Optical microcavity co-doped with gain material and loss control material and preparation method thereof
By doping gain and loss modulating materials into the optical microcavity, the problem of suppressing the number of modes in microlasers in the prior art has been solved, achieving an easy-to-operate, low-cost, and universal mode suppression effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUAZHONG UNIV OF SCI & TECH
- Filing Date
- 2022-09-28
- Publication Date
- 2026-06-02
AI Technical Summary
Existing technologies lack a reliable, easy-to-operate, and low-cost method to suppress the number of lasing modes in microlasers, and existing methods often require high-precision processing and control, and are easily affected by thermal effects and the environment.
By doping gain and loss modulators into an optical microcavity, where the absorption peak wavelength of the loss modulator is longer than that of the gain modulator, and the loss modulator is uniformly doped into the matrix material, the absorption effect of the loss modulator is used to suppress lasing modes, thereby reducing the number of modes.
It achieves easy and low-cost suppression of the number of lasing modes in microlasers, with no spatial limitations in mode suppression effect. It is applicable to different matrix materials and microlaser types and has good robustness.
Smart Images
Figure CN115548851B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of optoelectronic technology, and more specifically, relates to an optical microcavity co-doped with gain material and loss control material and its preparation method. Background Technology
[0002] Miniature lasers have become a research hotspot in recent years. Single-mode lasers offer better stability, lower noise, and higher spectral purity. For applications in optical communication, sensing, and quantum technology, single-mode lasing miniature lasers are crucial. Various schemes have been reported to achieve single-mode lasing, such as reducing microcavity size, the vernier effect, selective mode extraction, spatial shaping of the pump light, and parity-time symmetry. However, among these schemes, reducing the microcavity size requires higher fabrication precision and reduces the quality factor and net gain of the microcavity; selective mode extraction cannot achieve intrinsic single-mode lasing; and spatial shaping of the pump light requires a complex optical shaping system and a high-precision displacement control platform. The vernier effect and parity-time symmetry, on the other hand, require strict control of the coupling between the two microcavities, placing extremely high demands on device fabrication and testing, and are easily affected by thermal effects and environmental factors, leading to coupling mismatch. In addition, there is a scheme to selectively increase scattering loss by placing nanoparticles on the surface of the microcavity to tune coupling loss, but this also requires extremely high coupling control precision, and its mode suppression effect is also spatially limited, and cannot guarantee a similar suppression effect for all low-gain transverse modes.
[0003] In summary, existing technologies still lack a reliable, easy-to-operate, and low-cost method for suppressing the number of lasing modes in microlasers. Summary of the Invention
[0004] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides an optical microcavity co-doped with gain material and loss control material and its preparation method. The purpose is to obtain a reliable, easy-to-operate, and low-cost method for suppressing the number of lasing modes of microlasers by doping with loss control material.
[0005] To achieve the above objectives, according to one aspect of the present invention, an optical microcavity co-doped with a gain material and a loss control material is provided, comprising a matrix material and a gain material and a loss control material uniformly doped into the matrix material; wherein the absorption peak wavelength of the loss control material is longer than that of the absorption peak wavelength of the gain material, and the loss control material is used to reduce the number of lasing modes in the doped microcavity.
[0006] Preferably, the loss-regulating material has material physical and chemical properties similar to those of the gain material, and can be uniformly mixed and co-doped with the gain material.
[0007] Preferably, the gaining substance is a rare earth element or an organic material; more preferably, the gaining substance is erbium or Rhodamine 640.
[0008] Preferably, when the gaining substance is a rare earth element, the loss regulating substance is thulium; when the gaining substance is an organic material, the loss regulating substance is Rhodamine 800.
[0009] Preferably, when the doping ratio of the loss-regulating material is increased, the number of lasing modes in the doped microcavity will decrease.
[0010] Preferably, when the gaining substance is a rare earth element, the matrix material is one of silicon dioxide, alumina, fluoride glass, lithium niobate, and silicon nitride; when the gaining substance is an organic material, the matrix material is one of SU8 polymer, PMMA polymer, and PDMS polymer.
[0011] Preferably, the doping mass of the loss-regulating material is 5%-25% of erbium.
[0012] Preferably, when the doping mass of the loss control material is 25% of erbium, the doped microcavity achieves single-mode lasing.
[0013] Preferably, the doping mass of the loss-regulating material is 0.5%-2% of Rhodamine 640.
[0014] Preferably, when the doping mass of Rhodamine 800 in the dye-doped microcavity is 2% of that of Rhodamine 640, the doped microcavity achieves few-mode lasing.
[0015] Preferably, the doped microcavity is one of the following: microsphere cavity, microbottle cavity, micropillar cavity, microring cavity, microdisk cavity, microring core cavity, polygonal microcavity, microFP cavity, photonic crystal microcavity, and surface plasmon cavity.
[0016] According to another aspect of the present invention, a method for fabricating an optical microcavity co-doped with a gain material and a loss control material is provided. The method includes: mixing the gain material and the loss control material uniformly and then co-doping them into a matrix material, and using the doped matrix material to fabricate a microresonant cavity.
[0017] Preferably, the doping method is one of thermal diffusion doping, sol-gel method, ion implantation, ion exchange, and mixed doping. Preferably, the mixed doping is polymer-assisted thermal diffusion doping.
[0018] Overall, the technical solutions conceived in this invention, compared with the prior art, can achieve at least the following beneficial effects.
[0019] (1) This invention employs a co-doping method with gain material and loss control material, allowing the loss control material to be uniformly distributed with the gain material. The absorption peak wavelength of the loss control material is longer than the gain peak wavelength of the gain material. The addition of the loss element, on the one hand, narrows the effective gain cross-sectional linewidth at the gain wavelength, suppressing the lasing of low-gain longitudinal modes; on the other hand, it introduces additional loss to low-gain transverse modes in terms of spatial distribution, suppressing the lasing of low-gain transverse modes. Thus, the number of lasing modes in the doped microcavity is reduced in an easy-to-operate and low-cost manner, and the mode suppression effect is not spatially limited, and can be applied to all low-gain modes.
[0020] (2) The present invention is simple to implement, low in cost, highly operable, has good mode suppression effect, and is robust.
[0021] (3) This invention can be applied to micro lasers based on different matrix materials and different types, and has universality. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of the lasing of the thulium-erbium (thulium:erbium = 25%) co-doped microcavity in Example 1;
[0023] Figure 2 This is the gain cross-sectional evolution diagram with population inversion in Example 1;
[0024] Figure 3 This is a schematic diagram of the lasing process in the erbium-doped microcavity of Comparative Example 1;
[0025] Figure 4 This is a graph showing the evolution of the gain cross section as the particle number inverts in Comparative Example 1;
[0026] Figure 5 The results are statistical results of the number of optical microcavity lasing modes prepared in Comparative Example 1 and Examples 1, 2, 3, 4, and 5.
[0027] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, including: 1. Schematic laser spectrum 2. Detailed Implementation
[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.
[0029] Example 1
[0030] This embodiment provides an erbium-thulium co-doped silica microsphere cavity, the preparation method of which is shown below:
[0031] (1) A standard single-mode fiber with its coating stripped is fixed on a support and heated and melted using a focused carbon dioxide laser beam with a wavelength of 10.6 micrometers. Under the influence of the fiber's own gravity, the fiber is heated at the focal point with a 300-milliwatt carbon dioxide laser power, thinning it to a diameter of approximately 50 micrometers. Finally, the single-mode fiber is melted and broken from below using a laser, forming a bottle-shaped whispering-gallery mode optical microcavity with a diameter of approximately 50 micrometers.
[0032] (2) A mixed solution was prepared by mixing acetone, polymethyl methacrylate, erbium nitrate pentahydrate, and thulium nitrate hexahydrate in a ratio of 1:0.038:0.0049:0.001225, where the mass of thulium nitrate hexahydrate was 25% of that of erbium nitrate pentahydrate. The prepared micro-bottle cavity was then immersed in the above solution and extracted from the mixed solution to obtain a micro-bottle cavity with a polymer film covering its surface.
[0033] (3) The polymer film on the surface of the micro-cavity was heated with a 300 mW carbon dioxide laser for 20 seconds to remove it; the laser power was further increased to heat the micro-cavity to the point of melting, forming a microsphere cavity under the action of surface tension, and erbium and thulium were co-doped into the micro-cavity. Finally, an erbium-thulium co-doped microsphere cavity with a diameter of about 80 micrometers was obtained.
[0034] Example 2
[0035] The difference between this embodiment and Embodiment 1 is that, when preparing the mixed solution, the mass of erbium nitrate hexahydrate is 20% of that of erbium nitrate pentahydrate.
[0036] Example 3
[0037] The difference between this embodiment and Embodiment 1 is that, when preparing the mixed solution, the mass of erbium nitrate hexahydrate is 15% of that of erbium nitrate pentahydrate.
[0038] Example 4
[0039] The difference between this embodiment and Embodiment 1 is that, when preparing the mixed solution, the mass of erbium nitrate hexahydrate is 10% of that of erbium nitrate pentahydrate.
[0040] Example 5
[0041] The difference between this embodiment and Embodiment 1 is that, when preparing the mixed solution, the mass of erbium nitrate hexahydrate is 5% of that of erbium nitrate pentahydrate.
[0042] Comparative Example 1
[0043] The difference between this comparative example and Example 1 is that erbium nitrate hexahydrate was not added when preparing the mixed solution.
[0044] Test Implementation Examples
[0045] The number of lasing modes was tested on the optical microcavities prepared in Comparative Example 1 and Examples 1, 2, 3, 4, and 5. A microfiber with a diameter of approximately 2 micrometers was used to couple the microcavities to the rare-earth-doped microcavities. The microcavities were then pumped with a tunable laser with a center wavelength of approximately 1515 nanometers. When the power coupled into the microcavities was approximately 400 microwatts, the emitted laser power approached saturation. At this point, the statistical results of the number of lasing modes are as follows: Figure 5 As shown.
[0046] See Figures 1 to 4 When erbium is doped alone, the effective gain linewidth is relatively wide, resulting in multimode lasing. However, when erbium and thulium are co-doped, the effective gain linewidth is narrowed, and low-gain modes are effectively suppressed.
[0047] Depend on Figure 5 It is evident that doping with thulium (a loss-regulating material) can effectively reduce the number of lasing modes. Increasing the doping ratio of the loss-regulating material further reduces the number of lasing modes. When the thulium doping mass reaches 25% of the erbium doping mass, all 20 erbium-thulium co-doped microcavities achieve single-mode lasing. This demonstrates that the proposed method exhibits good mode suppression performance and robustness.
[0048] The microcavity structures used in the tests were microsphere cavities and microbottle cavities. Microsphere cavities and microbottle cavities have relatively large axial dimensions, allowing them to support more resonant modes compared to other microcavity types such as microdisk cavities, microring cavities, microring core cavities, photonic crystal microcavities, and surface plasmon cavities. Therefore, microsphere cavities are more likely to generate multimode lasing. However, all microsphere cavities fabricated using this improved method achieved single-mode lasing, indicating that this method can be applied to microlasers with other structures.
[0049] Example 6
[0050] This embodiment provides a SU8 micro-vial cavity co-doped with Rhodamine 640 and Rhodamine 800, and its preparation method is as follows:
[0051] (1) A standard single-mode optical fiber with the coating stripped was fixed on a support, heated by an oxyhydrogen flame and stretched to both ends to prepare a micro-optical fiber with a diameter of about 8 micrometers.
[0052] (2) Mix SU8 polymer, cyclopentanone, rhodamine 640 and rhodamine 800 in a mass ratio of 1:0.6:0.0016:0.000032. At this time, the mass of rhodamine 800 is 2% of that of rhodamine 640.
[0053] (3) The prepared solution is dropped onto the surface of the microfiber. Under the action of liquid surface tension, the liquid will form a micro-bottle shape with a diameter of about 25 micrometers on the microfiber. The microfiber is then heated at 60 degrees Celsius for 40 minutes to solidify and form the shape.
[0054] Comparative Example 2
[0055] The difference between this comparative example and Example 6 is that Rhodamine 800 was not added when preparing the mixed solution.
[0056] Examples 7-9
[0057] The difference between Examples 7-9 and Example 6 is that the mass of the loss control element is different.
[0058] Test Implementation Examples
[0059] The number of lasing modes was tested on the optical microcavities prepared in Comparative Example 2 and Examples 6, 7, 8, and 9. A pulsed laser with a center wavelength of 532 nm (pulse width of 5 nanoseconds and repetition frequency of 10 Hz) was used as the light source to pump the microcavities at a pump power of approximately 2 microwatts. A large numerical aperture fiber bundle was used to collect the laser spectrum. The statistical results of the number of lasing modes are shown in Table 1.
[0060] Table 1. Statistical results of the number of lasing modes in 50 Rhodamine 640 and Rhodamine 800 co-doped SU8 microcavities.
[0061]
[0062] As shown in Table 1, with the increase of Rhodamine 800 doping ratio, the number of SU8 microcavity lasing modes decreases significantly, demonstrating a clear mode suppression effect. This indicates that the mode suppression method has a certain degree of universality and can be applied to microlasers based on different gain materials and different matrix materials.
[0063] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. An optical microcavity co-doped with a gain material and a loss control material, characterized in that, Includes a matrix material and a gain substance and a loss control substance uniformly doped into the matrix material; The absorption peak wavelength of the loss-regulating material is longer than the gain peak wavelength of the gain material, and the loss-regulating material is used to reduce the number of lasing modes in the doped microcavity. The gaining substance is erbium or rhodamine 640.
2. The optical microcavity co-doped with gain material and loss control material as described in claim 1, characterized in that, When the gain material is erbium, the loss control material is thulium; when the gain material is Rhodamine 640, the loss control material is Rhodamine 800.
3. The optical microcavity co-doped with gain material and loss material as described in any one of claims 1-2, characterized in that, When the doping ratio of the loss-regulating material increases, the number of lasing modes in the doped microcavity decreases.
4. The optical microcavity co-doped with gain and loss materials as described in claim 1, characterized in that, When the gaining substance is erbium, the matrix material is one of silicon dioxide, alumina, fluoride glass, lithium niobate, and silicon nitride; when the gaining substance is Rhodamine 640, the matrix material is one of SU8 polymer, PMMA polymer, and PDMS polymer.
5. The optical microcavity co-doped with gain and loss materials as described in claim 1, characterized in that, The doping mass of the loss-regulating material is 5%-25% of erbium.
6. The optical microcavity co-doped with gain and loss materials as described in claim 5, characterized in that, When the doping mass of the loss-regulating material is 25% of erbium, the doped microcavity achieves single-mode lasing.
7. The optical microcavity co-doped with gain and loss materials as described in claim 2, characterized in that, The doping mass of the loss-regulating material is 0.5%-2% of Rhodamine 640.
8. The optical microcavity co-doped with gain and loss materials as described in claim 1, characterized in that, The doped microcavities are of one type, including microsphere cavity, microbottle cavity, micropillar cavity, microring cavity, microdisk cavity, microring core cavity, polygonal microcavity, microFP cavity, photonic crystal microcavity, and surface plasmon cavity.
9. A method for fabricating an optical microcavity co-doped with a gain material and a loss control material as described in any one of claims 1-8, characterized in that, The method includes: After uniformly mixing the gain material and the loss control material, they are co-doped into the matrix material, and the micro resonant cavity is prepared using the doped matrix material.
10. The preparation method according to claim 9, characterized in that, The doping method is one of the following: thermal diffusion doping, sol-gel method, ion implantation, ion exchange, or mixed doping.