End pump solar laser device based on total reflection principle

Abstract

The invention relates to an end pump solar laser device based on a total reflection principle. According to the device, sunlight is coupled into the laser medium and totally reflected in the laser medium, so that the length of a pumping absorption path is increased, and the purpose of improving the conversion efficiency from solar energy to laser energy is achieved. According to the specific scheme, sunlight passes through a condenser, is gathered to the position where a laser device is located and enters a conical reflector, the transmission angle of light can be modulated through multiple times of reflection in the reflector, then the sunlight enters a laser medium from the end face of the laser medium, and due to the fact that the refractive index of the laser medium is higher than that of cooling liquid, the sunlight can be emitted. Sunlight can be totally reflected in the laser medium, and the transmission distance of the sunlight in the laser medium is increased, so that the absorption of the laser medium to the sunlight is increased, and the sunlight-laser conversion capability is enhanced.

Description

Technical Field

[0001] The present application relates to the fields of optical laser technology, optical waveguide technology, and solar energy technology, and specifically to a solar laser device based on the principle of total reflection. Background Art

[0002] Solar energy is a clean and abundant natural energy source, and solar energy conversion has long been a hot topic of research. Solar-pumped lasers, devices that convert sunlight directly into laser light without requiring an electrical conversion step, offer greater potential than traditional optical-electrical-optical conversion methods. However, the conversion efficiency of solar-pumped lasers remains low, primarily due to the poor match between the pump absorption spectrum of the laser medium and sunlight, and the need to optimize the coupling of sunlight into the laser medium. Summary of the Invention

[0003] In view of this, the present application provides an end-pumped solar laser device based on the total reflection principle, which couples sunlight from the end face into the laser medium at a total reflection angle, causing it to be totally reflected in the medium, thereby increasing the transmission distance of sunlight in the medium, thereby promoting the medium's absorption of sunlight, and ultimately improving the conversion efficiency of the solar-pumped laser.

[0004] To achieve the above objectives, the technical solutions of the embodiments of the present application are as follows:

[0005] An exemplary embodiment includes a concentrator, a window, a coolant, a conical reflector, a laser medium, and a laser output mirror. Sunlight strikes the parabolic reflector, focusing toward the window. It is refracted by the window and the coolant before entering the conical reflector, where it reflects multiple times. The angle of the light is modulated by the conical reflector before ultimately entering the laser medium, where it is totally reflected due to the refractive index difference between the laser medium and the coolant. The laser medium is pumped by sunlight, ultimately producing laser output.

[0006] In some embodiments, the conical reflector can be a solid reflector, utilizing the refractive index difference between the solid material and the coolant for total reflection or by coating the solid material with a reflective film for reflection. The solid reflector and the laser medium are made of the same material, and the two are bonded at the contact surface, including but not limited to bonding yttrium aluminum garnet (YAG) to neodymium-doped yttrium aluminum garnet (Nd:YAG), bonding yttrium aluminum garnet (YAG) to cerium-neodymium doped yttrium aluminum garnet (Ce:Nd:YAG), and bonding yttrium aluminum garnet (YAG) to chromium-neodymium doped yttrium aluminum garnet (Gr:Nd:YAG). Laser devices with solid reflectors require coating the solid reflector's sunlight incident surface with a total reflection film corresponding to the laser wavelength, and coating the laser medium's sunlight exit surface with an anti-reflection film corresponding to the laser wavelength. Ultimately, a laser resonant cavity is formed between the solid reflector's sunlight incident surface and the laser output mirror.

[0007] In some embodiments, the conical reflector can be a cavity reflector, which reflects sunlight by coating the surface of a conical cavity with a reflective film, and the cavity is filled with coolant. Cavity reflector laser devices require coating the sunlight incident surface of the laser medium with a total reflection film corresponding to the laser wavelength, and coating the sunlight exit surface with an anti-reflection film corresponding to the laser wavelength. Ultimately, a laser resonant cavity is formed between the sunlight incident surface of the laser medium and the laser output mirror.

[0008] In some embodiments, the side surface of the conical reflector can be modified into an arc, the main feature of which is to guide sunlight into the end face of the laser medium at a total reflection angle.

[0009] In some embodiments, the coolant can be replaced by a gas or solid, primarily characterized by a lower refractive index than the laser medium.

[0010] Beneficial effects:

[0011] This application utilizes a conical reflector structure to allow sunlight to be fully reflected and transmitted in the laser medium, thereby increasing the length of the sunlight transmission path, promoting the laser medium's absorption of sunlight, and effectively increasing the conversion efficiency of sunlight-pumped laser solar energy to laser energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The basic structure of the end-pumped solar laser device based on the total reflection principle of the present application is described.

[0013] Figure 2 Describes the calculation parameter settings of the conical reflector of this application. DETAILED DESCRIPTION

[0014] The following is combined with Figure 1 The present application is described in detail with reference to embodiments.

[0015] The solar laser device based on the total reflection principle includes a concentrator 1 and a laser output structure 2. The laser output structure 2 includes a window 3, a coolant 4, a conical reflector 5, a laser medium 6, a laser output mirror 7 and a mechanical housing 8.

[0016] The specific working process of this embodiment is as follows:

[0017] Sunlight is incident on the concentrator 1, which concentrates the incident light to the laser output structure 2;

[0018] The window 3 and the mechanical structure 8 form a sealed space inside the laser output structure 2 for the coolant 4 to flow and refrigerate;

[0019] The mechanical structure 8 fixes the window 3, the conical reflector 5 and the laser medium;

[0020] The window 3 and the coolant 4 in the laser output structure 2 refract the incident sunlight, and the sunlight enters the conical reflector 5;

[0021] The conical surface of the conical reflector 5 reflects the sunlight multiple times, and each reflection changes the angle between the light and the optical axis. After multiple reflections, the sunlight enters the laser medium 6;

[0022] There is a refractive index difference between the laser medium 6 and the coolant 4. The laser medium 6 has a high refractive index and the coolant 4 has a low refractive index. The light modulated by the conical reflector 5 can be totally reflected in the laser medium 6.

[0023] The laser medium 6 absorbs sunlight, causing a population inversion, and cooperates with the laser output mirror 7 to generate laser output.

[0024] In some embodiments, the conical reflector 5 is a total reflection solid reflector. Figure 2 , the size parameters are calculated as follows:

[0025] Sunlight is incident at a divergence angle δ and is focused by concentrator 1 into a light spot. Given the diameter D and focal length f of concentrator 1, the range of the incident angle i1 at window 3 can be calculated based on the geometric relationship.

[0026]

[0027] Assume the thickness of fused silica d, the thickness of the water layer at the front end of the conical reflector 5 l0, and the distance Δl between the intersection of the incident light and the optical axis and the front surface of the window 3. The intersection position r0′ of the front end of the conical reflector 5 is calculated as follows

[0028] r0′=Δltani1+dtani2+l0tani3

[0029] Δl and r0′ have positive and negative properties. When the incident light intersects the optical axis to the left of window 3, Δl is positive, otherwise it is negative; when the light intersects the front face of the conical reflector 5 below the optical axis, r0′ is positive, otherwise it is negative. In the formula, the incident light's exit angles i2, i3, and α in each medium are calculated using the following relationships:

[0030] sini1=n1sini2=n2sini3=n3sinα

[0031] n1, n2 and n3 are the refractive indices of the window 3, the coolant 4 and the conical reflector 5, respectively.

[0032] All the light rays of the selected wavelength band can be incident on the conical reflector 5, then the following relationship holds true

[0033] |r0′|≤r0

[0034] When the focal plane of the concentrator 1 is located on the left side of the sunlight incident surface of the conical reflector 5, the maximum value of |r0′| is determined by i 1max Decision, otherwise and i 1min Related.

[0035] Assume that the distance between the front face of window 3 and the focal plane of the condenser in air is d0. When the focal plane is on the left side of the window, it is positive, otherwise it is negative. Then Δl can be rewritten as

[0036]

[0037] By solving the above formula, we can calculate the corresponding d0 when all light in the selected wavelength band can be incident on the conical reflector.

[0038] i1=i 1max When the angle of the cone reflector is 1, the intersection of the light and the side of the conical reflector 5 is the farthest from the laser medium 6. If the light incident at this angle can enter the laser medium and undergo total reflection, then the light incident at a smaller angle must also be able to enter the laser medium and undergo total reflection. Therefore, when calculating the cone angle of the conical reflector, i is used. 1max As the basis.

[0039] The light incident on the conical reflector 5 can be reflected multiple times and guided into the laser medium 6. The incident angle β1 of the first reflection, the axial transmission distance l1 before the next reflection and the reflection point position r1 are as follows:

[0040] β1=90°-α-θ

[0041]

[0042]

[0043] Starting from the second reflection, the parameters of each reflection position have regularity, β n 、l n and r n (n≥2) is calculated as follows

[0044] β n =β1-2(n-1)θ

[0045]

[0046] Wherein, θ is the opening angle of the conical reflector 5. According to β n The calculation formula shows that each reflection will reduce the incident angle of the light and the side of the conical reflector 5. When the number of reflections is large enough, β n It will become a negative number, which means that the light has been transmitted in the reverse direction before entering the laser medium. Therefore, the longer the length of the conical reflector is, the better. At the same time, only when the side of the conical reflector 5 is totally reflected can enough energy be retained to enter the laser medium. Therefore, βn (n≥1) needs to meet the total reflection condition

[0047] β n ≥arcsin(n2 / n3)

[0048] Assuming that after the nth (n≥1) total reflection, the light enters the laser medium 6 from the conical reflector 5, and the refractive index of the two is the same, according to the calculation method of the optical fiber numerical aperture, the incident angle γ at the laser medium 6 must meet the following conditions

[0049]

[0050] According to the geometric relationship in conical reflector 5

[0051] γ=90°+θ-β n

[0052] Then the value range of θ is

[0053]

[0054] According to β n The total reflection condition, the relationship of γ is rewritten as

[0055]

[0056] This formula shows that if light can enter the laser medium 6 and undergo total reflection, then each reflection in the conical reflector 5 must be total reflection. Suppose the radius of the laser medium 6 is r m The radius r0 of the incident surface of the conical reflector 5 is known. Once the length L of the conical reflector 5 is determined, its opening angle θ can be determined. The relationship is as follows:

[0057]

[0058] If the edge ray is reflected n times into the laser medium, the length of the conical reflector 5 is effective when the length satisfies the following relationship

[0059] l1+l2+...+l n <L<l1+l2+...+l n +l n+1

[0060] Combining the above formulas, L, n and Δl of the conical reflector 5 can be calculated.

[0061] In some embodiments, the conical reflector 5 is a reflective film solid reflector, then β n The total reflection condition does not need to be met.

[0062] In some embodiments, the conical reflector 5 is a cavity reflector, and the size parameters are calculated as follows:

[0063] Since the conical reflector 5 cavity is filled with coolant 4, it is necessary to correct α and γ

[0064] α=i3

[0065]

[0066] At the same time β n There is no need to meet the total reflection condition, and the value range of θ is recalculated as

[0067]

[0068] Using the corrected parameters, the parameters of the conical reflector 5 can be calculated.

[0069] In some embodiments, the coolant 4 can be replaced by other materials with a lower refractive index than the laser medium 6, which can be solid, liquid, or gas.

[0070] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An end-pumped solar laser device based on the total reflection principle, characterized in that: The laser output structure includes a concentrator and a solar laser, and includes a window, a coolant, a conical reflector, a laser medium, a laser output mirror and a mechanical housing; The concentrator is used to focus sunlight to the position of the solar laser device; The window and the mechanical structure are used to seal the interior of the laser output structure, and the mechanical structure is also used to fix the conical reflector and the laser medium; The coolant is used to cool the end-pumped solar laser device and provide the optically thinning medium required for total reflection; The conical reflector is immersed in the coolant and is used to collect the sunlight spots concentrated by the concentrator and modulate the transmission angle of the sunlight so that it can be totally reflected in the laser medium; The laser medium is an optically dense medium and is immersed in a cooling liquid to generate a total reflection condition; The laser medium absorbs solar energy and converts it into laser energy in cooperation with the output mirror.

2. The end-pumped solar laser device based on the total reflection principle according to claim 1 is characterized in that The conical reflector may be a solid reflector, which utilizes the refractive index difference between the solid material and the coolant to perform total reflection or is formed by coating a reflective film on the side of the solid material to perform reflection.

3. The end-pumped solar laser device based on the total reflection principle according to claim 1 is characterized in that The conical reflector may be a cavity reflector, which reflects sunlight by coating a reflective film on the surface of the conical cavity, and the interior of the cavity is filled with cooling liquid.

4. The end-pumped solar laser device based on the total reflection principle according to claim 1 is characterized in that The side surface of the conical reflector can be a special curved surface other than the cone surface, and its main function is to guide sunlight into the end face of the laser medium at a total reflection angle.

5. The end-pumped solar laser device based on the total reflection principle according to claim 1 is characterized in that The coolant can replace a gas or solid with a lower refractive index than the laser medium.

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