阅读说明：本技术 一种基于稀土掺杂纳米晶的片上微环白光激光器的制备方法 (Preparation method of on-chip micro-ring white light laser based on rare earth doped nanocrystalline ) 是由 金立敏 张宇琦 刘伟松 肖淑敏 于 2020-06-04 设计创作，主要内容包括：本发明属于激光显示、可见光通讯和传感等领域,具体涉及一种基于稀土掺杂纳米晶的片上微环白光激光器的制备方法,以及片上白光激光器件、发光波长任意可调谐的片上微激光器件。所述制备方法为：选取的CaF<Sub>2</Sub>为基质,Yb<Sup>3+</Sup>-Tm<Sup>3+</Sup>-Er<Sup>3+</Sup>稀土三掺杂体系,利用溶胶凝胶法合成稀土离子复合掺杂的玻璃样品,再通过调整稀土离子掺杂比,获得红/绿/蓝光复合的白光输出。该制备过程简单,能够与半导体标准加工工艺相结合并具备大工艺制造容差,可获得由单种材料组成、单一泵浦光源激发的片上白光微激光器,具有高Q值、低阈值,尺寸小,易集成等优点。(The invention belongs to the fields of laser display, visible light communication, sensing and the like, and particularly relates to a preparation method of an on-chip micro-ring white light laser based on rare earth doped nanocrystalline, an on-chip white light laser device and an on-chip micro laser device with randomly tunable light emitting wavelength. The preparation method comprises the following steps: selected CaF 2 As a matrix, Yb 3+ ‑Tm 3+ ‑Er 3+ The rare earth three-doping system is characterized in that a rare earth ion composite doped glass sample is synthesized by a sol-gel method, and then the red/green/blue light composite white light output is obtained by adjusting the rare earth ion doping ratio. The preparation process is simple, can be combined with semiconductor standard processing technology, has large process manufacturing tolerance, can obtain an on-chip white light micro laser consisting of a single material and excited by a single pump light source, and has high performanceQ value, low threshold, small size, easy integration and the like.)

1. A method for preparing an on-chip micro-ring white light laser based on rare earth doped nano-crystal is characterized by comprising the following steps:

first, selected CaF₂As a matrix, a specific rare earth ion doping ratio Yb³⁺-Tm³⁺-Er³⁺A rare earth three-doping system, which synthesizes a rare earth ion composite doped glass sample by using a sol-gel method to obtain a red/green/blue light composite white light output glass sample;

and secondly, preparing an on-chip micro-ring core cavity array by using a micro-nano photoetching process to obtain a micro-ring white light laser.

2. The method for preparing the on-chip micro-ring white light laser based on the rare earth doped nano-crystal as claimed in claim 1, wherein Yb is³⁺-Tm³⁺-Er³⁺The rare earth ion doping ratio of the rare earth three-doped system is preferably CaF₂:35％Yb³⁺-1.5％Tm³⁺-0.5％Er³⁺。

3. The method for preparing the on-chip micro-ring white light laser based on the rare earth doped nano-crystal according to claim 1, wherein the synthesis by the sol-gel method comprises the following steps:

(1) diluting a tetraethyl silicate (TEOS) solution by using absolute ethyl alcohol with the same volume, adding deionized water and glacial acetic acid, wherein the molar ratio of TEOS to deionized water to absolute ethyl alcohol is 1:10:0.5, and placing the prepared solution into a magnetic stirrer for heating and stirring, wherein the set rotating speed is 350r/min, and the set temperature is 70 ℃;

(2) weighing an acetate solution of rare earth ions, mixing the acetate solution with trifluoroacetic acid (TFA), placing the mixture on a magnetic stirrer for heating and stirring, wherein the quantity Ln of the rare earth ions in the solution³⁺(Ln³⁺＝Er³⁺，Yb³⁺，Tm³⁺) And F^-Has a molecular ratio Ln³⁺F- ═ l:10, where addition of small amounts of water can be advantageous for accelerating Ln³⁺The rotating speed is set to be 350r/min, the temperature is set to be 70 ℃, and the materials are fully dissolved;

(3) slowly pouring the fully dissolved solution containing the rare earth ions into a TEOS hydrolyzed solution to obtain a precursor solution doped with the rare earth ions, continuously heating and stirring to obtain sol, slowly pouring the sol into a sample box, covering the sol with anti-volatilization paper to slow the cracking phenomenon caused by the over-quick evaporation of the solvent, keeping the obtained gel at room temperature for three weeks, and fully volatilizing the solvent in the gel to finally obtain dry gel;

(4) the obtained xerogel is put in a tube furnace, the heating rate is 1 ℃/min, the calcination is carried out at 800 ℃, and the annealing treatment is carried out, thus obtaining the transparent CaF doped with rare earth ions₂And (3) glass.

4. The method for preparing the on-chip micro-ring white light laser based on the rare earth doped nanocrystal, according to claim 1, wherein the micro-nano lithography process for preparing the on-chip micro-ring core cavity array specifically comprises:

(1) rotationally coating photoresist on a wafer, and performing microscopic structure mould pressing processing on the interior of the photoresist by using a photoetching technology;

(2) adopting an inductively coupled plasma etching process, firstly using C₄F₈Transferring the microstructure pattern to the silicon dioxide layer for an anisotropic etching gas;

(3) then with SF₆Etching the silicon layer below the silicon oxide disc for isotropic etching gas;

(4) removing the photoresist by soaking to finally obtain a silicon dioxide disc microcavity with a suspended structure;

(5) the white light glass sample is coated on the micro-disk in a spinning mode, the surface of the disk micro-cavity is directly irradiated by a carbon dioxide laser serving as a laser light source, and the edge of the micro-disk which is slightly melted is curled inwards to form an annular structure under the action of surface tension.

5. The method for preparing the on-chip micro-ring white light laser based on the rare earth doped nano-crystal according to claim 1, wherein the step (1) comprises: after ultrasonic cleaning is carried out on a silicon oxide wafer by acetone, isopropanol and deionized water in sequence, photoresist is coated on the wafer in a rotating mode, microscopic structure mould pressing processing is carried out on the interior of the photoresist by a photoetching technology, and the processing technical scheme is as follows: pre-baking at 110 deg.C for 60 sec; post-baking at 110 deg.C for 60 sec; contact exposure with energy density of 10 μ w cm^-2Exposure time 25 sec.

6. The method for preparing the on-chip micro-ring white light laser based on the rare earth doped nano-crystal as claimed in claim 1, wherein the etching in the step (2) comprises: the gas flow is 20sccm, the temperature is 70 ℃, the power is 1300W, the video power is 20W, and the etching time is 7 min.

7. The method for preparing the on-chip micro-ring white light laser based on the rare earth doped nano-crystal as claimed in claim 1, wherein the etching in the step (3) comprises: the gas flow is 20sccm, the temperature is 40 ℃, the power is 1200W, the video power is 0W, and the etching time is 20 min.

8. An on-chip micro-ring white light laser based on rare earth doped nano-crystal, which is prepared by the preparation method of any one of the claims 1 to 7.

9. An on-chip micro-laser device with randomly tunable light emission wavelength, comprising the on-chip micro-ring white light laser based on rare earth doped nanocrystal of claim 8.

Technical Field

The invention belongs to the fields of laser display, visible light communication, sensing and the like, and particularly relates to a preparation method of an on-chip micro-ring white light laser based on rare earth doped nanocrystalline, an on-chip white light laser device and an on-chip micro laser device with randomly tunable light emitting wavelength.

Background

Compared with the existing white light LED, the white light laser as a novel solid lighting technology has the advantages of higher energy efficiency, wider color gamut, larger application range and the like, can be applied to the fields of full-color laser imaging, visible light communication, biochemical sensing and the like, and further has the increasingly miniaturized and integrated function requirement on the white light laser. At present, the main way to realize white laser output is to combine the lasers of a plurality of monochromatic lasers or an optical process based on high nonlinearity: the former is based on the traditional semiconductor processing method, and combines a plurality of discrete high-quality crystals into a monolithic device in an isomeric mode, and the method has the problems of high preparation cost, luminous color change caused by lattice distortion, heavy absorption and later longer wavelength emission when a multilayer device is subjected to down-conversion and the like; the latter obtains the output of white light laser through the strong interaction of high-power femtosecond laser and nonlinear crystal, and the application of the white light laser is greatly limited by strict optical path control, huge system volume and extremely high-power pumping energy. The on-chip white light laser device based on the rare earth doped nano-crystal avoids all the problems.

In recent years, much research has been reported on the realization of up-converted white light output by various means, but on-chip integratable white lasers have not been reported due to the lack of suitable laser cavities, which is the ultimate requirement for various highly integrated and multifunctional photonic devices. At present, the rare earth element is doped into a regular hexagon micron rod by a hydrothermal method to obtain whisper gallery mode white light laser, and the stable output of the single mode white light laser can be obtained by optimizing the radius of the micron rod, but the material is difficult to combine with a device, and on-chip integration cannot be realized. In addition, it has recently been reported that an upconversion material and a multilayer hyperbolic metamaterial are combined to obtain enhanced white light random laser output, however, due to the random angle emission characteristic of random laser and the difficulty, the time consumption and the large preparation difficulty of the multilayer metamaterial, the application of the design in the aspect of on-chip devices is hindered.

Disclosure of Invention

The invention provides a method for preparing an on-chip micro-ring white laser based on a rare earth doped nanocrystal, which is to prepare a rare earth doped micro-ring core cavity array by preparing a film from a rare earth doped up-conversion material and combining with a micro-nano process, so as to realize the on-chip white laser output with a high Q value and a whispering gallery mode. The broad significance of the laser is that by selecting a proper sensitizing agent-activating agent multi-element doping system, not only can white light laser output which is composed of a single material and is excited by a single pump light source (such as a low-cost commercial infrared small continuous solid-state laser) be obtained, but also laser output with tunable light-emitting wavelength (ultraviolet-visible-near infrared) can be realized; through a laser reflow process, a high-quality on-chip laser device can be prepared, and white light laser output with a low threshold value is obtained; the on-chip white light micro laser can be combined with a semiconductor standard processing technology, has large process manufacturing tolerance, and can realize low processing cost and large-scale integration; the optical function microcavity array doped with the rare earth can be combined with a flexible substrate, and has a wide application prospect in the aspect of flexible devices.

The invention is based on a sol-gel preparation method and a micro-nano processing technology, and rare earth is doped compositely (Yb)³⁺-Tm³⁺-Er³⁺) The upconversion material is made into a film, a micro-nano processing technology and a laser backflow process from top to bottom are combined to prepare a rare earth doped on-chip micro-ring core cavity array with a high Q value, and stable and high-quality red/green/blue light composite white laser output in a whispering gallery mode is obtained under the pumping of near infrared light. Due to the high flexibility and adjustability of the rare earth doping type and the doping amount, the method can also realize the design of the on-chip laser device with tunable light-emitting wavelength (ultraviolet-visible-near infrared).

Drawings

FIG. 1, Yb³⁺-Tm³⁺-Er³⁺Up-conversion level map of ions.

FIG. 2, XRD patterns of samples at different heat treatment temperatures (CaF as standard card in the figure)₂PDF#35-0816)。

FIG. 3, (a) CaF₂:30％Yb³⁺-x％Tm³⁺(x ═ 0.5, 1.0, 1.5, 2.0, 2.5) continuous laser (1.6kW cm) at 980nm^-2) Fluorescence spectrogram under pumping; (b) blue light (475nm) intensity with Tm³⁺Graph of increase in content.

FIG. 4, CaF₂:y％Yb³⁺-1.5％Tm³⁺(y 25, 30, 35, 40, 45) continuous laser at 980nm (0.17 kWcm)^-2) Fluorescence spectra under pump.

FIG. 5, (a) CaF₂:35％Yb³⁺-1.5％Tm³⁺-α％Er³⁺(α ═ 0.3, 0.5, 1.0, 2.0) continuous laser (0.64kW cm) at 980nm^-2) Fluorescence spectrogram under pumping; (b) different Er³⁺Concentration fluorescence spectrum corresponding to CIE1931 color coordinates.

FIG. 6 shows a process flow for fabricating a core cavity of a silicon dioxide microring.

Fig. 7, microring core cavity SEM image (D ═ 80 μm): (a) a top view; (b) side view.

FIG. 8 is a plot of red (a), green (b), and blue emission spectra of a 120 μm diameter micro-ring core cavity at different powers, corresponding to red (green/blue) intensity versus pump power for (d), where P_th-R、P_th-GAnd P_th-BThreshold for red, green and blue lasers, respectively.

FIG. 9, (a) CaF₂:35％Yb³⁺-1.5％Tm³⁺-0.5％Er³⁺A fluorescence spectrogram of a glass sample; (b) a laser spectrogram of a micro-ring core cavity (D is 120 mu m) doped with the fluorescent sample in the step (a) as a gain medium; (c) CIE1931 color coordinates corresponding to the laser spectra of the micro-ring core cavities with different sizes, and the sizes and the pumping power densities of the micro-ring core cavities corresponding to the coordinate points of the various colors are respectively A points (120 mu m, 2.4MW cm)^-2) Point B (80 μm, 3.2MW cm)^-2) And point C (40 μm, 3.8MW cm)^-2)。

The specific embodiment is as follows:

a method for preparing an on-chip micro-ring white light laser based on rare earth doped nano-crystal comprises the following steps:

first, selected CaF₂As a matrix, a specific rare earth ion doping ratio Yb³⁺-Tm³⁺-Er³⁺A rare earth three-doping system, which synthesizes a rare earth ion composite doped glass sample by using a sol-gel method to obtain a red/green/blue light composite white light output glass sample;

and secondly, preparing an on-chip micro-ring core cavity array by using a micro-nano photoetching process to obtain a micro-ring white light laser.

As a preferred embodiment of the present invention, Yb³⁺-Tm³⁺-Er³⁺The rare earth ion doping ratio of the rare earth three-doped system is preferably CaF₂:35％Yb³⁺-1.5％Tm³⁺-0.5％Er³⁺。

As a preferred technical scheme of the invention, the preparation steps of the synthesis by the sol-gel method comprise:

(1) diluting a tetraethyl silicate (TEOS) solution by using absolute ethyl alcohol with the same volume, adding deionized water and glacial acetic acid (catalyst), wherein the molar ratio of TEOS to deionized water to absolute ethyl alcohol is 1:10:0.5, and heating and stirring the prepared solution in a magnetic stirrer at the set rotating speed of 350r/min and the set temperature of 70 ℃;

(2) weighing an acetate solution of rare earth ions, mixing the acetate solution with trifluoroacetic acid (TFA), placing the mixture on a magnetic stirrer for heating and stirring, wherein the quantity Ln of the rare earth ions in the solution³⁺(Ln³⁺＝Er³⁺，Yb³⁺，Tm³⁺) And F^-Has a molecular ratio Ln³⁺F- ═ l:10, where addition of small amounts of water can be advantageous for accelerating Ln³⁺The rotating speed is set to be 350r/min, the temperature is set to be 70 ℃, and the materials are fully dissolved;

(3) slowly pouring the fully dissolved solution containing the rare earth ions into a TEOS hydrolyzed solution to obtain a precursor solution doped with the rare earth ions, continuously heating and stirring to obtain sol, slowly pouring the sol into a sample box, covering the sol with anti-volatilization paper to slow the cracking phenomenon caused by the over-quick evaporation of the solvent, keeping the obtained gel at room temperature for three weeks, and fully volatilizing the solvent in the gel to finally obtain dry gel;

(4) the xerogel obtained is placed in a tube furnaceThe temperature rise rate is 1 ℃/min, the annealing treatment is carried out at the temperature of 800 ℃ after calcination, and the transparent CaF doped with rare earth ions can be obtained₂And (3) glass.

As a preferred technical scheme of the invention, the preparation of the on-chip micro-ring core cavity array by the micro-nano photoetching process specifically comprises the following steps:

(1) rotationally coating photoresist on a wafer, and performing microscopic structure mould pressing processing on the interior of the photoresist by using a photoetching technology;

the preferable technical scheme of the step is as follows: after ultrasonic cleaning is carried out on a silicon oxide wafer by acetone, isopropanol and deionized water in sequence, photoresist is coated on the wafer in a rotating mode, microscopic structure mould pressing processing is carried out on the interior of the photoresist by a photoetching technology, and the optimized processing technical scheme is as follows: pre-baking at 110 deg.C for 60 sec; post-baking at 110 deg.C for 60 sec; contact exposure with energy density of 10 μ wcm^-2Exposure time 25 sec;

(2) adopting an inductively coupled plasma etching process, firstly using C₄F₈Transferring the microstructure pattern to the silicon dioxide layer for an anisotropic etching gas;

the preferable technical scheme of the step is as follows: the gas flow is 20sccm, the temperature is 70 ℃, the power is 1300W, the video power is 20W, and the etching time is 7 min;

(3) then with SF₆Etching the silicon layer below the silicon oxide disc for isotropic etching gas;

the preferable technical scheme of the step is as follows: the gas flow is 20sccm, the temperature is 40 ℃, the power is 1200W, the video power is 0W, and the etching time is 20 min;

(4) removing the photoresist by soaking to finally obtain a silicon dioxide disc microcavity with a suspended structure;

(5) the white light glass sample is coated on the micro-disk in a spinning mode, the surface of the disk micro-cavity is directly irradiated by a carbon dioxide laser serving as a laser light source, and the edge of the micro-disk which is slightly melted is curled inwards to form an annular structure under the action of surface tension.

The invention further provides an on-chip micro-ring white light laser based on the rare earth doped nano-crystal, which is prepared by the preparation method.

An on-chip micro laser device with randomly tunable light emitting wavelength comprises an on-chip micro-ring white light laser based on rare earth doped nano-crystal.

The beneficial effects of the invention compared with the prior art comprise:

1) the preparation process is simple, can be combined with a semiconductor standard processing technology and has large manufacturing tolerance.

2) The on-chip white light micro laser which is composed of a single material and is excited by a single pump light source can be obtained.

3) The random tuning of the emission wavelength (ultraviolet-visible-near infrared) of the on-chip micro laser can be realized by adjusting the doping of the rare earth ions.

4) The on-chip micro laser with high Q value and low threshold value can be obtained.

5) The rare earth doped optical function microcavity array can be combined with a flexible substrate.

6) The designed device has small size and is easy to integrate.