A white light laser

Abstract

This invention discloses a white light laser, belonging to the field of laser and nonlinear crystal device technology. It includes a pump source, a coupling focusing system, and a resonant cavity arranged sequentially along the light source direction. The pump source is a diode laser used to generate the original pump light. Within the resonant cavity, independent first and second self-frequency doubling crystals are arranged sequentially along the optical path to form sub-cavities for exciting two lasers of different wavelengths in the same direction. The fundamental frequency laser generated by the first self-frequency doubling crystal after absorbing the original pump light serves as the pump light for the second self-frequency doubling crystal. The fundamental frequency lasers generated in the two sub-cavities are frequency-doubled by the corresponding self-frequency doubling crystals to generate frequency-doubled lasers. The different frequency-doubled lasers are mixed to generate white light output. This invention can achieve high-power, high-beam-quality white light laser output and has advantages such as simple and compact structure and high reliability.

Description

Technical Field

[0001] This invention relates to the field of laser and nonlinear crystal device technology, and in particular to a white laser. Background Technology

[0002] White lasers, as a novel light source possessing high brightness, high directionality, and a broad spectrum, have shown enormous application potential in high-end lighting, color displays, biomedical imaging, spectral analysis, and the processing of special materials. Traditional methods for generating white light mainly include: first, mixing red, green, and blue primary color lasers; however, this method requires multiple independent lasers and a complex optical beam combining system, resulting in complex structures, large size, high cost, and challenges to stability; second, using lasers to excite fluorescent materials (such as phosphors) to generate broadband white light; while this method is relatively simple in structure, it suffers from low conversion efficiency, difficulty in thermal management, and significant degradation of luminous brightness and directionality due to scattering by the fluorescent material, making it difficult to obtain high-quality white laser light; and third, directly generating white light using the broad spectrum emission of a single laser or nonlinear optical processes, but this usually results in low power or difficulty in spectral control.

[0003] In recent years, the technical route of obtaining multicolor lasers based on nonlinear optical frequency conversion techniques (such as frequency doubling and sum-frequency conversion) and then synthesizing white light has attracted widespread attention. Among them, self-frequency doubling laser crystals have become an effective solution for realizing compact monochromatic visible light lasers because they can integrate laser generation and nonlinear frequency conversion functions into the same crystal, thereby simplifying the system structure. However, how to efficiently and compactly generate two or more high-power visible light sources using a single pump source and achieve high beam quality mixing to form high-quality white light with tunable color temperature remains a key challenge in this field. In existing technologies, attempts to use combinations of multiple different laser crystals and nonlinear crystals, or to use the same crystal to generate multiple wavelengths and then perform frequency doubling, often face problems such as system complexity, difficulty in accurately controlling the power ratio of each channel, difficulty in managing thermal effects, and low overall efficiency.

[0004] Therefore, there is an urgent need in this field for a novel laser solution that is simple and compact in structure, highly reliable, and capable of achieving high-power and high-beam-quality white light output. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a white laser that can directly output white laser light with only one laser device. Furthermore, it effectively reduces the crystal thermal effect during laser operation, ensuring high-power, high-stability, and high-beam-quality white laser output.

[0006] To achieve the above objectives, the present invention provides a white light laser, comprising a pump source, a coupling focusing system, and a resonant cavity arranged sequentially along the light source direction;

[0007] The pump source is a diode laser, used to generate the original pump light; The resonant cavity is provided with independent first and second self-frequency doubling crystals arranged in front and behind each other along the optical path to form a sub-resonant cavity for exciting two lasers of different wavelengths in the same direction. The fundamental frequency laser generated by the first self-frequency doubling crystal after absorbing the original pump light is used as the pump light of the second self-frequency doubling crystal. The fundamental frequency lasers generated in the two sub-resonant cavities are frequency doubled by the frequency conversion of the corresponding self-frequency doubling crystals. The output of the frequency doubled lasers of different wavelengths is mixed to generate white light output.

[0008] Preferably, the wavelength of the original pump light emitted by the pump source is 790-890nm.

[0009] Preferably, the first self-frequency doubling crystal is a neodymium-doped self-frequency doubling crystal, and the second self-frequency doubling crystal is a ytterbium-doped self-frequency doubling crystal.

[0010] Preferably, the first laser crystal is one of neodymium-doped yttrium aluminum borate, gadolinium calcium oxy borate, lanthanum calcium oxy borate, yttrium calcium oxy borate crystal, and lithium niobate crystal, or a mixed crystal formed by two or three of neodymium-doped yttrium aluminum borate, gadolinium calcium oxy borate, lanthanum calcium oxy borate, and yttrium calcium oxy borate crystal; the doping concentration is 0.01 to 30 at.%, and the light transmission is along the optimal phase-matching direction.

[0011] Preferably, the second laser crystal is one of ytterbium-doped yttrium aluminum borate, gadolinium borate, lanthanum borate, and yttrium borate, or a mixed crystal formed by two or three of ytterbium-doped yttrium aluminum borate, gadolinium borate, lanthanum borate, and yttrium borate; the doping concentration is 0.01 to 30 at.%, and the light transmission is along the optimal phase-matching direction.

[0012] Preferably, the coupling focusing system uses two or more lenses in combination to amplify or reduce the pump light before it is incident on the laser crystal.

[0013] Preferably, the different band frequency-doubled laser outputs from the two sub-resonators include blue light output from the sub-resonator composed of the first self-frequency-doubled crystal and yellow-orange light output from the sub-resonator composed of the second self-frequency-doubled crystal.

[0014] Preferably, by adjusting the reflectivity of each resonant cavity, the absorption coefficient of the crystal, or the distance between crystals or between crystals and resonant cavities, the output power ratio of two co-directional lasers of different wavelengths can be controlled, thereby achieving white light output in different color temperature ranges.

[0015] Preferably, the resonant cavity and / or the first laser crystal and / or the second laser crystal are coated with corresponding film systems to ensure that the generated laser light is output unidirectionally through the output terminal; after mixing at the output terminal, white light is output.

[0016] Preferably, the first and second self-frequency doubling crystals are fixed in a cooling heat sink with high thermal conductivity, and the heat sink is filled with constant-temperature cooling water or uses a TEC cooling chip to ensure the constant temperature of the self-frequency doubling crystals.

[0017] This invention discloses a white laser, which has the following beneficial effects: Structural Integration and Simplified Gain: By employing two independent self-frequency-doubling crystals as the core gain and frequency conversion medium, the two physical processes of "laser generation" and "frequency doubling conversion," which are separate in traditional schemes, are integrated into a single crystal. The self-frequency doubling process occurs within the high-intensity cavity of the laser oscillation, resulting in high nonlinear conversion efficiency. Compared to schemes with externally placed independent nonlinear crystals, this reduces additional losses caused by optical interface reflections and beam coupling, facilitating the achievement of higher visible light output power. Simultaneously, the fundamental frequency laser generated by the first laser crystal pumps the second laser crystal, avoiding multi-stage losses from pump light reabsorption through efficient intracavity optical pumping, thus improving overall optical-to-optical conversion efficiency. These two design features fundamentally simplify the system, reduce the number of independent optical components, and result in a compact structure, easy assembly and adjustment, and significantly improved stability and reliability.

[0018] In this invention, two laser resonators oscillate independently and generate fundamental frequency light, which is then converted into blue and yellow-orange light respectively within their respective crystals. This design allows for better control of the modes of each resonator, ensuring that the generated visible light has a high beam quality (e.g., low divergence angle, near-Gaussian beam) similar to the fundamental frequency light. The resulting mixed white light thus possesses both the directionality and high brightness characteristics of laser light, a key advantage that phosphor-converted white light cannot match. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the energy levels in the intracavitary cascaded pumping method of the present invention; Figure 2 This is a schematic diagram of the laser structure in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the laser structure in Embodiment 4 of the present invention; Figure 4 This is a schematic diagram of the laser structure in Embodiment 8 of the present invention; Figure 5 This is a schematic diagram of the laser structure in Embodiment 9 of the present invention; Figure 6 This is a schematic diagram of the laser structure in Embodiment 10 of the present invention; Figure 7 The image shows the spectral curve of the hybrid light source in Embodiment 1 of the present invention, in which blue and yellow lasers work together. The horizontal axis represents wavelength (nm), the vertical axis represents intensity, and the intensity ratio of blue light to yellow light is 1:1. Figure 8 The image shows the spectral curve of the hybrid light source in Embodiment 5 of the present invention, in which blue and yellow lasers work together. The horizontal axis represents wavelength (nm), the vertical axis represents intensity, and the intensity ratio of blue light to yellow light is 1:1. Figure 9 The image shows the spectral curve of the hybrid light source in Embodiment 7 of the present invention, in which blue and yellow lasers work together. The horizontal axis represents wavelength (nm) and the vertical axis represents intensity. The intensity ratio of blue light to yellow light is 1:2. Figure 10 This provides the chromaticity coordinate information of the hybrid light source used in Examples 1-2 under different intensity ratio conditions; Figure 11 The chromaticity coordinates of the hybrid light source used in Examples 5-6 under different intensity ratios are shown. Figure 12 The chromaticity coordinates of the hybrid light source used in Example 7 under different intensity ratio conditions are shown.

[0020] In the picture: 1. Pump source; 2. Coupled focusing system; 3. Input cavity mirror; 4. First crystal incident end face; 5. First laser crystal; 6. First crystal output end face; 7. Second crystal incident end face; 8. Second laser crystal; 9. Second crystal output end face; 10. Output cavity mirror. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of the present invention and are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0022] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or server that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0023] Similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0024] The terms mentioned in the following embodiments are explained as follows: LD: Laser Diode.

[0025] High transmittance: refers to a transmittance of more than 99% for a specific wavelength or band of light.

[0026] High reflectivity: refers to a reflectivity of more than 99% for light of a specific wavelength or band.

[0027] Phase matching: The phase matching condition is that the fundamental frequency light and the frequency-doubled light have the same refractive index when propagating within the crystal. Among all phase matching angles, there exists an angle that achieves the highest frequency doubling efficiency; this angle is called the optimal phase matching direction.

[0028] Example 1 Example 1 discloses a white light laser, such as Figure 2 As shown.

[0029] The laser includes a pump source 1, a coupling focusing system 2, an input cavity mirror 3, a first crystal incident end face 4, a first laser crystal 5, a first crystal output end face 6, a second crystal incident end face 7, a second laser crystal 8, a second crystal output end face 9, and an output cavity mirror 10, arranged sequentially along the optical path.

[0030] Pump source 1 is a laser diode with an emission center wavelength of 808 nm.

[0031] The coupling focusing system 2 magnifies the spot of pump source 1 by 1:2, with a focal length of 6 cm.

[0032] The first laser crystal 5 is a gadolinium borate crystal with a neodymium ion doping concentration of 7 at.%. The crystal is cut along the phase-matching direction with the largest effective nonlinear coefficient at 946 nm, and the cutting angle is (θ=110°±5°, φ=60°±5°). The size of the light-transmitting surface of the first laser crystal 5 is 3 mm×3 mm, and the length of the light-transmitting direction is 8 mm.

[0033] The second laser crystal 8 is a yttrium calcium oxide borate crystal with a ytterbium ion doping concentration of 15 at.%. The crystal is cut along the phase-matching direction with the largest effective nonlinear coefficient at 1150 nm, with a cutting angle of (θ = 111° ± 5°, φ = 30° ± 5°). The size of the light-transmitting surface of the second laser crystal 8 is 3 mm × 3 mm, and the length of the light-transmitting direction is 6 mm. In particular, ytterbium ion doping, as a tunable self-frequency doubling crystal, can achieve continuous or quasi-continuous tuning of the output wavelength under external control. The tunable self-frequency doubling crystal is selected from Yb:YCOB crystals or tunable self-frequency doubling crystals with electron-phonon coupling.

[0034] The first crystal incident end face 4, the first crystal output end face 6, the second crystal incident end face 7, and the second crystal output end face 9 are optically polished.

[0035] The first laser crystal 5 and the second laser crystal 8 form an intracavity cascaded pump, and the corresponding energy level diagram is shown below. Figure 1 As shown. The first laser crystal 5 can emit laser light at 946 nm, and the second crystal 8 has absorption at 946 nm. The 946 nm laser light generated by the first laser crystal 5 can be directly used as the pump source of the second laser crystal 8.

[0036] The input cavity mirror 3 is coated with a dielectric film that has high transmittance to 808 nm, 1000-1100 nm and 1200-1500 nm and high reflectance to 946 nm and 473 nm.

[0037] The output cavity mirror 10 is coated with a dielectric film that has high transmittance to 473nm, 1000-1100nm, 1200-1500nm and 575nm and high reflectance to 946nm and 1150nm.

[0038] The first crystal incident end face 4, the first crystal output end face 6, and the second crystal output end face 9 were optically polished but not coated.

[0039] The incident end face 7 of the second crystal is coated with a dielectric film that has high transmittance to 473 nm, 946 nm, 1000-1100 nm, and 1200-1500 nm and high reflectance to 1150 nm, 575 nm, and 808 nm.

[0040] Pump source 1 is turned on, and the laser power of pump source 1 is increased. Input cavity mirror 3 and output cavity mirror 10 form a 946nm sub-laser resonant cavity. When the first laser crystal 5 (a calcium oxy borate crystal with a neodymium ion doping concentration of 7 at.%) absorbs the 808nm pump light from the pump source, a 946nm fundamental frequency laser oscillation can be achieved under the action of the resonant cavity. At the same time, the first laser crystal 5 has a frequency conversion effect, which can convert the 946nm fundamental frequency laser into a 473nm blue laser. The generated 473nm blue light passes through the second laser crystal 8 (a calcium oxy borate crystal with a ytterbium ion doping concentration of 15 at.%) and is output from the output cavity mirror 10. Crucially, the second laser crystal 8 (yttrium borate crystal with a ytterbium ion doping concentration of 15 at.%) can strongly absorb the 946 nm wave. The incident end face 7 of the second crystal and the output cavity mirror 10 form a 1150 nm sub-resonant cavity. After the second laser crystal 8 absorbs the 946 nm laser energy, it will generate 1150 nm laser oscillation. At the same time, the frequency conversion capability of the second crystal 8 converts the 1150 nm light into 575 nm yellow-orange light, which is output through the output cavity mirror 10. Since the output 575 nm yellow-orange light and the output 473 nm light are on the same straight line, they can be directly mixed to generate white laser output.

[0041] By adjusting the working power ratio of the blue and yellow lasers to achieve a peak intensity ratio of 1:1, denoted as B1-Y1, this mixed laser source is used to obtain the final white light chromaticity coordinates (0.3211, 0.326) displayed in the standard chromaticity system 1931 CIE using the principle of chromaticity synthesis. Figure 10 As shown. Figure 7 The spectral curve of a hybrid light source that combines blue and yellow lasers.

[0042] Example 2 A white laser, with the same structure as in Example 1, differs in that: the peak intensity ratio of the blue and yellow lasers is adjusted to 1:2, denoted as B1-Y2. This mixed laser source is then used to achieve the final white light chromaticity coordinates (0.3723, 0.3887) in the standard chromaticity system 1931 CIE using the principle of chromaticity synthesis. Figure 10 As shown.

[0043] Example 3 A white laser has the same structure as in Example 1, except that the first crystal incident end face 4 and the first crystal output end face 6 are optically polished and then coated with a dielectric film with high transmittance to 473 nm, 946 nm, 1000-1100 nm, 1200-1500 nm and 808 nm.

[0044] After optical-grade polishing, the output end face 9 of the second crystal is also coated with a dielectric film that has high transmittance to 473 nm, 946 nm, 1000-1500 nm and 575 nm.

[0045] After the three end faces are treated with anti-reflection coating, the loss of the resonant cavity can be effectively reduced and the laser output efficiency can be improved.

[0046] Example 4 A white laser, such as Figure 3 As shown, the laser structure is basically the same as that in Example 1, except that: Remove input endoscope 3 and input endoscope 10; The incident end face 4 of the first crystal is coated with a dielectric film that has high transmittance to 808 nm, 1000-1100 nm and 1200-1500 nm and high reflectance to 946 nm and 473 nm.

[0047] The output end face 9 of the second crystal is coated with a dielectric film that has high transmittance to 473 nm, 1000-1100 nm, 1200-1500 nm and 575 nm and high reflectance to 946 nm and 1150 nm.

[0048] The first crystal incident end face 4 and the second crystal output end face 9 form a 946 nm laser resonant cavity, and the second crystal incident end face 7 and the second crystal output end face 9 form an 1150 nm laser resonant cavity.

[0049] Example 5 A white laser, the structure of which is basically the same as that in Example 1, except that: The first laser crystal 5 is a yttrium borate crystal with a neodymium ion doping concentration of 8 at.%. The crystal is cut along the phase-matching direction with the largest effective nonlinear coefficient at 946 nm, and the cutting angle is (θ=110°±5°, φ=45°±5°). The size of the light-transmitting surface of the first laser crystal 5 is 3 mm×3 mm, and the length of the light-transmitting direction is 6 mm.

[0050] The second laser crystal 8 is a yttrium borate crystal with a ytterbium ion doping concentration of 10 at.%. The crystal is cut along the phase-matching direction with the largest effective nonlinear coefficient at 1160 nm, and the cutting angle is (θ=112°±5°, φ=32°±5°). The size of the light-transmitting surface of the second laser crystal 8 is 3 mm×3 mm, and the length of the light-transmitting direction is 7 mm.

[0051] The output cavity mirror 10 is coated with a dielectric film that has high transmittance to 473 nm, 1000-1100 nm, 1200-1500 nm and 575 nm and high reflectance to 946 nm and 1160 nm.

[0052] The incident end face 7 of the second crystal is coated with a dielectric film that has high transmittance to 473 nm, 946 nm, 1000-1100 nm, and 1200-1500 nm and high reflectance to 1160 nm, 575 nm, and 808 nm.

[0053] Pump source 1 is activated, and its laser power is increased, ultimately outputting white light composed of 473 nm blue light and 580 nm yellow-orange light. By changing the positions of the first laser crystal 5 and the second laser crystal 8, the power ratio of the two lights can be adjusted, thus achieving color temperature regulation. The working power ratio of the blue and yellow lasers is adjusted to achieve a peak intensity ratio of 1:1, denoted as B1-YY1. Using the principle of chromaticity synthesis, this mixed laser source ultimately yields white light with chromaticity coordinates (0.3358, 0.314) displayed in the standard chromaticity system 1931cie. Figure 11 As shown. Figure 8 The spectral curve of a hybrid light source that combines blue and yellow lasers.

[0054] Example 6 A white laser, with a structure basically the same as in Example 1, differs in that: the peak intensity ratio of the blue and yellow lasers is adjusted to 1:4, denoted as B1-Y4. This mixed laser source is then used to achieve the final white light chromaticity coordinates (0.4339, 0.4074) in the standard chromaticity system 1931 CIE using the principle of chromaticity synthesis. Figure 11 As shown.

[0055] Example 7 A white laser, the structure of which is basically the same as that in Example 1, except that: The first laser crystal 5 is cut along the phase-matching direction with the largest effective nonlinear coefficient at 900 nm, and the cutting angle is (θ=113°±5°, φ=48°±5°). The size of the light-transmitting surface of the first laser crystal 5 is 3 mm×3 mm, and the length of the light-transmitting direction is 6 mm.

[0056] The second laser crystal 8 is cut along the phase-matching direction with the largest effective nonlinear coefficient at 1140 nm, with a cutting angle of (θ=112°±5°, φ=323°±5°). The size of the light-transmitting surface of the second laser crystal 8 is 3 mm × 3 mm, and the length of the light-transmitting direction is 7 mm.

[0057] The input cavity mirror 3 is coated with a dielectric film that has high transmittance to 808 nm, 1000-1100 nm and 1200-1500 nm and high reflectance to 900 nm and 473 nm.

[0058] The output cavity mirror 10 is coated with a dielectric film that has high transmittance to 473 nm, 1000-1100 nm, 1200-1500 nm and 575 nm and high reflectance to 900 nm and 1100-1200 nm.

[0059] The incident end face 7 of the second crystal is coated with a dielectric film that has high transmittance at 473 nm, 900 nm, 1000-1100 nm, and 1200-1500 nm and high reflectance at 1100-1200 nm, 575 nm, and 808 nm.

[0060] Pump source 1 is activated, and its laser power is increased, ultimately outputting white light composed of 450 nm blue light and 570 nm yellow light. By changing the positions of the first laser crystal 5 and the second laser crystal 8, the power ratio of the two lights can be adjusted, thus achieving color temperature regulation. The working power ratio of the blue and yellow lasers is adjusted to a peak intensity ratio of 1:2, denoted as B1-YY2. Using the principle of chromaticity synthesis, this mixed laser source ultimately yields white light chromaticity coordinates (0.3382, 0.3547) displayed in the standard chromaticity system 1931 CIE. Figure 12 As shown. Figure 9 The spectral curve of a hybrid light source that combines blue and yellow lasers.

[0061] Example 8 A white laser, such as Figure 4 As shown, the laser structure is basically the same as that in Example 3, except that: The first crystal output end face 6 is coated with a dielectric film that has high transmittance at 473 nm, 1000-1100 nm and 1200-1500 nm, high reflectance at 808 nm and partial transmittance at 946 nm.

[0062] The incident end face 7 of the second crystal is coated with a dielectric film that has high transmittance to 473 nm, 946 nm, 1000-1100 nm, and 1200-1500 nm and high reflectance to 1150 nm and 575 nm.

[0063] The first crystal incident end face 4 and the first crystal output end face 6 form a 946 nm laser resonant cavity, and the second crystal incident end face 7 and the second crystal output end face 9 form an 1150 nm laser resonant cavity.

[0064] Pump source 1 is turned on, and the laser power of pump source 1 is increased. After the first laser crystal 5 absorbs the pump light, it can achieve laser oscillation at 946 nm. At the same time, the first laser crystal 5 has a frequency conversion effect, which can convert the 946 nm laser into 473 nm blue laser. The generated 473 nm blue light is output after passing through the second laser crystal 8. Meanwhile, the output end face 6 of the first crystal has partial transmittance at 946 nm, and some 946 nm light will be incident on the second laser crystal 8. The incident end face 7 of the second crystal and the output end face 9 of the second crystal form an 1150 nm laser resonant cavity. After the second laser crystal 8 absorbs the 946 nm laser energy, it will generate 1150 nm laser oscillation. At the same time, the frequency conversion capability of the second crystal 8 converts the 1150 nm light into 575 nm yellow-orange light, which is output through the output cavity mirror 10. It is on the same straight line as the output 473 nm, and can be directly mixed to generate white laser output.

[0065] By changing the transmittance of the first crystal output end face 6 to 946 nm, and the positions of the first laser crystal 5 and the second laser crystal 8, the power ratio of the two types of light can be adjusted to achieve color temperature regulation.

[0066] Example 9 A white laser, such as Figure 5 As shown, the laser structure is basically the same as that in Example 3, except that: The incident end face 4 of the first crystal is coated with a dielectric film that has high transmittance to 808 nm, 1000-1100 nm and 1200-1500 nm and high reflectance to 575 nm, 946 nm, 473 nm and 1150 nm.

[0067] The output end face 9 of the second crystal is coated with a dielectric film that has high transmittance to 473 nm, 1000-1100 nm, 1200-1500 nm and 575 nm and high reflectance to 808 nm, 946 nm and 1150 nm.

[0068] The first crystal incident end face 4 and the second crystal output end face 9 are simultaneously 946 nm and 1150 nm laser resonant cavities.

[0069] The first crystal output end face 6 and the second crystal incident end face 7 were optically polished but not coated.

[0070] Example 10 A white laser, such as Figure 6 As shown, the laser structure is basically the same as that in Example 7, except that the length of the first laser crystal 5 in the light transmission direction is 3 mm, and the length of the second laser crystal 8 in the light transmission direction is 3 mm.

[0071] After the first laser crystal 5 and the second laser crystal 8 are bonded together, corresponding films are deposited on the incident end face 4 of the first crystal and the output end face 9 of the second crystal. At this time, the crystal can be regarded as a single crystal. By optimizing the crystal doping concentration and crystal length, white light output can be obtained directly from a single crystal. This structure effectively reduces the complexity of the laser and is called a microchip laser.

[0072] The present invention uses the above-mentioned white laser, and the laser device prepared using the above laser structure can realize white laser output, and has the advantages of compact structure, high reliability and stable laser output.

[0073] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0074] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A white light laser, characterized in that, It includes a pump source, a coupling focusing system, and a resonant cavity arranged sequentially along the light source direction; The pump source is a diode laser, used to generate the original pump light; The resonant cavity is provided with independent first and second self-frequency doubling crystals arranged in front and behind each other along the optical path to form a sub-resonant cavity for exciting two lasers of different wavelengths in the same direction. The fundamental frequency laser generated by the first self-frequency doubling crystal after absorbing the original pump light is used as the pump light of the second self-frequency doubling crystal. The fundamental frequency lasers generated in the two sub-resonant cavities are frequency doubled by the frequency conversion of the corresponding self-frequency doubling crystals. The output of the different wavelength frequency doubled lasers is mixed to generate white light output.

2. A white laser according to claim 1, characterized in that, The original pump light emitted by the pump source has a wavelength of 790-890nm.

3. A white laser according to claim 1, characterized in that, The first self-frequency doubling crystal is a neodymium-doped self-frequency doubling crystal, and the second self-frequency doubling crystal is a ytterbium-doped self-frequency doubling crystal.

4. A white laser according to claim 3, characterized in that, The first laser crystal is one of neodymium-doped yttrium aluminum borate, gadolinium borate, lanthanum borate, yttrium borate, or lithium niobate, or a mixed crystal formed by two or three of neodymium-doped yttrium aluminum borate, gadolinium borate, lanthanum borate, or yttrium borate; the doping concentration is from 0.01 to 30 at.%.

5. A white laser according to claim 3, characterized in that, The second laser crystal is one of the following: ytterbium-doped aluminum yttrium borate, calcium oxy gadolinium borate, calcium oxy lanthanum borate, calcium oxy yttrium borate crystal, and lithium niobate crystal; or a mixed crystal formed by two or three of the following: ytterbium-doped aluminum yttrium borate, calcium oxy gadolinium borate, calcium oxy lanthanum borate, and calcium oxy yttrium borate crystal; the doping concentration is 0.01 to 30 at.%.

6. A white laser according to claim 1, characterized in that, Coupled focusing systems use two or more lenses to amplify or reduce the pump light before it is incident on the laser crystal.

7. A white laser according to claim 1, characterized in that, The different frequency-doubled laser outputs from the two sub-resonators include blue light output from the sub-resonator composed of the first self-frequency-doubled crystal, and yellow-orange light output from the sub-resonator composed of the second self-frequency-doubled crystal.

8. A white laser according to claim 1, characterized in that, By adjusting the reflectivity of each resonant cavity, the absorption coefficient of the crystal, or the distance between crystals or between crystals and resonant cavities, the output power ratio of two co-directional lasers of different wavelengths can be controlled, thereby achieving white light output in different color temperature ranges.

9. A white laser according to claim 1, characterized in that, The resonant cavity and / or the first laser crystal and / or the second laser crystal are coated with corresponding films to ensure that the generated laser light is output unidirectionally through the output terminal; after mixing at the output terminal, white light is output.

10. The white laser according to claim 1, characterized in that, The first and second self-frequency doubling crystals are fixed in a cooling heat sink with high thermal conductivity. The heat sink is filled with cooling water at a constant temperature or a TEC cooling chip is used to ensure that the self-frequency doubling crystals are kept at a constant temperature.

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