Saturable absorber based on tantalum phosphide quantum dots and preparation method and application thereof

Abstract

The present application relates to the technical field of fiber lasers, and particularly relates to a saturable absorber based on tantalum phosphide quantum dots and a preparation method and application thereof.The present application provides a saturable absorber based on tantalum phosphide quantum dots, comprising: tantalum phosphide quantum dots and a fused taper fiber, wherein the tantalum phosphide quantum dots are attached to the surface of the waist of the fused taper fiber; the saturable absorber based on tantalum phosphide quantum dots is used in a passively mode-locked laser, can output pulses with good stability, and has good stability and a wide working wavelength range.

Description

Technical Field

[0001] This invention relates to the field of fiber laser technology, and in particular to a saturable absorber based on tantalum phosphide quantum dots, its preparation method, and its application. Background Technology

[0002] Ultrafast lasers, as an emerging technology, represent a significant development direction in the laser field. Their pulse widths can reach picosecond or femtosecond levels, resulting in extremely short interaction times between the generated ultrashort pulses and materials. This minimizes the impact on molecular thermal motion, leading to less thermal interference; hence, ultrafast laser processing is also known as cold processing. Furthermore, the smooth, crack-free surfaces produced by ultrafast laser processing make it an ideal tool for precision, non-destructive machining, giving it significant academic research value in fields such as scientific research, medicine, and precision manufacturing. However, practical applications of ultrafast lasers require energy release within extremely short timeframes. Existing mode-locked ultrashort pulse lasers perfectly meet this requirement, offering advantages such as simple construction, portability, easy maintenance, and stable light output performance, making them a widely used high-tech tool across various industries.

[0003] Passive mode-locking is a technique for generating stable ultrashort pulse lasers. The main types of passive mode-locking are saturable absorbers, nonlinear amplification environments, and nonlinear polarization rotation mode-locking. Its basic principle is to add a saturable absorber into the optical path. After the pump light source passes through the saturable absorber, the light intensity on both sides is low and the loss is high, while the light intensity in the middle is high and the loss is low. As a result, the light pulse is narrowed and continuously circulates in the oscillating cavity to generate ultrashort pulses.

[0004] In the existing technology, the saturable absorber of mode-locked lasers is SESAM. Although SESAM can optimize the generation of ultrashort pulses by passive mode-locking devices, it still has the problems of a narrow operating wavelength range (less than 100nm) and poor stability. Summary of the Invention

[0005] In view of this, the present invention provides a saturable absorber based on tantalum phosphide quantum dots, its preparation method and application, to solve the technical problems of poor stability and narrow operating wavelength range of saturable absorber materials in mode-locked lasers in the prior art.

[0006] The first aspect of the present invention provides a saturable absorber based on tantalum phosphide quantum dots, comprising: tantalum phosphide quantum dots and fused taper optical fiber;

[0007] The tantalum phosphide quantum dots are attached to the waist surface of the fused taper optical fiber.

[0008] The second aspect of this invention provides a method for preparing a saturable absorber based on tantalum phosphide quantum dots, characterized by comprising the following steps:

[0009] Step 1: Drop the tantalum phosphide quantum dot solution onto the waist of the fused taper fiber;

[0010] Step 2: Allow the fused taper fiber to stand until the solvent in the tantalum phosphide quantum dot solution has completely evaporated, so that the tantalum phosphide quantum dots are deposited at the waist of the fused taper fiber, thus obtaining a saturable absorber based on tantalum phosphide quantum dots.

[0011] Specifically, when a saturable absorber based on tantalum phosphide quantum dots is used in a passively mode-locked laser, the two ends of the fused taper fiber of the aforementioned saturable absorber based on tantalum phosphide quantum dots are fused to fiber optic jumpers, thereby connecting the saturable absorber based on tantalum phosphide quantum dots to the passively mode-locked laser.

[0012] Preferably, the method for preparing the tantalum phosphide quantum dot solution includes the following steps:

[0013] Tantalum phosphide powder was mixed with anhydrous ethanol and sonicated to obtain a suspension.

[0014] The supernatant of the suspension was centrifuged to obtain a tantalum phosphide quantum dot solution.

[0015] Preferably, the frequency of the ultrasound is 40kHz, the power of the ultrasound is 300W, and the duration of the ultrasound is 15 hours.

[0016] Preferably, the centrifugation speed is 5000 rbm / min, the centrifugation time is 20 min, and the centrifugation temperature is 30℃.

[0017] Preferably, the method for fabricating fused taper optical fibers includes the following steps:

[0018] S1. First, straighten the single-mode fiber and clamp it on two fiber clamps. The fiber clamps are fixed on two precision stepper motors respectively.

[0019] S2. Then, the optical fiber is burned with a high-temperature flame while a computer-controlled stepper motor stretches the optical fiber clamp to both sides to obtain a fused taper optical fiber.

[0020] S3. Place the fused taper fiber on a glass slide and fix it on both sides with UV adhesive to prevent the fused taper part of the fiber from being pulled and broken by external force.

[0021] Preferably, in step S2, the stretching length of the fused taper fiber is 8 mm, and the waist diameter of the fused taper fiber is 13 nm.

[0022] The third aspect of this invention provides the application of the above-mentioned saturable absorber based on tantalum phosphide quantum dots in the preparation of passively mode-locked lasers.

[0023] The fourth aspect of the present invention provides a passive mode-locked laser, comprising: a laser pump source, a wavelength division multiplexer, a gain fiber, a polarization-independent isolator, a polarization controller, a single-mode transmission fiber, an output coupler, and the above-mentioned saturable absorber based on tantalum phosphide quantum dots or the saturable absorber based on tantalum phosphide quantum dots prepared by the above-mentioned preparation method.

[0024] The laser pump source, the first input terminal of the wavelength division multiplexer, the gain fiber, the polarization-independent isolator, the saturable absorber based on tantalum phosphide quantum dots, the polarization controller, and the output coupler are connected in sequence through the single-mode transmission fiber.

[0025] The 50% output terminal of the output coupler is connected to the second input terminal of the wavelength division multiplexer through the single-mode transmission optical fiber to form a ring resonant cavity.

[0026] Preferably, the laser pump source is a semiconductor laser source with a wavelength of 980 nm;

[0027] The center wavelength of the wavelength division multiplexer is 980–1550 nm.

[0028] As can be seen from the above technical solutions, the present invention has the following advantages:

[0029] This invention provides a saturable absorber based on tantalum phosphide quantum dots, comprising: tantalum phosphide quantum dots and fused taper fiber; the tantalum phosphide quantum dots are attached to the tapered waist surface of the fused taper fiber. This saturable absorber based on tantalum phosphide quantum dots is used in a passively mode-locked laser, which can output pulses with good stability and has good stability and a wide operating wavelength range. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 A flowchart of the preparation process of a saturable absorber based on tantalum phosphide quantum dots is provided for this invention;

[0032] Figure 2 The X-ray diffraction pattern of the tantalum phosphide quantum dot material provided in Embodiment 1 of the present invention;

[0033] Figure 3 An atomic force microscope image of the tantalum phosphide quantum dot material provided in Embodiment 1 of the present invention;

[0034] Figure 4 This is a transmission electron microscope image of the tantalum phosphide quantum material provided in Embodiment 1 of the present invention;

[0035] Figure 5 This is a schematic diagram of a mode-locked fiber laser provided in Embodiment 3 of the present invention;

[0036] Figure 6 This is a fundamental frequency mode-locked spot spectrum of a mode-locked fiber laser provided in Embodiment 3 of the present invention;

[0037] Figure 7 This is the output spectrum of a mode-locked fiber laser provided in Embodiment 3 of the present invention;

[0038] Figure 8 This is the autocorrelation curve of a mode-locked fiber laser provided in Embodiment 3 of the present invention, obtained by Gaussian fitting.

[0039] Figure 4 In the image, part a is a low-resolution transmission electron microscope (TEM) image of tantalum phosphide quantum material, and part b is a high-resolution TEM image.

[0040] Figure 5 In the diagram, 1 is the laser pump source, 2 is the wavelength division multiplexer, 3 is the erbium-doped gain fiber, 4 is the polarization-independent isolator, 5 is the polarization controller, 6 is the output coupler, 7 is the saturable absorber, 8 is the first 50% output terminal, and 9 is the second 50% output terminal.

[0041] Figure 6 In the diagram, part a is the mode-locked pulse sequence diagram of the mode-locked fiber laser, part b is the broadband spectrum diagram of the mode-locked fiber laser, and part c is the pulse emission spectrum of the mode-locked fiber laser. Detailed Implementation

[0042] In the current technology, the most commonly used saturable absorber in mode-locked lasers is SESAM. However, SESAM still has some drawbacks, such as complex manufacturing process, high environmental requirements, many external interference factors, and unresolved issues in terms of performance, such as narrow operating wavelength range (less than 100nm), long recovery time, and difficulty in controlling modulation depth. Therefore, developing a saturable absorber material that can overcome these drawbacks of SESAM is a problem that must be solved in the field of ultrashort pulse lasers.

[0043] In view of this, the present invention provides a saturable absorber based on tantalum phosphide quantum dots, its preparation method, and its application. Please refer to [link to relevant documentation]. Figure 1This invention provides a method for preparing a saturable absorber based on tantalum phosphide quantum dots. The method involves dropping a tantalum phosphide quantum dot solution onto the waist of a fused taper fiber, thereby depositing the tantalum phosphide quantum dots at the waist of the fiber. This saturable absorber material can improve the stability and operating wavelength range of a mode-locked laser when used in a mode-locked laser.

[0044] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; or they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0045] In the description of this application, it should be noted that fiber fusion taper is an abbreviation for fiber fusion tapering, an important technique for altering the properties of ordinary optical fibers. Ordinary optical fibers are fabricated by heating a relatively thick preform to a molten state, and then manually or mechanically drawing it to the diameter of an ordinary optical fiber. In contrast, the fusion-tapered fiber in this application is formed by drawing the ends of a single-mode fiber. After fusion tapering, the thinnest part in the middle is called the waist, and the portion between the waist and the undrawn fiber is called the transition region.

[0046] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0047] All raw materials or reagents used in the following examples are commercially available or self-made.

[0048] Example 1

[0049] Example 1 of this application provides a method for preparing tantalum phosphide quantum dot material, the method comprising the following steps:

[0050] Step 1: Mix 200 mg of tantalum phosphide powder with anhydrous ethanol and then sonicate to obtain a tantalum phosphide suspension;

[0051] Step 2: Take the supernatant of the tantalum phosphide suspension obtained in Step 1 and put it into a centrifuge. Centrifuge at 5000 rpm for 20 minutes to obtain tantalum phosphide quantum dot solution.

[0052] In step 1, the amount of anhydrous ethanol is 100 ml, the frequency of the ultrasound is 40 kHz, the power is 300 W, the time is 15 h, and the temperature is 30 °C.

[0053] This embodiment also characterizes the tantalum phosphide quantum dot material, and the results are as follows: Figure 2-4 As shown.

[0054] in, Figure 2 The X-ray diffraction image of tantalum phosphide shown has a good match with the standard PDF#65-8241 card, indicating that the raw material is indeed tantalum phosphide and has good purity.

[0055] To further analyze the size of tantalum phosphide quantum dots, atomic force microscopy analysis was also performed on the tantalum phosphide quantum dots, and the results are as follows: Figure 3 As shown, from Figure 3 Part (a) shows that the lateral dimensions of the prepared quantum dots are relatively small and uniform, with the heights of three typical tantalum phosphide quantum dots being statistically significant. Figure 3 In section (b), the heights of the three typical tantalum phosphide quantum dots are 2.493 nm, 2.329 nm, and 3.898 nm, respectively.

[0056] Transmission electron microscopy (TEM) was performed on the tantalum phosphide quantum material of this embodiment, yielding both low-resolution and high-resolution TEM images, as shown below. Figure 4 As shown. From Figure 4 It can be seen that the tantalum phosphide quantum material prepared in Example 1 has very small thickness and lateral dimensions. This finding is consistent with the conclusions of atomic force microscopy (AFM) image analysis, suggesting that the sample size has reached the quantum dot level and its crystal structure is intact with a lattice spacing of 0.185 nanometers.

[0057] Example 2

[0058] This application provides a method for preparing a saturable absorber based on tantalum phosphide quantum dots, the method comprising the following steps:

[0059] Step 1: First, straighten the single-mode fiber and clamp it in two fiber clamps. The fiber clamps are then fixed to two precision stepper motors.

[0060] Step 2: Then, the optical fiber is scorched with a high-temperature flame while a computer-controlled stepper motor stretches the optical fiber clamp to both sides, with a stretching length of 8mm and a waist diameter of 13nm, to obtain fused taper optical fiber.

[0061] Step 3: Place the stretched fused taper fiber on the glass slide and fix it to the glass slide on both sides with UV glue to prevent the fused taper part of the fiber from being pulled and broken by external force.

[0062] Step 4: Apply the tantalum phosphide quantum dot solution to the waist of the fused-tap fiber using a chemical dropper.

[0063] Step 5: Let stand until the anhydrous ethanol solvent evaporates completely, and tantalum phosphide quantum dots are deposited at the waist of the fused taper fiber. Then, fused the two ends of the fused taper fiber to the fiber jumper to obtain a saturable absorber based on tantalum phosphide quantum dots in the fused taper fiber.

[0064] Example 3

[0065] This application provides an application example based on a tantalum phosphide quantum dot saturable absorber. Specifically, the tantalum phosphide quantum dot saturable absorber is connected to an optical path via an optical fiber patch cord to form a mode-locked fiber laser, the structure of which is as follows: Figure 5 As shown.

[0066] A mode-locked fiber laser includes: a laser pump source 1, a wavelength division multiplexer 2, an erbium-doped gain fiber 3, a polarization-independent isolator 4, a polarization controller 5, an output coupler 6, and a saturable absorber 7 prepared in Example 2.

[0067] The laser pump source is a 980nm semiconductor laser, and the center wavelength of the wavelength division multiplexer (WDM) is 980–1550nm. The WDM includes a first input terminal and a second input terminal, and the output coupler includes a first 50% output terminal and a second 50% output terminal. The laser pump source 1, the first input terminal of the WDM 2, the gain fiber 3, the polarization-independent isolator 4, the saturable absorber 7, the polarization controller 5, and the output coupler 6 are sequentially connected through a single-mode transmission fiber (SMF-28e). Then, the first 50% output terminal of the output coupler is connected to the second input terminal of the WDM 2 through a single-mode fiber to form a ring resonant cavity.

[0068] In this embodiment, a saturable absorber based on fused taper fiber optic tantalum phosphide quantum dot is coupled into the cavity of a pulsed laser via fiber optic jumpers. This coupler can achieve amplitude self-modulation, suppress the continuous wave of the laser, and realize pulsed nanosecond output. The pulse sequence has a uniform period, a signal-to-noise ratio as high as 57.47 dB, and a frequency of 21.01 MHz. This indicates that the mode-locked fiber laser based on tantalum phosphide quantum dot saturable absorber has good output stability and can solve the problem of insufficient stability of saturable absorber materials in the prior art.

[0069] Furthermore, the cavity length of the ring resonant cavity is approximately 10.5m.

[0070] Furthermore, the second 50% output terminal 9 of the output coupler is used to connect relevant instruments to measure the laser output characteristics of the fiber laser.

[0071] Furthermore, this embodiment provides a mode-locking test for a mode-locked fiber laser. During the mode-locking test, a saturable absorber based on fused taper fiber tantalum phosphide quantum dots was not initially inserted to observe whether self-mode-locking occurred in the constructed optical path. After repeatedly adjusting the polarization controller, no mode-locking signal was observed on the oscilloscope; therefore, it was determined that no self-mode-locking phenomenon existed in the optical path.

[0072] After confirming the absence of mode-locking in the optical path, a saturable absorber based on tantalum phosphide quantum dots was inserted into the optical path. By adjusting the polarization state and pump power within the cavity, mode-locking of the fundamental frequency was successfully achieved. The results are as follows: Figure 6-8 As shown.

[0073] in, Figure 6 The fundamental frequency mode-locked mode dot plot of a mode-locked fiber laser is shown below. Figure 6 As shown in part a, the mode-locked pulse sequence is stable, with a mode-locking period of approximately 47.6 ns, corresponding to a repetition frequency of 21.01 MHz, which matches the cavity length of the entire optical path, 10.5 m. From... Figure 6 As shown in section c, the fundamental frequency spectrum of this mode-locked signal has a signal-to-noise ratio as high as 57.47 dB, indicating extremely strong signal stability. Figure 6 Part b, the broadband spectrum in the 0-350MHz range further verifies this conclusion. It is evident that the mode-locked fiber laser based on tantalum phosphide quantum dot saturable absorbers can output pulses with good stability, a signal-to-noise ratio as high as 57.47dB, and a frequency of 21.01MHz.

[0074] Figure 7 The graph shows the test results of the output spectrum of a mode-locked fiber laser. Figure 7 It can be seen that the center wavelength of mode-locking is 1564.06nm, and the 3-dB bandwidth is approximately 6.76nm.

[0075] Figure 8 For the autocorrelation curve fitted by Gaussian, from Figure 8 It is known that the pulse width of the mode-locked pulse is 552 fs. This indicates that the mode-locked fiber laser based on fused taper fiber tantalum phosphide quantum dot saturable absorber can output good stability and can output ultrashort pulse sequences with a pulse width of up to 552 fs. This solves the technical problem that the existing saturable absorber material SESAM is not stable enough and cannot meet the requirements of passive mode-locked laser applications.

[0076] The above provides a detailed description of a saturable absorber based on tantalum phosphide quantum dots, its preparation method, and its applications. For those skilled in the art, based on the ideas of the embodiments of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A saturable absorber based on tantalum phosphide quantum dots, characterized in that, It includes tantalum phosphide quantum dots and fused taper optical fiber; the tantalum phosphide quantum dots are attached to the tapered waist surface of the fused taper optical fiber; the tapered waist diameter of the fused taper optical fiber is 13 nm; The saturable absorber based on tantalum phosphide quantum dots is prepared by the following steps: Step 1: Drop the tantalum phosphide quantum dot solution onto the waist of the fused taper fiber; Step 2: Let the fused taper fiber stand until the solvent in the tantalum phosphide quantum dot solution evaporates completely, so that the tantalum phosphide quantum dots are deposited at the waist of the fused taper fiber, to obtain a saturable absorber based on tantalum phosphide quantum dots; The tantalum phosphide quantum dot solution is prepared by the following steps: Tantalum phosphide powder was mixed with anhydrous ethanol and then sonicated to obtain a suspension; the frequency of the sonication was 40 kHz, the power of the sonication was 300 W, and the duration of the sonication was 15 h. The supernatant of the suspension was centrifuged to obtain a tantalum phosphide quantum dot solution.

2. The phosphorus tantalum quantum dot-based saturable absorber of claim 1, wherein, The centrifuge speed is 5000 rpm, the centrifugation time is 20 min, and the centrifugation temperature is 30℃.

3. The saturable absorber based on tantalum phosphide quantum dots according to claim 1, characterized in that, The fabrication method of fused taper optical fiber includes the following steps: S1. First, straighten the single-mode fiber and clamp it on two fiber clamps. The fiber clamps are fixed on two precision stepper motors respectively. S2. Then, the optical fiber is burned with a high-temperature flame while a computer-controlled stepper motor stretches the optical fiber clamp to both sides to obtain a fused taper optical fiber. S3. Place the fused taper fiber on a glass slide and fix it on both sides with UV adhesive to prevent the fused taper part of the fiber from being pulled and broken by external force.

4. The saturable absorber based on tantalum phosphide quantum dots according to claim 3, characterized in that, In step S2, the stretching length of the fused taper fiber is 8 mm.

5. The application of the saturable absorber based on tantalum phosphide quantum dots as described in any one of claims 1-4 in the preparation of a passively mode-locked laser.

6. A passively mode-locked laser, characterized in that, include: The laser pump source, wavelength division multiplexer, gain fiber, polarization-independent isolator, polarization controller, single-mode transmission fiber, output coupler, and the saturable absorber based on tantalum phosphide quantum dots as described in any one of claims 1-4; The laser pump source, the first input terminal of the wavelength division multiplexer, the gain fiber, the polarization-independent isolator, the saturable absorber based on tantalum phosphide quantum dots, the polarization controller, and the output coupler are connected in sequence through the single-mode transmission fiber. The 50% output terminal of the output coupler is connected to the second input terminal of the wavelength division multiplexer through the single-mode transmission optical fiber to form a ring resonant cavity.

7. A passive mode-locked laser according to claim 6, characterized in that, The laser pump source is a semiconductor laser source with a wavelength of 980nm; The center wavelength of the wavelength division multiplexer is 980–1550 nm.

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