the surface plasmon nanoarray can be spheres, cylinders, bow ties, or other polygons; the diameter and height of the nanoparticles are not strictly limited; the type and thickness of the coating metal of the surface plasmon nanoarray are not strictly limited, and the coating metal material includes but is not limited to gold, silver, aluminum, copper, etc., with a thickness of 1-500 nm.

[0014] In this invention, the type of gain medium is not strictly limited. The gain medium can be a range of luminescent materials such as laser dyes, perovskites, quantum dots, semiconductors, transition metal dichalcogenides (TMDs), MOFs, and COFs; for example, laser dye LDS-751 can be used. The emission wavelength of the gain medium is not strictly limited.

[0015] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0016] A low-threshold, wavelength-tunable nanolaser at room temperature and a research device, comprising the following steps:

[0017] (1) The optical path is constructed. The pump light emitted by the pump source is filtered to remove stray light, then passes through an adjustable neutral density filter to change the light intensity, and then passes through a focusing lens to irradiate the surface of the nanolaser fabrication chip.

[0018] (2) Assemble the variable angle optical detection device, and install the linear polarizer and fiber collimating lens on the lens cantilever of the variable angle optical detection device in sequence.

[0019] (3) Loading a gain medium onto the surface of a surface plasmon nanoarray to form a nanolaser fabrication system;

[0020] (4) Place the nanolaser fabrication system on the sample holder of the variable angle optical detection device;

[0021] (5) After the modulated pump light is focused, it irradiates the surface of the nanolaser system. The emitted nanolaser signal passes through the linear polarizer on the lens cantilever in sequence, and is collected by the fiber collimating lens and transmitted to the spectrometer to complete the detection and analysis of the signal.

[0022] The light source mentioned in step (1) can be a pulsed laser, a continuous laser, an LED lamp, or other light sources; the present invention does not impose strict limitations on the bandwidth of the filter, the optical density range of the neutral density filter, or the focal length of the convex lens.

[0023] In step (2), the rotation angle range of the lens cantilever in the variable angle optical detection system is 0-360°, the rotation angle range of the sample holder in the variable angle optical detection system is 0-360°, and the rotation angle range of the plasmonic nanoarray on the upper surface of the sample rotating holder is also 0-360°.

[0024] The present invention has the following advantages:

[0025] 1. The surface plasmon nanoarray in this invention can support both extremely high quality factor (Q) and extremely small mode volume (V). m The SPR resonance mode of ).

[0026] 2. This invention lowers the threshold of nanolasers, enabling the development of SPR nanolasers that are continuously laser-pumped at room temperature.

[0027] 3. This invention provides a simple tuning device for the emission wavelength of a nanolaser. By simply rotating the lens cantilever to change the acquisition angle, the peak wavelength of the nanolaser can be modulated within the optical profile of the gain medium. Attached Figure Description

[0028] Figure 1 is the detection optical path diagram of an ultra-low threshold tunable nanolaser at room temperature.

[0029] Figure 2 is a photograph of the nanolaser fabrication system with surface-loaded gain medium prepared in Example 1.

[0030] Figure 3 shows scanning electron microscope (SEM) images of the surface plasmon nanoarray prepared in Example 1, where: (a) top view, (b) side view.

[0031] Figure 4 is a schematic diagram of the variable angle optical detection device assembled in this invention, which realizes detection at different acquisition angles and detection at different reflection angles, wherein: (a) detection is performed using the variable angle optical detection device at different acquisition angles, and (b) detection is performed using the variable angle optical detection device at different reflection angles.

[0032] Figure 5 is a photograph of the variable angle optical detection device in this invention.

[0033] Figure 6 is a schematic diagram of the appearance and assembly of the variable angle optical detection device in this invention.

[0034] Figure 7 shows the modulation characteristics of the emitted wavelength of the nanolaser signal in Example 1. Specifically, by adjusting the acquisition angle from 30° to 76°, the wavelength of the nanolaser moves from 708nm to 823nm. Detailed Implementation

[0035] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0036] Example 1

[0037] As shown in Figure 1, in this embodiment, a 532 nm continuous-wave laser is used as the pump source, and the pump light is incident on the sample surface at a 45° angle. LDS-751 laser dye is used as the gain medium for the nanolaser, dissolved in dimethyl sulfoxide (DMSO) to prepare a 20 mM solution. The LDS-751 solution is pipetted onto the surface of a two-dimensional periodic silver nanoarray, forming a sandwich structure with a coverslip covering the surface to fabricate the nanolaser chip. The nanolaser system under test is placed on a rotating sample holder, as shown in Figure 5. The nanolaser signal emitted from the surface of the two-dimensional silver nanoarray is acquired at a 45° acquisition angle. At a 45° acquisition angle, the wavelength of the nanolaser signal is 764.1 nm, and the linewidth is 3.97 nm. Next, the energy of the pump light is adjusted by adjusting a tunable neutral density filter, and the signal intensity of the nanolaser at different pump energies is acquired.

[0038] Example 2

[0039] Figure 6 is a schematic diagram of the components and assembly of the variable-angle optical detection device of the present invention. The device includes (1) a support rod, (2) a rotating stage, (3) a lens cantilever, (4) a rotating stage with holes, and (5) a support base. Among them, device (5) has four M6 screw holes, which can be fixed to the optical platform with screws. Device (4) has a concave structure at the bottom, the shape of which complements device (5). When (4) is placed on (5) and fixed with screws, device (5) plays a supporting role. Device (3) can be fixed to the surface of (4) with M6 screws. Device (2) has three M4 screw holes, which can be fixed to three of the four screw holes on the surface of (4) with M4 screws. Device (1) has screws at the bottom, which can be fixed to the screw holes at the center of the surface of (2). The sample can be fixed in (1) by connecting the support rod. As shown in Figure 5, the device uses a circular rotating stage with scales to adjust the relative position between the incident light, the reflected light and the sample to achieve variable angle incident and measurement. Figure 7 shows the signals of the nanolaser at different acquisition angles. Similar to Example 1, in this example, 5 μL of LDS-751 solution was dropped onto the silver nanoarray and covered with a coverslip to prevent solution flow. A 532 nm continuous laser was used as the pump source, and the pump light was incident on the surface of the chip under test at a 45° angle. The nanolaser emitted from the surface of the array and was collected at different acquisition angles. Since the resonant wavelength of the surface plasmon resonance of the periodic array redshifts with the increase of the acquisition angle, changing the acquisition angle is a simple way to achieve wavelength tuning of the laser emission. As shown in Figure 7, when the acquisition angle increases from 30° to 76°, the peak position of the nanolaser redshifts from 708 nm to 823 nm, and the wavelength modulation bandwidth can reach ~120 nm.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-threshold, wavelength-tunable nanolaser at room temperature and a research device, comprising the following steps: (1) An optical detection system consisting of a light source, a filter, a focusing lens, a self-made coaxial variable angle optical detection device, a linear polarizer, a fiber collimating lens, an optical fiber, and a compact small CCD spectrometer; (2) A surface plasmon nanoarray providing a nano-optical resonant cavity; (3) A laser gain medium (working material) coated on the surface plasmon array; (4) The resonant wavelength of the plasmon array and the emission wavelength of the laser gain medium have spectral overlap, and the two form a nanolaser system; (5) The nanolaser system is placed in the above optical detection system for research on laser intensity, wavelength tuning, polarization characteristics, etc.

2. The preparation method according to claim 1, characterized in that, In step (1), the light source can be a continuous laser, a pulsed laser, or an LED or other light source.

3. The preparation method according to claim 1, characterized in that, In step (1), the operating wavelength of the light source is matched with the absorption wavelength of the gain medium.

4. The preparation method according to claim 1, characterized in that, In step (2), the variable-angle optical detection device consists of a support base, a perforated rotary stage, a lens cantilever, a rotary stage, a support, a support rod, and a rotating sample holder from bottom to top. The lens cantilever is connected to the perforated rotary stage and can be controlled to rotate in the xoy plane. The rotary stage can control the rotation of the sample stage in the xoy plane, and the rotating sample holder can control the rotation of the nanolaser system in the xoz plane.

5. The preparation method according to claim 1, characterized in that, In step (3), the surface plasmon nanoarray can be prepared by chemical self-assembly, direct writing lithography, nanoimprinting, ultraviolet holographic lithography, or nanosphere lithography, etc.

6. The preparation method according to claim 1, characterized in that, In step (3), the period of the surface plasmon nanoarray is 100nm-2000nm.

7. The preparation method according to claim 1, characterized in that, In step (3), the surface plasmon nanoarrays can be arranged in an orthogonal arrangement, a regular hexagonal arrangement, or other arrangements.

8. The preparation method according to claim 1, characterized in that, In step (3), the shape of the nanoparticles in the surface plasmon nanoarray can be spheres, cylinders, bow ties or other polygons.

9. The preparation method according to claim 1, characterized in that, In step (3), the coating material of the surface plasmon nanoarray can be gold, silver, aluminum, copper or other metals or compounds.

10. The preparation method according to claim 1, characterized in that, In step (3), the thickness of the surface plasmon nanoarray coating material is 1-500 nm.

11. The preparation method according to claim 1, characterized in that, In step (3), the gain medium can be a series of luminescent materials such as laser dyes, perovskites, quantum dots, semiconductors, transition metal dichalcogenides, MOFs, and COFs.

12. The preparation method according to claim 1, characterized in that, In step (3), the light emission range of the gain medium is 200-2000nm.

13. The preparation method according to claim 1, characterized in that, In step (5), the output wavelength of the nanolaser is modulated by changing the acquisition angle by rotating the lens cantilever.

14. A low-threshold, wavelength-tunable nanolaser at room temperature and a research device according to any one of claims 1-13, characterized in that, Includes the following steps: (1) Construct an optical path. The pump light emitted by the light source is filtered to remove stray light. Then, it passes through an adjustable neutral density filter to change the light intensity. After passing through a focusing lens, it illuminates the surface of the nanolaser chip. (2) Assemble a variable angle optical detection device and install a linear polarizer and a fiber collimating lens on the lens cantilever of the variable angle optical detection device in sequence. (3) Load a gain medium on the surface of the plasmonic nanoarray to form a nanolaser system. (4) Place the nanolaser system on the sample holder of the variable angle optical detection device. (5) After being focused by the modulated pump light, it illuminates the surface of the nanolaser system. The emitted nanolaser signal passes through the linear polarizer on the lens cantilever in sequence and is collected by the fiber collimating lens and transmitted to the spectrometer for detection and analysis.

15. The manufacturing method according to claim 4, characterized in that... The assembly method of the variable-angle optical inspection device includes: a support base with four M6 screw holes for fixing to the optical platform; a perforated rotary stage with a concave bottom shape that complements the support base, placed on the support base and secured with screws, the support base providing support; a lens cantilever fixed to the surface of the perforated rotary stage with M6 screws; three M4 screw holes on the rotary stage for fixing to the four holes on the surface of the perforated rotary stage with M4 screws; and a base fixed to the center of the rotary stage surface with screws. The sample can be fixed to the base via a support rod.

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