WGM laser based on micron-sized doped ice balls

Abstract

The invention provides an echo wall mode laser based on micron-sized doped ice balls and a preparation method of the echo wall mode laser. The micron-sized doped ice balls are prepared in a low-temperature environment by adding ions (such as rare earth ions) or fluorescent dye and the like into distilled water. Geometric parameters of the doped ice hockey are designed and optimized to ensure that the doped ice hockey has a high quality factor at a target frequency. The doped ice balls are combined with a pump light source, and ions or fluorescent dye and the like in the doped ice balls are excited to generate laser output. The temperature and humidity are monitored by adopting a temperature and humidity control technology, the structural stability of the doped ice balls is guaranteed, and the ice balls are prevented from being melted and deformed. According to the WGM laser, the wavelength, the output power and the like of the laser can be modulated by controlling the volume of the doped ice ball to be increased or decreased, and the WGM laser has the advantages of being efficient, easy to modulate and environmentally friendly and can be widely applied to the fields of high-precision sensing, optical communication and the like in the polar region or the space or other low-temperature environments.

Description

Technical Field

[0001] The invention relates to optoelectronic technology, and is a whispering gallery mode (WGM) laser based on micron-level doped ice balls and a preparation method thereof. Background Art

[0002] With the progress of modern science and technology, optical communication and quantum information technology have gradually developed, and the research on optical resonators and laser devices has continued to deepen. WGM (Whispering Gallery Mode) resonators occupy an important position in the field of optics with their high quality factor and high sensitivity. WGM is an optical phenomenon in which light waves are trapped by total internal reflection at the boundary of a tiny spherical, disc-shaped or ring-shaped resonator and propagate along the cavity wall. The high quality factor of the WGM resonator allows light to remain in the cavity for a longer time with lower losses, which is suitable for optical and quantum information processing applications.

[0003] At present, the preparation materials and methods of WGM lasers are constantly improving, mainly focusing on dielectric materials, semiconductor materials, organic materials, liquid crystal materials, etc. Commonly used dielectric materials have the advantages of high transparency and low light loss. Semiconductor materials such as silicon, gallium arsenide and indium phosphide are widely used in integrated optical and electro-optical devices, especially in the infrared and visible light bands. Organic materials such as organic dyes are widely used in organic WGM lasers due to their high tunability and low threshold characteristics. Liquid crystal materials such as smectic liquid crystals can realize high-performance WGM lasers by utilizing their unique refractive properties and stability.

[0004] However, WGM lasers made of traditional materials have some disadvantages when working in low-temperature environments such as the polar regions or space. First, the thermomechanical properties of these materials may change at low temperatures, resulting in a decrease in the stability of the resonant cavity structure, which in turn affects the performance and life of the laser. Second, the optical properties of some semiconductors change in low-temperature environments, resulting in a decrease in optical gain. In addition, the manufacturing and maintenance costs of traditional WGM resonant cavity materials in low-temperature environments are high, making it difficult to meet application requirements in low-temperature environments. The advantage of choosing ice as a material for preparing WGM lasers lies in its unique physical and optical properties. Ice not only has high transparency, but can also be used for the propagation and resonance of light waves. At the same time, in low-temperature environments, the optical loss of ice is very low, which can effectively maintain a high quality factor, thereby improving the performance of the laser.

[0005] Patent application number 202311234333.6 proposes an ice microsphere optical resonant cavity and a preparation device and method. However, ordinary ice balls themselves do not have the ability to emit light. They are mainly used as optical resonant cavities. They resonate by guiding and reflecting external light, but cannot actively generate or amplify light. Therefore, they can only be used as a passive optical cavity. However, doped ice balls have the ability to photoluminesce due to the fluorescent dyes or rare earth elements doped inside them, and can produce a light amplification effect when stimulated externally.

[0006] In summary, the combination of micron-sized doped ice balls and WGM technology not only has great potential in the innovative use of materials and low-temperature applications, but also can promote the development of high-performance lasers and bring new research and application opportunities to the fields of optics and photonics. Summary of the invention

[0007] The purpose of the present invention is to provide a WGM laser based on a micron-sized doped ice ball and a preparation method thereof, so as to solve the problem that ordinary ice balls have no optical gain capability and light can only be reflected and resonated in the cavity.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A whispering gallery mode laser based on a micron-sized doped ice ball comprises a doped ice ball, a pump light source, an optical fiber and a packaging system, wherein the doped ice ball is formed by low-temperature processing, and temperature and humidity control technology is used to ensure its structural stability; the pump light source is used to excite ions or dyes in the doped ice ball to generate lasers; and the optical fiber is used to guide and adjust the output laser signal.

[0010] The geometric shape of the doped ice ball is spherical, ellipsoidal or cylindrical, and the gain material is rare earth ions or fluorescent dyes.

[0011] The doping ions or fluorescent dyes used in the doped ice ball need to avoid the absorption peak of water when selected, and the wavelength of the pump light source is far away from the water peak position to avoid loss caused by the water peak.

[0012] The optical fiber and the doped ice ball are mounted on a displacement platform, and their relative positions are adjusted by the displacement platform.

[0013] Pulse laser is selected as pump light source to reduce the heat generation per unit time.

[0014] The temperature and humidity control system can detect and adjust the temperature and humidity around the doped ice ball; the laser increases or decreases the volume of the doped ice ball through the temperature and humidity control system, thereby modulating the output power, wavelength or line width of the laser.

[0015] The temperature and humidity control system uses a low-temperature medium circulation refrigeration method to control the temperature around the doped ice ball to ensure the stability of the doped ice ball structure.

[0016] The two ends of the optical fiber used for coupling with the doped ice ball are ordinary optical fibers, and the middle coupling part is the tapered optical fiber core with the cladding removed to prevent the tapered optical fiber part from being affected by icing when the volume or shape of the doped ice ball changes.

[0017] The doped ice ball is a solid or hollow ice ball. The solid doped ice ball can be prepared by directly pouring distilled water uniformly mixed with doping elements or fluorescent dyes into a mold and solidifying the doping solution in a low-temperature environment; the hollow doped ice ball can be prepared by the following steps: first, a metal with a refractive index lower than that of the doped ice layer is selected as the core part, and the metal is gold, silver or aluminum, and then the metal core is placed in a low-temperature environment, and a water mist uniformly mixed with doping elements or fluorescent dyes is sprayed onto the surface of the metal core by an ultrasonic atomizer or a spray device, so that the solvent is gradually frozen under low-temperature conditions, thereby achieving the growth of the doped ice ball on the surface of the metal core and forming an ice layer covering the metal core.

[0018] After the doped ice ball is prepared, the thickness or uniformity of the doped ice ball is adjusted by a carbon dioxide laser so that the doped ice ball reaches a predetermined size and geometric shape; the surface of the doped ice ball is smoothed by a carbon dioxide laser to reduce the surface roughness so as to improve the optical quality of the doped ice ball.

[0019] Beneficial effects of the present invention:

[0020] The present invention can achieve high-efficiency and high-stability laser output by doping excitation ions or fluorescent dyes in the ice ball and combining appropriate preparation and packaging technology. In addition, the temperature and humidity control system in the present invention can freely control the size and shape of the doped ice ball to change multiple times according to needs, thereby achieving the purpose of modulating the laser.

[0021] The doped ice ball is combined with a pump light source to excite the ions or fluorescent dyes in the doped ice ball to produce laser output. The temperature and humidity control technology is used to monitor the temperature and humidity to ensure the structural stability of the doped ice ball and prevent it from melting and deforming. The WGM laser of the present invention can modulate the wavelength, output power, etc. of the laser by controlling the increase or decrease of the volume of the doped ice ball. It has the characteristics of high efficiency, easy modulation and environmental protection, and can be widely used in the fields of high-precision sensing and optical communication in low-temperature environments such as polar regions or space. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Attached Figure 1 : Schematic diagram of laser assembly.

[0023] Attached Figure 2: Schematic diagram of the molecular structure of the doped ice ball.

[0024] Attached Figure 3 : Schematic diagram of the coupling of tapered fiber and doped ice ball.

[0025] Attached Figure 4 : Schematic diagram of the temperature and humidity control system. DETAILED DESCRIPTION

[0026] The present invention proposes a WGM laser based on a micron-sized doped ice ball and a preparation method thereof. First, the whispering gallery mode resonant cavity has a high Q value. By doping gain media such as ions or fluorescent dyes into the ice ball, the preparation of the WGM laser can be realized at the micron level. Compared with ordinary ice balls, the doped ice balls have unique energy level transitions, which provide the WGM laser with the ability of active luminescence, optical gain and a lower excitation threshold, so that it can have a wider range of use prospects in a variety of optical and application occasions. Secondly, for the doped ice balls, the stability of the doped ice ball structure can be guaranteed by fixing the doped ice balls in a specific temperature and humidity control system. Similarly, the volume of the doped ice balls can be increased or decreased according to actual needs, ultimately achieving the purpose of modulating the output power, wavelength or line width of the laser. Based on the above characteristics, the preparation of WGM lasers based on micron-sized doped ice balls can be realized.

[0027] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings.

[0028] The overall structure of the micron-scale doped ice ball WGM laser provided by the present invention is as follows: Figure 1 As shown, it consists of a pump light source, a doped ice ball, a temperature and humidity control system and a spectrometer. Figure 2 The molecular structure diagram of the doped ice ball doped with rare earth ions or fluorescent dyes and other gain media, the doped ice ball is spherical, ellipsoidal or cylindrical in shape; the radius of the doped ice ball ranges from 10μm to 100μm, and the specific diameter of the doped ice ball can be adjusted within the range according to the needs and application environment; a solid doped ice ball can be directly prepared through a mold, or a hollow doped ice ball can be prepared by growing a doped ice ball on the surface of the core metal with a metal with a refractive index lower than that of the doped ice layer as the core. The two ends of the optical fiber used for coupling with the doped ice ball are ordinary optical fibers, and the middle coupling part is a tapered optical fiber after the cladding is removed to prevent the tapered optical fiber part from being affected by icing when the volume or shape of the doped ice ball changes. Figure 3 The figure is a schematic diagram of the coupling between the tapered fiber and the doped ice ball. In order to ensure that the tapered fiber will not break easily, the fiber is fixed on the fiber bracket of the displacement platform, and the displacement platform and the support of the doped ice ball are fixed on the same substrate, and then the whole is moved to the temperature and humidity control system, such as Figure 4Then pass the common optical fibers at both ends of the optical fiber through the sealing holes of the sealed hatch to ensure the sealing of the entire system.

[0029] The present invention provides the following embodiments:

[0030] A WGM laser based on micron-sized doped ice balls is provided, combined with Figure 2 Schematic diagram of the molecular structure of the doped ice ball. Figure 3 Schematic diagram of the coupling between the tapered fiber and the doped ice ball. Figure 4 Schematic diagram of the temperature and humidity control system. The specific steps are: (1) resonant cavity design and optimization; (2) preparation of micron-sized doped ice balls; (3) low-temperature packaging; (4) application testing.

[0031] 1. Resonant cavity design and optimization:

[0032] First, the geometric parameters of the doped ice ball, such as diameter, thickness, and curvature, were designed and optimized through numerical simulation methods. Software was used to simulate the propagation of light waves in the doped ice ball. Then, based on the numerical simulation results, the geometric shape and size of the doped ice ball were adjusted to ensure that it had a 10 6 And above high quality factor.

[0033] According to the Lorentz formula:

[0034]

[0035] Where n is the refractive index, N is the number of molecules per unit volume, and α is the molecular polarizability.

[0036] Dyes or rare earth elements have extremely high polarizability, which leads to a higher refractive index for the ice ball after doping with gain media such as fluorescent dyes or rare earth elements. The total internal reflection principle of WGM relies on the refractive index difference, so the doped ice ball has a stronger confinement effect on the totally internally reflected light, which helps to increase the intensity of the light field and make the laser output stronger and more stable.

[0037] The increase in refractive index after doping will also change the propagation path and resonance mode of light in the WGM cavity, making some modes of light more resonant. This can be used to adjust the output wavelength and mode of the laser, making the output beam quality of the doped laser higher and improving the adjustability of the laser. The size and shape of the doped ice ball directly affect the resonance condition of the WGM. The relationship between the resonance wavelength λ and the doped ice ball radius R and the refractive index n of the material is as follows:

[0038]

[0039] Where λ is the wavelength of the resonant mode (resonant wavelength), R is the radius of the cavity, n is the refractive index, and m is the mode number, which is a positive integer representing the number of times the light resonates.

[0040] Dyes and other materials usually have a wide emission bandwidth, which is suitable for the design of broadband tunable lasers, while rare earth elements and other materials can be used to produce precise single wavelength output. By selecting different doping materials (such as different types of fluorescent dyes or rare earth elements, etc.), the doped ice ball can precisely control the refractive index, giving the laser better tuning capabilities.

[0041] When the refractive index of the doped ice ball is increased, the total internal reflection efficiency of light inside the ice ball is improved, the light loss is reduced, and the light remains in resonance in the cavity for a longer time. This will make it easier to achieve a high quality factor of 10 for the WGM laser. 6 As well as above.

[0042] 2. Preparation of micron-sized doped ice balls:

[0043] Add an appropriate amount of gain media such as excitation ions or fluorescent dyes, such as salt solutions doped with rare earth ions, to distilled water to ensure uniform mixing. Rare earth ions can be erbium ions, ytterbium ions, etc., and fluorescent dyes can be rhodamine, fluorescein, etc. Then place the mixed liquid or other dyes in a refrigeration device to prepare doped ice balls. When selecting gain media such as ions or dyes, it is necessary to avoid the absorption peak of water as much as possible. Materials usually have broadband emission spectra, while rare earth ions have specific emission wavelengths. For example, erbium ions have an emission wavelength at 1550nm, which enables doped ice balls to be used for spontaneous laser emission.

[0044] The doped ice ball is a solid or hollow ice ball. The solid doped ice ball can be prepared by directly pouring distilled water uniformly mixed with doping elements or fluorescent dyes into a mold and solidifying the doping solution in a low-temperature environment; the hollow doped ice ball can be prepared by the following steps: first, a metal with a refractive index lower than that of the doped ice layer is selected as the core part, and the metal is gold, silver or aluminum, and then the metal core is placed in a low-temperature environment, and a water mist uniformly mixed with doping elements or fluorescent dyes is sprayed onto the surface of the metal core through an ultrasonic atomizer or a spray device, so as to promote the gradual freezing of the solvent under low-temperature conditions, thereby achieving the growth of the doped ice ball on the surface of the metal core and forming an ice layer covering the metal core.

[0045] Figure 2 Schematic diagram of the molecular structure of the doped ice ball. Finally, the prepared doped ice ball is placed in a low temperature environment to ensure the stability of its shape and structure. Since the high quality factor Q is related to the surface roughness, the surface of the doped ice ball can be smoothed using a laser after the doped ice ball is made.

[0046] 3. Low temperature packaging:

[0047] The prepared doped ice ball is fixed on the support. The two ends of the optical fiber used for coupling with the doped ice ball are ordinary optical fibers, and the middle is a specially treated tapered optical fiber to prevent the tapered optical fiber part from being affected by ice when the volume or shape of the doped ice ball changes. Figure 3 The schematic diagram of the coupling between the tapered fiber and the doped ice ball. The fiber is fixed on the fiber holder of the displacement platform, and the support of the doped ice ball is fixed on the same substrate as the displacement platform, and then the whole is moved to Figure 4 In the temperature and humidity control system shown in the figure, the support material should have good low temperature resistance and high mechanical strength. The low temperature environment can be achieved by using liquid nitrogen or other low temperature media in the temperature and humidity control system.

[0048] Changes in humidity and temperature will not only cause the volume of the doped ice ball to increase or decrease, but also affect the change in the refractive index of the doped ice ball, and the tapered fiber has the problem of low mechanical strength. In order to ensure the stability of the tapered fiber and the doped ice ball structure, the doped ice ball and the tapered fiber are first fixed to the support and the fiber holder, respectively, and then the whole is packaged in a low-temperature environment of the temperature and humidity control system. In the temperature and humidity control system, the humidity and temperature can be changed as needed, thereby changing the size and shape of the doped ice ball, and the purpose of modulating the laser output power, wavelength or line width can be achieved by changing the refractive index or volume of the doped ice ball in a low-temperature environment.

[0049] 4. Application testing:

[0050] Laser structure: The pump light source can be a laser diode or other suitable light source. Light is emitted from the pump light source, coupled into the doped ice ball through the tapered fiber, and undergoes total internal reflection, forming a whispering gallery mode resonance, which excites the gain medium such as doped ions or fluorescent dyes to generate laser light, which is then output from the output end of the fiber.

[0051] In this example, the loss of water absorption peak is taken into account, and a 980nm pump light source with an output power of 10μw is used, the pumping time is 1min, and a doped ice ball with a doping content of 1% Er and a radius of 100μm is used. The entire substrate is placed in a temperature and humidity control system at -20℃. The melting problem of the doped ice ball due to the laser thermal effect also needs to be considered, which can be calculated according to the following formula:

[0052] Q=mcΔT

[0053] Where Q is the amount of heat absorbed or released, m is the mass of the substance, c is the specific heat capacity of the substance, and ΔT is the change in temperature.

[0054] Because it is placed in a temperature and humidity control system, the temperature can be quickly reduced to maintain the stability of the doped ice ball structure. In order to avoid the melting problem caused by the laser thermal effect, the pulse energy or duty cycle of the pulsed laser can be adjusted to reduce the heat generated per unit time.

[0055] By measuring the change in the resonant frequency of the doped ice ball, adjusting the power of the pump light source or changing the volume of the doped ice ball, a stable laser output can be obtained. The output power, stability and line width of the laser can be verified through experiments such as output power measurement, power stability test or line width measurement, so as to optimize the design of the laser and improve its performance.

[0056] The above disclosures are only several specific embodiments of the present invention; however, the present invention is not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A whispering gallery mode laser based on micron-sized doped ice balls, characterized by: It includes a doped ice ball, a pump light source, an optical fiber and a packaging system. The doped ice ball is formed by low-temperature processing, and temperature and humidity control technology is used to ensure its structural stability. The pump light source is used to excite ions or dyes in the doped ice ball to generate lasers. The optical fiber is used to guide and adjust the output laser signal.

2. The whispering gallery mode laser based on micron-sized doped ice balls according to claim 1, characterized in that: The geometric shape of the doped ice ball is spherical, ellipsoidal or cylindrical, and the gain material is rare earth ions or fluorescent dyes.

3. The whispering gallery mode laser based on micron-sized doped ice balls according to claim 1, characterized in that: The doping ions or fluorescent dyes used in the doped ice ball need to avoid the absorption peak of water when selected, and the wavelength of the pump light source is far away from the water peak position to avoid loss caused by the water peak.

4. The whispering gallery mode laser based on micron-sized doped ice balls according to claim 1, characterized in that: The optical fiber and the doped ice ball are mounted on a displacement platform, and their relative positions are adjusted by the displacement platform.

5. The whispering gallery mode laser based on micron-sized doped ice balls according to claim 1, characterized in that: Pulse laser is selected as pump light source to reduce the heat generation per unit time.

6. The whispering gallery mode laser based on micron-sized doped ice balls according to claim 1, characterized in that: The temperature and humidity control system can detect and adjust the temperature and humidity around the doped ice ball; the laser increases or decreases the volume of the doped ice ball through the temperature and humidity control system, thereby modulating the output power, wavelength or line width of the laser.

7. The whispering gallery mode laser based on micron-sized doped ice balls according to claim 6, characterized in that: The temperature and humidity control system uses a low-temperature medium circulation refrigeration method to control the temperature around the doped ice ball to ensure the stability of the doped ice ball structure.

8. The whispering gallery mode laser based on micron-sized doped ice balls according to any one of claims 1 to 7, characterized in that: The two ends of the optical fiber used for coupling with the doped ice ball are ordinary optical fibers, and the middle coupling part is the tapered optical fiber core with the cladding removed to prevent the tapered optical fiber part from being affected by icing when the volume or shape of the doped ice ball changes.

9. The whispering gallery mode laser based on micron-sized doped ice balls according to claim 8, characterized in that: The doped ice ball is a solid or hollow ice ball. The solid doped ice ball can be prepared by directly pouring distilled water uniformly mixed with doping elements or fluorescent dyes into a mold and solidifying the doping solution in a low-temperature environment; the hollow doped ice ball can be prepared by the following steps: first, a metal with a refractive index lower than that of the doped ice layer is selected as the core part, and the metal is gold, silver or aluminum, and then the metal core is placed in a low-temperature environment, and a water mist uniformly mixed with doping elements or fluorescent dyes is sprayed onto the surface of the metal core by an ultrasonic atomizer or a spray device, so that the solvent is gradually frozen under low-temperature conditions, thereby achieving the growth of the doped ice ball on the surface of the metal core and forming an ice layer covering the metal core.

10. The whispering gallery mode laser based on micron-sized doped ice balls according to claim 9, characterized in that: After the doped ice ball is prepared, the thickness or uniformity of the doped ice ball is adjusted by a carbon dioxide laser so that the doped ice ball reaches a predetermined size and geometric shape; the surface of the doped ice ball is smoothed by a carbon dioxide laser to reduce the surface roughness so as to improve the optical quality of the doped ice ball.

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