Isopropanol-based saturable absorber device and preparation method thereof

Abstract

The invention discloses an isopropanol-based saturable absorber device and a preparation method thereof in the fields of ultrashort pulse laser technology and nonlinear optics. The device is mainly composed of isopropanol, a D-type optical fiber, a capillary glass tube and ultraviolet glue, the D-type optical fiber is manufactured through a side face polishing method, the length of a flat area is 17 mm, and the thickness from a plane to a fiber core is 1-2 microns. The D-type optical fiber and the isopropanol are wrapped in the capillary glass tube, and the two ends of the capillary glass tube are sealed by ultraviolet glue, so that the preparation of the saturable absorber device is completed. The thickness of an isopropanol liquid layer in a flat area of the D-type optical fiber is between 20 microns and 40 microns, and saturable absorption of light is realized by utilizing an evanescent field coupling principle. The special structure of the D-type optical fiber enables a laser light field to be locally enhanced when the laser light field is transmitted in a plane area, and the optical absorption performance of the isopropanol-saturable absorber can be improved. The isopropanol-based saturable absorber device has the advantages of being simple in preparation method, easy to operate, high in anti-damage threshold value, low in price and the like, can be widely applied to mode locking and Q switching of lasers, and is beneficial to integration and industrial development of all-fiber laser systems.

Description

Technical Field

[0001] This invention belongs to the fields of ultrashort pulse laser technology and nonlinear optics, and more specifically, relates to a saturable absorber device based on isopropanol and its fabrication method. Background Technology

[0002] Mode-locked pulsed lasers can generate ultrashort pulses in the picosecond to femtosecond range. They possess excellent characteristics such as high peak power and high temporal resolution, leading to their widespread application in precision optical processing, fiber optic sensing, medical imaging, and rapid process detection. Among these, pulsed lasers using saturable absorbers for passive mode-locking are simple in structure, stable in performance, and highly competitive in the market.

[0003] With advancements in materials science, saturable absorbers have played a crucial role in ultrashort pulse laser technology. Saturable absorber devices fabricated from various materials have emerged, including graphene, semiconductor saturable absorber mirrors (SESAMs), carbon nanotubes (CNTs), black phosphorus (BP), transition metal sulfides (TMDs), two-dimensional topological insulators (TIs), and perovskites. However, each of these saturable absorbers has its drawbacks. Graphene typically exhibits weak light absorption and a low damage threshold; SESAMs, currently the most commercially mature saturable absorber, have relatively complex fabrication processes and are expensive; carbon nanotubes have poor dispersibility and are prone to aggregation; black phosphorus is chemically unstable in air and easily oxidized; TMDs, TIs, and perovskites are typically fabricated using methods such as chemical vapor deposition, photoinduced deposition, and magnetron sputtering, which are cumbersome and difficult. Exploring new and superior optical materials for fabricating saturable absorbers can further broaden the application scope and market potential of ultrashort pulse lasers in commercial development, industrial processing, and scientific research. Summary of the Invention

[0004] To address the problems of low damage threshold, cumbersome fabrication process, small modulation depth, and high cost associated with various saturable absorbers, this invention proposes a saturable absorber device based on isopropanol and its fabrication method. The isopropanol-based saturable absorber offers advantages such as a wide spectral tuning range, high damage threshold, and low cost, effectively overcoming the shortcomings of the aforementioned saturable absorbers. Furthermore, the modulation depth of the saturable absorber can be altered by adjusting the thickness of the isopropanol liquid layer filling the flat region of the D-shaped optical fiber. The saturable absorber device fabricated using D-shaped optical fiber is highly compatible with all-fiber laser systems, facilitating the further development of highly integrated industrialization.

[0005] The first aspect of this invention provides a saturable absorber device based on isopropanol, comprising: a standard single-mode fiber cladding, a standard single-mode fiber core, a capillary glass tube, isopropanol, a left transition region of a D-type fiber, a flat region of a D-type fiber, a right transition region of a D-type fiber, and ultraviolet adhesive; the standard single-mode fiber cladding is sleeved with the capillary glass tube, the sleeved region including the left transition region, the flat region, and the right transition region of the D-type fiber; the standard single-mode fiber cladding and the standard single-mode fiber core utilize the principle of total internal reflection to achieve waveguide output of light; the isopropanol is filled into the flat region of the D-type fiber using a syringe, and saturable absorption of light is achieved using the principle of evanescent field coupling; the ultraviolet adhesive is used to seal the D-type fiber and the isopropanol; the standard single-mode fiber passes through the capillary glass tube and has pigtails of a certain length at both ends for connecting other passive optical devices.

[0006] In the isopropanol-based saturable absorber device according to the first aspect of the present invention, the thickness of the isopropanol liquid layer in the flat region of the D-type optical fiber is between 20 μm and 40 μm.

[0007] In the isopropanol-based saturable absorber device described in the first aspect of the present invention, the D-type optical fiber is fabricated by side polishing, the length of the flat region is 17 mm, the thickness from the plane to the fiber core is 1 to 2 μm, and the length of the transition region on the left and right sides is 1 to 3 mm.

[0008] In the isopropanol-based saturable absorber device described in the first aspect of the present invention, the capillary glass tube has an inner diameter of 0.5 to 5 mm and a length of 50 to 100 mm.

[0009] The second aspect of this invention provides a method for fabricating a saturable absorber device based on isopropanol, comprising the following steps: First, under microscopic observation, an appropriate amount of isopropanol is filled into the flat region of a D-shaped optical fiber using a syringe; Second, a capillary glass tube with an inner diameter of 1 mm, an outer diameter of 1.3 mm, and a length of 60 mm is prepared and fitted onto the flat region and transition region of the D-shaped optical fiber; Third, the left and right ends of the capillary glass tube are sealed with ultraviolet glue. The insertion loss of the D-shaped optical fiber is less than 0.1 dB, and after sealing with the isopropanol solution, the insertion loss is approximately 1 dB.

[0010] The beneficial effects of this invention are as follows:

[0011] The saturable absorber device prepared with isopropanol as the material described in this invention has strong absorption in the 1μm to 2μm wavelength range. Compared with other saturable absorbers, isopropanol is easy to obtain, has low thermal effect, high damage resistance threshold, and low price, and can work stably in mode-locked lasers.

[0012] The saturable absorber device fabricated using isopropanol described in this invention allows for adjustment of the modulation depth of the saturable absorber by varying the thickness of the isopropanol liquid layer filling the flat region of a D-shaped optical fiber, thus meeting the design requirements of various ultrashort pulse lasers. Furthermore, the good contact between isopropanol and the polished surface of the D-shaped fiber effectively reduces light reflection and scattering losses at the interface, facilitating evanescent wave coupling. The saturable absorber device fabricated using D-shaped optical fibers enables the construction of all-fiber laser systems, promoting the further development of highly integrated industrialization. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the isopropanol-based saturable absorber device structure of the present invention;

[0014] Figure 2 The absorption spectrum test results of isopropanol according to the present invention are shown in the figure.

[0015] Figure 3 This is a schematic diagram of the all-fiber ultrashort pulse laser that utilizes an isopropanol saturable absorber device for mode locking according to the present invention. Detailed Implementation

[0016] The invention will now be described in further detail with reference to the technical solution and accompanying drawings. No particular limitations are imposed on the invention. Unless otherwise specified, the technical means employed in the embodiments are considered conventional means mastered by those skilled in the art, and the reagents, methods, and devices used are all conventional reagents, methods, and devices used by those skilled in the art.

[0017] The first aspect of the present invention provides a saturable absorber device based on isopropanol.

[0018] Figure 1This is a schematic diagram of the isopropanol-based saturable absorber device structure of the present invention. The isopropanol-based saturable absorber device includes: a standard single-mode fiber cladding (1), a standard single-mode fiber core (2), a capillary glass tube (3), isopropanol (4), a left transition region (5) of a D-type fiber, a flat region (6) of a D-type fiber, a right transition region (7) of a D-type fiber, ultraviolet adhesive (8) and (9); the standard single-mode fiber cladding (1) is sleeved with the capillary glass tube (3), and the sleeved area includes the left transition region (5) of the D-type fiber, the flat region (6) of the D-type fiber, and the right transition region (7) of the D-type fiber. Side transition region (7); the standard single-mode fiber cladding (1) and the standard single-mode fiber core (2) use the principle of total internal reflection to realize the waveguide output of light; the isopropanol (4) is filled into the flat area (6) of the D-type fiber with a syringe, and the saturable absorption of light is realized by using the principle of evanescent field coupling; the ultraviolet glue (8) and (9) are used to seal the D-type fiber and isopropanol; the standard single-mode fiber passes through the capillary glass tube and leaves a certain length of pigtail at both ends for connecting other passive optical devices.

[0019] In an embodiment of the present invention, the thickness of the isopropanol liquid layer in the flat region of the D-type optical fiber is between 20 μm and 40 μm.

[0020] In this embodiment of the invention, the D-type optical fiber is fabricated using a side polishing method, with a flat area length of 17 mm, a thickness from the plane to the fiber core of 1 to 2 μm, and a transition area length of 1 to 3 mm on both sides.

[0021] In an embodiment of the present invention, the capillary glass tube has an inner diameter of 0.5 to 5 mm and a length of 50 to 100 mm.

[0022] A second aspect of this invention provides a method for fabricating an isopropanol-based saturable absorber device: First, under microscopic observation, an appropriate amount of isopropanol is filled into the flat region of a D-shaped optical fiber using a syringe; second, a capillary glass tube with an inner diameter of 1 mm, an outer diameter of 1.3 mm, and a length of 60 mm is prepared and fitted onto the flat region and transition region of the D-shaped optical fiber; third, the left and right ends of the capillary glass tube are sealed with ultraviolet adhesive. The isopropanol-based saturable absorber device is then fabricated, with an insertion loss of approximately 1 dB.

[0023] Figure 2 The absorption spectrum of isopropanol described in this invention shows strong absorption in the 1μm to 2μm wavelength range.

[0024] A third aspect of the present invention provides a passive mode-locked pulsed laser, including the isopropanol saturable absorber device mentioned in the first aspect above.

[0025] Figure 3 This is a schematic diagram of the all-fiber ultrashort pulse laser constructed using the aforementioned isopropanol saturable absorber device according to the present invention. An embodiment of the all-fiber ultrashort pulse laser constructed using the aforementioned mode-locking device includes: a pump source 2-1 for providing energy excitation; a wavelength division multiplexer 2-2 for coupling the pump light into the gain fiber; an erbium-doped fiber or thulium-doped fiber 2-3 as the gain fiber for optical amplification; a polarization-independent isolator 2-4 to ensure unidirectional propagation of light in the resonant cavity; a 10% port of a 10:90 coupler 2-5 for signal detection; an isopropanol-saturable absorber device 2-6 for mode-locking; and a three-loop polarization controller 2-7 for adjusting the polarization state within the cavity. When the gain and loss, dispersion, and nonlinearity of this system reach equilibrium, ultrashort pulse laser output can be achieved.

[0026] The above embodiments are for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention. Based on a thorough understanding of the present invention, those skilled in the art can make various modifications and optimizations, and unless these modifications and optimizations involve changes to the innovative principles, these equivalent modifications and optimizations still fall within the scope of the claims of the present invention.

Claims

1. A saturable absorber device based on isopropanol and its preparation method, characterized in that, include: The standard single-mode fiber cladding (1), standard single-mode fiber core (2), capillary glass tube (3), isopropanol (4), left transition region of D-type fiber (5), flat region of D-type fiber (6), right transition region of D-type fiber (7), ultraviolet glue (8) and (9); the standard single-mode fiber cladding (1) is sleeved with the capillary glass tube (3), and the sleeved area includes the left transition region of D-type fiber (5), flat region of D-type fiber (6) and right transition region of D-type fiber (7); the standard single-mode fiber cladding (1) and standard single-mode fiber core (2) use the principle of total internal reflection to realize the waveguide output of light; the isopropanol (4) is filled into the flat region of D-type fiber (6) with a syringe, and the saturable absorption of light is realized by using the principle of evanescent field coupling; the ultraviolet glue (8) and (9) are used to seal the D-type fiber and the isopropanol solution; the standard single-mode fiber passes through the capillary glass tube and leaves a certain length of pigtail at both ends for connecting other passive optical devices.

2. The isopropanol-based saturable absorber device and its preparation method according to claim 1, characterized in that, The nonlinear optical absorption material used in the saturable absorber device is an organic compound called isopropanol, with the chemical formula C3H8O.

3. The isopropanol in the isopropanol-based saturable absorber device according to claim 1 has strong absorption in the 1μm to 2μm wavelength range.

4. The isopropanol-based saturable absorber device according to any one of claims 1-3, characterized in that, The thickness of the isopropanol liquid layer in the flat region of the D-type optical fiber is between 20 μm and 40 μm.

5. The isopropanol-based saturable absorber device according to claim 1, characterized in that, The modulation depth of the saturable absorber can be changed by adjusting the thickness of the isopropanol liquid layer filling the flat region of the D-type optical fiber.

6. The isopropanol-based saturable absorber device and its preparation method according to claim 1, characterized in that, The D-type optical fiber is fabricated using a side polishing method. The flat area is 17 mm long, the thickness from the plane to the fiber core is 1–2 μm, and the length of the transition area on the left and right sides is 1–3 mm.

7. The isopropanol-based saturable absorber device and its preparation method according to claim 1, characterized in that, The capillary glass tube has an inner diameter of 0.5–5 mm and a length of 50–100 mm.

8. The D-type optical fiber according to claim 6 is fabricated using a side polishing method, characterized in that, The isopropanol has good contact with the polished surface of the D-type fiber, which can effectively reduce the reflection and scattering loss of light at the interface and facilitate evanescent wave coupling.

9. A method for fabricating a saturable absorber device based on isopropanol, characterized in that, Includes the following steps: The first step involves filling the flat area of ​​the D-type optical fiber with an appropriate amount of isopropanol using a syringe under microscopic observation. The second step involves preparing a capillary glass tube with an inner diameter of 1 mm, an outer diameter of 1.3 mm, and a length of 60 mm, and fitting it over the flat and transition areas of the D-type optical fiber. The third step involves sealing both ends of the capillary glass tube with UV adhesive. The insertion loss of the D-type optical fiber is less than 0.1 dB, and after sealing with isopropanol, the insertion loss is approximately 1 dB.

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