Tunable laser and preparation method thereof

Abstract

The present invention relates to a tunable laser and a method for fabricating the same. The tunable laser comprises a bottom Bragg reflector, a wedge-shaped active region, and a top Bragg reflector, all grown sequentially on a substrate. The bottom Bragg reflector, the wedge-shaped active region, and the top Bragg reflector form a resonant cavity. The side surfaces of the wedge-shaped active region contacting the top Bragg reflector and / or the bottom Bragg reflector are inclined. The present invention introduces a wedge-shaped gain layer structure into the conventional two-layer structure of the bottom and top Bragg reflectors, achieving precise and continuous wavelength tunability within the same laser device.

Description

Technical Field

[0001] The present invention relates to a laser device, in particular to a tunable laser and a preparation method thereof. Background Art

[0002] Tunable lasers are a very important laser source, widely used in spectroscopy, photochemistry, medicine, biology, integrated optics, pollution monitoring, semiconductor material processing, information processing, and communications. Depending on the tuning method, common tunable lasers include distributed feedback (DFB) lasers, distributed Bragg reflector (DBR) lasers, microelectromechanical system (MEMS)-based tunable vertical cavity surface emitting lasers (VCSELs), and tunable fiber lasers.

[0003] Perovskite has been considered a promising laser material in recent years due to its unique optical properties, tunable spectrum, high defect tolerance, low cost and easy processing. The most prominent advantage of perovskite material is that the emission wavelength can be adjusted through molecular design. Its wavelength tuning range covers the ultraviolet to infrared light region, so it can be used in tunable lasers or broadband amplifiers.

[0004] Perovskite laser resonators are primarily implemented using whispering gallery modes (WGMs), distributed feedback (DFBs), or distributed Bragg reflectors (DBRs). Among them, vertical-cavity surface-emitting lasers (VCSELs) with DBR resonators have attracted considerable attention due to their single-mode output and ease of integration.

[0005] At present, lead-based perovskite is used as the gain material of the laser, combined with a DBR resonator with spectral matching to realize perovskite VCSEL (Pe-VCSEL). For example, 10 pairs of alternating HfO2 / SiO2 layers are used to form a DBR resonator, and FAPbBr3 is used as the gain material to prepare a low threshold (~18.3μJ / cm 2 )'s 552.4nm green laser; in addition, for example, 11 layers of perovskite nanocrystals (CsPbX3, X=Cl, Br, I) were prepared on the DBR by a solution method, and then the top DBRs were bonded together to prepare red, green and blue Pe-VCSELs.

[0006] However, most of the existing DBR structure perovskite lasers are fixed wavelength output modes, and their output wavelength is mainly determined by the resonance peak of the DBR structure and the FP peak of the resonant cavity, and the wavelength is single and cannot be tunable. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, the present invention provides a wavelength tunable laser. In order to achieve wavelength tunability, a wedge-shaped gain layer structure is introduced into the conventional two-layer structure of bottom Bragg reflector and top Bragg reflector, thereby achieving the purpose of precise and continuous wavelength tunability in the same laser device.

[0008] The present invention provides a tunable laser, comprising a bottom Bragg reflector, a wedge-shaped active region, and a top Bragg reflector sequentially grown on a substrate. The bottom Bragg reflector, the wedge-shaped active region, and the top Bragg reflector constitute a resonant cavity, and the side surface of the wedge-shaped active region that contacts the top Bragg reflector and / or the bottom Bragg reflector is an inclined surface.

[0009] It should be noted that, in this application, "active region" and "gain region" have the same meaning and can be used interchangeably. In addition, "active layer" and "gain layer" have the same meaning and can be used interchangeably.

[0010] According to an embodiment of the present invention, "wedge-shaped" refers to a structure having two parallel first end faces and a second end face, and four side faces connecting the first end faces and the second end faces, wherein two of the four side faces are in contact with the top Bragg reflector and the bottom Bragg reflector, and at least one of the contacting side faces is an inclined face.

[0011] According to an embodiment of the present invention, the side surface of the wedge-shaped active region in contact with the top Bragg reflector is an inclined surface.

[0012] According to an embodiment of the present invention, the angle (tilt angle) between the side surfaces of the wedge-shaped active region in contact with the top Bragg reflector and the bottom Bragg reflector is 4×10 -6 -4×10 -5 rad, preferably, the angle (inclination angle) between the side surfaces of the wedge-shaped active region contacting the top Bragg reflector and the bottom Bragg reflector is 8×10 -6 -2.0×10 -5 rad.

[0013] According to an embodiment of the present invention, the two parallel first end surfaces and the second end surface are both rectangular, and the rectangular area of ​​the first end surface is smaller than the rectangular area of ​​the second end surface.

[0014] According to an embodiment of the present invention, the length h of the side of the first end face and the second end face of the wedge-shaped active region that is not in contact with the top Bragg reflector and the bottom Bragg reflector (i.e., the thickness of the wedge-shaped active region in the longitudinal section of the laser, see for example Figure 2) is 100 nm to 1100 nm, preferably 200 nm to 800 nm, for example, 130 nm, 150 nm, 380 nm, 230 nm and 430 nm.

[0015] According to an embodiment of the present invention, the emission wavelength of the tunable laser is in the visible light band, which refers to a band with a wavelength of 400-760nm, and preferably the wavelength of the visible light band is 450-600nm; illustratively, under the excitation of incident light with an excitation wavelength of 288nm, its emission wavelength is 444-471.8nm.

[0016] According to an embodiment of the present invention, the substrate is made of a material with low absorption to the emission wavelength and the pump source, such as quartz, silicon or sapphire.

[0017] According to an embodiment of the present invention, the reflectivity of the bottom Bragg reflector is greater than 99.9%; the thickness of the bottom Bragg reflector is 1500-4000 nm, for example, 2025.7 nm.

[0018] According to an embodiment of the present invention, the reflectivity of the top Bragg reflector is greater than 99%; the thickness of the top Bragg reflector is 600-1500 nm, for example, 745.3 nm.

[0019] According to an embodiment of the present invention, the bottom Bragg reflector and the top Bragg reflector include first structure layers and second structure layers that are alternately arranged.

[0020] According to an embodiment of the present invention, the first structural layer and the second structural layer are selected from materials with low absorption to the pump source and emission wavelength.

[0021] According to an embodiment of the present invention, the material of the first structural layer in the bottom Bragg reflector is the same as or different from the material of the first structural layer in the top Bragg reflector.

[0022] According to an embodiment of the present invention, the material of the second structure layer in the bottom Bragg reflector is the same as or different from the material of the second structure layer in the top Bragg reflector.

[0023] According to an embodiment of the present invention, in the top Bragg reflector and the bottom Bragg reflector, the materials of the first structural layer and the second structural layer include at least one selected from oxides, halides and sulfides, the oxides include TeO2, Ta2O5, SiOx (x=1~2), SiNx (x=1~1.5), the halides include LiF and MgF2, and the sulfides include ZnS. For example, the material of the first structural layer is TeO2 and Ta2O5, and the material of the second structural layer is LiF and SiO2.

[0024] According to an embodiment of the present invention, in the top Bragg reflector and the bottom Bragg reflector, the refractive index of the first structural layer is n1, and the refractive index of the second structural layer is n2, wherein n1 is 2.0-3.0, and n2 is 1.3-1.7; n1 is the same as or different from n2, for example, different, and preferably n1 is greater than n2.

[0025] According to an embodiment of the present invention, in the top Bragg reflector and the bottom Bragg reflector, the thickness of the first structure layer is the same or different, for example, different.

[0026] According to an embodiment of the present invention, in the top Bragg reflector and the bottom Bragg reflector, the thickness of the second structure layer is the same or different, for example, different.

[0027] According to an embodiment of the present invention, in the top and bottom Bragg reflectors, the optical thickness L1 of the first structure layer and the optical thickness L2 of the second structure layer are the same or different. The relationship between L1 and L2 and the emission wavelength λ is: L1 = M1λ / 4, L2 = M2λ / 4, where M1 and M2 are odd numbers. For example, in the bottom Bragg reflector, the thickness of the first structure layer is 54.7 nm, and the thickness of the second structure layer is 76.7 nm; in the top Bragg reflector, the thickness of the first structure layer is 54.8 nm, and the thickness of the second structure layer is 84.3 nm.

[0028] According to an embodiment of the present invention, in the bottom Bragg reflector and the top Bragg reflector, the total number of the first structure layer and the second structure layer is an odd number, for example, the total number of the bottom Bragg reflector is 31 layers, and the total number of the top Bragg reflector is 11 layers.

[0029] According to an embodiment of the present invention, the material of the wedge-shaped active region comprises a perovskite material, and the perovskite material is selected from one of ternary halide perovskites. Preferably, the ternary halide perovskite is selected from Cs x Cu y I x+y 、Cs x Cu y Br x+y 、Cs x Cu y Cl x+y (wherein x and y are integers greater than 0, such as: Cs3Cu2I5, x=3, y=2), at least one of CsSnBr3, CsSnCl3, CsPbBr3 and CsPbCl3.

[0030] According to an embodiment of the present invention, the refractive index n of the wedge-shaped active region is in the range of 1.7-2.

[0031] According to an embodiment of the present invention, the thickness of the wedge-shaped active region is gradually changed in a wedge shape along the direction perpendicular to the optical axis, and the optical effective thickness (the product of the refractive index and the thickness) ranges from λ / 2 to 2λ, where λ is 400-650 nm.

[0032] According to an embodiment of the present invention, the wedge-shaped active region is a film structure, for example, a single-layer film structure, or a film structure formed by alternately stacking several film layers.

[0033] According to an embodiment of the present invention, in a membrane structure formed by alternately stacking several membrane layers, the materials of different membrane layers may be the same or different, preferably different.

[0034] According to an embodiment of the present invention, the thicknesses of different film layers may be the same or different, preferably different.

[0035] According to an embodiment of the present invention, the wedge-shaped active region is grown by evaporation coating. Specifically, the wedge-shaped gradient active layer is obtained by adding a periodically rotating baffle in a coating machine, for example, the baffle is a fan-shaped structure.

[0036] According to an embodiment of the present invention, the tilt angle of the wedge-shaped active region can be controlled by controlling the angle of the sector of the sector-shaped baffle.

[0037] The present invention also provides a method for preparing the above-mentioned tunable laser, which comprises the following steps:

[0038] Step 1: Depositing a bottom Bragg reflector on the substrate surface;

[0039] Step 2: Under periodic shading conditions, depositing a ternary halide perovskite as a gain medium on the surface of the bottom Bragg reflector to form a wedge-shaped active region;

[0040] Step 3: Deposit a top Bragg reflector on the surface of the wedge-shaped active area.

[0041] According to an embodiment of the present invention, the periodic shielding is achieved by a rotatable baffle disposed above the substrate. The baffle may be a trapezoidal or fan-shaped structure. Preferably, the baffle is a fan-shaped structure.

[0042] According to an embodiment of the present invention, in step 1, before depositing the bottom Bragg reflector on the substrate surface, the following steps are also included: cleaning the substrate, for example, ultrasonically cleaning the substrate in acetone, isopropyl alcohol, and deionized water in sequence for 5 to 20 minutes, and then treating it with ultraviolet ozone for 10 to 20 minutes.

[0043] Preferably, the substrate has the meaning as described above.

[0044] According to an embodiment of the present invention, in step 1, depositing a bottom Bragg reflector on the substrate surface includes: alternately evaporating a first structure layer material and a second structure layer material on the substrate surface.

[0045] Preferably, the first structural layer material and the second structural layer material have the meanings as described above.

[0046] According to an embodiment of the present invention, in step 1, evaporating the first structural layer material and the second structural layer material on the surface of the substrate includes: placing the first structural layer material and the second structural layer material as evaporation source materials into a vacuum coating machine, and when the vacuum degree reaches below 5E-4Pa, alternately evaporating the first structural layer material and the second structural layer material.

[0047] As an example, a cleaned substrate is placed in a vacuum coating machine, Ta2O5 and SiO2 are placed in a crucible as evaporation source materials, and the vacuum system of the coating machine is turned on. When the vacuum degree of the vacuum system of the coating machine reaches below 5E-4Pa, 15.5 pairs of Ta2O5 and SiO2 are alternately evaporated to obtain a bottom Bragg reflector.

[0048] According to an embodiment of the present invention, step 2 includes: placing an evaporation source material corresponding to the ternary halide perovskite serving as a gain medium into a coating machine for evaporation deposition.

[0049] According to an embodiment of the present invention, in step 2, the evaporation source material corresponding to the gain medium includes CsX and at least one selected from PbY2, CuY, and SnY2, wherein X and Y are selected from any one of Cl, Br, and I. X and Y in different evaporation source materials may be the same or different. Preferably, the evaporation source material corresponding to the gain medium is CsI or CuI.

[0050] According to an embodiment of the present invention, in step 2, a dual-source co-evaporation method is adopted when depositing the ternary halide perovskite.

[0051] According to an embodiment of the present invention, the evaporation rates of different evaporation source materials are different, and the molar masses of different evaporation source materials are the same or different, for example, different. Preferably, the evaporation rate of the evaporation source material is

[0052] As an example, when the gain medium is Cs3Cu2I5, the evaporation source materials are CsI and CuI, the molar ratio of CsI and CuI is 1.5:1-1:2, and the evaporation rate of CsI is The evaporation rate of CuI is

[0053] According to an embodiment of the present invention, step 2 includes: placing the evaporation source material corresponding to the gain medium into a crucible in a coating machine equipped with a fan-shaped baffle with adjustable speed, placing the substrate with a bottom Bragg reflector on a turntable, turning on the vacuum system of the coating machine, and adjusting the evaporation current so that the evaporation rate of the evaporation source material reaches and stabilizing, adjusting the rotation rate of the baffle to 10-20 revolutions / min, and evaporating the gain medium film to reach a set thickness to obtain a wedge-shaped active region.

[0054] According to an embodiment of the present invention, during the evaporation process in step 2, the sector baffle rotates at a fixed speed in the range of 10-20 rpm, preferably 12-18 rpm, and more preferably 14-16 rpm.

[0055] According to the embodiment of the present invention, the sector baffles with different sector angles can be selected to control the wedge tilt angle, and the wedge tilt angle range is 4×10 -6 -4×10 -5 rad.

[0056] Preferably, in step 2, the vacuum degree during evaporation in the coating machine is below 5E-4Pa.

[0057] According to an embodiment of the present invention, in step 3, depositing a top Bragg reflector on the surface of the wedge-shaped active area includes: alternately evaporating a first structure layer material and a second structure layer material on the surface of the wedge-shaped active area.

[0058] According to an embodiment of the present invention, in step 3, alternately evaporating the first structural layer material and the second structural layer material on the surface of the wedge-shaped active area includes: placing the first structural layer material and the second structural layer material as evaporation source materials into a vacuum coating machine, and when the vacuum degree reaches below 5E-4Pa, alternately evaporating the first structural layer material and the second structural layer material.

[0059] As an example, a substrate with a wedge-shaped active area is placed in a vacuum coating machine, TeO2 and LiF materials are placed in a crucible as evaporation source materials, and the vacuum system of the coating machine is turned on. When the vacuum degree of the vacuum system of the coating machine reaches below 5E-4Pa, 5.5 pairs of TeO2 and LiF are alternately evaporated on the active layer material to obtain a top Bragg reflector.

[0060] According to an embodiment of the present invention, step 3 is followed by the following steps: venting the coating machine and releasing the pressure, taking out the device, and obtaining a tunable laser.

[0061] The present invention provides a tunable laser, which is prepared by adopting the above method.

[0062] The present invention also provides an evaporation device for evaporating the above-mentioned wedge-shaped active area, comprising a turntable and at least one crucible, wherein the turntable is used to carry the substrate, and the crucible is used to place the evaporation source material and evaporate it. A baffle is arranged between the turntable and the crucible, and one end of the baffle is connected to a power mechanism and can rotate under the drive of the power mechanism.

[0063] According to an embodiment of the present invention, the structure of the baffle has the meaning as described above.

[0064] According to an embodiment of the present invention, the baffle is preferably a fan-shaped structure, the angular radian of the fan-shaped structure is 0.5236-3.1 rad, and the radius is 2-4 inches. Preferably, the angular radian of the fan-shaped structure is 1.2-2.1 rad, and the radius is 2.2-3 inches. Further, the angular radian of the fan-shaped structure is 1.2-1.57 rad, and the radius is 2.5-2.7 inches.

[0065] According to an embodiment of the present invention, the baffle is arranged parallel to the turntable.

[0066] According to an embodiment of the present invention, the distance between the baffle and the turntable is 2-5 cm, preferably the distance between the baffle and the turntable is 3-4 cm.

[0067] The evaporation device in the present invention includes a baffle located at the bottom of the turntable. The baffle rotates at a certain rate during use. Since the substrate is periodically shielded during the rotation of the baffle, when the shielding is formed, the evaporation source material in the crucible is blocked and cannot enter the bottom of the substrate, so that the thickness of the evaporated material in different areas of the substrate is different. During specific use, fan-shaped baffles with different angular curvatures and radii are selected according to actual needs to achieve control of the inclination angle of the wedge-shaped film layer.

[0068] Beneficial effects

[0069] The present invention introduces a wedge-shaped gain layer structure into a conventional two-layer structure of a bottom Bragg reflector and a top Bragg reflector, thereby enabling accurate and continuous tunability of wavelength in the same laser device.

[0070] The present invention rotates the baffle at a fixed speed driven by a power mechanism during the deposition of a wedge-shaped film layer. During the rotation of the baffle, the substrate is periodically shielded. When the shielding is formed, the evaporation source material in the crucible is blocked and cannot enter the bottom of the substrate, so that the thickness of the evaporated material in different areas of the substrate is different, thereby forming a wedge-shaped gain layer structure. The method is relatively simple and can also achieve control of the inclination angle of the wedge-shaped film layer by controlling the rotation speed and fan-shaped baffles of different angles and radii. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1It is a schematic structural diagram of the evaporation device of the laser with a wedge-shaped active region prepared in Example 1 of the present invention; wherein 1001 and 1002 are crucibles, 1003 is a turntable, 1004 is a baffle, and 1005 is a substrate.

[0072] Figure 2 Schematic diagram of the structure of the tunable laser prepared in Example 2 of the present invention.

[0073] Figure 3 1 and 2 are the reflection spectra of the top Bragg reflector and the bottom Bragg reflector of the tunable laser prepared in Example 2 of the present invention.

[0074] Figure 4 This is the reflection spectrum of the tunable laser prepared in Example 2 of the present invention.

[0075] Figure 5 This is a spectrum test chart of the tunable laser prepared in Example 2 of the present invention.

[0076] Figure 6 This is a spectrum test chart of the tunable laser prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0077] The technical solutions of the present invention will be described in further detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are encompassed within the scope of protection that the present invention is intended to protect.

[0078] Example 1: Evaporation device for preparing wedge-shaped structure laser

[0079] See also Figure 1 As shown, an evaporation device for preparing a wedge-shaped structure laser includes a turntable 1003 and two crucibles (1001, 1002). The turntable 1003 is used to support a substrate 1005. The crucibles (1001, 1002) are used to place and evaporate an evaporation source material. The turntable 1003 is located above the crucibles (1001, 1002). A baffle 1004 is provided between the turntable 1003 and the crucibles (1001, 1002). One end of the baffle 1004 is connected to a power mechanism and can be driven by the power mechanism to rotate away from the bottom of the turntable 1003. In this embodiment, the baffle 1004 is a fan-shaped structure with an angular arc of 1.57 rad and a radius of 2.5 inches. The distance between the baffle 1004 and the turntable 1003 is 4 cm.

[0080] When the evaporation device of this embodiment evaporates a wedge-shaped film layer, the baffle 1004 rotates at a fixed speed driven by the power mechanism. Since the baffle 1004 periodically blocks the substrate 1005 during the rotation process, when the blockage is formed, the evaporation source material in the crucible (1001, 1002) is blocked and cannot enter the bottom of the substrate 1005, resulting in different thicknesses of the evaporated material in different areas of the substrate 1005. During specific use, fan-shaped baffles with different angular arcs and radii are selected according to actual needs to achieve control of the inclination angle of the wedge-shaped film layer.

[0081] Example 2 Preparation of tunable laser

[0082] Reference Figure 2 As shown in Figure 2, the preparation process of the tunable laser is as follows:

[0083] Step 1: The quartz substrate was ultrasonically cleaned in acetone, isopropanol, and deionized water for 15 minutes, and then treated with UV-ozone for 20 minutes.

[0084] Step 2: Place the substrate processed in step 1 into a vacuum coating machine, place Ta2O5 and SiO2 as evaporation source materials into the crucible, and start the vacuum system of the coating machine.

[0085] Step 3: When the vacuum degree of the vacuum system of the coating machine in step 2 reaches below 5E-4Pa, start to alternately evaporate 15.5 pairs of Ta2O5 and SiO2, where the first and last layers are both Ta2O5, that is, Ta2O5 is 16 layers, each layer is 54.7nm thick; SiO2 is 15 layers, each layer is 76.7nm thick, to obtain a bottom Bragg reflector.

[0086] Step 4: Take out the substrate after coating the bottom Bragg reflector in step 3, put it into a dual-source co-evaporation coating machine, put CsI and CuI as evaporation source materials into a quartz crucible, and start the vacuum system of the coating machine.

[0087] Step 5: When the vacuum degree of the vacuum system of the dual-source co-evaporation coating machine in step 4 reaches below 5E-4Pa, adjust the evaporation power supply current to make the evaporation rate of CsI The evaporation rate of CuI is

[0088] Step 6: After the evaporation rate in step 5 stabilizes, open the substrate stage baffle and start evaporating Cs3Cu2I5 titanium ore film as the active layer; in order to form a tilt angle of 1×10 -5rad wedge-shaped active area, a fan-shaped baffle as described in the above embodiment 1 is introduced into the coating machine, and the fan-shaped baffle rotates at an angular velocity of 15 revolutions per minute during the evaporation process. The lengths h of the edges of the first end face and the second end face of the wedge-shaped film layer that are not in contact with the top Bragg reflector and the bottom Bragg reflector are respectively 130 nm and 380 nm.

[0089] Step 7: After the perovskite film evaporation in the gain area in step 6 is completed, the coating machine is vented and depressurized, the evaporation source materials are replaced with TeO2 and LiF, and the vacuum system of the coating machine is reopened.

[0090] Step 8: When the vacuum degree of the vacuum system of the coating machine in step 7 reaches below 5E-4Pa, start alternately evaporating 5.5 pairs of TeO2 and LiF to obtain a top Bragg reflector, in which the first and last layers are both TeO2, that is, TeO2 has 6 layers, each layer is 54.8nm thick, and LiF has 5 layers, each layer is 84.3nm thick.

[0091] Step 9: After the top Bragg reflector is prepared in step 8, the coating machine is vented and the pressure is released, and the device is taken out to obtain a tunable laser.

[0092] The tunable laser prepared by the method comprises a substrate, a bottom Bragg reflector, a wedge-shaped gain region and a top Bragg reflector.

[0093] Example 3 Preparation of tunable laser

[0094] In step 6, when the sector angle is selected as 1.2 rad, the sector baffle rotates at an angular velocity of 10 rpm, and the tilt angle of the wedge-shaped active region is 8×10 -6 rad, the lengths h of the sides of the first and second end faces of the wedge-shaped film layer that are not in contact with the top Bragg reflector and the bottom Bragg reflector are 230 nm and 430 nm, respectively. Except for this, the other steps and conditions are the same as those in Example 2 to prepare a tunable laser.

[0095] Example 4 Preparation of tunable laser

[0096] In step 3, the thickness of each Ta2O5 layer is 91.7nm; the thickness of each SiO2 layer is 96.5nm, and a bottom Bragg reflector is obtained; in steps 4, 5, and 6, CsBr and SnBr2 are placed in a quartz crucible as evaporation source materials, and the evaporation rate of CsBr is The evaporation rate of SnBr2 is A CsSnBr3 titanium ore film was evaporated as an active layer; in step 8, the thickness of each TeO2 layer was 91.8 nm, and the thickness of each LiF layer was 98.9 nm, to obtain a top Bragg reflector. Apart from this, the other steps and conditions were the same as those in Example 2 to prepare a tunable laser.

[0097] Test Example 1

[0098] See also Figure 3 As shown in FIG. 1 , the reflection spectra of the top Bragg reflector and the bottom Bragg reflector of the tunable laser prepared in Example 2 are obtained by simulating the transmission matrix method. Figure 3 It can be seen that in the wavelength range of 440-480nm, the reflectivity of the top Bragg reflector is greater than 99.9%, and the reflectivity of the bottom Bragg reflector is greater than 99%. Therefore, laser light can be generated within this wavelength range. The top and bottom Bragg reflectors can be designed to match the position and half-width of the photoluminescence spectrum of the gain region material. By changing the material and thickness of each structural layer of the Bragg reflector, the reflection spectrum of the Bragg reflector can be placed within the photoluminescence spectrum range of the gain region material. The reflectivity can be adjusted by changing the number of layers of each structural layer of the Bragg reflector to achieve the resonant condition for laser generation.

[0099] See also Figure 4 The figure shows the reflection spectrum of the tunable laser fabricated in Example 2. The gray line represents the result simulated using the transfer matrix method, and the black line represents the result directly measured using a UV-visible spectrophotometer. Compared to the simulated results, the central wavelength of the reflection spectrum is red-shifted by approximately 20 nm, primarily due to thickness and refractive index errors during the thin film deposition process.

[0100] See also Figure 5 The figure shows a spectrum test of the tunable laser prepared in Example 2. A femtosecond laser with an excitation wavelength of 288 nm (repetition rate of 1 kHz, pulse width of 120 fs) was used as the pump light source. The pump light's incident position was controlled to move along the direction of the tunable laser's active layer thickness change, resulting in a laser output with a wavelength range of 444-471.8 nm. During the test, the effective size of the femtosecond laser pump spot was controlled to keep the spot diameter less than 40 μm. Within this range, it can be assumed that the laser resonance conditions remain unchanged and the laser maintains single-mode output operation.

[0101] See also Figure 6 As shown, referring to the test method of Example 2, a spectrum test diagram of the tunable laser prepared in Example 4 can be obtained, and the corresponding laser output wavelength range is 610.5-666nm.

[0102] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A tunable laser, characterized in that: The laser comprises a bottom Bragg reflector, a wedge-shaped active region and a top Bragg reflector sequentially grown on a substrate, wherein the bottom Bragg reflector, the wedge-shaped active region and the top Bragg reflector constitute a resonant cavity; The side surface of the wedge-shaped active region in contact with the top Bragg reflector is an inclined surface; The angle between the side surfaces of the wedge-shaped active region and the top Bragg reflector and the bottom Bragg reflector is 4×10 -6 -4×10 -5 rad; The length h of the sides of the first end face and the second end face of the wedge-shaped active region that are not in contact with the top Bragg reflector and the bottom Bragg reflector is 100 nm to 1100 nm; The emission wavelength of the tunable laser is in the visible light band, and the visible light band refers to the band with a wavelength of 400-760nm; The reflectivity of the bottom Bragg reflector is greater than 99.9%; the thickness of the bottom Bragg reflector is 1500-4000 nm; the reflectivity of the top Bragg reflector is greater than 99%; the thickness of the top Bragg reflector is 600-1500 nm; The bottom Bragg reflector and the top Bragg reflector include first structural layers and second structural layers that are alternately arranged; in the top Bragg reflector and the bottom Bragg reflector, the materials of the first structural layers and the second structural layers are selected from at least one of oxides, halides and sulfides; In the top Bragg reflector and the bottom Bragg reflector, the refractive index of the first structure layer is n1, the refractive index of the second structure layer is n2, the n1 is 2.0-3.0, and the n2 is 1.3-1.7; In the top Bragg reflector and the bottom Bragg reflector, the optical thickness of the first structure layer is L1, and the optical thickness of the second structure layer is L2. The relationship between L1, L2 and the emission wavelength λ is: L1= M1λ / 4, L2= M2λ / 4, where M1 and M2 are odd numbers.

2. The tunable laser according to claim 1, characterized in that The material of the wedge-shaped active region comprises a perovskite material, wherein the perovskite material is selected from one of ternary halide perovskites, wherein the ternary halide perovskite is selected from Cs x Cu y I x+y 、Cs x Cu y Br x+y 、Cs x Cu y Cl x+y , one of CsSnBr3, CsSnCl3, CsPbBr3 and CsPbCl3, wherein x and y are integers greater than 0; The refractive index n of the wedge-shaped active region is in the range of 1.7-2; The thickness of the wedge-shaped active region is gradually changed in a wedge shape along the direction perpendicular to the optical axis, and the optically effective thickness ranges from λ / 2 to 2λ, where λ is 400-650nm; The wedge-shaped active region is formed by adding a periodically rotating baffle in a coating machine to obtain a wedge-shaped gradient active layer.

3. A method for preparing the tunable laser according to claim 1 or 2, characterized in that: The method comprises the following steps: Step 1: Depositing a bottom Bragg reflector on the substrate surface; Step 2: Under periodic shading conditions, depositing a ternary halide perovskite as a gain medium on the surface of the bottom Bragg reflector to form a wedge-shaped active region; Step 3: Deposit a top Bragg reflector on the surface of the wedge-shaped active area.

4. The preparation method according to claim 3, wherein: In step 1, depositing a bottom Bragg reflector on the substrate surface includes: alternately evaporating a first structural layer material and a second structural layer material on the substrate surface; In step 1, evaporating the first structural layer material and the second structural layer material on the surface of the substrate includes: placing the first structural layer material and the second structural layer material as evaporation source materials into a vacuum coating machine, and when the vacuum degree reaches below 5E-4Pa, alternately evaporating the first structural layer material and the second structural layer material; In step 2, the periodic shielding is achieved by a rotatable baffle disposed above the substrate, wherein the baffle is a fan-shaped structure.

5. The preparation method according to any one of claims 3 to 4, characterized in that: Step 2 includes: placing an evaporation source material corresponding to the ternary halide perovskite as a gain medium into a coating machine for evaporation deposition; In step 2, the evaporation source material corresponding to the gain medium includes CsX and at least one selected from PbY2, CuY and SnY2, and the X and Y are selected from any one of Cl, Br and I; The evaporation rate of the evaporation source material is 0.05-0.2 Å / s.

6. The preparation method according to claim 5, characterized in that: Step 2 includes: placing an evaporation source material corresponding to the gain medium into a crucible in a coating machine equipped with a fan-shaped baffle with adjustable speed, placing a substrate with a bottom Bragg reflector on a turntable, starting the vacuum system of the coating machine, adjusting the evaporation current so that the evaporation rate of the evaporation source material reaches 0.05-0.2Å / s and stabilizes, adjusting the rotation rate of the baffle to 10-20 revolutions / min, and evaporating the gain medium film until it reaches a set thickness to obtain a wedge-shaped active area.

7. The preparation method according to any one of claims 3 to 4, characterized in that: In step 3, depositing a top Bragg reflector on the surface of the wedge-shaped active area includes: alternately evaporating a first structural layer material and a second structural layer material on the surface of the wedge-shaped active area; In step 3, alternately evaporating the first structural layer material and the second structural layer material on the surface of the wedge-shaped active area includes: placing the first structural layer material and the second structural layer material as evaporation source materials into a vacuum coating machine, and when the vacuum degree reaches below 5E-4Pa, alternately evaporating the first structural layer material and the second structural layer material.

8. An evaporation device for evaporating the wedge-shaped active area according to any one of claims 1 to 2, characterized in that: The turntable comprises a turntable and at least one crucible, wherein the turntable is used to carry a substrate, and the crucible is used to place an evaporation source material and evaporate it. A baffle is provided between the turntable and the crucible, and one end of the baffle is connected to a power mechanism and can rotate under the drive of the power mechanism. The baffle is a fan-shaped structure with an angular arc of 0.5236-3.1 rad and a radius of 2-4 inches; The baffle is arranged parallel to the turntable, and the distance between the baffle and the turntable is 2-5 cm.

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