Laser pumping device with pump light guided by cooling liquid

Abstract

A laser pumping device includes a pump light emitter, a dielectric tube, and a laser gain material. The pump light emitter is configured to emit pump light and has a pump axis. The dielectric tube is hollow and includes a receiving space, an incident surface, and multiple reflecting surfaces; the pump light emitter is disposed adjacent to the incident surface. The laser gain material is mounted in the receiving space filled with cooling water. The dielectric tube is configured to receive the pump light into the incident surface, guide the pump light along the pump axis around the reflecting surfaces, and converge the pump light into the laser gain material. The cooling water has a dual purpose: guiding the pump light into the laser gain material and removing heat from the laser gain material.

Description

Laser pumping device using coolant to guide pump light The present invention relates to a laser pumping device, and more particularly to a laser pumping device that utilizes a cooling liquid confined within a dielectric to focus light to pump a laser rod while simultaneously removing heat from the laser rod. The present invention also encompasses laser oscillators and laser amplifiers that operate using the pumping scheme. In a typical laser system, atoms are pumped from a low energy level to a high energy level by external energy. As the high-energy atoms drop to the lower energy level, they release radiative energy, forming the basis for laser emission. For example, the energy levels E0, E1, E2, and E3 represent the ascending energy levels in a typical four-level atomic system, such as that found in a neodymium (Nd) laser. Initially, the atoms are in the ground state energy level E0. External pump light drives the ground state atoms from E0 to E3, where they rapidly drop from E3 to the slightly lower energy level E2, which has a longer lifetime, achieving the atomic inversion between E2 and E1 that is common in laser emission. As the atoms drop from E3 to E2, the wasted energy heats the laser crystal and may potentially drive atoms from E0 to E1, disrupting the population inversion, a necessary phenomenon in typical four-level laser operation. Therefore, removing heat from the laser crystal is crucial to laser manufacturing. In practice, for efficiency, pump light must be focused onto the laser gain medium, typically a rod with a small aperture diameter to allow laser emission along the rod's axis. In existing technologies, for unfocusable pump light, a glass wedge-shaped light guide is typically used to focus the pump light onto a laser rod mounted within a glass tube containing cooling water. The water in the glass tube removes heat from the laser crystal. However, in this laser pumping structure, the glass wedge is fragile and expensive to manufacture. Furthermore, the thickness of the water tube between the wedge output and the laser rod prevents the pump light from reaching the laser rod quickly enough for efficient laser pumping. Any unnecessary interface between the rapidly diverging pump light and the laser rod reduces the amount of pump light reaching the laser rod, thereby reducing pumping efficiency. In view of the shortcomings of the prior art, there is a real need to invent an efficient and effective laser pumping device that takes into account the guidance and concentration of the pump light and the removal of heat from the laser rod. According to one embodiment of the present invention, a laser pumping device includes a pump light emitter, a dielectric tube, and a laser gain material. The pump light emitter is configured to emit pump light and has a pump axis. The dielectric tube is hollow and includes a housing, a light incident surface, and multiple reflective surfaces. The housing can be filled with a cooling liquid. The pump light emitter is positioned adjacent to the light incident surface. The laser gain material is mounted in the housing. The dielectric tube can be filled with a cooling liquid and is configured to receive pump light into the light incident surface, guide the pump light along the pump axis surrounding the reflective surfaces, and transmit the pump light to the laser gain material. According to the laser pumping device of the aforementioned embodiment, the pump light emitter may be an LED board including a plurality of LED chip arrays, and the pump axis is parallel to the normal direction of the surface of the pump light emitter. According to the laser pumping device of the aforementioned embodiment, the pump light emitter may include a blue-green LED. According to the laser pumping device of the aforementioned embodiment, two facing reflection surfaces may be parallel to each other and surround the pumping axis. According to the laser pumping device of the aforementioned embodiment, two facing reflective surfaces may have a wedge angle to focus the pump light from the light incident surface with a larger aperture to the laser gain material with a smaller aperture. According to the laser pumping device of the aforementioned embodiment, the laser gain material may be a laser rod having a rod axis, and the pumping axis and the rod axis are perpendicular to each other. According to the laser pumping device of the aforementioned embodiment, the accommodating space may be filled with liquid for cooling, air surrounds the dielectric tube, and the refractive index of the liquid is greater than that of the air. According to the aforementioned embodiments of the laser pumping device, the liquid may be configured to remove heat generated by the pump light emitter and the laser gain material. According to the laser pumping device of the aforementioned embodiment, the liquid may be water, and the material of the dielectric tube may be glass or plastic. According to the laser pumping device of the aforementioned embodiment, each reflective surface of the dielectric tube at the dielectric-air boundary can provide total internal reflection for the incident pump light. According to another embodiment of the present invention, a laser pumping device includes a plurality of pump light emitters, a tube structure, and a laser gain material. Each pump light emitter is configured to emit pump light and has a pump axis. The tube structure is hollow and includes at least one receiving space and at least one dielectric tube. The dielectric tube includes at least one light incident surface and a plurality of reflection surfaces. The number of pump light emitters and the number of light incident surfaces are plural and equal, and each pump light emitter is positioned adjacent to a corresponding one of the light incident surfaces. The laser gain material is mounted in the receiving space, which can be filled with a cooling liquid. The dielectric tube can be filled with cooling liquid and is configured to receive at least one of the pump lights into the corresponding light incident surface, guide the pump light along a corresponding one of the pump axes surrounding the reflection surfaces, and converge the pump light into the laser gain material. According to the laser pumping device of the aforementioned embodiment, the laser gain material may be a laser rod having a rod axis, and the pumping axis and the rod axis are perpendicular to each other. According to the laser pumping device of the aforementioned embodiment, the number of dielectric tubes, the number of pump light emitters, and the number of light incident surfaces can each be greater than two. The dielectric tubes extend along the pump axes of the pump light emitters, and the pump axes intersect in the laser gain material. According to the laser pumping device of the aforementioned embodiment, the laser gain material can be a laser rod having a rod axis. Each pump axis is parallel to the rod axis. There are two light incident surfaces, and two ends of the laser gain material are respectively adjacent to the two light incident surfaces. According to another embodiment of the present invention, a laser pumping device includes at least one pump light emitter, a dielectric tube, and a laser gain material. The at least one pump light emitter is configured to emit at least one pump light. The dielectric tube is hollow and includes a receiving space and a light incident surface, with the pump light emitter positioned adjacent to the light incident surface. The laser gain material is mounted in the receiving space. The dielectric tube is configured to receive the pump light into the light incident surface and transmit the pump light to the laser gain material. According to the laser pumping device of the aforementioned embodiment, the accommodating space may be filled with liquid for cooling, air surrounds the dielectric tube, and the refractive index of the liquid is greater than that of the air. According to the laser pumping device of the aforementioned embodiment, the laser gain material may be a laser rod having a rod axis, and the rod axis is perpendicular to at least one emission direction of the pump light from the at least one pump light emitter. According to the laser pumping device of the aforementioned embodiment, the number of the at least one pump light emitter may be at least three, each pump light emitter is an LED board including a plurality of LED chip arrays, and the pump light emitters are arranged in a polygonal shape and surround the dielectric tube. According to the aforementioned embodiment of the laser pump device, the cross-section of the laser pump device is oriented such that the normal direction is parallel to the rod axis. In the cross-section, the dielectric tube and the laser gain material can both be circular and coaxially arranged, with the width of the light-emitting surface of each pump light emitter being greater than or equal to the diameter of the dielectric tube. According to the laser pumping device of the aforementioned embodiment, the number of the at least one pump light emitter may be at least three. The pump light emitters are arranged in a polygonal shape and surround the dielectric tube. At least one of the pump light emitters is at least one passive high-reflection mirror, and at least another of the pump light emitters is at least one active pump light emitter. The passive high-reflection mirror is used to reflect the pump light emitted by the active pump light emitter toward the laser gain material. Thus, in the laser pump device of the present invention, the dielectric tube is hollow and includes a chamber that can be filled with a cooling liquid. A laser gain material is mounted within the chamber. The dielectric tube, which can be filled with cooling liquid, is configured to receive pump light into the light-entry surface and transmit the pump light to the laser gain material. Therefore, the dielectric tube design of the laser pump device of the present invention facilitates guiding and focusing the pump light while also further removing heat from the laser gain material. The following describes various embodiments of the present invention with reference to the accompanying drawings. For clarity, many practical details are included in the following description. However, it should be understood that these practical details are not intended to limit the present invention. In other words, these practical details are not essential to the embodiments of the present invention. Furthermore, to simplify the drawings, some commonly used structures and components are depicted in simplified schematic form; and repeated components may be represented using the same reference numerals. Furthermore, the combination of components in the present invention is not generally known, conventional, or familiar in the art. Whether the components themselves are familiar cannot be used to determine whether the combination can be easily accomplished by a person skilled in the art. FIG1A is a schematic diagram showing the theory supporting the present invention. Referring to FIG1A, assuming that light is emitted from the air environment at an angle θ a The incident light is incident on the dielectric plate (optical dielectric plate) 816. At the material interface, part of the energy of the incident light is reflected at an angle θ. a Reflection, part of the energy of the incident light is reflected at an angle θ d refracted into the dielectric plate 816, part of the refracted light is at an angle θ a The light is emitted from the dielectric plate 816, and the angle θ of the light in the dielectric plate 816 is a ,θ d Governed by Snell's law: (1). In formula (1), n a and n d are the refractive indices of air and dielectric plate 816, respectively. From a geometric point of view, the incident angle of light at the dielectric-air interface is also angle θ d Therefore, the same Snell's law in equation (1) is applied to obtain the transmission angle of light emitted from the upper surface of the dielectric plate 816 = θ a This means that, for the configuration in FIG. 1A , some of the light energy is always lost as the light passes through the dielectric slab 816 . FIG1B illustrates another schematic diagram supporting the theory of the present invention. Referring to FIG1B , consider water 935 filling the bottom of dielectric plate 916 (which may have a different refractive index than dielectric plate 816 in FIG1A ) and light entering from the left side of the air. At the air-water interface, Snell's law can be expressed as Equation (2) or Equation (3): (2); and (3). In formula (2) and formula (3), n w is the refractive index of water 935, angle θ w is the incident angle of the refracted light on the water-dielectric interface. At the water-dielectric interface, Snell's law can be written as: (4). Assuming that the goal is to force the energy of the light path back from the dielectric-air interface to the water region, the following equation (5) is the condition for total internal reflection of light at the dielectric-air interface: (5). Substituting equations (3) and (5) into equation (4) simultaneously, we can obtain the following equation (6): (6). Formula (6) is the condition for all the energy in the optical path to return to the water side. It is known that Formula (6) is the numerical aperture of the optical system in Figure 1B. It is worth noting that the refractive index of the dielectric wall does not exist in Formula (6). This means that as long as the refractive index of liquid water is greater than the refractive index of air (the refractive index of air is almost 1), Formula (6) supports a non-zero numerical aperture to achieve total internal reflection at the dielectric-air interface, as shown in Figure 1B. When the refractive indices of air and water 935 are equal to 1 and 1.33 respectively, in Figure 1B, due to the total internal reflection at the dielectric-air interface, it can be obtained that the incident light is confined to the incident angle θ in water 935. a <61.26 degrees. Therefore, a simple conclusion is that, in the absence of water 935, light incident on the dielectric plate 816 in FIG. 1A will never undergo total internal reflection; in the presence of water 935, total internal reflection at the dielectric-air interface provides an acceptance angle range between 0 degrees and 61 degrees, thereby confining the incident light to the water region in FIG. 1B. FIG2 schematically illustrates a laser pumping device 1000 according to a first embodiment of the present invention. Referring to FIG2 , the laser pumping device 1000 includes a pump light emitter 100, a dielectric tube 115, and a laser gain material 120. The pump light emitter 100 is configured to emit pump light 145 and has a pump axis 125. The dielectric tube 115 is hollow and includes a housing, a light incident surface 114, and a plurality of reflection surfaces 150. The laser gain material 120 is mounted in the housing and filled with a cooling liquid 135. The pump light emitter 100 is disposed adjacent to the light incident surface 114. The dielectric tube 115 is configured to receive the pump light 145 into the light incident surface 114, guide the pump light 145 along the pump axis 125 surrounded by the reflection surface 150, and transmit the pump light 145 to the laser gain material 120. Thus, the dielectric tube 115 of the laser pump device 1000 is designed to facilitate the guidance and concentration of the pump light 145, while further removing the heat of the laser gain material 120. In addition, the laser gain material 120 can be Nd:YAG, Nd:YAP, Nd:YVO 4. Nd:GdVO 4. One of Nd:KGW, Nd:YLF, Nd:glass, Cr:YAG, Cr:LiSAF, Yb:YAG, Yb:glass, Er:YAG, Er:glass, Tm:glass and Ti:sapphire crystal. Specifically, the pump light emitter 100 can be an LED panel comprising a plurality of LED chip arrays, and the pump axis 125 is parallel to the surface normal of the pump light emitter 100. Specifically, the pump axis 125 of the pump light emitter 100 is a straight line passing through the geometric center of the pump light emitter 100 and extending along the surface normal of the pump light emitter 100. Thus, the laser pumping device 1000 effectively focuses the pump light 145 onto the laser gain material 120. Two facing reflective surfaces 150 may be wedge-shaped with a non-zero wedge angle α to focus the pump light 145 from the larger aperture of the light-entering surface 114 onto the smaller aperture of the laser gain material 120. This facilitates further effective focusing of the pump light 145 onto the laser gain material 120. In another embodiment of the present invention, the two facing reflective surfaces may be parallel to each other and surround the pump axis. The laser gain material 120 can be a laser rod having a rod axis 128 that coincides with the laser emission axis, and the pump axis 125 is perpendicular to the rod axis 128, as shown in FIG2 . The accommodation space can be filled with a liquid 135, and air surrounds the dielectric tube 115. The refractive index of the liquid 135 is greater than that of the air, such that the numerical aperture calculated according to equation (6) has a non-zero value. Thus, the liquid 135 can be used to guide, confine, and focus the pump light 145 toward the laser gain material 120 of the laser pumping device 1000. It should be noted that in the drawings of the first to seventh embodiments of the present invention (FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6A, FIG. 7, and FIG. 8), each pump light does not bend after being refracted from the liquid-dielectric boundary. This shows a special case where the refractive index of the liquid is very similar to that of the dielectric tube. Therefore, the θ in equation (4) is d Almost the same as θ w same. Each reflective surface 150 at the dielectric-air boundary of the dielectric tube 115 can provide total internal reflection for the incident pump light 145 , thereby facilitating the liquid 135 to guide, confine, and focus the pump light 145 onto the laser gain material 120 . Liquid 135 can be water, and dielectric tube 115 can be made of glass that is transparent to pump light 145 and has a refractive index of 1.5. Water has a refractive index of 1.33, which is close to the refractive index of most optical dielectric materials used to form dielectric tubes. This means that pump light 145 incident on and totally reflected from the liquid-dielectric boundary / interface will propagate toward laser gain material 120. Furthermore, the typical half-angle of LED emission is approximately 60 degrees, which falls within the acceptance angle range of a glass tube filled with water. This means that all LED pump light can be guided through the water-filled dielectric tube 115 to reach the laser gain material 120 for laser pumping. In another embodiment of the present invention, the dielectric tube can be made of glass, quartz, fused silica, or plastic. It should be noted that if the containment space is empty or filled with air, the pump light will not be guided within the dielectric tube, and most of the pump light / light may escape through the dielectric-air boundary. The present invention aims to fill a containment space with a liquid to focus pump light onto a laser gain material and remove heat from the laser gain material. The pump light emitter 100 may include a blue, green, or blue-green LED. Thus, water, which has minimal absorption of blue-green light, is advantageously used as the liquid 135 . Liquid 135 can be configured to flow into and out of dielectric tube 115 to remove heat generated by pump light emitter 100 and laser gain material 120. Thus, pump light 145 is guided to laser gain material 120 by total internal reflection at the dielectric-air boundary on reflective surface 150 through liquid 135, such as cooling water, in dielectric tube 115, thereby pumping laser gain material 120. Simultaneously, the flow of liquid 135 circulating in dielectric tube 115 removes heat from laser gain material 120. Therefore, laser pumping device 1000 of the present invention provides an efficient and powerful solution for utilizing cooling water to guide and focus pump light 145 to laser gain material 120 while removing heat from a laser rod immersed therein. FIG3 schematically illustrates a laser pumping device 2000 according to a second embodiment of the present invention. Referring to FIG3 , the laser pumping device 2000 includes a plurality of pump light emitters 200, a tube structure 210, and a laser gain material 220. Each pump light emitter 200 is configured to emit pump light 245 and has a pump axis 225. The tube structure 210 is hollow and includes at least one accommodating space filled with a cooling liquid 235 and at least one dielectric tube 215. The dielectric tube 215 includes at least one light incident surface 214 and multiple reflection surfaces 250. The number of pump light emitters 200 and the number of light incident surfaces 214 are plural and equal, and each pump light emitter 200 is disposed adjacent to a corresponding one of the light incident surfaces 214. The laser gain material 220 is mounted at the geometric center of the accommodating space. The dielectric tube 215 is configured to receive at least one of the pump lights 245 into the corresponding light-incident surface 214, guide the pump light 245 along a corresponding one of the pump axes 225 around the reflective surface 250, and transmit and focus the pump light 245 into the laser gain material 220. Thus, the at least one dielectric tube 215 of the laser pumping device 2000 is designed to facilitate guiding and focusing the pump light 245 into the laser gain material 220 while further removing heat from the laser gain material 220. Specifically, the laser gain material 220 is a laser rod having a rod axis 228 that coincides with the laser emission axis, and each pump axis 225 is perpendicular to the rod axis 228 , as shown in FIG. 3 . The number of dielectric tubes 215, the number of pump light emitters 200, and the number of light incident surfaces 214 can each be greater than or equal to two. Specifically, for the dielectric tube 215 shown in FIG3 , the number of pump light emitters 200 and corresponding light incident surfaces 214 is four. This number is not fixed for the laser pumping device of the present invention; those skilled in the art may increase or decrease this number based on a set of specified laser output parameters. In FIG3 , the dielectric tube 215 extends along the four pump axes 225 of the four pump light emitters 200, respectively. The four pump axes 225 intersect within the laser gain material 220. Each pump light emitter 200 is an LED board comprising a plurality of LED chip arrays, and each pump axis 225 is parallel to the normal direction of the surface of the corresponding pump light emitter 200. For each dielectric tube 215, the two facing reflective surfaces 250 are wedge-shaped with a non-zero wedge angle α to focus the corresponding pump light 245 from the corresponding light-entry surface 214 having a larger aperture to the laser gain material 220 having a smaller aperture. The accommodation space can be filled with liquid 235, and air surrounds the dielectric tube 215. The refractive index of liquid 235 is greater than that of air, so that the numerical aperture calculated according to equation (6) has a non-zero value. Thus, liquid 235 can be used to confine and focus pump light 245 for the laser pump device 2000 onto the laser gain material 220. Each reflective surface 250 at the dielectric-air boundary can focus the pump light 245 onto the laser gain material 220 by total internal reflection at the non-zero numerical aperture calculated according to equation (6). Liquid 235 is specifically flowing water, and dielectric tube 215 can be made of glass or plastic that is transparent to pump light 245. Each pump light emitter 200 comprises a blue or green LED. Liquid 235 is configured to focus pump light 245 onto laser gain material 220 and simultaneously remove heat generated by pump light emitters 200 and laser gain material 220. FIG4 schematically illustrates a laser pumping device 3000 according to a third embodiment of the present invention. Referring to FIG4 , the laser pumping device 3000 includes two pump light emitters 300, a tube structure 310, and a laser gain material 320. Each pump light emitter 300 is configured to emit pump light 345 and has a pump axis (coinciding with the rod axis 328). The tube structure 310 is hollow and includes at least one receiving space filled with a cooling liquid 335 and two dielectric tubes 315 connected to face each other and aligned along the two pump axes. Each dielectric tube 315 includes a light incident surface 314 and a complex reflection surface 350. There are two pump light emitters 300, each positioned adjacent to a corresponding light incident surface 314. The laser gain material 320 is mounted within the receiving space. Each dielectric tube 315 is configured to receive the corresponding pump light 345 into the corresponding light incident surface 314 , guide the corresponding pump light 345 along a corresponding one of the pump axes around the reflective surface 350 , and focus the corresponding pump light 345 into the laser gain material 320 . Specifically, for each dielectric tube 315 , two facing reflection surfaces 350 are parallel to each other and surround the corresponding pump axis, thereby facilitating the repeated reflection of pump light toward the laser gain material 320 in the laser pumping device 3000 . The laser gain material 320 is a laser rod having a rod axis 328, with each pump axis parallel to the rod axis 328. Specifically, the rod axis 328 coincides with the two pump axes, as shown in FIG4 , and the laser pump device 3000 has a longitudinal pumping structure. There are two light incident surfaces 314, with the two ends of the laser gain material 320 adjacent to each of the two light incident surfaces 314. Specifically, two pump light emitters 300 are mounted at opposite ends of the laser gain material 320 to increase pump absorption by the laser gain material (laser rod) 320. Each pump light emitter 300 is an LED board including a plurality of LED chip arrays, and each pump axis is parallel to the normal direction of the surface of the corresponding pump light emitter 300 . The accommodating space is filled with flowing liquid 335, with liquid inlet 333 and liquid outlet 334 connected to tube structure 310. Air surrounds dielectric tube 315, and the refractive index of liquid 335 is greater than that of air. Each reflective surface 350 at the dielectric-air boundary can focus pump light 345 onto laser gain material 320 through total internal reflection with a non-zero numerical aperture calculated by equation (6). Liquid 335 is specifically water, and dielectric tube 315 can be made of glass or plastic that is transparent to pump light 345. Each pump light emitter 300 comprises a blue or green LED. The flowing liquid 335 is configured to focus pump light 345 onto laser gain material 320 while simultaneously removing heat generated by pump light emitters 300 and laser gain material 320. FIG5 schematically illustrates a laser pumping device 4000 according to a fourth embodiment of the present invention. Referring to FIG5 , the laser pumping device 4000 includes two pump light emitters 400, a tube structure 410, and a laser gain material 420. Each pump light emitter 400 is configured to emit pump light 445 and has a pump axis (coinciding with the rod axis 428). The tube structure 410 is hollow and includes at least one receiving space filled with a cooling liquid 435 and two dielectric tubes 415 connected to face each other. Each dielectric tube 415 includes a light incident surface 414 and a complex reflection surface 450. There are two pump light emitters 400, each positioned adjacent to a corresponding light incident surface 414. The laser gain material 420 is mounted within the receiving space. Each dielectric tube 415 is configured to receive the corresponding pump light 445 into the corresponding light incident surface 414 , guide the corresponding pump light 445 along a corresponding one of the pump axes around the reflective surface 450 , and focus the corresponding pump light 445 into the laser gain material 420 . Specifically, the laser gain material 420 is a laser rod having a rod axis 428, with each pump axis parallel to the rod axis 428. Specifically, the rod axis 428 coincides with the two pump axes, as shown in FIG5 , and the laser pump device 4000 has a longitudinal pumping structure. There are two light incident surfaces 414, with the two ends of the laser gain material 420 adjacent to each of the two light incident surfaces 414. Specifically, two pump light emitters 400 are mounted at opposite ends of the laser gain material 420 to increase pump absorption by the laser gain material (laser rod) 420. Each pump light emitter 400 is an LED board comprising a plurality of LED chip arrays, and each pump axis is parallel to the normal direction of the surface of the corresponding pump light emitter 400. For each dielectric tube 415, the two facing reflective surfaces 450 are wedge-shaped with a non-zero wedge angle α to focus the corresponding pump light 445 from the corresponding light-entry surface 414 having a larger aperture to the laser gain material 420 having a smaller aperture. The accommodating space is filled with flowing liquid 435, with liquid inlet 433 and liquid outlet 434 connected to tube structure 410. Air surrounds dielectric tube 415, and the refractive index of liquid 435 is greater than that of air. Each reflective surface 450 at the dielectric-air boundary can focus pump light 445 onto laser gain material 420 through total internal reflection with a non-zero numerical aperture calculated by equation (6). Liquid 435 is specifically water, and dielectric tube 415 can be made of glass or plastic that is transparent to pump light 445. Each pump light emitter 400 comprises a blue or green LED. The flowing liquid 435 is configured to focus pump light 445 onto laser gain material 420 while simultaneously removing heat generated by pump light emitters 400 and laser gain material 420. FIG6A schematically illustrates a laser pumping device 5000 according to a fifth embodiment of the present invention. Referring to FIG6A , the laser pumping device 5000 includes at least one pump light emitter 500, a dielectric tube 515, and a laser gain material 520. The at least one pump light emitter 500 is configured to emit pump light 545, 546. The dielectric tube 515 is hollow and includes a receiving space and a light incident surface 514. The pump light emitter 500 is disposed adjacent to the light incident surface 514. The laser gain material 520 is mounted within the receiving space. The dielectric tube 515 is configured to receive the pump light 545, 546 into the light incident surface 514 and transmit the pump light 545, 546 to the laser gain material 520. Thus, the dielectric tube 515 of the laser pump device 5000 is designed to facilitate the collection of pump light 545, 546, while further removing heat from the laser gain material 520. In addition, the laser gain material 520 can be Nd:YAG, Nd:YAP, Nd:YVO 4. Nd:GdVO 4. One of Nd:KGW, Nd:YLF, Nd:glass, Cr:YAG, Cr:LiSAF, Yb:YAG, Yb:glass, Er:YAG, Er:glass, Tm:glass and Ti:sapphire crystal. Specifically, the accommodating space is filled with a cooling liquid 535 (e.g., water), and air surrounds the dielectric tube 515. The refractive index of the liquid 535 is greater than that of the air. Thus, the liquid 535 can be used to guide, confine, and focus the pump light 545, 546 onto the laser gain material 520 of the laser pumping device 5000. Based on equation (2), when n a < n w When θ a > θ w In other words, the incident angle θ of the pump light 545, 546 incident on the air-dielectric tube 515 interface is 1 is greater than the refraction angle θ of the pump light 545, 546 refracted by the dielectric tube 515-liquid 535 interface 2. Due to the presence of liquid 535, pump light (incident light) 545 is directed toward laser gain material 520, as shown in FIG6A . Furthermore, dielectric tube 515 can be made of glass or plastic that is transparent to pump light 545 and 546. Liquid 535 can be configured to flow into and out of dielectric tube 515 to remove heat generated by pump light emitter 500 and laser gain material 520. The laser gain material 520 is a laser rod having a rod axis 528. The rod axis 528 is perpendicular to the direction in which the pump lights 545 and 546 exit from the pump light emitter 500 (e.g., the directions of the pump lights 545 and 546 indicated in FIG. 6A ). Thus, the liquid 535 can be used to guide, confine, and focus the pump lights 545 and 546 onto the laser gain material 520 of the laser pumping device 5000. There are four pump light emitters 500, each of which is an LED board comprising a plurality of LED chip arrays. The pump light emitters 500 are arranged in a rectangular shape and surround the dielectric tube 515. Thus, the laser pumping device 5000 effectively focuses the pump lights 545 and 546 onto the laser gain material 520. Furthermore, the pump light emitters 500 can include blue, green, or blue-green LEDs. According to an embodiment of the present invention, a laser pumping device may include one or more pump light emitters arranged to surround a dielectric tube. When the number of pump light emitters is at least three, each pump light emitter is an LED board. The pump light emitters may be arranged in a polygonal shape (e.g., a triangle, a quadrilateral, or a rectangle, but not limited thereto) to surround the dielectric tube. The light-emitting surface of the pump light emitter may be a flat surface, a curved surface, or a passive high-reflection mirror to reflect the other pump light emitters (active pump light emitters having multiple LED chip arrays) back to the laser gain material, thereby increasing the energy conversion efficiency of the pump light. The normal to the cross-section of the laser pump device 5000 (shown in FIG. 6A ) is parallel to the rod axis 528. In cross-section, the dielectric tube 515 and the laser gain material 520 are both circular and coaxially arranged. The width of the light-emitting surface 507 of each pump light emitter 500 is greater than or equal to (specifically, equal to) the diameter of the dielectric tube 515. This improves pumping efficiency within the same space. Pump light 545 emitted from pump light emitter 500 does not pass through laser gain material 520, and pump light 545 is transmitted into laser gain material 520. Laser gain material 520 is mounted in a housing filled with cooling liquid 535. Pump light 545a that misses laser gain material 520 in FIG. 6B (the housing is filled with air) is directed toward laser gain material 520 due to refraction of pump light 545 in FIG. Effectively, liquid 535 in FIG. 6A guides and concentrates pump light 545 toward laser gain material 520. Furthermore, for dielectric tube 515 with a limited wall thickness, since pump light 545 changes its direction upon passing through the partially parallel walls of dielectric tube 515, liquid 535 guides and concentrates pump light 545 toward laser gain material 520. In addition, the pump light 546 passes through the laser gain material 520 from the light output direction of the pump light emitter 500 , and the pump light 546 is transmitted into the laser gain material 520 . FIG6B illustrates a comparative example (laser pumping device 5000a) of the laser pumping device 5000 of the fifth embodiment. Referring to FIG6B , FIG6B differs from FIG6A in that the space within the dielectric tube 515 is filled with air (i.e., not filled with liquid 535). In FIG6B , the pump light 545a does not pass through the laser gain material 520 and is not transmitted into the laser gain material 520. Therefore, the pump light 545a emitted by the pump light emitter 500 of the comparative example laser pumping device 5000a does not transmit into the laser gain material 520, and only the pump light 546a is transmitted into the laser gain material 520. Therefore, the pumping efficiency of the laser pumping device 5000 of FIG6A according to the present invention is significantly better than that of the comparative example laser pumping device 5000a of FIG6B . In addition, compared to the comparative example laser pumping device 5000 a in FIG. 6B , the laser pumping device 5000 in FIG. 6A according to the present invention can further remove heat generated by the pump light emitter 500 and the laser gain material 520 . FIG7 schematically illustrates a laser pumping device 6000 according to a sixth embodiment of the present invention. Referring to FIG7 , the laser pumping device 6000 includes four pump light emitters 600, a dielectric tube 515, and a laser gain material 520. The pump light emitters 600 are configured to emit pump light 645 and 646. The dielectric tube 515 is hollow and includes a receiving space and a light incident surface 514. The pump light emitters 600 are positioned adjacent to the light incident surface 514. The laser gain material 520 is mounted within the receiving space. The dielectric tube 515 is configured to receive the pump light 645 and 646 into the light incident surface 514 and transmit the pump light 645 and 646 to the laser gain material 520. Specifically, the accommodating space is filled with a cooling liquid 635 (e.g., water), and air surrounds the dielectric tube 515. The refractive index of the liquid 635 is greater than that of the air. The width of the light-emitting surface 607 of each pump light emitter 600 is greater than the diameter of the dielectric tube 515. Pump light 645 does not pass through the laser gain material 520 in the light-emitting direction of the pump light emitter 600, and the pump light 645 is transmitted into the laser gain material 520. Pump light 646 passes through the laser gain material 520 in the light-emitting direction of the pump light emitter 600, and the pump light 646 is transmitted into the laser gain material 520. Furthermore, the laser pumping device 6000 of FIG. 7 differs from the laser pumping device 5000 of FIG. 6A in that the width of the light-emitting surface 607 of each pump light emitter 600 is greater than the width of the light-emitting surface 507 of each pump light emitter 500. In other words, the distance between each pump light emitter 600 and the light-incident surface 514 of the dielectric tube 515 is greater than the distance between each pump light emitter 500 and the light-incident surface 514 of the dielectric tube 515. For other details of the laser pumping device 6000, please refer to the aforementioned description of the laser pumping device 5000 and will not be further described here. FIG8 is a schematic diagram of a laser pumping device 7000 according to a seventh embodiment of the present invention. Referring to FIG8 , the laser pumping device 7000 includes four pump light emitters 700, a dielectric tube 715, and three laser gain materials 720. The pump light emitters 700 are configured to emit pump light 745 and 746. The dielectric tube 715 is hollow and includes a receiving space and a light incident surface 714. The pump light emitters 700 are positioned adjacent to the light incident surface 714. The laser gain materials 720 are mounted in the receiving space. The dielectric tube 715 is configured to receive the pump light 745 and 746 into the light incident surface 714 and transmit the pump light 745 and 746 to the laser gain materials 720. Thus, the laser pumping device 7000 is equipped with multiple laser gain materials 720 to generate multiple laser beams. Specifically, the accommodating space is filled with a cooling liquid 735 (e.g., water), and air surrounds the dielectric tube 715. The refractive index of the liquid 735 is greater than that of the air. Furthermore, the dielectric tube 715 can be made of glass or plastic that is transparent to the pump light 745 and 746. The liquid 735 can be configured to flow in and out of the dielectric tube 715 to remove heat generated by the pump light emitter 700 and the laser gain material 720. Each laser gain material 720 is a laser rod having a rod axis 728 , and each rod axis 728 is perpendicular to the emission direction of the pump light 745 , 746 on the pump light emitter 700 (such as the directions of the pump light 745 , 746 indicated in FIG. 8 ). There are four pump light emitters 700, each of which is an LED board comprising a plurality of LED chip arrays. The pump light emitters 700 are arranged in a rectangular shape and surround the dielectric tube 715. Furthermore, the pump light emitters 700 may include blue, green, or blue-green LEDs. The normal direction of the cross-section of the laser pump device 7000 (shown in FIG. 8 ) is parallel to the rod axis 728. In the cross-section, the dielectric tube 715 and each laser gain material 720 are circular, and the width of the light-emitting surface 707 of each pump light emitter 700 is equal to the diameter of the dielectric tube 715. Specifically, the three rod axes 728 of the three laser gain materials 720 are parallel, and the line connecting the intersection points of the three rod axes 728 in the cross-section forms an equilateral triangle. Pump light 745 does not pass through any of the laser gain materials 720 in the direction of light emitted from the pump light emitter 700, and is transmitted into one of the laser gain materials 720. Furthermore, pump light 746 passes through the laser gain materials 720 in the direction of light emitted from the pump light emitter 700, and is transmitted into the laser gain materials 720. Although the present invention has been disclosed above in terms of embodiments, this is not intended to limit the present invention. Anyone skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope of the appended patent applications. 100,200,300,400,500,600,700: Pump light emitter 114,214,314,414,514,714: Light incident surface 115,215,315,415,515,715: Dielectric tube 120,220,320,420,520,720: Laser gain material 125,225: Pump axis 128,228,328,428,528,728: Rod axis 135,235,335,435,535,635,735: Liquid 145, 245,345,445,545,545a,546,546a,645,646,745,746: Pump light 150,250,350,450: Reflecting surface 210,310,410: Tube structure 333,433: Liquid inlet 334,434: Liquid outlet 507,607,707: Light-emitting surface 816,916: Dielectric plate 935: Water 1000,2000,3000,4000,5000,5000a,6000,7000: Laser pump device α: Wedge angle θ 1: Incidence θ 2: Refraction angle θ a ,θ d ,θ w :angle In order to enable a more comprehensive understanding of the present invention by reading the details of the following embodiments, the accompanying drawings are described as follows: Figure 1A is a schematic diagram supporting the theory of the present invention; Figure 1B is another schematic diagram supporting the theory of the present invention; Figure 2 is a schematic diagram of the laser pumping device of the first embodiment of the present invention; Figure 3 is a schematic diagram of the laser pumping device of the second embodiment of the present invention; Figure 4 is a schematic diagram of the laser pumping device of the third embodiment of the present invention; Figure 5 is a schematic diagram of the laser pumping device of the fourth embodiment of the present invention; Figure 6A is a schematic diagram of the laser pumping device of the fifth embodiment of the present invention; Figure 6B is a schematic diagram of a comparative example of the laser pumping device of the fifth embodiment; Figure 7 is a schematic diagram of the laser pumping device of the sixth embodiment of the present invention; and Figure 8 is a schematic diagram of the laser pumping device of the seventh embodiment of the present invention. 100: Pump light emitter 114: light-entering surface 115: Dielectric tube 120: Laser gain material 125: Pump shaft 128: Rod shaft 135:Liquid 145: Pump light 150:Reflective surface 1000: Laser pump device α: wedge angle

Claims

1. A laser pumping device, comprising: a pump light emitter configured to emit a pump light and having a pump axis; a hollow dielectric tube comprising a receiving space, a light-incident surface, and a plurality of reflecting surfaces, wherein the pump light emitter is disposed adjacent to the light-incident surface, the receiving space is filled with a liquid for cooling, an air surrounds the dielectric tube, and the refractive index of the liquid is greater than the refractive index of the air; and a laser gain material mounted in the receiving space; wherein... The dielectric tube is configured to receive the pump light into the incident surface, guide the pump light along the pump axis around the reflective surfaces, and transmit the pump light into the laser gain material.

2. The laser pumping apparatus as claimed in claim 1, wherein the pump light emitter is an LED board comprising a plurality of LED chip arrays, and the pump axis is parallel to a normal direction of a surface of the pump light emitter.

3. The laser pumping apparatus as claimed in claim 2, wherein the pump light emitter includes a blue-green LED.

4. The laser pumping apparatus as claimed in claim 1, wherein the opposing surfaces of the reflective surfaces are parallel to each other and surround the pump axis.

5. The laser pumping apparatus of claim 1, wherein the opposing surfaces of the reflective surfaces are wedge-shaped at a wedge angle to converge the pump light from the incident surface having a larger aperture to the laser gain material having a smaller aperture.

6. The laser pumping apparatus as claimed in claim 1, wherein the laser gain material is a laser rod having a rod axis, and the pump axis is perpendicular to the rod axis.

7. The laser pumping apparatus as claimed in claim 1, wherein the liquid is configured to remove heat generated by the pump light emitter and the laser gain material.

8. The laser pumping device as claimed in claim 1, wherein the liquid is water and one material of the dielectric tube is glass or plastic.

9. The laser pumping apparatus of claim 1, wherein the dielectric tube provides total internal reflection of an incident pump light at each of the reflective surfaces at a dielectric-air boundary.

10. A laser pumping device, comprising: a plurality of pump light emitters, each of the pump light emitters being configured to emit a pump light and having a pump axis; a hollow tube structure including at least one receiving space and at least one dielectric tube, wherein the dielectric tube includes at least one light-incident surface and a plurality of reflective surfaces, the number of the pump light emitters and the number of the at least one light-incident surface are a plurality and the same, and each of the pump light emitters is adjacent to one of the corresponding light-incident surfaces, the receiving space is filled with a liquid for cooling, an air surrounds the tube structure, and the refractive index of the liquid is greater than the refractive index of the air; and a laser gain material mounted in the receiving space; wherein... The dielectric tube is configured to receive at least one of the pump lights into the corresponding incident surface, guide the pump light along a corresponding pump axis around the reflective surfaces, and focus the pump light into the laser gain material.

11. The laser pumping apparatus of claim 10, wherein the laser gain material is a laser rod having a rod axis, and the pump axes are perpendicular to the rod axis.

12. The laser pumping apparatus of claim 11, wherein each of the number of dielectric tubes, the number of pump light emitters, and the number of incident surfaces is greater than two, the dielectric tubes extending along the pump axes of the pump light emitters, and the pump axes intersecting in the laser gain material.

13. The laser pumping apparatus of claim 10, wherein the laser gain material is a laser rod having a rod axis, each of the pump axes being parallel to the rod axis, the number of incident surfaces being two, and the two ends of the laser gain material being adjacent to the two incident surfaces.

14. A laser pumping device, comprising: at least one pump light emitter configured to emit at least one pump light; a dielectric tube, hollow in shape and including a receiving space and a light-incident surface, wherein the at least one pump light emitter is disposed adjacent to the light-incident surface, the receiving space is filled with a liquid for cooling, an air surrounds the dielectric tube, and the refractive index of the liquid is greater than the refractive index of the air; and a laser gain material mounted in the receiving space; wherein... The dielectric tube is configured to receive at least one pump light into the incident surface and transmit the at least one pump light into the laser gain material.

15. The laser pumping apparatus of claim 14, wherein the laser gain material is a laser rod having a rod axis, and the rod axis is perpendicular to at least one emission direction of the at least one pump light on the at least one pump light emitter.

16. The laser pumping apparatus of claim 15, wherein the number of the at least one pump light emitter is at least three, each pump light emitter being an LED panel comprising a plurality of LED chip arrays, the pump light emitters being arranged in a polygon and surrounding the dielectric tube.

17. The laser pumping apparatus as claimed in claim 16, wherein a normal direction of a section of the laser pumping apparatus is parallel to the rod axis; wherein, In this cross-section, the dielectric tube and the laser gain material are both circular and coaxially arranged, and the width of the light-emitting surface of each pump light emitter is greater than or equal to the diameter of the dielectric tube.

18. The laser pumping apparatus of claim 15, wherein the number of the at least one pump light emitter is at least three, the pump light emitters are arranged in a polygon and surround the dielectric tube, at least one of the pump light emitters is at least one passive high reflectivity mirror, at least another of the pump light emitters is at least one active pump light emitter, and the at least one passive high reflectivity mirror is used to reflect the at least one pump light emitted by the at least one active pump light emitter onto the laser gain material.

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