A colloidal quantum dot continuous laser based on microfluidic fiber and its preparation method

Abstract

The present invention discloses a colloidal quantum dot continuous laser based on a microfluidic fiber and a preparation method thereof. The laser comprises three parts: a pump optical path, a detection optical path, and a microfluidic platform. For the pump optical path, a continuous pump laser (1), a variable neutral density filter (2), and a first focusing lens (3) are sequentially provided along the incident direction of the pump beam. For the detection optical path, two side-by-side second focusing lenses (4), a high-resolution CCD probe (5), and a computer display (6) are sequentially provided along the signal collection direction. For the microfluidic platform, the laser mainly comprises a microinjection pump and a microinjector (7), a microtranslation stage (8), a microfluidic fiber, and a high-concentration quantum dot solution (9). The method provided by the present invention is simple and efficient to operate, realizes low-threshold, highly stable continuous laser output, and effectively fills the gap in the prior art of colloidal quantum dot continuous lasers.

Description

Technical Field

[0001] The present invention belongs to the technical field of continuous laser equipment, and in particular relates to a colloidal quantum dot continuous laser based on microfluidic optical fiber and a preparation method thereof. Background Art

[0002] Continuous-wave (CW) lasers have widespread applications in modern science and industry, including integrated light sources, data communications, and medical diagnostics. The first report of a semiconductor CW laser dates back 50 years; however, until now, commercial semiconductor CW lasers have been fabricated using demanding epitaxial growth techniques and rely heavily on high temperatures and vacuum conditions. In contrast, solution-processable materials, due to their advantages such as ease of fabrication, large-area fabrication, and compatibility with various flexible substrates and optical resonators, are becoming increasingly attractive gain media for the next generation of integrated lasers. Among these, colloidal quantum dots (QDs) or semiconductor nanocrystals stand out as highly attractive solution-processable materials due to their high photoluminescence quantum yield, large gain coefficient, and broadband spectral tunability achieved through quantum confinement. Over the past few decades, lasers based on CQD films have been intensively studied, and lasing has been successfully achieved under quasi-continuous nanosecond pulse pumping, marking the beginning of the practical application of CQD lasers. However, quantum dot films have high optical losses and severe heat accumulation effects, which greatly inhibit their excitation emission under continuous laser pumping. In addition, the slow degradation of the sample cannot maintain long-term laser operation. These factors hinder the realization of continuous laser. Therefore, designing a laser with high performance, high stability and high heat dissipation is of great significance to the application and development of colloidal quantum dot continuous laser. Summary of the Invention

[0003] In order to solve the defects of the prior art, the present invention provides a colloidal quantum dot continuous laser based on microfluidic fiber, which adopts the method of wrapping quantum dot liquid with microfluidic fiber to reduce the heat accumulation effect, and designs a quantum dot microfluidic platform, which successfully realizes low threshold and high stability quantum dot continuous laser output, including three parts: pump optical path, detection optical path and microfluidic platform; for the pump optical path, along the incident direction of the pump beam, there are: continuous pump laser (1), variable neutral density filter (2) and first focusing lens (3); for the detection optical path, along the signal collection direction, there are: two side-by-side second focusing lenses (4), high-resolution CCD probe (5) and computer display (6); for the microfluidic platform, it mainly includes: micro-injection pump and micro-injector (7), micro-translation displacement stage (8), micro-fluidic fiber and high-concentration quantum dot solution (9);

[0004] A method for preparing a colloidal quantum dot continuous laser based on a microfluidic fiber comprises the following steps:

[0005] Step 1: The pump light path is always kept at a fixed height and transmitted horizontally. The power is adjusted by a variable neutral density filter, and then focused into a small light spot in the radial direction of the microfluidic fiber by the first focusing lens (3), providing uniform high-power excitation;

[0006] Step 2: The microfluidic platform is mainly composed of a microfluidic optical fiber filled with a high-concentration quantum dot solution. One end of the microfluidic optical fiber is connected to a microsyringe (7) filled with a quantum dot solution, which serves as an injection port for the microflow of the quantum dot solution. The end of the microfluidic optical fiber opposite to the injection port is connected to a beaker to collect the outflowing quantum dot solution. The microsyringe pump is started to push the quantum dot solution in the microsyringe (7) to flow in the optical fiber.

[0007] Step 3: The detection light path collects the continuous spontaneous emission (ASE) signal emitted by the quantum dots through two second focusing lenses (4), and then collects it through the CCD probe (5) and transmits it to the computer monitor (6);

[0008] Step 4: To achieve continuous laser output from quantum dots, the resonant cavity is constructed by two distributed Bragg reflectors (DBRs), and the quantum dot microfluidic platform is sandwiched between the DBRs to create a vertical-cavity surface emitting laser (VCSEL).

[0009] As an optimization solution: the microfluidic optical fiber of the present invention uses high-gain CdZnSe / ZnSeS / ZnS alloy quantum dots as a demonstration example of colloidal quantum dot continuous laser; the quantum dot size is 14 nanometers, wherein the ZnSeS and ZnS shell thicknesses are 2 nanometers and 1 nanometer, respectively.

[0010] As an optimization solution: The continuous laser used in step 2 is a commercial solid-state diode laser with a wavelength of 440 nm and a pump intensity of 5.09 kW / cm2 through a focusing lens. 2 .

[0011] As an optimization solution: the concentration of the quantum dot dispersion in toluene in step 3 is not less than 200 mg / mL; the inner diameter and cladding thickness of the microfluidic fiber are 50 μm and 75 μm respectively, and the length is not less than 5 cm.

[0012] As a further optimization solution: the specification of the microsyringe in step 3 is 10 mL; the microsyringe pump is an automatic perfusion type with a flow rate of 0.12 mL / min.

[0013] As an optimization solution: The continuous ASE achieved in step 4 has a peak position of 660 nm, a half-height width of 10 nm, and a threshold as low as 340 W / cm 2 ;Continuous ASE at 710 W / cm 2 The pump power can output stably for 1.5 hours and keep the intensity almost unchanged.

[0014] As a further optimization solution: the continuous laser achieved in step 5 has a threshold of 380 W / cm 2 , with a line width of only 0.5 nanometers.

[0015] Beneficial effects: The method provided by the present invention is simple and efficient to operate, and realizes low-threshold, highly stable continuous laser output, effectively filling the gap in the existing technology of continuous lasers based on colloidal quantum dots. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 A schematic diagram of the structure of a colloidal quantum dot continuous laser based on microfluidic fiber designed for the present invention;

[0018] Figure 2 The luminescence spectra collected at different pump powers of the present invention, in which the nonlinear growth of luminescence intensity and the narrowing of half-height width at high power indicate the occurrence of continuous ASE;

[0019] Figure 3 The graph of continuous ASE intensity changing with pumping time in the quantum dot microfluidic platform;

[0020] Figure 4 Photos of the quantum dot VCSEL designed for this invention and laser spectra collected at different pump powers. DETAILED DESCRIPTION

[0021] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention.

[0022] See Figure 1 ,like Figure 1 The figure shows a schematic diagram of the structure of a colloidal quantum dot continuous laser based on a microfluidic optical fiber designed by the present invention, which comprises three parts: a pump optical path, a detection optical path and a microfluidic platform; for the pump optical path, along the incident direction of the pump beam, there are provided in sequence: a continuous pump laser (1), a variable neutral density filter (2) and a focusing lens (3); for the detection optical path, along the signal collection direction, there are provided in sequence: a focusing lens (4), a high-resolution CCD probe (5) and a computer display (6); for the microfluidic platform, it mainly comprises: a microinjection pump and a microinjector (7), a microtranslation stage (8), a microfluidic optical fiber and a high-concentration quantum dot solution (9).

[0023] The working process of the device of the present invention is as follows: a high concentration of CdZnSe / ZnSeS / ZnS alloy quantum dot solution is injected into a microfluidic optical fiber. Then, the two ends of the optical fiber are connected to a micro syringe and a beaker containing the quantum dot solution respectively. The quantum dot solution in the syringe is pushed through the optical fiber by a micro syringe pump. The pump light is focused into a small spot by a focusing lens to radially excite the quantum dot solution in the microfluidic optical fiber. The continuous ASE signal generated is collected by a CCD and transmitted to a computer, such as Figure 2 As shown. The continuous ASE threshold of quantum dots is 340 W / cm 2 , and can output stably for more than 1.5 hours and maintain almost unchanged intensity ( Figure 3 ). Two distributed Bragg reflectors were used as resonant cavities to clamp the quantum dot microfluidics, and a vertical cavity surface emitting laser was established. Figure 4 The laser spectrum in Figure 1 shows the evolution of the spectrum from spontaneous emission to continuous laser as the pump power increases.

[0024] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A colloidal quantum dot continuous laser based on microfluidic fiber, characterized by The invention comprises three parts: a pump optical path, a detection optical path and a microfluidic platform; for the pump optical path, a continuous pump laser (1), a variable neutral density filter (2) and a first focusing lens (3) are sequentially arranged along the incident direction of the pump beam; for the detection optical path, two side-by-side second focusing lenses (4), a high-resolution CCD probe (5) and a computer display (6) are sequentially arranged along the signal collection direction; and for the microfluidic platform, it mainly comprises a microinjection pump and a microinjector (7), a microtranslation stage (8), a microfluidic optical fiber and a high-concentration quantum dot solution (9); A method for preparing a colloidal quantum dot continuous laser based on a microfluidic fiber comprises the following steps: Step 1: The pump light path is always kept at a fixed height and transmitted horizontally, the power is adjusted by a variable neutral density filter, and then focused into a small light spot in the radial direction of the microfluidic fiber by a first focusing lens (3), providing uniform high-power excitation; Step 2: The microfluidic platform is mainly composed of a microfluidic optical fiber filled with a high-concentration quantum dot solution. One end of the microfluidic optical fiber is connected to a microsyringe (7) filled with a quantum dot solution, serving as an injection port for the microflow of the quantum dot solution; the end of the microfluidic optical fiber opposite to the injection port is connected to a beaker to collect the outflowing quantum dot solution; the microsyringe pump is started to push the quantum dot solution in the microsyringe (7) to flow in the optical fiber; Step 3: The detection light path collects the continuous spontaneous emission (ASE) signal emitted by the quantum dots through two second focusing lenses (4), and then collects it through the CCD probe (5) and transmits it to the computer display (6); Step 4: To achieve continuous laser output from quantum dots, the resonant cavity is constructed by two distributed Bragg reflectors (DBRs), and the quantum dot microfluidic platform is sandwiched between the DBRs to establish a vertical-cavity surface emitting laser (VCSEL).

2. The colloidal quantum dot continuous laser based on microfluidic fiber according to claim 1, characterized in that: High-gain CdZnSe / ZnSeS / ZnS alloy quantum dots are used in microfluidic optical fibers as a demonstration example of colloidal quantum dot continuous lasers; the quantum dot size is 14 nanometers, with the ZnSeS and ZnS shell thicknesses of 2 nanometers and 1 nanometer, respectively.

3. The colloidal quantum dot continuous laser based on microfluidic fiber according to claim 1, characterized in that: The continuous laser used in step 2 is a commercial solid-state diode laser with a wavelength of 440 nm and a pump intensity of 5.09 kW / cm2 through a focusing lens. 2 .

4. The colloidal quantum dot continuous laser based on microfluidic fiber according to claim 1, characterized in that: In step 3, the concentration of the dispersion of quantum dots in toluene is not less than 200 mg / mL; the inner diameter and cladding thickness of the microfluidic optical fiber are 50 μm and 75 μm respectively, and the length is not less than 5 cm.

5. The colloidal quantum dot continuous laser based on microfluidic fiber according to claim 1, characterized in that: The specification of the micro-syringe (7) in step 3 is 10 mL; the micro-injection pump is an automatic perfusion type with a flow rate of 0.12 mL / min.

6. The colloidal quantum dot continuous laser based on microfluidic fiber according to claim 1, characterized in that: The continuous ASE achieved in step 4 has a peak position of 660 nm, a half-width of 10 nm, and a threshold as low as 340 W / cm 2 ;Continuous ASE at 710W / cm 2 The pump power can output stably for 1.5 hours and keep the intensity almost unchanged.

7. The colloidal quantum dot continuous laser based on microfluidic fiber according to claim 1, characterized in that: The continuous laser achieved in step 5 has a threshold of 380W / cm 2 , with a line width of only 0.5 nanometers.

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